Stormwater Site Plan Fairhaven Harbor Frontage ...files.freelandengineering.com/files/projects/15038/Frontage Storm/1… · Fairhaven Harbor Frontage Improvements Harris Avenue, 9th

Stormwater Site Plan Fairhaven Harbor

Frontage Improvements Harris Avenue, 9th Street, & McKenzie Avenue

Bellingham, Washington

Prepared By: Freeland & Associates, Inc.

220 West Champion Street, Suite 200 Bellingham, WA 98225

(360) 650-1408

Prepared For: Dominion Sustainable Development Corporation

PO Box 31548 Bellingham, WA 98228-3548

(360) 319-0898

July 2016

Freeland & Associates, Inc. 2

Table of Contents ENGINEER'S DECLARATION ................................................................................................... 3

STORMWATER SITE PLAN ...................................................................................................... 4

Existing Conditions Summary ............................................................................................... 4

Project Overview .................................................................................................................. 6

Offsite Analysis .................................................................................................................... 7

Receiving Water Analysis ..................................................................................................... 8

DOE AND CITY OF BELLINGHAM MINIMUM REQUIREMENTS .............................................. 9

Minimum Requirement #1 - Preparation of Stormwater Site Plans (“SSP”) .........................10

Minimum Requirement #2 - Construction Stormwater Pollution Prevention Plan (SWPPP) .10

Minimum Requirement #3 - Source Control of Pollution ......................................................10

Minimum Requirement #4 - Preservation of Natural Drainage Systems and Outfalls...........11

Minimum Requirement #5 - On-site Stormwater Management ............................................11

Minimum Requirement #6 - Runoff Treatment .....................................................................11

Minimum Requirement #7 - Flow Control ............................................................................12

Minimum Requirement #8 - Wetlands Protection .................................................................12

Minimum Requirement #9 - Basin/Watershed Planning .......................................................12

Minimum Requirement #10 - Operation & Maintenance ......................................................12

FIGURES .................................................................................................................................. 13

Figure 1 - Vicinity Map .........................................................................................................14

Figure 2 – Aerial Photo ........................................................................................................15

Figure 3 – Aerial Photo – Close-up View .............................................................................16

Figure 4 - Downstream Drainage Map .................................................................................17

Figure 5 - Water Quality Assessment Map ..........................................................................18

Figure 6 - Treatment Facilities Basin Map ...........................................................................19

CALCULATIONS ...................................................................................................................... 20

Stormwater Modeling Overview ...........................................................................................21

Stormwater Treatment - Contech StormFilter Sizing ............................................................22

Flow Control Modeling Input & Output .................................................................................24

APPENDIX ............................................................................................................................... 33

Stormwater Permit Calculations ..........................................................................................34

Contech StormFilter GULD & Maintenance .........................................................................35

Geotechnical Report............................................................................................................36

Source Control BMPs ..........................................................................................................37

Construction Erosion Control BMPs ....................................................................................38


STORMWATER SITE PLAN

The Stormwater Site Plan (SSP) is the comprehensive report containing all of the technical

information and analysis necessary for regulatory agencies to evaluate the proposed

development for compliance with stormwater requirements.

Existing Conditions Summary

A private, residential project located at 800 Harris Street (Fairhaven Harbor) requires street

frontage improvements to adjacent right of ways bordering the property. These street

improvements include Harris Avenue, 9th Street, and McKenzie Avenue. These streets are

located within the Fairhaven Neighborhood according to the City of Bellingham Neighborhoods

maps. Adjacent properties include a mixed use/condominium development to the east, the

Bellingham Tennis Club to the south, and light industrial uses to the north. Padden Creek is to

the west, with the existing Lower Padden trailhead located at the western edge of the intersection

of 8th Street and McKenzie Avenue. Further west of Padden Creek are undeveloped gravel-

surfaced lots zoned for industrial use.

Phase 1 of Fairhaven Harbor is currently under construction, located on the western half of the

parcel. The construction consists of a mixed use development with residential townhouses and

a commercial space. Phase 1 construction has cleared the majority of the site and used the

eastern half of the site for a construction staging area.

Phase 2 of Fairhaven Harbor is moving forward with design of additional residential units and

commercial space to be located on the remainder of the eastern half of the site. This portion of

the work has not been permitted at this time.

Right of ways surrounding the Fairhaven Harbor private project are currently partially paved with

asphalt and gravel, with existing curb, gutter, and sidewalks bordering adjacent developed

properties opposite from the property. Existing gravel parking abuts the Fairhaven Harbor site

along 9th Street and McKenzie Avenue. Along Harris Avenue, existing ground fronting the project

site is a vegetated ditch. Aerial site photos showing conditions of the right of way prior to the

Phase 1 construction are shown in the Figures section of this report.


At the time Phase 1 was designed, a public works project by the City of Bellingham was currently

in progress along the western property boundary within 8th Street and Padden Creek. This project

is known as the EV0106 Water Quality for Padden Estuary and provides a regional water quality

facility for an area upstream of the project. Phase 1 construction coordinated with the City of

Bellingham project along the western property boundary at 8th Street all the way north to the

intersection of 8th Street and Harris Avenue.

Existing topography on Harris Avenue slopes to the west at grades between 4% and 7%. Existing

topography along 9th Street slopes to the northwest at grades between 2.5% and 5%. Grades

along McKenzie Avenue slope to the southwest between 3.5% and 9.5%.

Stormwater runoff from the roads generally follows the existing grades. Stormwater facilities

within the right of ways include a ditch along 8th Street that flows north to a 12-inch PVC culvert

adjacent to the northwest Fairhaven Harbor property corner. Stormwater runoff in Harris Avenue

is generally collected in the existing ditch along the south side of the road, and conveyed west to

the 12-inch PVC culvert. Stormwater runoff in McKenzie Avenue drains overland onto the

Fairhaven Harbor property.

From the 12-inch PVC culvert, stormwater discharges onto the embankment above Padden Creek

and flows west down to the creek bed. Within Padden Creek, stormwater flows north through a

concrete box culvert to Padden Lagoon eventually reaching Bellingham Bay north of the project

site. See the Offsite Analysis section of this report for a detailed description of the existing

drainage system downstream from the site.

Soils onsite are mapped as Squalicum-Urban land complex and Urban land, hydrologic group “B”.

In addition, GeoEngineers, Inc. (GeoEngineers) performed subsurface soil explorations onsite

and summarized their findings in a report dated June 30, 2005. According to the GeoEngineers

report, two different subsurface soil conditions were encountered at the site. The site was

originally the bluff line down to the beach, with the estimated location of the bluff shown on figures

in the GeoEngineers report. Subsurface conditions southeast (upland) within the site consist of

stiff to medium stiff brown sandy silt overlying dense silty sand with gravel. Subsurface conditions

northwest of the bluff (beach) portion of the site consist of fill with debris overlying sandy former

beach deposits overlying the “till-like” material. Groundwater was observed in one boring (B-6)

on the southeast portion of the site, and within nearly all of the borings in the northwest portion at


varying depths. A copy of the geotechnical report prepared by GeoEngineers is attached in the

Appendix of this report for reference.

Project Overview

Proposed right of way improvements for the Fairhaven Harbor project include frontage

improvements are proposed along Harris Avenue, McKenzie Avenue, and 9th Street.

Improvements street widening, parking, and curb, gutter and sidewalk. A summary of existing

and proposed ground cover areas within the work limits is provided in the Appendix of this report.

Stormwater infiltration and dispersion systems were analyzed for use with onsite stormwater

runoff for this project during the design of Phase 1 and both systems were determined to be

infeasible. Locating stormwater dispersion downhill of the proposed buildings would direct runoff

into the existing 8th Street road right of way and the steep slopes of Padden Creek shoreline, west

of the project. Although onsite soils are noted as hydrologic group “B”, infiltration systems also

do not appear to be practical for use onsite primarily due to the location of the proposed

improvements to the adjacent road right of way and Padden Creek shoreline. Slopes within the

Padden Creek shoreline are greater than 40%, and a geotechnical analysis would likely be

required if infiltration trenches were proposed within 200 feet of the top of this slope. There is not

enough room to install infiltration systems downstream of the proposed improvements and meet

typical setback requirements. In addition, the subsurface conditions indicated the presence of fill

with debris overlying sandy beach material, as well as a variable ground water table. Some areas

of fill consisted primarily of garbage.

Stormwater will be managed by collecting and conveying the proposed frontage improvements to

Contech StormFilter treatment systems. These systems will discharge to the existing municipal

stormwater systems and be routed downstream to Padden Creek and Padden Lagoon.

Downstream of Padden Lagoon stormwater flows into Bellingham Bay.


Offsite Analysis

Downstream from the project site, an existing 12-inch PVC culvert collects stormwater from

ditches converging at the intersection of Harris Avenue and 8th Street. The stormwater culvert

flows west and discharges on the embankment above Padden Creek approximately 60-feet west

of the northwest property corner. Stormwater flows down the slope to the creek bed and through

a box culvert that conveys Padden Creek under Harris Avenue to Padden Lagoon, approximately

130-feet north and west. Padden Lagoon is a tidally influenced body of water and connected to

Bellingham Bay which is located approximately 850 feet to the north of the project site as the crow

flies.

As discussed previously in the Existing Conditions section of this report, an existing City of

Bellingham project is currently in progress west of the subject parcel known as the EV0106 Water

Quality for Padden Estuary. As part of this project, significant stormwater management facilities

will be constructed on the east side of the Padden Creek embankment and within 8th Street,

providing a regional water quality treatment facility for untreated pollution-generating-surfaces.

Plans for this project were reviewed to coordinate areas that will overlap such as at the northwest

corner of the project site. A new 18-inch culvert is planned to replace the existing 12-inch PVC

culvert at this location.

Downstream from the project site, the entire drainage system is owned and maintained by the

City of Bellingham. No flooding hazards or significant erosion problems have been identified

between the project site and Bellingham Bay during site visits and drainage investigations. No

pollution-generating surfaces are proposed for this project, and runoff from impervious roof

surfaces will discharge into stable conveyance channels. Therefore, the proposed project will not

exacerbate existing problems (if any) that may exist downstream from the site.


Receiving Water Analysis

Stormwater runoff from the project site drains directly to Padden Creek and almost immediately

into Padden Lagoon which flows into Bellingham Bay. Padden Creek is listed as an impaired

waterbody in Department of Ecology’s Water Quality Assessment 303(d) list for Washington

between Lake Padden and Bellingham Bay. According to the department’s online Assessment

tool, Padden Creek is listed for bacteria (category 5), and dissolved oxygen (category 5).

Proposed work will construct frontage improvements for the roads surrounding the 800 Harris

Avenue project, and will provide basic water quality treatment for the site. Contech StormFilter

units are proposed for water quality treatment of typical pollutants found in the proposed

development such as sediments, debris, oil and grease, hydrocarbons from typical vehicle use,

fertilizers from landscaping activities, and pet waste. This development is not expected to

increase the bacteria or dissolved oxygen levels within stormwater runoff. No sources of bacteria

are known to exist on site and none are proposed. The new buildings will connect to city sewer

and any pet waste will be required to be collected and disposed of. Any chemicals for grounds

maintenance, including detergents, cleaning products, and fertilizers, will be stored indoors to

prevent contact with stormwater.


DOE AND CITY OF BELLINGHAM MINIMUM REQUIREMENTS

Minimum stormwater management requirements for this project have been determined using

BMC 15.42.060 and the 2012 Department of Ecology Stormwater Management Manual for

Western Washington with 2014 Amendments (2012 DOE SWMM or DOE Manual). With more

than 5,000 square feet new and replaced impervious surfaces, the project is subject to Minimum

Requirements 1 through 10 in BMC 15.42.060.

MINIMUM REQUIREMENT SUMMARY

LARGE PARCEL NEW DEVELOPMENT

Minimum Requirement Not

Applicable Variance

Requested

Standard Requirements Incorporated

Comments (Report Section

Reference or BMP Identifier)

# Description

1 Preparation of Stormwater Site Plans

2 Construction Stormwater Pollution Prevention Plan

See "Additional Comments"

3 Source Control of Pollution

4 Preservation of Natural Drainage Systems and Outfalls

5 On-Site Stormwater Management

6 Runoff Treatment

7 Flow Control

8 Wetlands Protection None identified on or near the site

9 Basin/Watershed Planning

10 Operation and Maintenance

# Additional Comments

2 A copy of the Construction SWPPP is included in the civil construction drawings.


Minimum Requirement #1 - Preparation of Stormwater Site Plans (“SSP”)

This report serves as a Stormwater Site Plan (SSP). All stormwater management systems have

been designed according Department of Ecology (DOE) and City of Bellingham standards. A

construction Stormwater Pollution Prevention Plan (SWPPP) has also been prepared and is

incorporated in the construction documents.

Minimum Requirement #2 - Construction Stormwater Pollution Prevention Plan (SWPPP)

A SWPPP narrative is provided within the civil site plan drawings to ensure that the SWPPP is on

site during construction. Each of the twelve elements of a SWPPP (as identified in BMC

15.42.060(F)(2)(e)) must be considered and included in a Construction SWPPP unless site

conditions render the element unnecessary and the exemption from that element is clearly

justified in the narrative of the SWPPP. The SWPPP shall include, at a minimum, the narrative,

the Stormwater Site Plan and copies of Best Management Practice detail sheets that will be

utilized as a part of the SWPPP.

During construction, the contractor shall maintain a copy of the SWPPP on site and shall update

or modify the SWPPP as necessary for the current conditions on site. The contractor's schedule

and available crew, equipment, and materials will be determined after this project goes to bid.

Accordingly, some BMPs that have been specified may not be necessary, while other additional

BMPs may be required.

Based on the total impervious area for this project including both Phase 1, 2 and the frontage

improvements, this project will disturb more than one acre of soil, and therefore, will require a

Construction General Stormwater NPDES permit from Washington State Department of Ecology.

As such, the project is required to retain a Certified Erosion and Sediment Control Lead (CESCL)

to determine which BMPs are necessary as site conditions change during construction. The

contractor and/or CESCL shall add any BMP specifications that have not already been included

in the SWPPP prepared by Freeland & Associates, Inc.

Minimum Requirement #3 - Source Control of Pollution

Pollutant sources for roads include vehicle traffic, vehicular washing and maintenance, landscape

fertilizers, and other types of detergents or chemicals related to commercial building maintenance

activities as the roads are adjacent to a mixed use commercial building development.


All known, available and reasonable source control BMPs have been applied to the design and

layout of the site and stormwater plans. Typical source control BMPs for this type of project have

been reproduced from the DOE Manual and are provided in the Appendix of this report.

Minimum Requirement #4 - Preservation of Natural Drainage Systems and Outfalls

The entire project site is contained within the Padden Creek watershed. No significant stormwater

diversions are proposed as a part of this project. Natural drainage patterns will be maintained by

discharging stormwater into existing municipal storm drain systems in adjacent streets, which

ultimately drain to Padden Creek and almost immediately into Padden Lagoon which flows into

Bellingham Bay.

Minimum Requirement #5 - On-site Stormwater Management

BMC 15.42.060(F)(5) states, "Projects shall employ On-site Stormwater Management BMPs to

infiltrate, disperse, and retain stormwater runoff onsite to the maximum extent feasible without

causing flooding or erosion impacts. On-site Stormwater Management BMPs shall be designed

and provided in accordance with the Ecology Manual."

As noted previously in this report, dispersion systems are not feasible onsite due to the lack of

suitable vegetated space downhill from the new improvements and the presence of steep slopes.

Likewise, infiltration systems are not feasible onsite due to limited space onsite downhill of the

proposed improvements, steep slopes, and groundwater levels.

Stormwater runoff will be managed within the roads with collection, conveyance, treatment, and

direct discharge to downstream municipal systems that will drain directly to Bellingham Bay. This

design provides basic stormwater treatment for pollution-generating surfaces in accordance with

City of Bellingham Municipal Code.

Minimum Requirement #6 - Runoff Treatment

Proposed pollution-generating surfaces include the paved road and parking on the surrounding

streets. Combined, these areas will create more than 5,000 square feet of Pollution-Generating

Impervious Surfaces (PGIS) and will require basic stormwater treatment systems.


Basic runoff treatment will be provided for the proposed PGIS by Contech StormFilter treatment

systems located as shown in the civil drawings. Each Contech StormFilter treatment system

consists of filter cartridges sized for the contributing basin.

The StormFilter cartridges will have the ZPG media, currently approved as General Use Level

(GULD) for Basic (TSS) Treatment by the Department of Ecology. Sizing for the filter was based

on WWHM2012. The sizing calculations and GULD are included in the Calculations section and

Appendix. Construction details are provided in the civil plans.

Minimum Requirement #7 - Flow Control

Stormwater flow control is not required for development on this parcel. Stormwater runoff will be

collected, treated, and conveyed to a flow control exempt receiving water body. Per the 2012

DOE SWMM, Bellingham Bay is a flow control exempt receiving water body (all salt waterbodies

are included on the list).

Minimum Requirement #8 - Wetlands Protection

No wetlands have been identified on site or in the immediate vicinity. However, Padden Creek

and Padden Lagoon are located directly west and northwest of the project and the project must

meet creek setback requirements for the shoreline.

Minimum Requirement #9 - Basin/Watershed Planning

The entire project site is contained within sub-basin PC223 of the Padden Creek Watershed. No

specific flow control or treatment requirements are identified for this location in the 2007 City of

Bellingham Stormwater Comprehensive Plan (2007 Comprehensive Plan).

Minimum Requirement #10 - Operation & Maintenance

Proposed storm drainage improvements consist of a series of catch basins, pipes, and Contech

StormFilter treatment systems. All proposed storm drainage improvements to be installed within

the street right of ways will be maintained by the City of Bellingham.

Contech StormFilters are a standard water quality treatment system, and the City of Bellingham

has many of these types of systems installed throughout the city. City Public Works Operations

personnel are familiar with the standard operations and maintenance required for these systems.

A copy of the manufacturer’s operations guide is included in the Appendix for reference.


FIGURES


Figure 1 - Vicinity Map

Vicinity Map

Figure 1

No

rth

PROJECT SITE


Figure 2 – Aerial Photo

Aerial Photo

Figure 2

No

rth

PROJECT SITE


Figure 3 – Aerial Photo – Close-up View

Aerial Photo – Close-up View

Figure 3

No

rth

PROJECT SITE


Figure 4 - Downstream Drainage Map

Downstream Drainage Map

Figure 4

No

rth

PROJECT OUTFALL

MUNICIPAL STORM DRAIN OUTFALL TO

PADDEN CREEK

PADDEN CREEK

PADDEN LAGOON


Figure 5 - Water Quality Assessment Map

Water Quality Assessment Map

Figure 5

No

rth

PROJECT SITE


Figure 6 - Treatment Facilities Basin Map

FIG

6

TR

EA

TM

EN

T F

AC

IL

IT

IE

S

BA

SIN

M

AP


CALCULATIONS


Stormwater Modeling Overview

In accordance with BMC 15.42.060(F)(7)(c), Western Washington Hydrology Model v2012

(WWHM2012) software is used to model the anticipated stormwater flows and durations from the

site. WWHM2012 software uses HSPF continuous simulation methodology to compare

predevelopment discharge rates to post-development discharge rates from 50% of the 2-year

peak flow up to the full 50-year peak flow. Predevelopment conditions are considered to be

forested.

Proposed stormwater management facilities will provide water quality and will be located within

the road right of way. WWHM2012 software is used to determine the required size of the

stormwater facilities. Contech StormFilters will be used to provide stormwater treatment, and

sizing calculations are included in the following section.


Stormwater Treatment - Contech StormFilter Sizing

Contech StormFilters are proposed to provide stormwater treatment for the pollution generating

surfaces. Pollution generating surfaces contributing runoff to the treatment system include

portions of pavement on Harris Avenue, 9th Street, and McKenzie Avenue. These units also will

handle flows off non-pollution generating surfaces such as sidewalks and street tree wells that

drain into the facilities.

Stormwater runoff from the new portion of McKenzie Avenue along the north side of the street as

well as from the future road re-development fronting the southern adjacent property will be

provided with water quality treatment. These flowrates are shown separately but treatment will

be provided with one Contech StormFilter unit, and are shown as McKenzie Avenue “North” and

“South”.

Each cartridge within the StormFilter unit can treat a maximum of 7.5 gallons per minute (0.0167

cfs). The maximum flow capacity of the Stormfilter system is 1.0 cubic foot per second. This

product has a General Use Level Designation (GULD) for basic stormwater treatment with the

Washington State Department of Ecology. See the Figures section of the report for the basin

map. A table summarizing the basin areas for each of the Contech StormFilter treatment units is

shown following.


Table C1

Proposed Ground Cover Summary

Type Area (Acres)

McKenzie Avenue - North

Pavement (Moderate) 0.223

Landscaping (Moderate) 0.002

Total Sub-Basin 0.225

McKenzie Avenue - South


Landscaping (Moderate) 0


9th Street

Pavement (Flat) 0.214

Landscaping (Flat) 0.003


Harris Avenue


Landscaping (Moderate) 0.002



Flow Control Modeling Input & Output

Screenshots of the software model are provided below. The left half of each screenshot shows

the entire pre- or post-development stormwater model layout with a single component selected.

The right half of each screenshot provides input information for the selected component of the

model.

Figure C1 – WWHM 2012 Treatment Basin – McKenzie Avenue North


Figure C2 – WWHM 2012 Water Quality Treatment Flow Rate

Figure C3 – WWHM 2012 Maximum Flow Rate


Per the above WWHM2012 model, the project requires a water quality flow rate of 0.0357 cfs,

which is equivalent to 16.02 gallons per minute. Each cartridge can treat up to 7.5 gallons per

minute; therefore, three cartridges are required. Also, the maximum contributing flow to the

cartridge system is 0.224 cfs during the 100-year storm event, which is less than the maximum

1.0 cfs allowed. The specified system meets all of the GULD design requirements.

Figure C4 – WWHM 2012 Treatment Basin – McKenzie Avenue South





Per the above WWHM2012 model, the project requires a water quality flow rate of 0.052 cfs,


minute; therefore, four cartridges are required. Also, the maximum contributing flow to the



Figure C7 – WWHM 2012 Treatment Basin – 9th Street





Per the above WWHM2012 model, the basin requires a water quality flow rate of 0.0304 cfs,


minute; therefore, two cartridges are required. Also, the maximum contributing flow to the



Figure C10 – WWHM 2012 Treatment Basin – Harris Avenue





Per the above WWHM2012 model, the basin requires a water quality flow rate of 0.036 cfs, which

is equivalent to 16.34 gallons per minute. Each cartridge can treat up to 7.5 gallons per minute;

therefore, three cartridges are required. Also, the maximum contributing flow to the cartridge

system is 0.228 cfs during the 100-year storm event, which is less than the maximum 1.0 cfs

allowed. The specified system meets all of the GULD design requirements.


APPENDIX


Stormwater Permit Calculations

Category Area (AC)

Offsite – Right of Way Improvements Only1

Existing Impervious (Pavement) 0.24

Removed Impervious Surface (Pavement) 0.24

Replaced Impervious Surface (Pavement) 0.24

New Impervious Surface (Proposed Road, Sidewalks) 0.75

1) Areas do not include frontage improvements proposed in the future for the south side of McKenzie Avenue


Contech StormFilter GULD & Maintenance

CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e | 1

September 2014

GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) TREATMENT

For

CONTECH Engineered Solutions

Stormwater Management StormFilter®

With ZPG Media at 1 gpm/sq ft media surface area

Ecology’s Decision:

Based on the CONTECH Engineered Solutions’ (CONTECH) application

submissions, Ecology hereby issues a General Use Level Designation (GULD) for the

Stormwater Management StormFilter® (StormFilter):

1. As a basic stormwater treatment practice for total suspended solids (TSS)

removal,

Using ZPG™ media (zeolite/perlite/granular activated carbon), with the size

distribution described below,

Sized at a hydraulic loading rate of 1 gpm/ft2 of media surface area, per

Table 1, and

Internal bypassing needs to be consistent with the design guidelines in

CONTECH’s current product design manual.

Table 1. StormFilter Design Flow Rates per Cartridge

2. Ecology approves StormFilter systems containing ZPG™ media for treatment at

the hydraulic loading rates shown in Table 1, to achieve the maximum water

quality design flow rate. The water quality design flow rates are calculated using

the following procedures:

Western Washington: For treatment installed upstream of detention or

retention, the water quality design flow rate is the peak 15-minute flow rate

as calculated using the latest version of the Western Washington Hydrology

Model or other Ecology-approved continuous runoff model.

Effective Cartridge Height (inches) 12 18 27

Cartridge Flow Rate (gpm/cartridge) 5 7.5 11.3


Eastern Washington: For treatment installed upstream of detention or

retention, the water quality design flow rate is the peak 15-minute flow rate

as calculated using one of the three methods described in Chapter 2.2.5 of the

Stormwater Management Manual for Eastern Washington (SWMMEW) or

local manual.

Entire State: For treatment installed downstream of detention, the water

quality design flow rate is the full 2-year release rate of the detention facility.

3. This designation has no expiration date, but Ecology may amend or revoke it.

Ecology’s Conditions of Use:

The StormFilter with ZPG media shall comply with the following conditions:

1. Design, install, operate, and maintain the StormFilter with ZPG media in

accordance with applicable Contech Engineered Solutions manuals,

documents, and the Ecology Decision.

2. Install StormFilter systems to bypass flows exceeding the water quality

treatment rate. Additionally, high flows will not re-suspend captured

sediments. Design StormFilter systems in accordance with the performance

goals in Ecology's most recent Stormwater Manual and CONTECH’s

Product Design Manual Version 4.1 (April 2006), or most current version,

unless otherwise specified.

3. Owners must follow the design, pretreatment, land use application, and

maintenance criteria in CONTECH’s Design Manual.

4. Pretreatment of TSS and oil and grease may be necessary, and designers

shall provide pre-treatment in accordance with the most current versions of

the CONTECH’s Product Design Manual (April 2006) or the applicable

Ecology Stormwater Manual. Design pre-treatment using the performance

criteria and pretreatment practices provided on Ecology’s “Evaluation of

Emerging Stormwater Treatment Technologies” website.

5. Maintenance: The required maintenance interval for stormwater treatment

devices is often dependent upon the degree of pollutant loading from a

particular drainage basin. Therefore, Ecology does not endorse or

recommend a “one size fits all” maintenance cycle for a particular model/size

of manufactured filter treatment device.

Typically, CONTECH designs StormFilter systems for a target filter

media replacement interval of 12 months. Maintenance includes

removing accumulated sediment from the vault, and replacing spent

cartridges with recharged cartridges.


Indications of the need for maintenance include effluent flow decreasing

to below the design flow rate, as indicated by the scumline above the

shoulder of the cartridge.

Owners/operators must inspect StormFilter with ZPG media for a

minimum of twelve months from the start of post-construction operation

to determine site-specific maintenance schedules and requirements. You

must conduct inspections monthly during the wet season, and every other

month during the dry season. (According to the SWMMWW, the wet

season in western Washington is October 1 to April 30. According to

SWMMEW, the wet season in eastern Washington is October 1 to June

30). After the first year of operation, owners/operators must conduct

inspections based on the findings during the first year of inspections.

Conduct inspections by qualified personnel, follow manufacturer’s

guidelines, and use methods capable of determining either a decrease in

treated effluent flowrate and/or a decrease in pollutant removal ability.

When inspections are performed, the following findings typically serve as

maintenance triggers:

Accumulated vault sediment depths exceed an average of 2 inches, or

Accumulated sediment depths on the tops of the cartridges exceed an

average of 0.5 inches, or

Standing water remains in the vault between rain events, or

Bypass occurs during storms smaller than the design storm.

Note: If excessive floatables (trash and debris) are present, perform a

minor maintenance consisting of gross solids removal, not cartridge

replacement.

6. CONTECH shall maintain readily available reports listed under

“Application Documents” (above) as public, as well as the documentation

submitted with its previous conditional use designation application.

CONTECH shall provide links to this information from its corporate

website, and make this information available upon request, at no cost and in

a timely manner.

7. ZPG™ media used shall conform with the following specifications:

Each cartridge contains a total of approximately 2.6 cubic feet of media.

The ZPG™ cartridge consists of an outer layer of perlite that is

approximately 1.3 cubic feet in volume and an inner layer, consisting of a

mixture of 90% zeolite and 10% granular activated carbon, which is

approximately 1.3 cubic feet in volume.

Perlite Media: Perlite media shall be made of natural siliceous volcanic

rock free of any debris or foreign matter. The expanded perlite shall


have a bulk density ranging from 6.5 to 8.5 lbs per cubic foot and particle

sizes ranging from 0.09” (#8 mesh) to 0.38” (3/8” mesh).

Zeolite Media: Zeolite media shall be made of naturally occurring

clinoptilolite. The zeolite media shall have a bulk density ranging from

44 to 50 lbs per cubic foot and particle sizes ranging from 0.13” (#6 mesh)

to 0.19” (#4 mesh). Additionally, the cation exchange capacity (CEC) of

zeolite shall range from approximately 1.0 to 2.2 meq/g.

Granular Activated Carbon: Granular activated carbon (GAC) shall be

made of lignite coal that has been steam-activated. The GAC media shall

have a bulk density ranging from 28 to 31 lbs per cubic foot and particle

sizes ranging from a 0.09” (#8 mesh) to 0.19” (#4 mesh).

Approved Alternate Configurations

Peak Diversion StormFilter

1. The Peak Diversion StormFilter allows for off-line bypass within the StormFilter

structure. Design capture flows and peak flows enter the inlet bay which contains an

internal weir. The internal weir allows design flows to enter the cartridge bay through

a transfer hole located at the bottom of the inlet bay while the unit routs higher flows

around the cartridge bay.

2. To select the size of the Peak Diversion StormFilter unit, the designer must determine

the number of cartridges required and size of the standard StormFilter using the site-

specific water quality design flow and the StormFilter Design Flow Rates per

Cartridge as described above.

3. New owners may not install the Peak Diversion StormFilter at an elevation or in a

location where backwatering may occur.

Applicant: Contech Engineered Solutions

Applicant’s Address: 11835 NE Glenn Widing Dr.

Portland, OR 97220

Application Documents:

The applicant’s master report, titled, “The Stormwater Management StormFilter

Basic Treatment Application for General Use Level Designation in Washington”,

Stormwater Management, Inc., November 1, 2004, includes the following reports:

(Public) Evaluation of the Stormwater Management StormFilter Treatment

System: Data Validation Report and Summary of the Technical Evaluation

Engineering Report (TEER) by Stormwater Management Inc., October 29, 2004

Ecology’s technology assessment protocol requires the applicant to hire an

independent consultant to complete the following work:


1. Complete the data validation report.

2. Prepare a TEER summary, including a testing summary and conclusions

compared with the supplier’s performance claims.

3. Provide a recommendation of the appropriate technology use level.

4. Work with Ecology to post recommend relevant information on Ecology’s

website.

5. Provide additional testing recommendations, if needed.”

6. This report, authored by Dr. Gary Minton, Ph. D., P.E., Resource Planning

Associates, satisfies the Ecology requirement.

(Public) “Performance of the Stormwater Management StormFilter Relative to the

Washington State Department of Ecology Performance Goals for Basic

Treatment,” is a summary of StormFilter performance that strictly adheres to the

criteria listed in the Guidance for Evaluating Emerging Stormwater Treatment

Technologies, Technology Assessment Protocol – Ecology (TAPE).

“Heritage Marketplace Field Evaluation: Stormwater Management StormFilter

with ZPG™ Media,” is a report showing all of the information collected at Site A

as stated in the SMI Quality Assurance Project Plan (QAPP). This document

contains detailed information regarding each storm event collected at this site, and

it provided a detailed overview of the data and project.

“Lake Stevens Field Evaluation: Stormwater Management StormFilter with

ZPG™ Media,” is a report that corresponds to Site E as stated in the SMI QAPP.

This document contains detailed information regarding each storm collected at

this site, and includes a detailed overview of the data and project.

(Public) “Evaluation of the Stormwater Management StormFilter for the removal

of SIL-CO-SIL 106, a standardized silica product: ZPG™ at 7.5 GPM” is a report

that describes laboratory testing at full design flow.

“Factors Other Than Treatment Performance.”

“State of Washington Installations.”

“Peak Diversion StormFilter” is a technical document demonstrating the Peak

Diversion StormFilter system complies with the Stormwater Management Manual

for Western Washington Volume V Section 4.5.1.

Above-listed documents noted as “public” are available by contacting CONTECH.

Applicant's Use Level Request:

That Ecology grant a General Use Level Designation for Basic Treatment for the

StormFilter using ZPG™ media (zeolite/perlite/granular activated carbon) at a hydraulic

loading rate of 1 gpm/ft2 of media surface area in accordance with Ecology's 2011

Technical Guidance Manual for Evaluating Emerging Stormwater Treatment

Technologies Technology Assessment Protocol – Ecology (TAPE).


Applicant's Performance Claim:

The combined data from the two field sites reported in the TER (Heritage Marketplace

and Lake Stevens) indicate that the performance of a StormFilter system configured for

inline bypass with ZPG™ media and a hydraulic loading rate of 1 gpm/ft2 of media

surface area meets Ecology performance goals for Basic Treatment.

Ecology’s Recommendations:

Based on the weight of the evidence and using its best professional judgment, Ecology

finds that:

StormFilter, using ZPG™ media and operating at a hydraulic loading rate of no more

than 1 gpm/ft2 of media surface area, is expected to provide effective stormwater

treatment achieving Ecology’s Basic Treatment (TSS removal) performance goals.

Contech demonstrated this is through field and laboratory testing performed in

accordance with the approved protocol. StormFilter is deemed satisfactory with

respect to factors other than treatment performance (e.g., maintenance; see the

protocol’s Appendix B for complete list).

Findings of Fact:

Influent TSS concentrations and particle size distributions were generally within the

range of what Ecology considers “typical” for western Washington (silt-to-silt loam).

Contech sampled thirty-two (32) storm events at two sites for storms from April 2003

to March 2004, of which Contech deemed twenty-two (22) as “qualified” and were

therefore included in the data analysis set.

Statistical analysis of these 22 storm events verifies the data set’s adequacy.

Analyzing all 22 qualifying events, the average influent and effluent concentrations

and aggregate pollutant load reduction are 114 mg/L, 25 mg/L, and 82%,

respectively.

Analyzing all 22 qualifying events based on the estimated average flow rate during

the event (versus the measured peak flow rate), and more heavily weighting those

events near the design rate (versus events either far above or well below the design

rate) does not significantly affect the reported results.

For the 7 qualifying events with influent TSS concentrations greater than 100 mg/L,

the average influent and effluent concentrations and aggregate pollutant load

reduction are 241 mg/L, 34 mg/L, and 89%, respectively. If we exclude the 2 of 7

events that exceed the maximum 300 mg/L specified in Ecology’s guidelines, the

average influent and effluent concentrations and aggregate pollutant load reduction

are 158 mg/L, 35 mg/L, and 78%, respectively.

For the 15 qualifying events with influent TSS concentrations less than 100 mg/L, the

average influent and effluent concentrations and aggregate pollutant load reduction

are 55 mg/L, 20 mg/L, and 61%, respectively. If the 6 of 15 events that fall below the

minimum 33 mg/L TSS specified in Ecology’s guidelines are excluded, the average


influent and effluent concentrations and aggregate pollutant load reduction are 78

mg/L, 26 mg/L, and 67%, respectively.

For the 8 qualifying events with peak discharge exceeding design flow (ranging from

120 to 257% of the design rate), results ranged from 52% to 96% TSS removal, with

an average of 72%.

Due to the characteristics of the hydrographs, the field results generally reflect flows

below (ranging between 20 and 60 percent of) the tested facilities’ design rate.

During these sub-design flow rate periods, some of the cartridges operate at or near

their individual full design flow rate (generally between 4 and 7.5 GPM for an 18”

cartridge effective height) because their float valves have opened. Float valves

remain closed on the remaining cartridges, which operate at their base “trickle” rate

of 1 to 1.5 GPM.

Laboratory testing using U.S. Silica’s Sil-Co-Sil 106 fine silica product showed an

average 87% TSS removal for testing at 7.5 GPM per cartridge (100% design flow

rate).

Other relevant testing at I-5 Lake Union, Greenville Yards (New Jersey), and Ski Run

Marina (Lake Tahoe) facilities shows consistent TSS removals in the 75 to 85%

range. Note that the evaluators operated the I-5 Lake Union at 50%, 100%, and

125% of design flow.

SMI’s application included a satisfactory “Factors other than treatment performance”

discussion.

Note: Ecology’s 80% TSS removal goal applies to 100 mg/l and greater influent TSS.

Below 100 mg/L influent TSS, the goal is 20 mg/L effluent TSS.

Technology Description:

The Stormwater Management StormFilter® (StormFilter), a flow-through stormwater

filtration system, improves the quality of stormwater runoff from the urban environment

by removing pollutants. The StormFilter can treat runoff from a wide variety of sites

including, but not limited to: retail and commercial development, residential streets,

urban roadways, freeways, and industrial sites such as shipyards, foundries, etc.

Operation:

The StormFilter is typically comprised of a vault that houses rechargeable, media-filled,

filter cartridges. Various media may be used, but this designation covers only the zeolite-

perlite-granulated activated carbon (ZPG™) medium. Stormwater from storm drains

percolates through these media-filled cartridges, which trap particulates and may remove

pollutants such as dissolved metals, nutrients, and hydrocarbons. During the filtering

process, the StormFilter system also removes surface scum and floating oil and grease.

Once filtered through the media, the treated stormwater is directed to a collection pipe or

discharged to an open channel drainage way.

This document includes a bypass schematic for flow rates exceeding the water quality

design flow rate on page 8.


StormFilter Configurations:

Contech offers the StormFilter in multiple configurations: precast, high flow, catch basin,

curb inlet, linear, volume, corrugated metal pipe, drywell, and CON/Span form. Most

configurations use pre-manufactured units to ease the design and installation process.

Systems may be either uncovered or covered underground units.

The typical precast StormFilter unit is composed of three sections: the energy dissipater,

the filtration bay, and the outlet sump. As Stormwater enters the inlet of the StormFilter

vault through the inlet pipe, piping directs stormwater through the energy dissipater into

the filtration bay where treatment will take place. Once in the filtration bay, the

stormwater ponds and percolates horizontally through the media contained in the

StormFilter cartridges. After passing through the media, the treated water in each

cartridge collects in the cartridge’s center tube from where piping directs it into the outlet

sump by a High Flow Conduit under-drain manifold. The treated water in the outlet

sump discharges through the single outlet pipe to a collection pipe or to an open channel

drainage way. In some applications where you anticipate heavy grit loads, pretreatment

by settling may be necessary.


Figure 1. Stormwater Management StormFilter Configuration with Bypass


Figure 2. The StormFilter Cartridge

Cartridge Operation:

As the water level in the filtration bay begins to rise, stormwater enters the StormFilter

cartridge. Stormwater in the cartridge percolates horizontally through the filter media

and passes into the cartridge’s center tube, where the float in the cartridge is in a closed

(downward) position. As the water level in the filtration bay continues to rise, more

water passes through the filter media and into the cartridge’s center tube. Water

displaces the air in the cartridge and it purges from beneath the filter hood through the

one-way check valve located in the cap. Once water fills the center tube there is enough

buoyant force on the float to open the float valve and allow the treated water to flow into

the under-drain manifold. As the treated water drains, it tries to pull in air behind it. This

causes the check valve to close, initiating a siphon that draws polluted water throughout

the full surface area and volume of the filter. Thus, water filters through the entire filter

cartridge throughout the duration of the storm, regardless of the water surface elevation in

the filtration bay. This continues until the water surface elevation drops to the elevation

of the scrubbing regulators. At this point, the siphon begins to break and air quickly

flows beneath the hood through the scrubbing regulators, causing energetic bubbling

between the inner surface of the hood and the outer surface of the filter. This bubbling

agitates and cleans the surface of the filter, releasing accumulated sediments on the

surface, flushing them from beneath the hood, and allowing them to settle to the vault

floor.

Adjustable cartridge flow rate:

Inherent to the design of the StormFilter is the ability to control the individual cartridge

flow rate with an orifice-control disc placed at the base of the cartridge. Depending on

the treatment requirements and on the pollutant characteristics of the influent stream as


specified in the CONTECH Product Design Manual, operators may adjust the flow rate

through the filter cartridges. By decreasing the flow rate through the filter cartridges, the

influent contact time with the media is increased and the water velocity through the

system is decreased, thus increasing both the level of treatment and the solids removal

efficiencies of the filters, respectively (de Ridder, 2002).

Recommended research and development:

Ecology encourages CONTECH to pursue continuous improvements to the StormFilter.

To that end, CONTECH recommends the following actions:

Determine, through laboratory testing, the relationship between accumulated solids

and flow rate through the cartridge containing the ZPG™ media. Completed 11/05.

Determine the system’s capabilities to meet Ecology’s enhanced, phosphorus, and oil

treatment goals.

Develop easy-to-implement methods of determining that a StormFilter facility

requires maintenance (cleaning and filter replacement).

Contact Information:

Applicant Contact: Sean Darcy

Contech Engineered Solutions

11835 NE Glenn Widing Drive

Portland, OR, 97220

503-258-3105

[email protected]

Applicant Web link http://www.conteches.com/

Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html

Ecology Contact: Douglas C. Howie, P.E.

Department of Ecology

Water Quality Program

(360) 407-6444

[email protected]

Revision History

Date Revision

Jan 2005 Original Use Level Designation

Dec 2007 Revision

May 2012 Maintenance requirements updated

November 2012 Design Storm and Maintenance requirements updated

January 2013 Updated format to match Ecology standard format

September 2014 Added Peak Diversion StormFilter Alternate Configuration

mailto:[email protected]

http://www.conteches.com/

http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html

mailto:[email protected]

StormFilter Inspection and Maintenance Procedures

ENGINEERED SOLUTIONS

In addition to these two activities, it is important to check the condition of the StormFilter unit after major storms for potential damage caused by high flows and for high sediment accumulation that may be caused by localized erosion in the drainage area. It may be necessary to adjust the inspection/ maintenance schedule depending on the actual operating conditions encountered by the system. In general, inspection activities can be conducted at any time, and maintenance should occur, if warranted, during dryer months in late summer to early fall.

Maintenance Frequency The primary factor for determining frequency of maintenance for the StormFilter is sediment loading.

A properly functioning system will remove solids from water by trapping particulates in the porous structure of the filter media inside the cartridges. The flow through the system will naturally decrease as more and more particulates are trapped. Eventually the flow through the cartridges will be low enough to require replacement. It may be possible to extend the usable span of the cartridges by removing sediment from upstream trapping devices on a routine as-needed basis, in order to prevent material from being re-suspended and discharged to the StormFilter treatment system.

The average maintenance lifecycle is approximately 1-3 years. Site conditions greatly influence maintenance requirements. StormFilter units located in areas with erosion or active construction may need to be inspected and maintained more often than those with fully stabilized surface conditions.

Regulatory requirements or a chemical spill can shift maintenance timing as well. The maintenance frequency may be adjusted as additional monitoring information becomes available during the inspection program. Areas that develop known problems should be inspected more frequently than areas that demonstrate no problems, particularly after major storms. Ultimately, inspection and maintenance activities should be scheduled based on the historic records and characteristics of an individual StormFilter system or site. It is recommended that the site owner develop a database to properly manage StormFilter inspection and maintenance programs..

2 3

Maintenance GuidelinesThe primary purpose of the Stormwater Management StormFilter® is to filter and prevent pollutants from entering our waterways. Like any effective filtration system, periodically these pollutants must be removed to restore the StormFilter to its full efficiency and effectiveness.

Maintenance requirements and frequency are dependent on the pollutant load characteristics of each site. Maintenance activities may be required in the event of a chemical spill or due to excessive sediment loading from site erosion or extreme storms. It is a good practice to inspect the system after major storm events.

Maintenance ProceduresAlthough there are many effective maintenance options, we believe the following procedure to be efficient, using common equipment and existing maintenance protocols. The following two-step procedure is recommended::

1. Inspection

• Inspection of the vault interior to determine the need for maintenance.

2. Maintenance

• Cartridge replacement

• Sediment removal

Inspection and Maintenance Timing At least one scheduled inspection should take place per year with maintenance following as warranted.

First, an inspection should be done before the winter season. During the inspection the need for maintenance should be determined and, if disposal during maintenance will be required, samples of the accumulated sediments and media should be obtained.

Second, if warranted, a maintenance (replacement of the filter cartridges and removal of accumulated sediments) should be performed during periods of dry weather.

2 3

Inspection ProceduresThe primary goal of an inspection is to assess the condition of the cartridges relative to the level of visual sediment loading as it relates to decreased treatment capacity. It may be desirable to conduct this inspection during a storm to observe the relative flow through the filter cartridges. If the submerged cartridges are severely plugged, then typically large amounts of sediments will be present and very little flow will be discharged from the drainage pipes. If this is the case, then maintenance is warranted and the cartridges need to be replaced.

Warning: In the case of a spill, the worker should abort inspection activities until the proper guidance is obtained. Notify the local hazard control agency and Contech Engineered Solutions immediately.

To conduct an inspection:

Important: Inspection should be performed by a person who is familiar with the operation and configuration of the StormFilter treatment unit.

1. If applicable, set up safety equipment to protect and notify surrounding vehicle and pedestrian traffic.

2. Visually inspect the external condition of the unit and take notes concerning defects/problems.

3. Open the access portals to the vault and allow the system vent.

4. Without entering the vault, visually inspect the inside of the unit, and note accumulations of liquids and solids.

5. Be sure to record the level of sediment build-up on the floor of the vault, in the forebay, and on top of the cartridges. If flow is occurring, note the flow of water per drainage pipe. Record all observations. Digital pictures are valuable for historical documentation.

6. Close and fasten the access portals.

7. Remove safety equipment.

8. If appropriate, make notes about the local drainage area relative to ongoing construction, erosion problems, or high loading of other materials to the system.

9. Discuss conditions that suggest maintenance and make decision as to weather or not maintenance is needed.

Maintenance Decision TreeThe need for maintenance is typically based on results of the inspection. The following Maintenance Decision Tree should be used as a general guide. (Other factors, such as Regulatory Requirements, may need to be considered)

1. Sediment loading on the vault floor.

a. If >4” of accumulated sediment, maintenance is required.

2. Sediment loading on top of the cartridge.

a. If >1/4” of accumulation, maintenance is required.

3. Submerged cartridges.

a. If >4” of static water above cartridge bottom for more than 24 hours after end of rain event, maintenance is required. (Catch basins have standing water in the cartridge bay.)

4. Plugged media.

a. If pore space between media granules is absent, maintenance is required.

5. Bypass condition.

a. If inspection is conducted during an average rain fall event and StormFilter remains in bypass condition (water over the internal outlet baffle wall or submerged cartridges), maintenance is required.

6. Hazardous material release.

a. If hazardous material release (automotive fluids or other) is reported, maintenance is required.

7. Pronounced scum line.

a. If pronounced scum line (say ≥ 1/4” thick) is present above top cap, maintenance is required.

8. Calendar Lifecycle.

a. If system has not been maintained for 3 years maintenance is required.

Important: Care must be used to avoid damaging the cartridges during removal and installation. The cost of repairing components damaged during maintenance will be the responsibility of the owner.

C. Set the used cartridge aside or load onto the hauling truck.

D. Continue steps a through c until all cartridges have been removed.

Method 2:A. This activity will require that maintenance personnel enter

the vault to remove the cartridges from the under drain manifold and place them under the vault opening for lifting (removal). Disconnect each filter cartridge from the underdrain connector by rotating counterclockwise 1/4 of a turn. Roll the loose cartridge, on edge, to a convenient spot beneath the vault access.

B. Unscrew the cartridge cap.

C. Remove the cartridge hood and float.

D. At location under structure access, tip the cartridge on its side.

E. Empty the cartridge onto the vault floor. Reassemble the empty cartridge.

F. Set the empty, used cartridge aside or load onto the hauling truck.

G. Continue steps a through e until all cartridges have been removed.

4 5

MaintenanceDepending on the configuration of the particular system, maintenance personnel will be required to enter the vault to perform the maintenance.

Important: If vault entry is required, OSHA rules for confined space entry must be followed.

Filter cartridge replacement should occur during dry weather. It may be necessary to plug the filter inlet pipe if base flows is occurring.

Replacement cartridges can be delivered to the site or customers facility. Information concerning how to obtain the replacement cartridges is available from Contech Engineered Solutions.

Warning: In the case of a spill, the maintenance personnel should abort maintenance activities until the proper guidance is obtained. Notify the local hazard control agency and Contech Engineered Solutions immediately.

To conduct cartridge replacement and sediment removal maintenance:

1. If applicable, set up safety equipment to protect maintenance personnel and pedestrians from site hazards.

2. Visually inspect the external condition of the unit and take notes concerning defects/problems.

3. Open the doors (access portals) to the vault and allow the system to vent.

4. Without entering the vault, give the inside of the unit, including components, a general condition inspection.

5. Make notes about the external and internal condition of the vault. Give particular attention to recording the level of sediment build-up on the floor of the vault, in the forebay, and on top of the internal components.

6. Using appropriate equipment offload the replacement cartridges (up to 150 lbs. each) and set aside.

7. Remove used cartridges from the vault using one of the following methods:

Method 1:A. This activity will require that maintenance personnel enter

the vault to remove the cartridges from the under drain manifold and place them under the vault opening for lifting (removal). Disconnect each filter cartridge from the underdrain connector by rotating counterclockwise 1/4 of a turn. Roll the loose cartridge, on edge, to a convenient spot beneath the vault access.

Using appropriate hoisting equipment, attach a cable from the boom, crane, or tripod to the loose cartridge. Contact Contech Engineered Solutions for suggested attachment devices.

B. Remove the used cartridges (up to 250 lbs. each) from the vault.

4 5

8. Remove accumulated sediment from the floor of the vault and from the forebay. This can most effectively be accomplished by use of a vacuum truck.

9. Once the sediments are removed, assess the condition of the vault and the condition of the connectors.

10. Using the vacuum truck boom, crane, or tripod, lower and install the new cartridges. Once again, take care not to damage connections.

11. Close and fasten the door.

12. Remove safety equipment.

13. Finally, dispose of the accumulated materials in accordance with applicable regulations. Make arrangements to return the used empty cartridges to Contech Engineered Solutions.

Related Maintenance Activities - Performed on an as-needed basisStormFilter units are often just one of many structures in a more comprehensive stormwater drainage and treatment system.

In order for maintenance of the StormFilter to be successful, it is imperative that all other components be properly maintained. The maintenance/repair of upstream facilities should be carried out prior to StormFilter maintenance activities.

In addition to considering upstream facilities, it is also important to correct any problems identified in the drainage area. Drainage area concerns may include: erosion problems, heavy oil loading, and discharges of inappropriate materials.

Material DisposalThe accumulated sediment found in stormwater treatment and conveyance systems must be handled and disposed of in accordance with regulatory protocols. It is possible for sediments to contain measurable concentrations of heavy metals and organic chemicals (such as pesticides and petroleum products). Areas with the greatest potential for high pollutant loading include industrial areas and heavily traveled roads.

Sediments and water must be disposed of in accordance with all applicable waste disposal regulations. When scheduling maintenance, consideration must be made for the disposal of solid and liquid wastes. This typically requires coordination with a local landfill for solid waste disposal. For liquid waste disposal a number of options are available including a municipal vacuum truck decant facility, local waste water treatment plant or on-site treatment and discharge.

Inspection Report

Date: Personnel:

Location: ————————————System Size: ———————————————————————————————————

System Type: Vault Cast-In-Place Linear Catch Basin Manhole Other

Sediment Thickness in Forebay: ———————————————————————————————————————————

Sediment Depth on Vault Floor: ———————————————————————————————————————————

Structural Damage: ————————————————————————————————————————————————

Estimated Flow from Drainage Pipes (if available): ————————————————————————————————————

Cartridges Submerged: Yes No Depth of Standing Water: ——————————————————————

StormFilter Maintenance Activities (check off if done and give description)

Trash and Debris Removal: ———————————————————————————————————————————

Minor Structural Repairs: ————————————————————————————————————————————

Drainage Area Report —————————————————————————————————————————————

Excessive Oil Loading: Yes No Source: ———————————————————————

Sediment Accumulation on Pavement: Yes No Source: ———————————————————————

Erosion of Landscaped Areas: Yes No Source: ———————————————————————

Items Needing Further Work: ————————————————————————————————————————————

Owners should contact the local public works department and inquire about how the department disposes of their street waste residuals.

Other Comments:

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

Review the condition reports from the previous inspection visits.

Date:

StormFilter Maintenance Report

Date: —————————————Personnel: ————————————————————————————————————

Location: ————————————System Size: ———————————————————————————————————

System Type: Vault Cast-In-Place Linear Catch Basin Manhole Other

List Safety Procedures and Equipment Used: ——————————————————————————————————————

—————————————————————————————————————————————————————————

—————————————————————————————————————————————————————————

System ObservationsMonths in Service:

Oil in Forebay (if present): Yes No

Sediment Depth in Forebay (if present): ————————————————————————————————————————

Sediment Depth on Vault Floor: ———————————————————————————————————————————

Structural Damage: ————————————————————————————————————————————————

Drainage Area ReportExcessive Oil Loading: Yes No Source: —————————————————————————

Sediment Accumulation on Pavement: Yes No Source: —————————————————————————

Erosion of Landscaped Areas: Yes No Source: —————————————————————————

StormFilter Cartridge Replacement Maintenance ActivitiesRemove Trash and Debris: Yes No Details: ——————————————————————————

Replace Cartridges: Yes No Details: ——————————————————————————

Sediment Removed: Yes No Details: ——————————————————————————

Quantity of Sediment Removed (estimate?):

Minor Structural Repairs: Yes No Details: —————————————————————————

Residuals (debris, sediment) Disposal Methods: ——————————————————————————————————————

Notes:

——————————————————————————————————————————————————————————

——————————————————————————————————————————————————————————

——————————————————————————————————————————————————————————

——————————————————————————————————————————————————————————

——————————————————————————————————————————————————————————

——————————————————————————————————————————————————————————

——————————————————————————————————————————————————————————

800.338.1122www.conteches.com

NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS AN ExPRESSED WARRANT Y OR AN IMPLIED WARRANT Y OF MERCHANTABILITY OR FITNESS FOR

AN Y PARTICULAR PURPOSE . SEE THE CONTECH STANDARD CONDITIONS OF SALE (VIEWABLE AT WWW.CONTECHES.COM /COS ) FOR MORE INFORMATION .

Contech Engineered Solutions LLC provides site solutions for the civil engineering industry. Contech’s portfolio includes bridges, drainage, sanitary sewer, stormwater and earth stabilization products. For information on other Contech division offerings, visit contech-cpi.com or call 800.338.1122.

Support

• Drawings and specifications are available at www.conteches.com.

• Site-specific design support is available from our engineers.

ENGINEERED SOLUTIONS

©2015 CONTECH ENGINEERED SOLUTIONS LLC.

800-338-1122

www.ContechES.com

All Rights Reserved. Printed in the USA.

StormFilter Inspection and Maintenance Procedures 10/15


Geotechnical Report


Source Control BMPs

Volume IV - Source Control BMPs – August 2012 2-2

Operators under the ISGP or Boatyard permits should take special care to review this chapter in its entirety to ensure that all of the applicable (mandatory) source control BMPs are included within their industrial or boatyard SWPPP (regardless of the listings in Appendix IV-A).

2.1 Applicable (Mandatory) Operational Source Control BMPs

Where required by local code or by an Ecology NPDES Stormwater General Permit, implement the following operational source control BMPs at:

• Commercial properties

• Industrial properties

• Multifamily properties

• Boatyards

• Sand and gravel mining operations

• Assign one or more individuals to be responsible for stormwater pollution control. Hold regular meetings to review the overall operation of the BMPs. Establish responsibilities for inspections, operation, maintenance, and for emergencies. Train all team members in the operation, maintenance, and inspections of BMPs, and reporting procedures.

• Promptly contain and clean up solid and liquid pollutant leaks and spills including oils, solvents, fuels, and dust from manufacturing operations on any exposed soil, vegetation, or paved area.

• Sweep all appropriate surfaces with vacuum sweepers quarterly or more frequently as needed for the collection and disposal of dust and debris that could contaminate stormwater.

• Do not hose down pollutants from any area to the ground, storm drains, conveyance ditches, or receiving water unless necessary for dust control purposes to meet air quality regulations. Convey pollutants before discharge, to a treatment system approved by the local jurisdiction.

• Clean oils, debris, sludge, etc. from all stormwater facilities regularly, including catch basins, settling/detention basins, oil/water separators, boomed areas, and conveyance systems to prevent the contamination of stormwater. Refer to Appendix IV-D R.3 for references to assist in handling potentially dangerous waste.

• Promptly repair or replace all substantially cracked or otherwise damaged paved secondary containment, high-intensity parking, and any other drainage areas, subjected to pollutant material leaks or spills. Promptly repair or replace all leaking connections, pipes, hoses, valves, etc., which can contaminate stormwater.

Formation of a Pollution Prevention Team

Good Housekeeping

Sites & facilities that require the implementation of source control BMPs


• Do not connect floor drains in potential pollutant source areas to storm drains, surface water, or to the ground.

Additional good housekeeping BMPs: • Clean up pollutant liquid leaks and spills in impervious uncovered

containment areas at the end of each working day.

• Use solid absorbents, e.g., clay and peat absorbents and rags for cleanup of liquid spills/leaks, where practicable.

• Promptly repair/replace/reseal damaged paved areas at industrial facilities

• Recycle materials, such as oils, solvents, and wood waste, to the maximum extent practicable.

• Prevent the discharge of unpermitted liquid or solid wastes, process wastewater, and sewage to ground or surface water, or to storm drains that discharge to surface water, or to the ground.Conduct all oily parts cleaning, steam cleaning, or pressure washing of equipment or containers inside a building, or on an impervious contained area, such as a concrete pad. Direct contaminated stormwater from such an area to a sanitary sewer where allowed by local sewer authority, or to other approved treatment.

• Pressure wash impervious surfaces contaminated with oils, metals, sediment, etc. Collect the resulting washwater for proper disposal (usually involves plugging storm drains, or otherwise preventing discharge and pumping or vactoring up washwater, for discharge to sanitary sewer or for vactor truck transport to a waste water treatment plant for disposal).

• Do not pave over contaminated soil unless it has been determined that ground water has not been and will not be contaminated by the soil. Call Ecology for assistance.

• Construct impervious areas that are compatible with the materials handled. Portland cement concrete, asphalt, or equivalent material may be considered.

• Use drip pans to collect leaks and spills from industrial/ commercial equipment such as cranes at ship/boat building and repair facilities, log stackers, industrial parts, trucks and other vehicles stored outside.

• At industrial and commercial facilities, drain oil and fuel filters before disposal. Discard empty oil and fuel filters, oily rags, and other oily solid waste into appropriately closed and properly labeled containers, and in compliance with the Uniform Fire Code or International Building Code.

• For the storage of liquids use containers, such as steel and plastic drums, that are rigid and durable, corrosion resistant to the weather

Preventive Maintenance


and fluid content, non-absorbent, water tight, rodent-proof, and equipped with a close fitting cover.

• For the temporary storage of solid wastes contaminated with liquids or other potential polluted materials use dumpsters, garbage cans, drums, and comparable containers, which are durable, corrosion resistant, non-absorbent, non-leaking, and equipped with either a solid cover or screen cover to prevent littering. If covered with a screen, the container must be stored under a roof or other form of adequate cover.

• Where exposed to stormwater, use containers, piping, tubing, pumps, fittings, and valves that are appropriate for their intended use and for the contained liquid.

Additional preventive maintenance BMPs:

• Where feasible, store potential stormwater pollutant materials inside a building or under a cover and/or containment.

• Minimize use of toxic cleaning solvents, such as chlorinated solvents, and other toxic chemicals.

• Use environmentally safe raw materials, products, additives, etc. such as substitutes for zinc used in rubber production.

• Recycle waste materials such as solvents, coolants, oils, degreasers, and batteries to the maximum extent feasible. Refer to Appendix IV-C for recommendations on recycling or disposal of vehicle waste liquids and other waste materials.

• Empty drip pans immediately after a spill or leak is collected in an uncovered area.

• Stencil warning signs at stormwater catch basins and drains, e.g., “Dump no waste – Drains to waterbody.”

Note: Evidence of stormwater contamination by oils and grease can include the presence of visible sheen, color, or turbidity in the runoff, or present or historical operational problems at the facility. Operators can use simple pH tests, for example with litmus or pH paper. These tests can screen for high or low pH levels (anything outside a 6.5-8.5 range) due to contamination in stormwater.

• Stop, contain, and clean up all spills immediately upon discovery.

• If pollutant materials are stored on-site, have spill containment and cleanup kits readily accessible.

• If the spill has reached or may reach a sanitary or a storm sewer, ground water, or surface water notify the local jurisdiction, Ecology, and the local sewer authority immediately. Notification must comply with and federal spill reporting requirements. (See also record keeping

Spill Prevention and Cleanup


at the end of this section and S406 BMPs for Spills of Oil and Hazardous Substances)

• Do not flush or otherwise direct absorbent materials or other spill cleanup materials to a storm drain. Collect the contaminated absorbent material as a solid and place in appropriate disposal containers.

Recommended additional BMP: Place and maintain emergency spill containment and cleanup kit(s) at outside areas where there is a potential for fluid spills. These kits should be appropriate for the materials and the size of a potential spill. Locate spill kits within 25 feet of all fueling/fuel transfer areas, including on-board mobile fuel trucks.

Facilities covered under Industrial Stormwater General Permit must provide secondary containment for all chemical liquids, fluids, and petroleum products stored on-site.

Note: Ecology recommends that the kit(s) include salvage drums or containers, such as high density polyethylene, polypropylene or polyethylene sheet-lined steel; polyethylene or equivalent disposal bags; an emergency response guidebook; safety gloves/clothes/equipment; shovels or other soil removal equipment; and oil containment booms and absorbent pads; all stored in an impervious container.

Train all employees that work in pollutant source areas in:

• Identifying pollutant sources

• Understanding pollutant control measures

• Responding to spills

• Handling practices that are environmentally acceptable. Particularly those related to vehicle/equipment liquids such as fuels, and vehicle/equipment cleaning.

Qualified personnel shall conduct visual inspections monthly. Make and maintain a record of each inspection on-site . Inspections shall:

• Verify the accuracy of the pollutant source descriptions in the SWPPP.

• Verify the performance of the stormwater operational and structural source controls and the treatment BMPs .

• Reflect current conditions on the site.

• Include written observations of the presence of floating materials, suspended solids, oil and grease, discoloration, turbidity and odor in the stormwater discharges; in outside vehicle maintenance/repair; and liquid handling, and storage areas. In areas where acid or alkaline materials are handled or stored use a simple litmus or pH paper to identify those types of stormwater contaminants where needed.

Employee Training

Inspections


• Eliminate or obtain a permit for unpermitted non-stormwater discharges to storm drains or receiving waters, such as process wastewater and vehicle/equipment washwater.

Retain the following reports for five years:

• Visual inspection reports which should include:

• Time and date of the inspection

• Locations inspected

• Statement on status of compliance with the permit

• Summary report of any remediation activities required

• Name, title, and signature of person conducting the inspection

• Reports on spills of oil or hazardous substances in greater than Reportable Quantities (Code of Federal Regulations Title 40 Parts 302.4 and 117). Report spills of the following: antifreeze, oil, gasoline, or diesel fuel, that cause:

• A violation of the State of Washington's Water Quality Standards.

• A film or sheen upon or discoloration of the waters of the State or adjoining shorelines.

• A sludge or emulsion to be deposited beneath the surface of the water or upon adjoining shorelines.

• To report a spill or to determine if a spill is a substance of a Reportable Quantity, call the Ecology regional office and ask for an oil spill operations or a dangerous waste specialist:

Northwest Region (425)649-7000 Southwest Region (360)407-6300 Eastern Region (509)329-3400 Central Region (509) 575-2490

In addition, call the Washington Emergency Management Division at 1-800-258-5990 or 1-800-OILS-911 AND the National Response Center at 1-800-424-8802.

Also, refer to Emergency Spill Response in Washington State, Publication # 97-1165-CP. The following is additional recommended record keeping: Maintain records of all related pollutant control and pollutant generating activities such as training, materials purchased, material use and disposal, maintenance performed, etc.

Record keeping


of the mixture. Stormwater could be conveyed to a sanitary sewer system if it is determined not to be explosive.

• Transfer the fuel from the delivery tank trucks to the fuel storage tank in impervious contained areas and ensure that appropriate overflow protection is used. Alternatively, cover nearby storm drains during the filling process and use drip pans under all hose connections.

Additional BMP for Vehicles 10 feet in height or greater A roof or canopy may not be feasible at fueling stations that regularly fuel vehicles that are 10 feet in height or greater, particularly at industrial or WSDOT sites. At those types of fueling facilities, the following BMPs apply, as well as the applicable BMPs and fire prevention (UFC requirements) of this BMP for fueling stations:

• If a roof or canopy is impractical, the concrete fueling pad must be equipped with emergency spill control including a shutoff valve for drainage from the fueling area. Maintain the valve in the closed position in the event of a spill. An electronically actuated valve is preferred to minimize the time lapse between spill and containment. Clean up spills and dispose of materials off-site in accordance with S406 BMPs for Spills of Oil and Hazardous Substances.

• The valve may be opened to convey contaminated stormwater to a sanitary sewer, if approved by the sewer authority, or to oil removal treatment such as an API or CP oil/water separator, catchbasin insert, or equivalent treatment, and then to a basic treatment BMP. Discharges from treatment systems to storm sewer or surface water or to the ground must not display ongoing or recurring visible sheen and must not contain greater than a significant amount of oil and grease.

S410 BMPs for Illicit Connections to Storm Drains

Description of Pollutant Sources: Illicit connections are unpermitted sanitary or process wastewater discharges to a storm sewer or to surface water, rather than to a sanitary sewer, industrial process wastewater, or other appropriate treatment. They can also include swimming pool water, filter backwash, cleaning solutions/washwaters, cooling water, etc. Experience has shown that illicit connections are common, particularly in older buildings.

Pollutant Control Approach: Identify and eliminate unpermitted discharges or obtain an NPDES permit, where necessary, particularly at industrial and commercial facilities.

Applicable Operational BMPs: • Eliminate unpermitted wastewater discharges to storm sewer, ground

water, or surface water.


• Convey unpermitted discharges to a sanitary sewer if allowed by the local sewer authority, or to other approved treatment.

• Obtain appropriate state and local permits for these discharges.

Recommended Additional Operational BMPs: At commercial and industrial facilities, conduct a survey of wastewater discharge connections to storm drains and to surface water as follows:

• Conduct a field survey of buildings, particularly older buildings, and other industrial areas to locate storm drains from buildings and paved surfaces. Note where these join the public storm drain(s).

• During non-stormwater conditions inspect each storm drain for non-stormwater discharges. Record the locations of all non-stormwater discharges. Include all permitted discharges.

• If useful, prepare a map of each area. Show on the map the known location of storm sewers, sanitary sewers, and permitted and unpermitted discharges. Aerial photos may be useful. Check records such as piping schematics to identify known side sewer connections and show these on the map. Consider using smoke, dye, or chemical analysis tests to detect connections between two conveyance systems (e.g., process water and stormwater). If desirable, conduct TV inspections of the storm drains and record the footage on videotape.

• Compare the observed locations of connections with the information on the map and revise the map accordingly. Note suspect connections that are inconsistent with the field survey.

• Identify all connections to storm sewers or to surface water and take the actions specified above as applicable BMPs.

S411 BMPs for Landscaping and Lawn/ Vegetation Management

Description of Pollutant Sources: Landscaping can include grading, soil transfer, vegetation removal, pesticide and fertilizer applications, and watering. Stormwater contaminants include toxic organic compounds, heavy metals, oils, total suspended solids, coliform bacteria, fertilizers, and pesticides.

Lawn and vegetation management can include control of objectionable weeds, insects, mold, bacteria, and other pests with pesticides. Examples include weed control on golf course lawns, access roads, and utility corridors and during landscaping; sap stain and insect control on lumber and logs; rooftop moss removal; killing nuisance rodents; fungicide application to patio decks, and residential lawn/plant care. It is possible to release toxic pesticides such as pentachlorophenol, carbamates, and organometallics to the environment by leaching and dripping from treated parts, container leaks, product misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the


vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater contamination. Pollutant Control Approach: Control of fertilizer and pesticide applications, soil erosion, and site debris to prevent contamination of stormwater. Develop and implement an Integrated Pest Management Plan (IPM) and use pesticides only as a last resort. Carefully apply pesticides/ herbicides, in accordance with label instructions. Maintain appropriate vegetation, with proper fertilizer application where practicable, to control erosion and the discharge of stormwater pollutants. Where practicable grow plant species appropriate for the site, or adjust the soil properties of the subject site to grow desired plant species.

Applicable Operational BMPs for Landscaping: • Install engineered soil/landscape systems to improve the infiltration

and regulation of stormwater in landscaped areas.

• Do not dispose of collected vegetation into waterways or storm sewer systems.

Recommended Additional Operational BMPs for Landscaping: • Conduct mulch-mowing whenever practicable

• Dispose of grass clippings, leaves, sticks, or other collected vegetation, by composting, if feasible.

• Use mulch or other erosion control measures on soils exposed for more than one week during the dry season or two days during the rainy season.

• Store and maintain appropriate oil and chemical spill cleanup materials in readily accessible locations when using oil or other chemicals. Ensure that employees are familiar with proper spill cleanup procedures.

• Till fertilizers into the soil rather than dumping or broadcasting onto the surface. Determine the proper fertilizer application rate for the types of soil and vegetation encountered.

• Till a topsoil mix or composted organic material into the soil to create a well-mixed transition layer that encourages deeper root systems and drought-resistant plants.

• Use manual and/or mechanical methods of vegetation removal rather than applying herbicides, where practical.


Applicable Operational BMPs for the Use of Pesticides: • Develop and implement an IPM (See section on IPM in Applicable

Operational BMPs for Vegetation Management) and use pesticides only as a last resort.

• Implement a pesticide-use plan and include at a minimum: a list of selected pesticides and their specific uses; brands, formulations, application methods and quantities to be used; equipment use and maintenance procedures; safety, storage, and disposal methods; and monitoring, record keeping, and public notice procedures. All procedures shall conform to the requirements of Chapter 17.21 RCW and Chapter 16-228 WAC (Appendix IV-D R.7).

• Choose the least toxic pesticide available that is capable of reducing the infestation to acceptable levels. The pesticide should readily degrade in the environment and/or have properties that strongly bind it to the soil. Conduct any pest control activity at the life stage when the pest is most vulnerable. For example, if it is necessary to use a Bacillus thuringiens application to control tent caterpillars, apply it to the material before the caterpillars cocoon or it will be ineffective. Any method used should be site-specific and not used wholesale over a wide area.

• Apply the pesticide according to label directions. Do not apply pesticides in quantities that exceed manufacturer’s instructions.

• Mix the pesticides and clean the application equipment in an area where accidental spills will not enter surface or ground waters, and will not contaminate the soil.

• Store pesticides in enclosed areas or in covered impervious containment. Do not discharge pesticide contaminated stormwater or spills/leaks of pesticides to storm sewers. Do not hose down the paved areas to a storm sewer or conveyance ditch. Store and maintain appropriate spill cleanup materials in a location known to all near the storage area.

• Clean up any spilled pesticides. Keep pesticide contaminated waste materials in designated covered and contained areas.

• The pesticide application equipment must be capable of immediate shutoff in the event of an emergency.

• Do not spray pesticides within 100 feet of open waters including wetlands, ponds, and streams, sloughs and any drainage ditch or channel that leads to open water except when following approval of Ecology or the local jurisdiction. Flag all sensitive areas including wells, creeks, and wetlands prior to spraying.

• Post notices and delineate the spray area prior to the application, as required by the local jurisdiction or by Ecology.

http://apps.leg.wa.gov/rcw/default.aspx?cite=17.21

http://apps.leg.wa.gov/WAC/default.aspx?cite=16-228


• Conduct spray applications during weather conditions as specified in the label direction and applicable local and state regulations. Do not apply during rain or immediately before expected rain.

Recommended Additional Operational BMPs for the use of pesticides: • Consider alternatives to the use of pesticides such as covering or

harvesting weeds, substitute vegetative growth, and manual weed control/moss removal.

• Consider the use of soil amendments, such as compost, that are known to control some common diseases in plants, such as Pythium root rot, ashy stem blight, and parasitic nematodes. The following are three possible mechanisms for disease control by compost addition (USEPA Publication 530-F-9-044):

1. Successful competition for nutrients by antibiotic production;

2. Successful predation against pathogens by beneficial microorganism; and

3. Activation of disease-resistant genes in plants by composts.

Installing an amended soil/landscape system can preserve both the plant system and the soil system more effectively. This type of approach provides a soil/landscape system with adequate depth, permeability, and organic matter to sustain itself and continue working as an effective stormwater infiltration system and a sustainable nutrient cycle.

• Once a pesticide is applied, evaluate its effectiveness for possible improvement. Records should be kept showing the effectiveness of the pesticides considered.

• Develop an annual evaluation procedure including a review of the effectiveness of pesticide applications, impact on buffers and sensitive areas (including potable wells), public concerns, and recent toxicological information on pesticides used/proposed for use. If individual or public potable wells are located in the proximity of commercial pesticide applications, contact the regional Ecology hydrogeologist to determine if additional pesticide application control measures are necessary.

• Rinseate from equipment cleaning and/or triple-rinsing of pesticide containers should be used as product or recycled into product.

For more information, contact the Washington State University (WSU) Extension Home-Assist Program, (253) 445-4556, or Bio-Integral Resource Center (BIRC), P.O. Box 7414, Berkeley, CA.94707, or EPA to obtain a publication entitled “Suspended, Canceled, and Restricted Pesticides” which lists all restricted pesticides and the specific uses that are allowed.


Applicable Operational BMPs for Vegetation Management: • Use at least an eight-inch "topsoil" layer with at least 8 percent organic

matter to provide a sufficient vegetation-growing medium. Amending existing landscapes and turf systems by increasing the percent organic matter and depth of topsoil can substantially improve the permeability of the soil, the disease and drought resistance of the vegetation, and reduce fertilizer demand. This reduces the demand for fertilizers, herbicides, and pesticides. Organic matter is the least water-soluble form of nutrients that can be added to the soil. Composted organic matter generally releases only between 2 and 10 percent of its total nitrogen annually, and this release corresponds closely to the plant growth cycle. Return natural plant debris and mulch to the soil, to continue recycling nutrients indefinitely.

• Select the appropriate turfgrass mixture for the climate and soil type. Certain tall fescues and rye grasses resist insect attack because the symbiotic endophytic fungi found naturally in their tissues repel or kill common leaf and stem-eating lawn insects. However, they do not, repel root-feeding lawn pests such as Crane Fly larvae, and are toxic to ruminants such as cattle and sheep. The fungus causes no known adverse effects to the host plant or to humans. Endophytic grasses are commercially available; use them in areas such as parks or golf courses where grazing does not occur. Local agricultural or gardening resources such as Washington State University Extension office can offer advice on which types of grass are best suited to the area and soil type.

• Use the following seeding and planting BMPs, or equivalent BMPs to obtain information on grass mixtures, temporary and permanent seeding procedures, maintenance of a recently planted area, and fertilizer application rates: Temporary and Permanent Seeding, Mulching, Plastic Covering, and Sodding as described in Volume II.

• Adjusting the soil properties of the subject site can assist in selection of desired plant species. For example, design a constructed wetland to resist the invasion of reed canary grass by layering specific strata of organic matters (e.g., composted forest product residuals) and creating a mildly acidic pH and carbon-rich soil medium. Consult a soil restoration specialist for site-specific conditions.

• Aerate lawns regularly in areas of heavy use where the soil tends to become compacted. Conduct aeration while the grasses in the lawn are growing most vigorously. Remove layers of thatch greater than ¾-inch deep.

• Mowing is a stress-creating activity for turfgrass. Grass decreases its productivity when mown too short and there is less growth of roots and rhizomes. The turf becomes less tolerant of environmental stresses, more disease prone and more reliant on outside means such as


pesticides, fertilizers, and irrigation to remain healthy. Set the mowing height at the highest acceptable level and mow at times and intervals designed to minimize stress on the turf. Generally mowing only 1/3 of the grass blade height will prevent stressing the turf.

Irrigation: • The depth from which a plant normally extracts water depends on the

rooting depth of the plant. Appropriately irrigated lawn grasses normally root in the top 6 to 12 inches of soil; lawns irrigated on a daily basis often root only in the top 1 inch of soil. Improper irrigation can encourage pest problems, leach nutrients, and make a lawn completely dependent on artificial watering. The amount of water applied depends on the normal rooting depth of the turfgrass species used, the available water holding capacity of the soil, and the efficiency of the irrigation system. Consult with the local water utility, Conservation District, or Cooperative Extension office to help determine optimum irrigation practices.

Fertilizer Management: • Turfgrass is most responsive to nitrogen fertilization, followed by

potassium and phosphorus. Fertilization needs vary by site depending on plant, soil, and climatic conditions. Evaluation of soil nutrient levels through regular testing ensures the best possible efficiency and economy of fertilization. For details on soils testing, contact the local Conservation District, a soils testing professional, or a Washington State University Extension office.

• Apply fertilizers in amounts appropriate for the target vegetation and at the time of year that minimizes losses to surface and ground waters. Do not fertilize when the soil is dry. Alternatively, do not apply fertilizers within three days prior to predicted rainfall. The longer the period between fertilizer application and either rainfall or irrigation, the less fertilizer runoff occurs.

• Use slow release fertilizers such as methylene urea, IDBU, or resin coated fertilizers when appropriate, generally in the spring. Use of slow release fertilizers is especially important in areas with sandy or gravelly soils.

• Time the fertilizer application to periods of maximum plant uptake. Ecology generally recommends application in the fall and spring, although Washington State University turf specialists recommend four fertilizer applications per year.

• Properly trained persons should apply all fertilizers. Apply no fertilizer at commercial and industrial facilities, to grass swales, filter strips, or buffer areas that drain to sensitive water bodies unless approved by the local jurisdiction.


Integrated Pest Management An IPM program might consist of the following steps:

Step 1: Correctly identify problem pests and understand their life cycle

Step 2: Establish tolerance thresholds for pests.

Step 3: Monitor to detect and prevent pest problems.

Step 4: Modify the maintenance program to promote healthy plants and discourage pests.

Step 5: Use cultural, physical, mechanical or biological controls first if pests exceed the tolerance thresholds.

Step 6: Evaluate and record the effectiveness of the control and modify maintenance practices to support lawn or landscape recovery and prevent recurrence.

For an elaboration of these steps, refer to Appendix IV-F.

S412 BMPs for Loading and Unloading Areas for Liquid or Solid Material

Description of Pollutant Sources: Operators typically conduct loading/unloading of liquid and solid materials at industrial and commercial facilities at shipping and receiving, outside storage, fueling areas, etc. Materials transferred can include products, raw materials, intermediate products, waste materials, fuels, scrap metals, etc. Leaks and spills of fuels, oils, powders, organics, heavy metals, salts, acids, alkalis, etc. during transfer may cause stormwater contamination. Spills from hydraulic line breaks are a common problem at loading docks. Pollutant Control Approach: Cover and contain the loading/unloading area where necessary to prevent run-on of stormwater and runoff of contaminated stormwater.

Applicable Operational BMPs: At All Loading/ Unloading Areas: • A significant amount of debris can accumulate at outside, uncovered

loading/unloading areas. Sweep these surfaces frequently to remove loose material that could contaminate stormwater. Sweep areas temporarily covered after removal of the containers, logs, or other material covering the ground.

• Place drip pans, or other appropriate temporary containment device, at locations where leaks or spills may occur such as hose connections, hose reels and filler nozzles. Always use drip pans when making and breaking connections (see Figure 2.2.2). Check loading/ unloading equipment such as valves, pumps, flanges, and connections regularly for leaks and repair as needed.


Recommended Treatment BMPs: Install biofiltration swales and filter strips – (See Chapter 9, Volume V) to treat roadside runoff wherever practicable and use engineered topsoils wherever necessary to maintain adequate vegetation. These systems can improve infiltration and stormwater pollutant control upstream of roadside ditches.

S417 BMPs for Maintenance of Stormwater Drainage and Treatment Systems

Description of Pollutant Sources: Facilities include roadside catch basins on arterials and within residential areas, conveyance systems, detention facilities such as ponds and vaults, oil/water separators, biofilters, settling basins, infiltration systems, and all other types of stormwater treatment systems presented in Volume V. Oil and grease, hydrocarbons, debris, heavy metals, sediments and contaminated water are found in catch basins, oil and water separators, settling basins, etc.

Pollutant Control Approach: Provide maintenance and cleaning of debris, sediments, and oil from stormwater collection, conveyance, and treatment systems to obtain proper operation.

Applicable Operational BMPs:

Maintain stormwater treatment facilities per the operations and maintenance (O&M) procedures presented in Section 4.6 of Volume V in addition to the following BMPs: • Inspect and clean treatment BMPs, conveyance systems, and catch

basins as needed, and determine necessary O&M improvements.

• Promptly repair any deterioration threatening the structural integrity of stormwater facilities. These include replacement of clean-out gates, catch basin lids, and rock in emergency spillways.

• Ensure adequacy of storm sewer capacities and prevent heavy sediment discharges to the sewer system.

• Regularly remove debris and sludge from BMPs used for peak-rate control, treatment, etc. and discharge to a sanitary sewer if approved by the sewer authority, or truck to an appropriate local or state government approved disposal site.

• Clean catch basins when the depth of deposits reaches 60 percent of the sump depth as measured from the bottom of basin to the invert of the lowest pipe into or out of the basin. However, in no case should there be less than six inches clearance from the debris surface to the invert of the lowest pipe. Some catch basins (for example, WSDOT Type 1L basins) may have as little as 12 inches sediment storage below the invert. These catch basins need frequent inspection and cleaning to prevent scouring. Where these catch basins are part of a stormwater collection and treatment system, the system


owner/operator may choose to concentrate maintenance efforts on downstream control devices as part of a systems approach.

• Clean woody debris in a catch basin as frequently as needed to ensure proper operation of the catchbasin.

• Post warning signs; “Dump No Waste - Drains to Ground Water,” “Streams,” “Lakes,” or emboss on or adjacent to all storm drain inlets where possible.

• Disposal of sediments and liquids from the catch basins must comply with “Recommendations for Management of Street Wastes” described in Appendix IV-G of this volume.

Additional Applicable BMPs: Select additional applicable BMPs from this chapter depending on the pollutant sources and activities conducted at the facility. Those BMPs include:

• S425 BMPs for Soil Erosion and Sediment Control at Industrial Sites

• S427 BMPs for Storage of Liquid, Food Waste, or Dangerous Waste Containers

• S406 BMPs for Spills of Oil and Hazardous Substances

• S410 BMPs for Illicit Connections to Storm Drains

• S430 BMPs for Urban Streets

S418 BMPs for Manufacturing Activities - Outside

Description of Pollutant Sources: Manufacturing pollutant sources include outside process areas, stack emissions, and areas where manufacturing activity has taken place in the past and significant exposed pollutant materials remain. Pollution Control Approach: Cover and contain outside manufacturing and prevent stormwater run-on and contamination, where feasible.

Applicable Operational BMP:

• Sweep paved areas regularly, as needed, to prevent contamination of stormwater.

• Alter the activity by eliminating or minimizing the contamination of stormwater.

• Applicable Structural Source Control BMPs:Enclose the activity (see Figure 2.2.6): If possible, enclose the manufacturing activity in a building.

• Cover the activity and connect floor drains to a sanitary sewer, if approved by the local sewer authority. Berm or slope the floor as needed to prevent drainage of pollutants to outside areas. (Figure 2.2.7)


Discharge Elimination System (NPDES) Permit Requirements, Washington Department of Ecology, March 2011,website: http://www.ecy.wa.gov/biblio/94146.html. Apply the BMPs in that guidance document to scrap material recycling facilities depending on the pollutant sources existing at those facilities.

S424 BMPs for Roof/ Building Drains at Manufacturing and Commercial Buildings

Description of Pollutant Sources: Stormwater runoff from roofs and sides of manufacturing and commercial buildings can be sources of pollutants caused by leaching of roofing materials, building vents, and other air emission sources. Research has identified vapors and entrained liquid and solid droplets/particles as potential pollutants in roof/building runoff. Metals, solvents, acidic/alkaline pH, BOD, and organics, are some of the pollutant constituents identified.

Ecology has performed a study on zinc in industrial stormwater. The study is presented in Ecology Publication 08-10-025 Suggested Practices to reduce Zinc Concentrations in Industrial Stormwater Discharges, website: http://www.ecy.wa.gov/biblio/0810025.html. The user should refer to this document for more details on addressing zinc in stormwater. Pollutant Control Approach: Evaluate the potential sources of stormwater pollutants and apply source control BMPs where feasible.

Applicable Operational Source Control BMPs: • If leachates and/or emissions from buildings are suspected sources of

stormwater pollutants, then sample and analyze the stormwater draining from the building.

• Sweep the area routinely to remove any zinc residuals.

• If a roof/building stormwater pollutant source is identified, implement appropriate source control measures such as air pollution control equipment, selection of materials, operational changes, material recycle, process changes, etc.

Applicable Structural Source Control BMPs: • Paint/coat the galvanized surfaces as described in Ecology Publication

# 08-10-025.

Applicable Treatment BMPs: Treat runoff from roofs to the appropriate level. The facility may use enhanced treatment BMPs as described in Volume V of the SWMMWW. Some facilities regulated by the Industrial Stormwater General Permit, or local jurisdiction, may have requirements than cannot be achieved with enhanced treatment BMPs. In these cases, additional treatment measures may be required. A treatment method for meeting stringent requirements such as Chitosan-Enhanced Sand Filtration may be appropriate.

http://www.ecy.wa.gov/biblio/94146.html





Construction Erosion Control BMPs

Volume II – Construction Stormwater Pollution Prevention - August 2012 4-7

BMP C105: Stabilized Construction Entrance / Exit

Purpose Stabilized Construction entrances are established to reduce the amount of sediment transported onto paved roads by vehicles or equipment. This is done by constructing a stabilized pad of quarry spalls at entrances and exits for construction sites.

Conditions of Use Construction entrances shall be stabilized wherever traffic will be entering or leaving a construction site if paved roads or other paved areas are within 1,000 feet of the site.

For residential construction provide stabilized construction entrances for each residence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient length/width to provide vehicle access/parking, based on lot size/configuration.

On large commercial, highway, and road projects, the designer should include enough extra materials in the contract to allow for additional stabilized entrances not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed.

Design and Installation Specifications

See Figure 4.1.1 for details. Note: the 100’ minimum length of the entrance shall be reduced to the maximum practicable size when the size or configuration of the site does not allow the full length (100’). Construct stabilized construction entrances with a 12-inch thick pad of 4-inch to 8-inch quarry spalls, a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed concrete, cement, or calcium chloride for construction entrance stabilization because these products raise pH levels in stormwater and concrete discharge to surface waters of the State is prohibited. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the following standards:

Grab Tensile Strength (ASTM D4751) 200 psi min. Grab Tensile Elongation (ASTM D4632)

30% max.

Mullen Burst Strength (ASTM D3786-80a)

400 psi min.

AOS (ASTM D4751) 20-45 (U.S. standard sieve size)

• Consider early installation of the first lift of asphalt in areas that will paved; this can be used as a stabilized entrance. Also consider the installation of excess concrete as a stabilized entrance. During large concrete pours, excess concrete is often available for this purpose.


• Fencing (see BMP C103) shall be installed as necessary to restrict traffic to the construction entrance.

• Whenever possible, the entrance shall be constructed on a firm, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance.

• Construction entrances should avoid crossing existing sidewalks and back of walk drains if at all possible. If a construction entrance must cross a sidewalk or back of walk drain, the full length of the sidewalk and back of walk drain must be covered and protected from sediment leaving the site.

Maintenance Standards

Quarry spalls shall be added if the pad is no longer in accordance with the specifications. • If the entrance is not preventing sediment from being tracked onto

pavement, then alternative measures to keep the streets free of sediment shall be used. This may include replacement/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of the entrance, or the installation of a wheel wash.

• Any sediment that is tracked onto pavement shall be removed by shoveling or street sweeping. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is ineffective and there is a threat to public safety. If it is necessary to wash the streets, the construction of a small sump to contain the wash water shall be considered. The sediment would then be washed into the sump where it can be controlled.

• Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high efficiency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches.

• Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately.

• If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing (see BMP C103) shall be installed to control traffic.

• Upon project completion and site stabilization, all construction accesses intended as permanent access for maintenance shall be permanently stabilized.


Figure 4.1.1 – Stabilized Construction Entrance

Approved as Equivalent

Ecology has approved products as able to meet the requirements of BMP C105. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to consideration for local use. The products are available for review on Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html

BMP C106: Wheel Wash

Purpose Wheel washes reduce the amount of sediment transported onto paved roads by motor vehicles.

Conditions of Use When a stabilized construction entrance (see BMP C105) is not preventing sediment from being tracked onto pavement.

• Wheel washing is generally an effective BMP when installed with careful attention to topography. For example, a wheel wash can be detrimental if installed at the top of a slope abutting a right-of-way where the water from the dripping truck can run unimpeded into the street.

Driveway shall meet the requirements of the permitting agency

It is recommended that the entrance be crowned so that runoff drains off the pad

Provide full width of ingress/egress area

12” min. thickness

Geotextile

4’ – 8” quarry spalls

Install driveway culvert if there is a roadside ditch present

http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html


BMP C107: Construction Road/Parking Area Stabilization

Purpose Stabilizing subdivision roads, parking areas, and other on-site vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or runoff.

Conditions of Use Roads or parking areas shall be stabilized wherever they are constructed, whether permanent or temporary, for use by construction traffic.

• High Visibility Fencing (see BMP C103) shall be installed, if necessary, to limit the access of vehicles to only those roads and parking areas that are stabilized.


• On areas that will receive asphalt as part of the project, install the first lift as soon as possible.

• A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course shall be applied immediately after grading or utility installation. A 4-inch course of asphalt treated base (ATB) may also be used, or the road/parking area may be paved. It may also be possible to use cement or calcium chloride for soil stabilization. If cement or cement kiln dust is used for roadbase stabilization, pH monitoring and BMPs (BMPs C252 and C253) are necessary to evaluate and minimize the effects on stormwater. If the area will not be used for permanent roads, parking areas, or structures, a 6-inch depth of hog fuel may also be used, but this is likely to require more maintenance. Whenever possible, construction roads and parking areas shall be placed on a firm, compacted subgrade.

• Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain. Drainage ditches shall be provided on each side of the roadway in the case of a crowned section, or on one side in the case of a super-elevated section. Drainage ditches shall be directed to a sediment control BMP.

• Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet-flows into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not adequate. If this area has at least 50 feet of vegetation that water can flow through, then it is generally preferable to use the vegetation to treat runoff, rather than a sediment pond or trap. The 50 feet shall not include wetlands or their buffers. If runoff is allowed to sheetflow through adjacent vegetated areas, it is vital to design the roadways and parking areas so that no concentrated runoff is created.

• Storm drain inlets shall be protected to prevent sediment-laden water entering the storm drain system (see BMP C220).


Inspect stabilized areas regularly, especially after large storm events.

Crushed rock, gravel base, etc. shall be added as required to maintain a


stable driving surface and to stabilize any areas that have eroded.

Following construction, these areas shall be restored to pre-construction condition or better to prevent future erosion.

Perform street cleaning at the end of each day or more often if necessary.

BMP C120: Temporary and Permanent Seeding

Purpose Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion.

Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days.

The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1.

Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established.

Between October 1 and March 30 seeding requires a cover of mulch with straw or an erosion control blanket until 75 percent grass cover is established.

Review all disturbed areas in late August to early September and complete all seeding by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average protection. • Mulch is required at all times for seeding because it protects seeds

from heat, moisture loss, and transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding. See BMP C121: Mulching for specifications.

• Seed and mulch, all disturbed areas not otherwise vegetated at final site stabilization. Final stabilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions or geotextiles) which will prevent erosion.


Seed retention/detention ponds as required.

Install channels intended for vegetation before starting major earthwork and hydroseed with a Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control blankets over hydroseed. Before allowing water to flow in vegetated channels, establish 75 percent vegetation cover. If vegetated channels cannot be established by seed before water flow; install sod in the channel bottom—over hydromulch and erosion control blankets.


• Confirm the installation of all required surface water control measures to prevent seed from washing away.

• Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 percent tackifier. See BMP C121: Mulching for specifications.

• Areas that will have seeding only and not landscaping may need compost or meal-based mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on the disturbed soil surface before application.

• When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up in contact with the soil surface. This reduces the ability to establish a good stand of grass quickly. To overcome this, consider increasing seed quantities by up to 50 percent.

• Enhance vegetation establishment by dividing the hydromulch operation into two phases: 1. Phase 1- Install all seed and fertilizer with 25-30 percent mulch

and tackifier onto soil in the first lift. 2. Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by: 1. Installing the mulch, seed, fertilizer, and tackifier in one lift. 2. Spread or blow straw over the top of the hydromulch at a rate of

800-1000 pounds per acre. 3. Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance vegetative establishment. The increased cost may be offset by the reduced need for: • Irrigation.

• Reapplication of mulch.

• Repair of failed slope surfaces.

This technique works with standard hydromulch (1,500 pounds per acre minimum) and BFM/MBFMs (3,000 pounds per acre minimum).

• Seed may be installed by hand if:

• Temporary and covered by straw, mulch, or topsoil.

• Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or erosion blankets.

• The seed mixes listed in the tables below include recommended mixes for both temporary and permanent seeding.


• Apply these mixes, with the exception of the wetland mix, at a rate of 120 pounds per acre. This rate can be reduced if soil amendments or slow-release fertilizers are used.

• Consult the local suppliers or the local conservation district for their recommendations because the appropriate mix depends on a variety of factors, including location, exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by the local authority may be used.

• Other mixes may be appropriate, depending on the soil type and hydrology of the area.

• Table 4.1.2 lists the standard mix for areas requiring a temporary vegetative cover.

Table 4.1.2 Temporary Erosion Control Seed Mix

% Weight % Purity % Germination Chewings or annual blue grass Festuca rubra var. commutata or Poa anna

40 98 90

Perennial rye - Lolium perenne

50 98 90

Redtop or colonial bentgrass Agrostis alba or Agrostis tenuis

5 92 85

White dutch clover Trifolium repens

5 98 90

• Table 4.1.3 lists a recommended mix for landscaping seed.

Table 4.1.3 Landscaping Seed Mix

% Weight % Purity % Germination Perennial rye blend Lolium perenne

70 98 90

Chewings and red fescue blend Festuca rubra var. commutata or Festuca rubra

30 98 90


• Table 4.1.4 lists a turf seed mix for dry situations where there is no need for watering. This mix requires very little maintenance.

Table 4.1.4 Low-Growing Turf Seed Mix

% Weight % Purity % Germination Dwarf tall fescue (several varieties) Festuca arundinacea var.

45 98 90

Dwarf perennial rye (Barclay) Lolium perenne var. barclay

30 98 90

Red fescue Festuca rubra

20 98 90

Colonial bentgrass Agrostis tenuis

5 98 90

• Table 4.1.5 lists a mix for bioswales and other intermittently wet areas.

Table 4.1.5 Bioswale Seed Mix*

% Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca elatior

75-80 98 90

Seaside/Creeping bentgrass Agrostis palustris

10-15 92 85

Redtop bentgrass Agrostis alba or Agrostis gigantea

5-10 90 80

* Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix


• Table 4.1.6 lists a low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wetlands. Apply this mixture at a rate of 60 pounds per acre. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable.

Table 4.1.6 Wet Area Seed Mix*

% Weight % Purity % Germination Tall or meadow fescue Festuca arundinacea or Festuca elatior

60-70 98 90

Seaside/Creeping bentgrass Agrostis palustris

10-15 98 85

Meadow foxtail Alepocurus pratensis

10-15 90 80

Alsike clover Trifolium hybridum

1-6 98 90

Redtop bentgrass Agrostis alba

1-6 92 85

* Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix

• Table 4.1.7 lists a recommended meadow seed mix for infrequently maintained areas or non-maintained areas where colonization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending the soil can reduce the need for clover.

Table 4.1.7 Meadow Seed Mix

% Weight % Purity % Germination Redtop or Oregon bentgrass Agrostis alba or Agrostis oregonensis

20 92 85

Red fescue Festuca rubra

70 98 90

White dutch clover Trifolium repens

10 98 90


• Roughening and Rototilling: • The seedbed should be firm and rough. Roughen all soil no matter

what the slope. Track walk slopes before seeding if engineering purposes require compaction. Backblading or smoothing of slopes greater than 4H:1V is not allowed if they are to be seeded.

• Restoration-based landscape practices require deeper incorporation than that provided by a simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to improve long-term permeability, infiltration, and water inflow qualities. At a minimum, permanent areas shall use soil amendments to achieve organic matter and permeability performance defined in engineered soil/landscape systems. For systems that are deeper than 8 inches complete the rototilling process in multiple lifts, or prepare the engineered soil system per specifications and place to achieve the specified depth.

• Fertilizers: • Conducting soil tests to determine the exact type and quantity of

fertilizer is recommended. This will prevent the over-application of fertilizer.

• Organic matter is the most appropriate form of fertilizer because it provides nutrients (including nitrogen, phosphorus, and potassium) in the least water-soluble form.

• In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer at a rate of 90 pounds per acre. Always use slow-release fertilizers because they are more efficient and have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agitate, more than 20 minutes before use. Too much agitation destroys the slow-release coating.

• There are numerous products available that take the place of chemical fertilizers. These include several with seaweed extracts that are beneficial to soil microbes and organisms. If 100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be necessary. Cottonseed meal provides a good source of long-term, slow-release, available nitrogen.

• Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix: • On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically

Bonded Fiber Matrix (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre of mulch with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application. Numerous products are available commercially. Installed products per manufacturer’s instructions. Most products require 24-36 hours to cure before rainfall and cannot be installed on wet or saturated soils.


Generally, products come in 40-50 pound bags and include all necessary ingredients except for seed and fertilizer.

• BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation establishment. Advantages over blankets include: • BFM and MBFMs do not require surface preparation. • Helicopters can assist in installing BFM and MBFMs in remote

areas. • On slopes steeper than 2.5H:1V, blanket installers may require

ropes and harnesses for safety. • Installing BFM and MBFMs can save at least $1,000 per acre

compared to blankets.


Reseed any seeded areas that fail to establish at least 80 percent cover (100 percent cover for areas that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such as sodding, mulching, or nets/blankets. If winter weather prevents adequate grass growth, this time limit may be relaxed at the discretion of the local authority when sensitive areas would otherwise be protected.

• Reseed and protect by mulch any areas that experience erosion after achieving adequate cover. Reseed and protect by mulch any eroded area.

• Supply seeded areas with adequate moisture, but do not water to the extent that it causes runoff.



BMP C121: Mulching

Purpose Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating soil temperatures. There is an enormous variety of mulches that can be used. This section discusses only the most common types of mulch.

Conditions of Use As a temporary cover measure, mulch should be used:

• For less than 30 days on disturbed areas that require cover.

• At all times for seeded areas, especially during the wet season and



during the hot summer months.

• During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief.

Mulch may be applied at any time of the year and must be refreshed periodically.

• For seeded areas mulch may be made up of 100 percent: cottonseed meal; fibers made of wood, recycled cellulose, hemp, kenaf; compost; or blends of these. Tackifier shall be plant-based, such as guar or alpha plantago, or chemical-based such as polyacrylamide or polymers. Any mulch or tackifier product used shall be installed per manufacturer’s instructions. Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application.


For mulch materials, application rates, and specifications, see Table 4.1.8. Always use a 2-inch minimum mulch thickness; increase the thickness until the ground is 95% covered (i.e. not visible under the mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or other areas highly susceptible to erosion.

Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter. Composted organic materials have higher specific gravities (densities) than straw, wood, or chipped material. Consult Hydraulic Permit Authority (HPA) for mulch mixes if applicable.


• The thickness of the cover must be maintained.

• Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched.


Table 4.1.8 Mulch Standards and Guidelines

Mulch Material Quality Standards Application

Rates Remarks Straw Air-dried; free from

undesirable seed and coarse material.

2"-3" thick; 5 bales per 1,000 sf or 2-3 tons per acre

Cost-effective protection when applied with adequate thickness. Hand-application generally requires greater thickness than blown straw. The thickness of straw may be reduced by half when used in conjunction with seeding. In windy areas straw must be held in place by crimping, using a tackifier, or covering with netting. Blown straw always has to be held in place with a tackifier as even light winds will blow it away. Straw, however, has several deficiencies that should be considered when selecting mulch materials. It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits. It should also not be used within the ordinary high-water elevation of surface waters (due to flotation).

Hydromulch No growth inhibiting factors.

Approx. 25-30 lbs per 1,000 sf or 1,500 - 2,000 lbs per acre

Shall be applied with hydromulcher. Shall not be used without seed and tackifier unless the application rate is at least doubled. Fibers longer than about ¾-1 inch clog hydromulch equipment. Fibers should be kept to less than ¾ inch.

Composted Mulch and Compost

No visible water or dust during handling. Must be produced in accordance with WAC 173-350, Solid Waste Handling Standards. .

2" thick min.; approx. 100 tons per acre (approx. 800 lbs per yard)

More effective control can be obtained by increasing thickness to 3". Excellent mulch for protecting final grades until landscaping because it can be directly seeded or tilled into soil as an amendment. Composted mulch has a coarser size gradation than compost. It is more stable and practical to use in wet areas and during rainy weather conditions. Do not use composted mulch near wetlands or near phosphorous impaired water bodies.

Chipped Site Vegetation

Average size shall be several inches. Gradations from fines to 6 inches in length for texture, variation, and interlocking properties.

2" thick min.; This is a cost-effective way to dispose of debris from clearing and grubbing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above approx. 10% because of its tendency to be transported by runoff. It is not recommended within 200 feet of surface waters. If seeding is expected shortly after mulch, the decomposition of the chipped vegetation may tie up nutrients important to grass establishment.

Wood-based Mulch or Wood Straw

No visible water or dust during handling. Must be purchased from a supplier with a Solid Waste Handling Permit or one exempt from solid waste regulations.

2” thick min.; approx. 100 tons per acre (approx. 800 lbs. per cubic yard)

This material is often called “hog or hogged fuel.” The use of mulch ultimately improves the organic matter in the soil. Special caution is advised regarding the source and composition of wood-based mulches. Its preparation typically does not provide any weed seed control, so evidence of residual vegetation in its composition or known inclusion of weed plants or seeds should be monitored and prevented (or minimized).

Wood Strand Mulch

A blend of loose, long, thin wood pieces derived from native conifer or deciduous trees with high length-to-width ratio.

2” thick min. Cost-effective protection when applied with adequate thickness. A minimum of 95-percent of the wood strand shall have lengths between 2 and 10-inches, with a width and thickness between 1/16 and ⅜-inches. The mulch shall not contain resin, tannin, or other compounds in quantities that would be detrimental to plant life. Sawdust or wood shavings shall not be used as mulch. (WSDOT specification (9-14.4(4))

http://apps.leg.wa.gov/WAC/default.aspx?cite=173-350


BMP C122: Nets and Blankets

Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. Nets (commonly called matting) are strands of material woven into an open, but high-tensile strength net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets.

Conditions of Use Erosion control nets and blankets should be used:

• To aid permanent vegetated stabilization of slopes 2H:1V or greater and with more than 10 feet of vertical relief.

• For drainage ditches and swales (highly recommended). The application of appropriate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can capture a great deal of sediment due to their open, porous structure. Nets and blankets can be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. 100 percent synthetic blankets manufactured for use in ditches may be easily reused as temporary ditch liners.

Disadvantages of blankets include:

• Surface preparation required.

• On slopes steeper than 2.5H:1V, blanket installers may need to be roped and harnessed for safety.

• They cost at least $4,000-6,000 per acre installed.

Advantages of blankets include:

• Installation without mobilizing special equipment.

• Installation by anyone with minimal training

• Installation in stages or phases as the project progresses.

• Installers can hand place seed and fertilizer as they progress down the slope.

• Installation in any weather.

• There are numerous types of blankets that can be designed with various parameters in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability, cost, and availability.



• See Figure 4.1.3 and Figure 4.1.4 for typical orientation and installation of blankets used in channels and as slope protection. Note: these are typical only; all blankets must be installed per manufacturer’s installation instructions.

• Installation is critical to the effectiveness of these products. If good ground contact is not achieved, runoff can concentrate under the product, resulting in significant erosion.

• Installation of Blankets on Slopes:

1. Complete final grade and track walk up and down the slope.

2. Install hydromulch with seed and fertilizer.

3. Dig a small trench, approximately 12 inches wide by 6 inches deep along the top of the slope.

4. Install the leading edge of the blanket into the small trench and staple approximately every 18 inches. NOTE: Staples are metal, “U”-shaped, and a minimum of 6 inches long. Longer staples are used in sandy soils. Biodegradable stakes are also available.

5. Roll the blanket slowly down the slope as installer walks backwards. NOTE: The blanket rests against the installer’s legs. Staples are installed as the blanket is unrolled. It is critical that the proper staple pattern is used for the blanket being installed. The blanket is not to be allowed to roll down the slope on its own as this stretches the blanket making it impossible to maintain soil contact. In addition, no one is allowed to walk on the blanket after it is in place.

6. If the blanket is not long enough to cover the entire slope length, the trailing edge of the upper blanket should overlap the leading edge of the lower blanket and be stapled. On steeper slopes, this overlap should be installed in a small trench, stapled, and covered with soil.

• With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer consult the manufacturer's information and that a site visit takes place in order to ensure that the product specified is appropriate. Information is also available at the following web sites:

1. WSDOT (Section 3.2.4):

http://www.wsdot.wa.gov/NR/rdonlyres/3B41E087-FA86-4717-932D-D7A8556CCD57/0/ErosionTrainingManual.pdf

2. Texas Transportation Institute:

http://www.txdot.gov/business/doing_business/product_evaluation/erosion_control.htm






• Use jute matting in conjunction with mulch (BMP C121). Excelsior, woven straw blankets and coir (coconut fiber) blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances.

• In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface.

• Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of synthetic blankets, as are riverbanks, beaches and other high-energy environments. If synthetic blankets are used, the soil should be hydromulched first.

• 100-percent biodegradable blankets are available for use in sensitive areas. These organic blankets are usually held together with a paper or fiber mesh and stitching which may last up to a year.

• Most netting used with blankets is photodegradable, meaning they break down under sunlight (not UV stabilized). However, this process can take months or years even under bright sun. Once vegetation is established, sunlight does not reach the mesh. It is not uncommon to find non-degraded netting still in place several years after installation. This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and small animals can become trapped in the netting.


• Maintain good contact with the ground. Erosion must not occur beneath the net or blanket.

• Repair and staple any areas of the net or blanket that are damaged or not in close contact with the ground.

• Fix and protect eroded areas if erosion occurs due to poorly controlled drainage.


Min. 2“Overlap

Slope surface shall be smooth beforeplacement for proper soil contact.

Stapling pattern as permanufacturer’s recommendations.

Do not stretch blankets/mattings tight -allow the rolls to mold to any irregularities.

For slopes less than 3H:1V, rollsmay be placed in horizontal strips.

If there is a berm at thetop of slope, anchorupslope of the berm.

Anchor in 6"x6" min. Trenchand staple at 12" intervals.

Min. 6" overlap.

Staple overlapsmax. 5" spacing.

Bring material down to a level area, turnthe end under 4" and staple at 12" intervals.

Lime, fertilize, and seed before installation.Planting of shrubs, trees, etc. Should occurafter installation.

Figure 4.1.3 – Channel Installation

Figure 4.1.4 – Slope Installation


BMP C123: Plastic Covering

Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas.

Conditions of Use

Plastic covering may be used on disturbed areas that require cover measures for less than 30 days, except as stated below.

• Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term (greater than six months) applications.

• Due to rapid runoff caused by plastic covering, do not use this method upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes.

• Plastic sheeting may result in increased runoff volumes and velocities, requiring additional on-site measures to counteract the increases. Creating a trough with wattles or other material can convey clean water away from these areas.

• To prevent undercutting, trench and backfill rolled plastic covering products.

• While plastic is inexpensive to purchase, the added cost of installation, maintenance, removal, and disposal make this an expensive material, up to $1.50-2.00 per square yard.

• Whenever plastic is used to protect slopes install water collection measures at the base of the slope. These measures include plastic-covered berms, channels, and pipes used to covey clean rainwater away from bare soil and disturbed areas. Do not mix clean runoff from a plastic covered slope with dirty runoff from a project.

• Other uses for plastic include:

1. Temporary ditch liner.

2. Pond liner in temporary sediment pond.

3. Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored.

4. Emergency slope protection during heavy rains.

5. Temporary drainpipe (“elephant trunk”) used to direct water.


• Plastic slope cover must be installed as follows:

1. Run plastic up and down slope, not across slope.

2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet.

3. Minimum of 8-inch overlap at seams.


4. On long or wide slopes, or slopes subject to wind, tape all seams.

5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope and backfill with soil to keep water from flowing underneath.

6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them together with twine to hold them in place.

7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This prevents high velocity runoff from contacting bare soil which causes extreme erosion.

8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be staked in place.

• Plastic sheeting shall have a minimum thickness of 0.06 millimeters.

• If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be installed at the toe of the slope in order to reduce the velocity of runoff.


• Torn sheets must be replaced and open seams repaired.

• Completely remove and replace the plastic if it begins to deteriorate due to ultraviolet radiation.

• Completely remove plastic when no longer needed.

• Dispose of old tires used to weight down plastic sheeting appropriately.



BMP C124: Sodding

Purpose The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize drainage ways where concentrated overland flow will occur.

Conditions of Use Sodding may be used in the following areas:

• Disturbed areas that require short-term or long-term cover.

• Disturbed areas that require immediate vegetative cover.

• All waterways that require vegetative lining. Waterways may also be seeded rather than sodded, and protected with a net or blanket.




Sod shall be free of weeds, of uniform thickness (approximately 1-inch thick), and shall have a dense root mat for mechanical strength.

The following steps are recommended for sod installation:

• Shape and smooth the surface to final grade in accordance with the approved grading plan. The swale needs to be overexcavated 4 to 6 inches below design elevation to allow room for placing soil amendment and sod.

• Amend 4 inches (minimum) of compost into the top 8 inches of the soil if the organic content of the soil is less than ten percent or the permeability is less than 0.6 inches per hour. See http://www.ecy.wa.gov/programs/swfa/organics/soil.html for further information.

• Fertilize according to the supplier's recommendations.

• Work lime and fertilizer 1 to 2 inches into the soil, and smooth the surface.

• Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:1V. Staple the upstream edge of each sod strip.

• Roll the sodded area and irrigate.

• When sodding is carried out in alternating strips or other patterns, seed the areas between the sod immediately after sodding.


If the grass is unhealthy, the cause shall be determined and appropriate action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and protected with a net or blanket.

BMP C125: Topsoiling / Composting

Purpose Topsoiling and composting provide a suitable growth medium for final site stabilization with vegetation. While not a permanent cover practice in itself, topsoiling and composting are an integral component of providing permanent cover in those areas where there is an unsuitable soil surface for plant growth. Use this BMP in conjunction with other BMPs such as seeding, mulching, or sodding.

Native soils and disturbed soils that have been organically amended not only retain much more stormwater, but they also serve as effective biofilters for urban pollutants and, by supporting more vigorous plant growth, reduce the water, fertilizer and pesticides needed to support

http://www.ecy.wa.gov/programs/swfa/organics/soil.html


• Use geotextile fabrics to increase the strength of new roads or roads undergoing reconstruction.

• Encourage the use of alternate, paved routes, if available.

• Restrict use of paved roadways by tracked vehicles and heavy trucks to prevent damage to road surface and base.

• Apply chemical dust suppressants using the admix method, blending the product with the top few inches of surface material. Suppressants may also be applied as surface treatments.

• Pave unpaved permanent roads and other trafficked areas.

• Use vacuum street sweepers.

• Remove mud and other dirt promptly so it does not dry and then turn into dust.

• Limit dust-causing work on windy days.

• Contact your local Air Pollution Control Authority for guidance and training on other dust control measures. Compliance with the local Air Pollution Control Authority constitutes compliance with this BMP.


Respray area as necessary to keep dust to a minimum.

BMP C150: Materials on Hand

Purpose Keep quantities of erosion prevention and sediment control materials on the project site at all times to be used for regular maintenance and emergency situations such as unexpected heavy summer rains. Having these materials on-site reduces the time needed to implement BMPs when inspections indicate that existing BMPs are not meeting the Construction SWPPP requirements. In addition, contractors can save money by buying some materials in bulk and storing them at their office or yard.

Conditions of Use • Construction projects of any size or type can benefit from having materials on hand. A small commercial development project could have a roll of plastic and some gravel available for immediate protection of bare soil and temporary berm construction. A large earthwork project, such as highway construction, might have several tons of straw, several rolls of plastic, flexible pipe, sandbags, geotextile fabric and steel “T” posts.

• Materials are stockpiled and readily available before any site clearing, grubbing, or earthwork begins. A large contractor or developer could keep a stockpile of materials that are available for use on several projects.

• If storage space at the project site is at a premium, the contractor could maintain the materials at their office or yard. The office or yard must be less than an hour from the project site.



Depending on project type, size, complexity, and length, materials and quantities will vary. A good minimum list of items that will cover numerous situations includes:

Material

Clear Plastic, 6 mil Drainpipe, 6 or 8 inch diameter Sandbags, filled Straw Bales for mulching, Quarry Spalls Washed Gravel Geotextile Fabric Catch Basin Inserts Steel “T” Posts Silt fence material Straw Wattles


• All materials with the exception of the quarry spalls, steel “T” posts, and gravel should be kept covered and out of both sun and rain.

• Re-stock materials used as needed.

BMP C151: Concrete Handling

Purpose Concrete work can generate process water and slurry that contain fine particles and high pH, both of which can violate water quality standards in the receiving water. Concrete spillage or concrete discharge to surface waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, concrete process water, and concrete slurry from entering waters of the state.

Conditions of Use Any time concrete is used, utilize these management practices. Concrete construction projects include, but are not limited to, the following:

• Curbs

• Sidewalks

• Roads

• Bridges

• Foundations

• Floors

• Runways

Design and Installation

• Wash out concrete truck chutes, pumps, and internals into formed areas only. Assure that washout of concrete trucks is performed off-


Specifications site or in designated concrete washout areas. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams. Refer to BMP C154 for information on concrete washout areas.

• Return unused concrete remaining in the truck and pump to the originating batch plant for recycling. Do not dump excess concrete on site, except in designated concrete washout areas.

• Wash off hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels into formed areas only.

• Wash equipment difficult to move, such as concrete pavers in areas that do not directly drain to natural or constructed stormwater conveyances.

• Do not allow washdown from areas, such as concrete aggregate driveways, to drain directly to natural or constructed stormwater conveyances.

• Contain washwater and leftover product in a lined container when no formed areas are available,. Dispose of contained concrete in a manner that does not violate ground water or surface water quality standards.

• Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface waters.

• Refer to BMPs C252 and C253 for pH adjustment requirements.

• Refer to the Construction Stormwater General Permit for pH monitoring requirements if the project involves one of the following activities:

• Significant concrete work (greater than 1,000 cubic yards poured concrete or recycled concrete used over the life of a project).

• The use of engineered soils amended with (but not limited to) Portland cement-treated base, cement kiln dust or fly ash.

• Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for high pH.


Check containers for holes in the liner daily during concrete pours and repair the same day.


BMP C152: Sawcutting and Surfacing Pollution Prevention

Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high pH (concrete cutting), both of which can violate the water quality standards in the receiving water. Concrete spillage or concrete discharge to surface waters of the State is prohibited. Use this BMP to minimize and eliminate process water and slurry created through sawcutting or surfacing from entering waters of the State.

Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Sawcutting and surfacing operations include, but are not limited to, the following:

• Sawing

• Coring

• Grinding

• Roughening

• Hydro-demolition

• Bridge and road surfacing


• Vacuum slurry and cuttings during cutting and surfacing operations.

• Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight.

• Slurry and cuttings shall not drain to any natural or constructed drainage conveyance including stormwater systems. This may require temporarily blocking catch basins.

• Dispose of collected slurry and cuttings in a manner that does not violate ground water or surface water quality standards.

• Do not allow process water generated during hydro-demolition, surface roughening or similar operations to drain to any natural or constructed drainage conveyance including stormwater systems. Dispose process water in a manner that does not violate ground water or surface water quality standards.

• Handle and dispose cleaning waste material and demolition debris in a manner that does not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an appropriate disposal site.


Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters of the state. If inspections show that a violation of water quality standards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and vacuum trucks.


BMP C153: Material Delivery, Storage and Containment

Purpose Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from material delivery and storage. Minimize the storage of hazardous materials on-site, store materials in a designated area, and install secondary containment.

Conditions of Use These procedures are suitable for use at all construction sites with delivery and storage of the following materials: • Petroleum products such as fuel, oil and grease • Soil stabilizers and binders (e.g. Polyacrylamide) • Fertilizers, pesticides and herbicides • Detergents • Asphalt and concrete compounds • Hazardous chemicals such as acids, lime, adhesives, paints, solvents

and curing compounds • Any other material that may be detrimental if released to the

environment Design and Installation Specifications

The following steps should be taken to minimize risk: • Temporary storage area should be located away from vehicular traffic,

near the construction entrance(s), and away from waterways or storm drains.

• Material Safety Data Sheets (MSDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers.

• Hazardous material storage on-site should be minimized. • Hazardous materials should be handled as infrequently as possible. • During the wet weather season (Oct 1 – April 30), consider storing

materials in a covered area. • Materials should be stored in secondary containments, such as earthen

dike, horse trough, or even a children’s wading pool for non-reactive materials such as detergents, oil, grease, and paints. Small amounts of material may be secondarily contained in “bus boy” trays or concrete mixing trays.

• Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, and within secondary containment.

• If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums, preventing water from collecting.


Material Storage Areas and Secondary Containment Practices: • Liquids, petroleum products, and substances listed in 40 CFR Parts

110, 117, or 302 shall be stored in approved containers and drums and shall not be overfilled. Containers and drums shall be stored in temporary secondary containment facilities.

• Temporary secondary containment facilities shall provide for a spill containment volume able to contain 10% of the total enclosed container volume of all containers, or 110% of the capacity of the largest container within its boundary, whichever is greater.

• Secondary containment facilities shall be impervious to the materials stored therein for a minimum contact time of 72 hours.

• Secondary containment facilities shall be maintained free of accumulated rainwater and spills. In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums. These liquids shall be handled as hazardous waste unless testing determines them to be non-hazardous.

• Sufficient separation should be provided between stored containers to allow for spill cleanup and emergency response access.

• During the wet weather season (Oct 1 – April 30), each secondary containment facility shall be covered during non-working days, prior to and during rain events.

• Keep material storage areas clean, organized and equipped with an ample supply of appropriate spill clean-up material (spill kit).

• The spill kit should include, at a minimum: • 1-Water Resistant Nylon Bag • 3-Oil Absorbent Socks 3”x 4’ • 2-Oil Absorbent Socks 3”x 10’ • 12-Oil Absorbent Pads 17”x19” • 1-Pair Splash Resistant Goggles • 3-Pair Nitrile Gloves • 10-Disposable Bags with Ties • Instructions


BMP C154: Concrete Washout Area

Purpose Prevent or reduce the discharge of pollutants to stormwater from concrete waste by conducting washout off-site, or performing on-site washout in a designated area to prevent pollutants from entering surface waters or ground water.

Conditions of Use Concrete washout area best management practices are implemented on construction projects where:

• Concrete is used as a construction material

• It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant, etc.).

• Concrete trucks, pumpers, or other concrete coated equipment are washed on-site.

• Note: If less than 10 concrete trucks or pumpers need to be washed out on-site, the washwater may be disposed of in a formed area awaiting concrete or an upland disposal site where it will not contaminate surface or ground water. The upland disposal site shall be at least 50 feet from sensitive areas such as storm drains, open ditches, or water bodies, including wetlands.


Implementation The following steps will help reduce stormwater pollution from concrete wastes:

• Perform washout of concrete trucks off-site or in designated concrete washout areas only.

• Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or streams.

• Do not allow excess concrete to be dumped on-site, except in designated concrete washout areas.

• Concrete washout areas may be prefabricated concrete washout containers, or self-installed structures (above-grade or below-grade).

• Prefabricated containers are most resistant to damage and protect against spills and leaks. Companies may offer delivery service and provide regular maintenance and disposal of solid and liquid waste.

• If self-installed concrete washout areas are used, below-grade structures are preferred over above-grade structures because they are less prone to spills and leaks.

• Self-installed above-grade structures should only be used if excavation is not practical.


Education • Discuss the concrete management techniques described in this BMP

with the ready-mix concrete supplier before any deliveries are made.

• Educate employees and subcontractors on the concrete waste management techniques described in this BMP.

• Arrange for contractor’s superintendent or Certified Erosion and Sediment Control Lead (CESCL) to oversee and enforce concrete waste management procedures.

• A sign should be installed adjacent to each temporary concrete washout facility to inform concrete equipment operators to utilize the proper facilities.

Contracts Incorporate requirements for concrete waste management into concrete supplier and subcontractor agreements.

Location and Placement • Locate washout area at least 50 feet from sensitive areas such as storm

drains, open ditches, or water bodies, including wetlands.

• Allow convenient access for concrete trucks, preferably near the area where the concrete is being poured.

• If trucks need to leave a paved area to access washout, prevent track-out with a pad of rock or quarry spalls (see BMP C105). These areas should be far enough away from other construction traffic to reduce the likelihood of accidental damage and spills.

• The number of facilities you install should depend on the expected demand for storage capacity.

• On large sites with extensive concrete work, washouts should be placed in multiple locations for ease of use by concrete truck drivers.

On-site Temporary Concrete Washout Facility, Transit Truck Washout Procedures: • Temporary concrete washout facilities shall be located a minimum of

50 ft from sensitive areas including storm drain inlets, open drainage facilities, and watercourses. See Figures 4.1.7 and 4.1.8.

• Concrete washout facilities shall be constructed and maintained in sufficient quantity and size to contain all liquid and concrete waste generated by washout operations.

• Approximately 7 gallons of wash water are used to wash one truck chute.

• Approximately 50 gallons are used to wash out the hopper of a concrete pump truck.


• Washout of concrete trucks shall be performed in designated areas only.

• Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and discharged into designated washout area or properly disposed of off-site.

• Once concrete wastes are washed into the designated area and allowed to harden, the concrete should be broken up, removed, and disposed of per applicable solid waste regulations. Dispose of hardened concrete on a regular basis.

• Temporary Above-Grade Concrete Washout Facility

• Temporary concrete washout facility (type above grade) should be constructed as shown on the details below, with a recommended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to contain all liquid and concrete waste generated by washout operations.

• Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free of holes, tears, or other defects that compromise the impermeability of the material.

• Temporary Below-Grade Concrete Washout Facility

• Temporary concrete washout facilities (type below grade) should be constructed as shown on the details below, with a recommended minimum length and minimum width of 10 ft. The quantity and volume should be sufficient to contain all liquid and concrete waste generated by washout operations.

• Lath and flagging should be commercial type.

• Plastic lining material shall be a minimum of 10 mil polyethylene sheeting and should be free of holes, tears, or other defects that compromise the impermeability of the material.

• Liner seams shall be installed in accordance with manufacturers’ recommendations.

• Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic lining material.


Inspection and Maintenance

• Inspect and verify that concrete washout BMPs are in place prior to the commencement of concrete work.

• During periods of concrete work, inspect daily to verify continued performance.

• Check overall condition and performance.

• Check remaining capacity (% full).


• If using self-installed washout facilities, verify plastic liners are intact and sidewalls are not damaged.

• If using prefabricated containers, check for leaks.

• Washout facilities shall be maintained to provide adequate holding capacity with a minimum freeboard of 12 inches.

• Washout facilities must be cleaned, or new facilities must be constructed and ready for use once the washout is 75% full.

• If the washout is nearing capacity, vacuum and dispose of the waste material in an approved manner.

• Do not discharge liquid or slurry to waterways, storm drains or directly onto ground.

• Do not use sanitary sewer without local approval.

• Place a secure, non-collapsing, non-water collecting cover over the concrete washout facility prior to predicted wet weather to prevent accumulation and overflow of precipitation.

• Remove and dispose of hardened concrete and return the structure to a functional condition. Concrete may be reused on-site or hauled away for disposal or recycling.

• When you remove materials from the self-installed concrete washout, build a new structure; or, if the previous structure is still intact, inspect for signs of weakening or damage, and make any necessary repairs. Re-line the structure with new plastic after each cleaning.

Removal of Temporary Concrete Washout Facilities • When temporary concrete washout facilities are no longer required for

the work, the hardened concrete, slurries and liquids shall be removed and properly disposed of.

• Materials used to construct temporary concrete washout facilities shall be removed from the site of the work and disposed of or recycled.

• Holes, depressions or other ground disturbance caused by the removal of the temporary concrete washout facilities shall be backfilled, repaired, and stabilized to prevent erosion.


Figure 4.1.7a – Concrete Washout Area


Figure 4.1.7b – Concrete Washout Area

Figure 4.1.8 – Prefabricated Concrete Washout Container w/Ramp


• New pipe outfalls can provide an opportunity for low-cost fish habitat improvements. For example, an alcove of low-velocity water can be created by constructing the pipe outfall and associated energy dissipater back from the stream edge and digging a channel, over-widened to the upstream side, from the outfall. Overwintering juvenile and migrating adult salmonids may use the alcove as shelter during high flows. Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. This work may require a HPA. See Volume V for more information on outfall system design.


• Inspect and repair as needed.

• Add rock as needed to maintain the intended function.

• Clean energy dissipater if sediment builds up.

BMP C220: Storm Drain Inlet Protection

Purpose Storm drain inlet protection prevents coarse sediment from entering drainage systems prior to permanent stabilization of the disturbed area.

Conditions of Use Use storm drain inlet protection at inlets that are operational before permanent stabilization of the disturbed drainage area. Provide protection for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless conveying runoff entering catch basins to a sediment pond or trap.

Also consider inlet protection for lawn and yard drains on new home construction. These small and numerous drains coupled with lack of gutters in new home construction can add significant amounts of sediment into the roof drain system. If possible delay installing lawn and yard drains until just before landscaping or cap these drains to prevent sediment from entering the system until completion of landscaping. Provide 18-inches of sod around each finished lawn and yard drain.

Table 4.2.2 lists several options for inlet protection. All of the methods for storm drain inlet protection tend to plug and require a high frequency of maintenance. Limit drainage areas to one acre or less. Possibly provide emergency overflows with additional end-of-pipe treatment where stormwater ponding would cause a hazard.


Table 4.2.2 Storm Drain Inlet Protection

Type of Inlet Protection

Emergency Overflow

Applicable for Paved/ Earthen

Surfaces Conditions of Use

Drop Inlet Protection Excavated drop inlet protection

Yes, temporary flooding will occur

Earthen Applicable for heavy flows. Easy to maintain. Large area Requirement: 30’ X 30’/acre

Block and gravel drop inlet protection

Yes Paved or Earthen Applicable for heavy concentrated flows. Will not pond.

Gravel and wire drop inlet protection

No Applicable for heavy concentrated flows. Will pond. Can withstand traffic.

Catch basin filters Yes Paved or Earthen Frequent maintenance required. Curb Inlet Protection Curb inlet protection with a wooden weir

Small capacity overflow

Paved Used for sturdy, more compact installation.

Block and gravel curb inlet protection

Yes Paved Sturdy, but limited filtration.

Culvert Inlet Protection Culvert inlet sediment trap

18 month expected life.


Excavated Drop Inlet Protection - An excavated impoundment around the storm drain. Sediment settles out of the stormwater prior to entering the storm drain.

• Provide a depth of 1-2 ft as measured from the crest of the inlet structure.

• Slope sides of excavation no steeper than 2H:1V.

• Minimum volume of excavation 35 cubic yards.

• Shape basin to fit site with longest dimension oriented toward the longest inflow area.

• Install provisions for draining to prevent standing water problems.

• Clear the area of all debris.

• Grade the approach to the inlet uniformly.

• Drill weep holes into the side of the inlet.

• Protect weep holes with screen wire and washed aggregate.

• Seal weep holes when removing structure and stabilizing area.


• Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass flow.

Block and Gravel Filter - A barrier formed around the storm drain inlet with standard concrete blocks and gravel. See Figure 4.2.8.

• Provide a height of 1 to 2 feet above inlet.

• Recess the first row 2-inches into the ground for stability.

• Support subsequent courses by placing a 2x4 through the block opening.

• Do not use mortar.

• Lay some blocks in the bottom row on their side for dewatering the pool.

• Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings.

• Place gravel just below the top of blocks on slopes of 2H:1V or flatter.

• An alternative design is a gravel donut.

• Provide an inlet slope of 3H:1V.

• Provide an outlet slope of 2H:1V.

• Provide a1-foot wide level stone area between the structure and the inlet.

• Use inlet slope stones 3 inches in diameter or larger.

• Use gravel ½- to ¾-inch at a minimum thickness of 1-foot for the outlet slope.


Figure 4.2.8 – Block and Gravel Filter

Gravel and Wire Mesh Filter - A gravel barrier placed over the top of the inlet. This structure does not provide an overflow.

• Use a hardware cloth or comparable wire mesh with ½-inch openings.

• Use coarse aggregate.

• Provide a height 1-foot or more, 18-inches wider than inlet on all sides.

• Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot beyond each side of the inlet structure.

• Overlap the strips if more than one strip of mesh is necessary.

Ponding Height

Notes: 1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas. (less than 5%) 2. Excavate a basin of sufficient size adjacent to the drop inlet. 3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent runoff from bypassing the inlet. A temporary dike may be necessary on the downslope side of the structure.


• Place coarse aggregate over the wire mesh.

• Provide at least a 12-inch depth of gravel over the entire inlet opening and extend at least 18-inches on all sides.

Catchbasin Filters – Use inserts designed by manufacturers for construction sites. The limited sediment storage capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. To reduce maintenance requirements combine a catchbasin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights-of-way.

• Provides 5 cubic feet of storage.

• Requires dewatering provisions.

• Provides a high-flow bypass that will not clog under normal use at a construction site.

• Insert the catchbasin filter in the catchbasin just below the grating.

Curb Inlet Protection with Wooden Weir – Barrier formed around a curb inlet with a wooden frame and gravel.

• Use wire mesh with ½-inch openings.

• Use extra strength filter cloth.

• Construct a frame.

• Attach the wire and filter fabric to the frame.

• Pile coarse washed aggregate against wire/fabric.

• Place weight on frame anchors.

Block and Gravel Curb Inlet Protection – Barrier formed around a curb inlet with concrete blocks and gravel. See Figure 4.2.9.

• Use wire mesh with ½-inch openings.

• Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks.

• Place a 2x4 stud through the outer holes of each spacer block to align the front blocks.

• Place blocks on their sides across the front of the inlet and abutting the spacer blocks.

• Place wire mesh over the outside vertical face.

• Pile coarse aggregate against the wire to the top of the barrier.

Curb and Gutter Sediment Barrier – Sandbag or rock berm (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure 4.2.10.


• Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet.

• Construct a horseshoe shaped sedimentation trap on the outside of the berm sized to sediment trap standards for protecting a culvert inlet.


• Inspect catch basin filters frequently, especially after storm events. Clean and replace clogged inserts. For systems with clogged stone filters: pull away the stones from the inlet and clean or replace. An alternative approach would be to use the clogged stone as fill and put fresh stone around the inlet.

• Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appropriate.





Figure 4.2.9 – Block and Gravel Curb Inlet Protection

A

Plan View

Wire Screen orFilter Fabric

Catch Basin

Curb Inlet

Concrete BlockPonding Height

Overflow

2x4 Wood Stud(100x50 Timber Stud)

Concrete BlockWire Screen orFilter Fabric

Curb Inlet

¾" Drain Gravel(20mm)

¾" Drain Gravel(20mm)Section A - A

Back of Curb Concrete Block

2x4 Wood Stud

Catch BasinBack of Sidewalk

NOTES:1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff.2. Barrier shall allow for overflow from severe storm event.3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately.


Figure 4.2.10 – Curb and Gutter Barrier


BMP C232: Gravel Filter Berm

Purpose A gravel filter berm is constructed on rights-of-way or traffic areas within a construction site to retain sediment by using a filter berm of gravel or crushed rock.

Conditions of Use Where a temporary measure is needed to retain sediment from rights-of-way or in traffic areas on construction sites.


• Berm material shall be ¾ to 3 inches in size, washed well-grade gravel or crushed rock with less than 5 percent fines.

• Spacing of berms:

− Every 300 feet on slopes less than 5 percent

− Every 200 feet on slopes between 5 percent and 10 percent

− Every 100 feet on slopes greater than 10 percent

• Berm dimensions:

− 1 foot high with 3H:1V side slopes

− 8 linear feet per 1 cfs runoff based on the 10-year, 24-hour design storm


• Regular inspection is required. Sediment shall be removed and filter material replaced as needed.

BMP C233: Silt Fence

Purpose Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. See Figure 4.2.12 for details on silt fence construction.

Conditions of Use Silt fence may be used downslope of all disturbed areas.

• Silt fence shall prevent soil carried by runoff water from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence.

• Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow. Convey any concentrated flows through the drainage system to a sediment pond.

• Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide an adequate method of silt control for anything deeper than sheet or overland flow.


Figure 4.2.12 – Silt Fence


• Use in combination with sediment basins or other BMPs.

• Maximum slope steepness (normal (perpendicular) to fence line) 1H:1V.

• Maximum sheet or overland flow path length to the fence of 100 feet.

• Do not allow flows greater than 0.5 cfs.

• The geotextile used shall meet the following standards. All geotextile properties listed below are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or exceed the values shown in Table 4.2.3):

Table 4.2.3 Geotextile Standards

Polymeric Mesh AOS (ASTM D4751)

0.60 mm maximum for slit film woven (#30 sieve). 0.30 mm maximum for all other geotextile types (#50 sieve). 0.15 mm minimum for all fabric types (#100 sieve).

Water Permittivity (ASTM D4491)

0.02 sec-1 minimum

Grab Tensile Strength (ASTM D4632)

180 lbs. Minimum for extra strength fabric.

100 lbs minimum for standard strength fabric.

Grab Tensile Strength (ASTM D4632)

30% maximum

Ultraviolet Resistance (ASTM D4355)

70% minimum

• Support standard strength fabrics with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the


fabric. Silt fence materials are available that have synthetic mesh backing attached.

• Filter fabric material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of 0°F. to 120°F.

• One-hundred percent biodegradable silt fence is available that is strong, long lasting, and can be left in place after the project is completed, if permitted by local regulations.

• Refer to Figure 4.2.12 for standard silt fence details. Include the following standard Notes for silt fence on construction plans and specifications:

1. The contractor shall install and maintain temporary silt fences at the locations shown in the Plans.

2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those activities.

3. The silt fence shall have a 2-feet min. and a 2½-feet max. height above the original ground surface.

4. The filter fabric shall be sewn together at the point of manufacture to form filter fabric lengths as required. Locate all sewn seams at support posts. Alternatively, two sections of silt fence can be overlapped, provided the Contractor can demonstrate, to the satisfaction of the Engineer, that the overlap is long enough and that the adjacent fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap.

5. Attach the filter fabric on the up-slope side of the posts and secure with staples, wire, or in accordance with the manufacturer's recommendations. Attach the filter fabric to the posts in a manner that reduces the potential for tearing.

6. Support the filter fabric with wire or plastic mesh, dependent on the properties of the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely to the up-slope side of the posts with the filter fabric up-slope of the mesh.

7. Mesh support, if used, shall consist of steel wire with a maximum mesh spacing of 2-inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh must be as resistant to the same level of ultraviolet radiation as the filter fabric it supports.

8. Bury the bottom of the filter fabric 4-inches min. below the ground surface. Backfill and tamp soil in place over the buried portion of the filter fabric, so that no flow can pass beneath the fence and


scouring cannot occur. When wire or polymeric back-up support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches min.

9. Drive or place the fence posts into the ground 18-inches min. A 12–inch min. depth is allowed if topsoil or other soft subgrade soil is not present and 18-inches cannot be reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of 3H:1V or steeper and the slope is perpendicular to the fence. If required post depths cannot be obtained, the posts shall be adequately secured by bracing or guying to prevent overturning of the fence due to sediment loading.

10. Use wood, steel or equivalent posts. The spacing of the support posts shall be a maximum of 6-feet. Posts shall consist of either:

• Wood with dimensions of 2-inches by 2-inches wide min. and a 3-feet min. length. Wood posts shall be free of defects such as knots, splits, or gouges.

• No. 6 steel rebar or larger.

• ASTM A 120 steel pipe with a minimum diameter of 1-inch.

• U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft.

• Other steel posts having equivalent strength and bending resistance to the post sizes listed above.

11. Locate silt fences on contour as much as possible, except at the ends of the fence, where the fence shall be turned uphill such that the silt fence captures the runoff water and prevents water from flowing around the end of the fence.

12. If the fence must cross contours, with the exception of the ends of the fence, place gravel check dams perpendicular to the back of the fence to minimize concentrated flow and erosion. The slope of the fence line where contours must be crossed shall not be steeper than 3H:1V.

• Gravel check dams shall be approximately 1-foot deep at the back of the fence. Gravel check dams shall be continued perpendicular to the fence at the same elevation until the top of the check dam intercepts the ground surface behind the fence.

• Gravel check dams shall consist of crushed surfacing base course, gravel backfill for walls, or shoulder ballast. Gravel check dams shall be located every 10 feet along the fence where the fence must cross contours.

• Refer to Figure 4.2.13 for slicing method details. Silt fence installation using the slicing method specifications:


1. The base of both end posts must be at least 2- to 4-inches above the top of the filter fabric on the middle posts for ditch checks to drain properly. Use a hand level or string level, if necessary, to mark base points before installation.

2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard applications.

3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as possible to the filter fabric, enabling posts to support the filter fabric from upstream water pressure.

4. Install posts with the nipples facing away from the filter fabric.

5. Attach the filter fabric to each post with three ties, all spaced within the top 8-inches of the filter fabric. Attach each tie diagonally 45 degrees through the filter fabric, with each puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post nipple when tightening to prevent sagging.

6. Wrap approximately 6-inches of fabric around the end posts and secure with 3 ties.

7. No more than 24-inches of a 36-inch filter fabric is allowed above ground level.

Compact the soil immediately next to the filter fabric with the front wheel of the tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the upstream side first and then each side twice for a total of four trips. Check and correct the silt fence installation for any deviation before compaction. Use a flat-bladed shovel to tuck fabric deeper into the ground if necessary.


Figure 4.2.13 – Silt Fence Installation by Slicing Method


• Repair any damage immediately.

• Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment pond.

• Check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment.


• Remove sediment deposits when the deposit reaches approximately one-third the height of the silt fence, or install a second silt fence.

• Replace filter fabric that has deteriorated due to ultraviolet breakdown.

BMP C234: Vegetated Strip

Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow.

Conditions of Use • Vegetated strips may be used downslope of all disturbed areas.

• Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment pond. The only circumstance in which overland flow can be treated solely by a strip, rather than by a sediment pond, is when the following criteria are met (see Table 4.2.4):

Table 4.2.4 Contributing Drainage Area for Vegetated Strips

Average Contributing area Slope

Average Contributing area Percent Slope

Max Contributing area Flowpath Length

1.5H:1V or flatter 67% or flatter 100 feet 2H:1V or flatter 50% or flatter 115 feet 4H:1V or flatter 25% or flatter 150 feet 6H:1V or flatter 16.7% or flatter 200 feet 10H:1V or flatter 10% or flatter 250 feet


• The vegetated strip shall consist of a minimum of a 25-foot flowpath length continuous strip of dense vegetation with topsoil. Grass-covered, landscaped areas are generally not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips shall consist of undisturbed native growth with a well-developed soil that allows for infiltration of runoff.

• The slope within the strip shall not exceed 4H:1V.

• The uphill boundary of the vegetated strip shall be delineated with clearing limits.


• Any areas damaged by erosion or construction activity shall be seeded immediately and protected by mulch.

• If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded, sod must be installed.

• If there are indications that concentrated flows are traveling across the buffer, surface water controls must be installed to reduce the flows