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Knightsen Town Community Services District (KTCSD)
PROPOSED STORM WATER PROJECTS – INITIAL REVIEW
UPDATED FOR MAY 2, 2019 KTCSD MEETING
Step-by-Step Review1. Tonight is initial review.
2. Background & Scope of Storm Water Projects
3. Project Definitions
4. Proposed Project Overview
5. High level walkthrough of 7 proposed projects and descriptions
6. Comments – general and specific to each project
7. Next steps after tonight
2
Background & Proposed Projects Scope In January 2017, KTCSD contracted with Environmental Science Associates
(ESA) to develop a Knightsen Storm Water Resources Plan.
Scope of Plan included:
1.Develop conceptual designs for storm water management projects along railroad alignment & within East Bay Regional Park Wetlands property.
2.Update sizing estimates for culverts and drainage ditches to reflect updated runoff estimates.
3.Update portions of previous assessments to reflect how new developments in Brentwood (that don’t drain into Marsh Creek) effect runoff into Knightsen.
4.Provide cost estimates for implementation (design, permitting, construction) of storm drain improvements and storm water management facilities.
5.Document results of the above that would be suitable to apply for Prop 1 grant funding.
3
Definitions – What is a Culvert?
4
A tunnel in various shapes (that carries a stream or open drain
under roads, driveways, railroad tracks, etc. Common types:
CMP is Corrugated Metal Pipe (very common). Lasts at least
50 yrs.
RCP – Reinforced Concrete Pipes. Concrete with reinforcing
material, typically rebar. Considered highly reliable/cost-effective,
and therefore widely used. Lasts 70-100 yrs.
HDPE – High Density Polyethylene Pipe. Plastic material
engineered to be strong enough to use in place of concrete or
metal pipes, but light enough to be more easily transported and
installed. HDPE is chemically inert, so it can be used to convey
water, gas, wastewater, and even hazardous materials. Lasts 50-
100 yrs.
Definitions – What is a Culvert?
5
While pipe culverts are most common. There are
several types:
1. Pipe – round shape
2. Box culvert - rectangular shape, usually
concrete. Not useful in dry periods. Used to
dispose of rain water.
3. Pipe Arch Culvert - half circle shaped culverts,
used for heavier flows, but flow should be
stable. Fish & sewage don’t get caught.
4. Arch Culvert – similar to pipe arch, but has a
bottom floor.
5. Bridge culvert – used for canals or rivers and
road bridges, surface laid on top.
1
2
3 4
55
Definitions – What is a Bioswale?
6
A vegetated, shallow, landscaped
depression designed to capture, treat,
and infiltrate stormwater runoff as it
moves downstream. They slow down the
speed of runoff while recharging
groundwater table.
They have a slight slope to move water
along the surface to allow sediments and
pollutants to settle out.
Different from a ditch. Ditches collect and
move water away as soon as possible.
Definitions – What is an Infiltration Basin?
7
Shallow, artificial pond or depression
designed to store runoff on the surface
and allow it to gradually infiltrate into soil.
Infiltration basins stay dry, except in
heavy rainfalls.
Has gently sloping sides.
Less effective in areas with:
high groundwater levels, compacted/clay
soils, high levels of sediment in storm
water.
Definitions – What is a Seasonal Wetland?
8
Seasonal wetlands are areas that form during
the wettest time of the year which can dry and
disappear with seasonal change.
They are present when water from rain or
flooding oversaturates the soil.
Definitions – More Terms
9
Term Definition
BMP Best Management Practices – Environmental Protection Agency (EPA)
defines stormwater BMPs as "methods that have been determined to be
most effective, practical means of preventing or reducing pollution from
nonpoint sources."
Biofilter A pollution filtering method where water can flow through dense vegetation
(such as a swale or basin) to clean the water.
HMS
Subbasin
HMS = Hydrologic Modeling System software. CC County Flood Control
uses software program designed by US Army Corp of Engineers.
Subbasin refers to a “watershed” defined by longitude, latitude and other
hydrology characteristics needed to run and create a model.
https://www.contracosta.ca.gov/DocumentCenter/View/3956/2018-03-06-
HEC-HMS-Guidance-for-CCCo?bidId=
7 Proposed
Projects
were
identified
10
Projects 1-4 are
interdependent
(water flows from
1 to 2 to 3 to 4).
Projects 5-7 each
have separate
entry points into
East Bay Regional
Park (Wetlands
Restoration
Project)
Project Revisions as of April 4, 2019On 4/4/19, ESA Consultant, Mark Lindley sent the following revisions:
Identified project elements essential to the BASE PROJECT and other elements as OPTIONAL. Some examples:
Listed “optional” elements include extended lengths of ditches which may not be absolutely essential.
Identified many driveway culverts now as OPTIONAL elements of these projects.
Downsized many of his roadway culvert recommendations (e.g. 30 inch culverts reduced to 24 inch culverts; 24 inch culverts reduced to 18 inch) to reduce costs.
Updated costs for each element.
Attempted to prioritize the seven projects.
11
Project #1:
Curlew
Connex
Infiltration
Basin
Retrofit
12
N = New
E = Existing
1
2
34
5
Project # 1: Curlew Connex Infiltration Basin Retrofit
13
Delta Road heading towards
Peach Lane/Curlew Connex
Delta Road @ Peach Lane
New Ditch
New Ditch
(OPTIONAL) Dig new 1,420 foot long ditch along south side of Delta Road and
install new 18 inch culverts at existing driveways and at Peach Lane. Ditch 3ft base
width and 3 ½ feet deep, $20 per linear foot = $28,000. Replacement of culverts on
Delta (+ culverts along Curlew Connex, next page) = $148,000.
Project # 1: Curlew Connex Infiltration Basin Retrofit
14
Delta Road
Delta Road @ Peach Lane
New Ditch
Curlew Connex
Culvert
(OPTIONAL) Dig new 550 foot long ditch along the west side of Curlew Connex and install
new 18 inch culverts at existing driveways. Ditch 3ft base width, 3 ½ ft deep, $20 per linear
foot = $11,000. (BASE PROJECT) Install two new 24 inch culverts across Delta Road and
across Curlew Connex to route water to the infiltration basin by the church. $66,000.
New Ditch
Culvert
Project # 1: Curlew Connex Infiltration Basin Retrofit
15
Culvert and
ditch into
Church Basin
Delta Road @ Church Basin
(BASE PROJECT) Install new 100 foot ditch at Delta Road and Curlew Connex, 3ft
base width, 4ft deep, $26 per linear foot = $3,000. (BASE PROJECT) Improve the
infiltration basin by amending topsoil and revegetating with native plants to improve
water quality treatment and infiltration, 2 ½ acres = $11,000. (OPTIONAL) an
additional 0.7 acres = an additional $3,000.
Project # 1: Curlew Connex Infiltration Basin Retrofit
16
Culvert
New Ditch
(Project #2)
(BASE PROJECT) Install a new basin outlet with a drop inlet outfitted with a flow
control orifice and a new 24 inch culvert across Delta Road. $45,000.
(BASE PROJECT) Install new 1,375 foot Ditch to flow water from the infiltration basin
to Project #2. 3ft base width, 3-5ft deep, $41 per linear foot. $57,000.
Install 24 inch culvert at Knightsen Avenue. $33,000.
NOTE 500 FEET OF DITCH AND THE CULVERT WERE PREVIOUSLY INCLUDED
IN PROJECT #2.
$395,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
not included)
18
Project #1: Curlew Connex Infiltration Basin - Construction Costs
REVISED BY ESA on 4/4/19
$375,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
not included)
19
Project #1: Curlew Connex Infiltration Basin - Construction Costs
Original Costs Provided by ESA on 3/7/19
Project # 1: Curlew Connex Infiltration Basin Retrofit -
Comments
1. Project assumes church basin collects/conveys storm water from neighboring roads/parcels, but approved plans for church did not provide for water to be conveyed in to basin from neighboring properties.
20
Project # 1: Curlew Connex Infiltration Basin Retrofit -
Comments2. Project provides for ditch improvements along
Delta Road west past Peach Tree Lane. Are there drainage concerns in this area?
3. Public works’ Capital Improvement Preservation Program (CRIPP). Does future road widening impact project?
21
Project # 1: Curlew Connex Infiltration Basin Retrofit -
Comments
4. Will county add ditches when it widens roads?
5. Who will be responsible for maintaining & monitoring Delta Rd basin?
6. Does the high water table impact the ability of the ditch to convey water?
22
Project #2:
Knightsen Ave
Bioswale
Stormwater
from #1 Flows
into Project #2
23
N = New
E = Existing
1
2
3
4
1
5
1
24
Culvert
New Ditch
(Project #2)
Project # 2: Knightsen Ave Bioswale
(BASE PROJECT) Improve existing 180 foot ditch (through downtown), 6ft base
width, 5ft deep, $58 per linear foot = $11,000. Replace 24 inch culvert crossing
Delta Road. $47,000. Improve existing 1,150 feet ditch along Knightsen Ave. south
of Delta Road (8ft base width, 4ft deep for 425 linear feet at $29 per linear foot =
$13,000. 12ft base width, 4ft deep for 725 linear feet at $60 per linear foot =
$44,000).
New Ditch –
Project #1 Existing
Ditch
25
Culvert
New Ditch
(Project #2)
Bioswale
Location
(approx.)
Project # 2: Knightsen Ave Bioswale
Improve 1,150 feet of existing
ditch Knightsen Ave (425 linear
feet north of culvert and 725
linear feet south of culvert.
Costs on prior screen).
Excavate new 560 foot bioswale
north of Knightsen Ave. between
Knightsen Ave. and the railroad.
$68,000. Install a new 30 inch
culvert at bioswale outlet to
drain in to Project #3 wetlands
basin. $38,000. Hydroseeding
and Planting $11,000.
New Ditch –
Project #1Improve Existing
Ditch – Project
#2
Culvert –
Project #1
Project #2: Knightsen Ave Bioswale - Construction Costs
$230,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
not included)
27
REVISED BY ESA on 4/4/19
Project #2: Knightsen Ave Bioswale - Construction Costs
$271,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
not included)
28
Original Costs Provided by ESA on 3/7/19
Project #2: Knightsen Ave Bioswale - Comments1. Memo on 4/4/17 from CC Flood Control to KTCSD noted:
29
Given this, can Project #2 even accept water from Project #1?
If Project #1 and Project #2 cannot be linked does that impact the need for
Project #2?
“KTCSD would be required to get an easement from
county.”
“According to County’s Real Property Division, easement
wording for flood water detention basin within a
transportation ROW might be limited to only flows
generated by the adjacent road and site area. This might
prohibit the KCSD from conveying flows generated west of
Delta Road and Knightsen Avenue intersection.”
Project #2: Knightsen Ave Bioswale - Comments
2. Public works’ CRIPP identified road improvements for Delta Road Widening (Sellers Ave/Byron Highway – III-34) & Knightsen Ave/Eden Plains Road Widening – Delta Rd to Chestnut St – III-40). How does future road widening impact project?
30
Project #2: Knightsen Ave Bioswale - Comments3. Per CC County Public Works Drainage
Responsibilities document, isn’t the county responsible for replacing this damaged culvert? This document also indicates that existing culvert is 18inch CMP culvert, but Project #2 states it is an existing 24in clogged/damaged culvert to be replaced with new 30inch.
4. Project description says “biofilter could be filled to permit widening of Knightsen Ave.” If biofilteris filled what happens to the water? If the biofilter can be filled for road widening, does that draw in to question whether this project is even necessary?
31
OTHER COMMENTS?
Project #2: Knightsen Ave Bioswale - Comments5. How will bioswale on Knightsen Ave affect land including water table that lies
east (opposite) of railroad tracks?
6. Why have a bioswale instead of ditches?
7. Will a bioswale effectively remove contaminants? Have containments been analyzed?
8. How do we (or do we need) to control what water is allowed to enter the system?
32
Project #3:
Eden Plains
Rd
Wetland
Basin
Stormwater
from #2 Flows
into Project #3
33
N = New
E = Existing
1
2
3 4
4
Project # 3: Eden Plains Rd Wetland Basin
34
Culvert
New Ditch
(Project #2)Wetland
Basin Area
(approx.)
Bioswale Project
#4 in distance
(approx.)
(BASE PROJECT) Add new 24 inch culvert across Eden Plains Road which combined
with existing 24 inch culvert doubles the capacity. $33,000. Ditch to treatment 3ft base
width, 4ft deep, 50 linear feet at $33 per linear foot = $2,000. Excavate a new wetlands
basin for water quality treatment between Eden Plains and the railroad. $149,000. Install
a new basin outlet structure with drop outlet and flow control device to empty in to Project
#4 bioswale. $48,000. New ditch to bioswale (Project #4), 6ft base width, 4ft deep, 150
linear feet at $44 per linear foot = $7,000. Hydroseeding and planting, $6,000.
.Ditch and
Culvert
(locations
approx.)
Culvert from
Project #2
Bioswale
Project #3: Eden Plains Rd Wetland Basin - Construction Costs
$245,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
not included)
36
Old
REVISED BY ESA on 4/4/19
Project #3: Eden Plains Rd Wetland Basin - Construction Costs
$248,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
not included)
37
Original Costs Provided by ESA on 3/7/19
Project #3: Comments1. 4/4/17 Public Works’ Preliminary Review memo to
KTCSD noted – Same questions regarding feasibility and need for projects #3 and #4 if project #2 cannot accept water from project #1.
2. Public works’ CRIPP identified road improvements for Knightsen Avenue/Eden Plains Road Widening (Delta Rd to Chestnut St – III-40). Widening is a result of increased development surrounding Knightsen. How does future road widening impact project (including culvert replacement across Eden Plains Road)?
38
Project #3: Comments3. CC County Public Works Drainage Responsibilities document indicates
existing culvert crossing Eden Plains Rd is 15 inch not 24 inch as stated in Project #3.
39
OTHER COMMENTS????
Project #4:
Railroad
Bioswale &
Infiltration
Basins
Stormwater from
#3 Flows into
Project #4
40
N = New
E = Existing
12
3
4
5
Series of alternating bioswales/treatment
wetland basins (#1,2&3) running along south
side of railroad tracks. Final treatment
wetland basin (#4) up to 700 feet long also
functions as an infiltration basin to increase
water supply/ groundwater recharge in sandy
soils. Existing 30 inch x 18 inch wooden box
culvert (#5) running under the railroad
maintained to promote positive drainage east
under railroad.
Project #4: Construction Costs
$ 214,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
not included)
42
Original Costs Provided by ESA on 3/7/19
Project #4: Comments1. 4/4/17 Public Works’ Preliminary Review memo to KTCSD noted – Same
questions regarding feasibility and need for projects #3 and #4 if project #2 cannot accept water from project #1.
2. What happens to the water (if any) that flows out of Project #4 under railroad through existing box culvert?
43
OTHER COMMENTS????
Project #5:
Eagle
Lane
Bioswale
44
N = New
E = Existing
12
3
4
Project # 5: Eagle Lane Bioswale
New Ditch
(Project #2)
(BASE PROJECT) Dig a new east/west ditch along Eagle Lane (west of bend). 3ft
base width, 3ft deep, 770 linear feet at $26 per linear foot = $20,000. (OPTIONAL)
Dig an additional 1,380 linear feet of ditch. $36,000. Install new 18 inch culverts at
driveways. $84,000.
(BASE PROJECT) Dig a north/south ditch along Eagle Lane (south of bend). 6ft
base width, 4ft deep, 570 linear feet at $40 per linear foot = $23,000. (OPTIONAL)
Dig an additional 1,130 linear feet of ditch. $45,000. Install new 24 inch culverts at
driveways. $168,000.
New Ditch
Project # 5: Eagle Lane Bioswale
New Ditch
(Project #2)
(BASE PROJECT) Install two new 24 inch culverts across Eagle Lane routing water to
the Parks wetlands restoration parcel. $78,000. (BASE PROJECT) Construct new 0.9
acre bioswale on Parks restoration parcel to treat water quality flows (Note: bioswale to
be constructed separately as part of wetlands restoration project). Hydroseeding and
planting, $4,000. (OPTIONAL) Construct an additional 1.6 acres of bioswale,
hydroseeding and planting, $7,000.
New
Culverts
Across
Eagle Lane
Bioswale on Park
Wetlands Property
Project #5: Eagle Lane Bioswale - Construction Costs
$ 465,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
and bioswale not included)
REVISED BY ESA on 4/4/19
Project #5: Eagle Lane Bioswale - Construction Costs
$ 480,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
and bioswale not included)
Original Costs Provided by ESA on 3/7/19
Project #5: Comments1. Need to determine if KTCSD has responsibility for construction and
maintenance of bioswale on EBRPD Wetlands property. If yes, what are costs?
50
OTHER COMMENTS????
Project #6:
Byron Hwy at
Ironhorse Rd
Infiltration
Basin and
Bioswale
51
N = New
E = Existing
1
2
46
5
3
52
Project #6 Byron Highway @ Ironhorse Rd Infiltration Basin and
Bioswale
(BASE PROJECT) 1,250ft ditch along Ironhorse Rd. Current estimate $56,000.
Note: this ditch was added with 4/4/2019 revisions.
Ditch along
Byron
Highway
New Culvert
across
Byron
Highway
Ditch down
Ironhorse Rd
53
Project #6 Byron Highway @ Ironhorse Rd Infiltration Basin and
Bioswale
(BASE PROJECT) Install two new 30 inch culverts across Byron Highway at
Ironhorse Road to route water on to the East Bay Parks wetlands restoration
parcel. $52,000 each, $104,000 total.
Ditch along
Byron
Highway
New Culvert
across
Byron
Highway
54
Project #6 Byron Highway @ Ironhorse Rd Infiltration Basin and
Bioswale
Construct new infiltration basin and bioswale on East Bay Parks wetlands parcel. (Note: both
constructed as part of wetlands restoration project). Hydroseeding and planting: BASE
PROJECT, 0.9 acres = $4,000. OPTIONAL an additional 2.9 acres = $13,000.
Infiltration Basin Area
with Bioswale extending
east from Basin
55
Project #6 Byron Highway @ Ironhorse Rd Infiltration Basin and
Bioswale
Block drainage ditch at Mountain View Drive to limit flows
north
56
Project #6 Byron Highway @ Ironhorse Rd Infiltration Basin and
Bioswale
(OPTIONAL) Improve 2,500 feet of ditch along west side of Byron Highway south of
Ironhorse Road. Replace existing driveway culverts with 30 inch culverts. Ditch
improvements cost $52,000. Replacing 4 culverts costs $56,000.
Existing
Ditch
57
Project #6 Byron Highway @ Ironhorse Rd Infiltration Basin and
Bioswale
(OPTIONAL) Improve 875 feet of ditch along Byron Highway north of Ironhorse Road.
Replace existing driveway culvert with 24 inch culvert. Ditch improvements cost $12,000.
Driveway culvert costs $12,000.
Existing
Ditch
Project #6: Byron Hwy @ Ironhorse Rd Infiltration Basin and Bioswale - Construction Costs
$ 423,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
and bioswale not included)
59
REVISED BY ESA on 4/4/19
Project #6: Byron Hwy @ Ironhorse Rd Infiltration Basin and Bioswale - Construction Costs
$ 294,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
and bioswale not included)
60
Original Costs Provided by ESA on 3/7/19
Project #6: Comments1. Need to determine if KTCSD has responsibility for construction and
maintenance of infiltration basin and bioswale on EBRPD Wetlands property. If yes, what are costs?
2. Public works’ CRIPP identified road improvements for Byron Highway Widening (Delta Road to Chestnut Street – III-26). How does future road widening impact project?
61
OTHER COMMENTS????
Project #7:
Delta Rd &
Byron Hwy
Bioswale
62
N = New
E = Existing
1
2
3
46
5
63
Project # 7: Delta Road & Byron Hwy Bio Bioswale
(BASE PROJECT) Improve 1,350 feet of ditch along Delta Road east of Byron Highway.
Replace driveway culverts. Ditch improvements $32,000 (Based on 6ft base width, 3-4ft
deep at $23 per linear foot. Driveway culverts $152,000.
Ditch along
Delta Road
east of
Byron
Highway
64
Project # 7: Delta Road & Byron Hwy Bio Bioswale
Install two new 30 inch culverts to route water on to East Bay Parks wetlands restoration parcel.
Construct bioswale and seasonal treatment wetlands on East Bay Parks land. (Note, both
constructed as part of wetlands restoration project). Hydroseeding and planting: BASE
PROJECT, 0.9 acres = $4,000; OPTIONAL, an additional 3 acres = $14,000.
Approximate
location of seasonal
wetlands and
bioswale.
65
(NOT SPECIFIED WHETHER BASE OR OPTIONAL)
Remove accumulated sediment from existing 30 inch culvert across Byron
Highway at Delta Road.
No cost estimates provided.
Project #7: Delta Road & Byron Highway Bioswale
Ditch along
Byron Highway
Culvert
66
Project # 7: Delta Road & Byron Hwy Bio Bioswale
(OPTIONAL) Improve 1,270 feet of ditch along Byron Highway south of Delta Road.
Replace driveway culverts. Ditch improvements $17,000 (Based on 3ft base width. 3-
4ft deep at $14 per linear foot). Driveway culverts $75,000.
Ditch along
Byron
Highway
67
Project # 7: Delta Road & Byron Hwy Bio Bioswale
(OPTIONAL) Improve 4,210 feet of ditch along Delta Road west of Byron Highway and
replace existing driveway and roadway culverts. Ditch improvements $122,000 (based
on 3ft base width, 3-4ft deep at $29 per linear foot). Driveway and roadway culverts
$383,000.
Ditch along
Delta Road
west of
Byron Hwy
Project #7: Byron Hwy @ Ironhorse Rd Infiltration Basin and Bioswale - Construction Costs
$ 799,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
bioswale, and seasonal treatment wetland not included)
69Changed drive
way culverts
from 30in to 24in
REVISED BY ESA on 4/4/19
Project #7: Byron Hwy @ Ironhorse Rd Infiltration Basin and Bioswale - Construction Costs
$ 936,000 construction estimate only
(permitting, ongoing operation/maintenance, and administration,
bioswale, and seasonal treatment wetland not included)
70
Original Costs Provided by ESA on 3/7/19,
but total actually is $936,000
Project #7: Comments
71
1. Public works’ CRIPP identified road improvements for Byron Highway Widening
(Delta Road to Chestnut Street – III-26); AND Delta Road Widening (Byron Highway
to Holland Tract Road – III-33); AND Delta Road Widening (Sellers Avenue to Byron
Highway – III-34). How do future road widenings impact project?
Project #7: Comments
2. Need to determine if KTCSD has responsibility for construction and maintenance of bioswale and seasonal treatment wetlands on EBRPD Wetlands property. If yes, what are costs?
3. Why are the diversion culverts to EBRPD property NOT included in the cost estimate for Project #7? Instead it says, “Implemented by Restoration Project.” (Note: the diversion culverts for projects #5 and #6 are included in those projects cost estimates).
4. Ditch costs vary considerably. 3ft base x 3-4ft deep quoted at both $14 per linear foot and $29 per linear foot. 6ft base x 3-4ft deep quoted at $23 per linear foot?
5. Why did driveway culverts go from 30 inch to 24 inch ($19,000 each to $14,000 each)?
72
OTHER COMMENTS????
KTCSD Proposed Projects - Cost Overview
Project Project Name Old Costs
1 Curlew Connex Infiltration Basin Retrofit $395,000 $375,000
2 Knightsen Ave Bioswale $230,000 $271,000
3 Eden Plains Rd Wetland Basin $245,000 $248,000
4 Railroad Bioswale & Infiltration Basins $214,000 $214,000
5 Eagle Lane Bioswale $340,000 $480,000
6 Byron Hwy @ Ironhorse Rd Infiltration
Basin/Bioswale
$423,000 $294,000
7 Delta Rd & Byron Hwy Bioswale $799,000 $645,000
Total Construction Costs
with 25% contingency,
design, permitting, Cal Env (CEQA) Report
$3,462,500 $2,530,000
$3,812,500
73
DOES NOT include: annual operating, maintenance, admin costs OR
construction of bioswales & culverts on East Bay Regional Park Land
New ESA’s Cost
$4,112,500
General Comments / Questions1. What sources and base year for cost data were used to estimate costs? (Why
are there variations in costs for ditches of the same size?)
2. Projects involve right-of-ways owned and managed by CC Public Works. What are County’s obligations for improving/maintaining these facilities?
3. Missing assumptions – what storm water event are we planning for?
4. Are there economies of scale associated with doing multiple projects at once? Do ESA’s estimated costs already account for them? Conversely, if only certain projects are done, or the projects are not done at once, do costs increase?
5. Which properties derive a direct benefit from each of these projects? Do some of these properties even have a storm water drainage issue?
74
General Comments / Questions6. What are the relative priorities of each of these projects, especially since
projects 1-4 are interdependent?
7. Are the elevations provided current? What source of information was used?
8. Will KTCSD be required to pay for any easements from the County? From East Bay Parks? From private property owners? Etc.
9. CC Public Works’ Capital Improvement Preservation Program (CRIPP) identifies road improvements for widening Knightsen’s roadways. How do these improvements impact these projects?
75
76
77
After Construction, What’s Next?
78
Bioswales, wetlands and infiltration
basins have ongoing operations,
maintenance, and monitoring costs.
Site inspections, water testing
Vegetation Maintenance – planting,
replanting, mowing, seeding, clearing,
etc.
Annual Maintenance Costs - % of Construction Costs
79
Table from EPA Publication https://www3.epa.gov/npdes/pubs/usw_d.pdf
Retention Basins
Constructed Wetlands = 3 - 6 %
Infiltration Basin = 1 - 10%
Swale = 5 - 7%
Detention Basin = < 1%
Cost per Parcel1. 600 parcels in KTCSD
2. Total cost for all projects (Base and Optional) of $4,112,500 divided by 600 parcels = $6,854 per parcel. (Note: cost would be more for developed parcels and less for undeveloped parcels).
3. Assuming ESA costs are accurate, no matching grant funding and zero inflation: Cost spread over five years = $1,371 per year; spread over ten years = $685 per year; spread over 20 years = $343 per year.
4. Does not account for possible costs for flood control projects KTCSD may need to pay for as part of the East Bay Regional Park Wetlands Restoration Project.
5. Does not take into account cost to employ an Operations Manager and other support staff (permanent or contracted).
6. Does not take into account maintenance costs. Assuming maintenance costs are between 5%-10% of construction costs ($173,000/year - $346,000), maintenance will cost between $288 - $577 per parcel, per year.
80
Evaluating KTCSD Potential Projects
According to California Stormwater Best Mgmt Practice (BMP) Handbook following factors:
Cost – does implementing exceed pollution control benefits? Does revenue stream exist for ongoing maintenance?
Public Acceptance – does BMP have public support?
Pollutant Removal – will it remove or control pollutants?
Implementation - compatible with land uses, facilities, or activities in question?
Technical Feasibility - feasible considering soils, geography, water resources, etc.?
81
ESA’s Ranking of Projects
82
Do projects 3, 4, & 7 provide no or minimal flood reduction benefit -- KTCSD’s primary
goal?
Explanation and justification of this ranking needs to be further explained in draft final
report.
Supporting ReferencesItem URL
Fact Sheet describes the final Municipal Separate
Storm Sewer System (MS4) General Permit Remand
Rule, signed by the Administrator, on November 17,
2016.
https://www.epa.gov/sites/production/files/2016-
11/documents/final_rule_fact_sheet_508.pdf
Army Corp of Engineers – Culvert Life Expectancy -
1997
https://www.publications.usace.army.mil/Portals/76/Publications/EngineerMa
nuals/EM_1110-2-2902.pdf
California Stormwater Quality Assn – Stormwater Best
Mgmt Practice Handbook, Municipal
https://www.casqa.org/sites/default/files/BMPHand
books/BMP_Municipal_Complete.pdf
83