UPDATED SITE DESIGN NARRATIVE AND CALCULATIONS · 2017-08-07 · UPDATED SITE DESIGN NARRATIVE AND CALCULATIONS Burlington Summit The Gutierrez Company One Wall Street, Burlington,

UPDATED SITE DESIGN NARRATIVE AND CALCULATIONS Burlington Summit

The Gutierrez Company

One Wall Street, Burlington, MA

July 17, 2015

Prepared by,

Symmes Maini & McKee Associates

Cambridge, MA SMMA No. 15062

Symmes Maini & McKee Associates 15062 July 2015

PROJECT DESCRIPTION

OVERVIEW

The project site is the combination of a series of parcels of land located at the end of Wheeler Road (West) in Burlington. The parcels comprise the existing 200 Wheeler Road Development, the adjacent undeveloped land including the “Land Swap” parcel, and a 15 acre parcel owned by the Massachusetts Highway Department (MassDOT) but under the control of The Gutierrez Company. The overall site measures 39.32 acres.

200 Wheeler Road (Lot 4A) 9.49 Acres 400 & 600 Wheeler Road (Lot 3A) 14.56 Acres MassDOT Parcel 15.27 Acres

The site is bounded to the north by Wheeler Road, to the east by commercial land properties and Middlesex Turnpike, to the south by commercial land properties, the Burlington Housing Authority land and to the west by land within the Town of Lexington.

The project site has been the subject of previous permitting by The Gutierrez including the most recent Site Plan Amendment approved in 2014 as well as an Erosion & Sediment Control Permit approved in 2014.

The approved project included the development of the 400 & 600 Wheeler Road site with two buildings with a total of 350,000 sf of Gross Floor Area and a total parking count for the overall site (including 200 Wheeler Road) of 1,933 parking spaces.

PROPOSED AMENDMENT

Following completion of the permitting efforts, The Gutierrez Company identified an opportunity for development of the site as a singular building constructed in phases, therefore the Gutierrez Company seeks to amend the site plan that was previously approved by the Planning Board and the Erosion & Sediment Control Approval from the Conservation Commission. The proposed amendment primarily consists of:

• Combine the two separate buildings (400 & 600 Wheeler Road) into a singular phased building

• Adjust the vehicular circulation and parking configuration to respond to a singular building

• Adjust the stormwater management and site utilities to support the revised parking and circulation


• Maintain the overall limit of disturbance of the project

• Maintain the overall stormwater design intent including quantities and size of Best Management Practices

STORMWATER MANAGEMENT

The proposed project was originally designed and approved in 2005 and was subject to the previous version of the Massachusetts Stormwater Management Policy. Subsequent to the original approval, MA DEP enacted the 2008 Stormwater Management Policy. The proposed project has been designed so that the additional impervious surface proposed to support the additional 100,000 sf Building area has been designed to comply with the 2008 Stormwater Management Policy. The stormwater management approach remains consistent with previously approved permits with minor modifications to support the revised layout.

CONSISTENCY WITH DEP STORMWATER MANAGEMENT POLICY

The project’s compliance with each of the standards of the DEP Stormwater Policy is discussed below.

Standard 1 – Untreated Stormwater

Standard 1 states that “No new stormwater conveyances (e.g. outfalls) will discharge untreated stormwater directly to or cause erosion in wetlands or waters of the Commonwealth.”

The project provides treatment of all impervious areas of the site, and therefore there will be no untreated stormwater conveyances from the proposed project.

Standard 2 – Post Development Peak Discharge Rates

Standard 2 states that “Stormwater management systems shall be designed so that post-development peak discharge rates do not exceed pre-development peak discharge rates.”

The proposed project is designed so that post-development peak discharge rates do not exceed pre-development peak discharge rates. The existing and proposed conditions hydrology was modeled using Hydrocad to compare existing and proposed conditions. A detailed description of the project hydrology is included in the following section, Hydrologic Analysis. As described in detail in the Hydrologic Analysis Section, the project is in compliance with Standard 2.


Standard 3 – Recharge to Groundwater

Standard 3 states that “Loss of annual recharge to groundwater shall be eliminated or minimized through the use of infiltration measures including environmentally sensitive site design, low impact development techniques, stormwater best management practices, and good operation and maintenance. At a minimum, the annual recharge from the post-development site shall approximate the annual recharge from pre-development conditions based on soil type. This condition is met when the stormwater management system is designed to infiltrate the required recharge volume as determined in accordance with the Massachusetts Stormwater Handbook.”

The Burlington Summit project was originally designed and permitted in 2005 and provided rooftop recharge to groundwater. The project was recently approved to increase the building area to 350,000 sf and increase the quantity of parking to support the increased building area. In order to mitigate the impact of the increased impervious surface associated with this increased development, the project provides an additional subsurface recharge area. The recharge area was designed to exceed the minimum recharge volume to mitigate the increased impervious area. Detailed calculations are provided in Appendix Two.

Standard 4 – Removal of 80% Total Suspended Solids (TSS)

Standard 4 states that “Stormwater management systems shall be designed to remove 80% of the average annual post-construction load of Total Suspended Solids (TSS). This Standard is met when: (a) Suitable practices for source control and pollution prevention are identified in long-term pollution prevention plan, and thereafter implemented and maintained; (b) Structural stormwater best management practices are sized to capture the required water quality volume determined in accordance with the Massachusetts Stormwater Handbook; and (c) Pretreatment is provided in accordance with the Massachusetts Stormwater Handbook.”

Removal of Total Suspended Solids (TSS) is proposed for the site. TSS removal is accomplished by the combination of the following structural BMPs:

• Deep sump Catch Basins with hoods

• Water Quality Treatment Units (sized to provide TSS removal based on the proposed location)

• Subsurface Infiltration Basin

• Extended Dry Detention Basins


In order to confirm that the project provides the minimum pre-treatment required, the TSS removal efficiencies were calculated for the pretreatment and full treatment trains. The pretreatment required for the project is 44% due to its characterization as a Land Use of Higher Potential Pollutant. The project meets the requirement for 80% minimum TSS removal.

Standard 5 – Land Uses with Higher Potential Pollutant Loads

Standard 5 states that “For land uses with higher potential pollutant loads, source control and pollution prevention shall be implemented in accordance with the Massachusetts Stormwater Handbook to eliminate or reduce the discharge of stormwater runoff from such land uses to the maximum extent practicable. If through source control and/or pollution prevention all land uses with higher potential pollutant loads cannot be completely protected from exposure to rain, snow, snow melt, and stormwater runoff, the proponent shall use the specific structural stormwater BMPs determined by the Department to be suitable for such uses as provided in the Massachusetts Stormwater Handbook.”

“In addition, land uses with higher potential pollutant loads include: exterior fleet storage areas; exterior vehicle service maintenance and cleaning areas; marinas and boatyards; and parking lots with high-intensity-uses (1000 vehicle trips per day or more).”

The project site is characterized as a Land Use of Higher Potential Pollutant Load (LUHPPL) due to the fact that the site will have more than 1,000 average daily trips (ADT). The design of the stormwater management system complies with the requirements for LUHPPLs.

Standard 6 – Critical Areas

Standard 6 states that “Stormwater discharges within the Zone II or Interim Wellhead Protection Area of a public water supply and stormwater discharges near or to any other critical area require the use of the specific source control and pollution prevention measures and the specific structural stormwater best management practices determined by the Department to be suitable for managing discharges to such areas as provided in the Massachusetts Stormwater Handbook.”

The site is not located within a critical area; therefore this standard does not apply.

Standard 7 - Redevelopment

Standard 7 states that “A redevelopment project is required to meet the following Stormwater Management Standards only to the maximum extent practicable: Standard 2, Standard 3, and the pretreatment and structural best management practice requirements of


Standards 4, 5 and 6. Existing stormwater discharges shall comply with Standard 1 only to the maximum extent practicable. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions.”

The site is not characterized as a Redevelopment.

Standard 8 – Erosion and Sedimentation Controls

Standard 8 states that “A plan to control construction related impacts including erosion, sedimentation and other pollutant sources during construction and land disturbance activities (construction period erosion, sedimentation, and pollution prevention plan) shall be developed and implemented.”

The project is required to comply with the National Pollutant Discharge Elimination System (NPDES). The plans indicate locations of erosion and sediment controls including haybales with silt fence and temporary swales and sedimentation basins. The Project complies with Standard 8.

Standard 9 – Operation and Maintenance Plans

Standard 9 states: “A long-term operation and maintenance plan shall be developed and implemented to ensure that stormwater management systems function as designed.”

A long-term operation and maintenance plan is included in Appendix Four. Therefore the Project complies with Standard 9.

Standard 10 – Illicit Discharges to Drainage System

Standard 10 states: “All illicit discharges to the stormwater management system are prohibited.”

There are no known or suspected illicit discharges to the stormwater management system at the project site. The project complies with Standard 10.

HYDROLOGIC ANALYSIS

EXISTING HYDROLOGY

The hydrologic analysis for the proposed site plan amendment represents an update to the hydrologic analysis for the previously approved site plan. The primary update to the existing conditions hydrology is to add new


subcatchments representing the additional land area which is being added to the overall project site.

The existing conditions hydrology for the overall site is split into two primary design points. Design Point 1 represents the overland flow which flows across the southern property boundary of the site. This Design Point includes the flow from Subcatchments 1S and 1SB. Design Point 2 represents the flow which discharges to the North across Route 128. This design point includes the flow from the remaining subcatchments and detention basins.

The existing site hydrology was modeled with a TR-20 analysis using the HydroCAD version 6.0 software package (see Appendix 1, for the Hydologic Analysis). The existing site hydrology for the analyzed area is divided into three drainage discharge points as documented in Appendix 1.

PROPOSED HYDROLOGY

The proposed stormwater management system has been designed to mitigate the impacts of the proposed development. The hydrologic calculations compare the peak rates of runoff from the existing and proposed development at the two same Design Points. Detailed breakdown of the proposed hydrology subcatchments are shown on the hydrology figures attached to this report. Within the developed land there are components which mitigate peak rates of runoff, and provide for TSS removal.

The proposed subcatchments are largely paved roadways, parking, sidewalk and landscaped areas as well as the proposed detention basin area. These areas all drain by deep sump, hooded, catch basins. Underground detention basins and the surface basin are routed and discharged to the Route 3 Commonwealth of Massachusetts/MassDOT Parcel. These subsystems provide the majority of TSS removal and contribute to peak flow mitigation.

The existing and proposed runoffs are summarized in Table 1 below.

In summary, the proposed site stormwater drainage system will decrease peak flows to the Route 3 Commonwealth of Massachusetts/MassDOT parcel, the land to the south and east, and the total discharge overall for the 2, 10 & 100-year storms, as shown in Table 1, and the Hydrologic Analysis in Appendix 1 . Additional benefits will also be provided by the use of hooded deep sump catch basins, the detention/recharge ponds, the roof recharge areas, and a site maintenance program. These benefits result in a TSS removal of over 80%.


Table 1: Hydrology Comparison

2 Year 10 Year 100 Year

Existing Proposed Existing Proposed Existing Proposed

Design Point 1

7.11 cfs 4.04 cfs 15.68 cfs 8.43 cfs 31.91 cfs 16.58 cfs

Design Point 2

9.72 cfs 9.27 cfs 21.06 cfs 18.73 cfs 45.38 cfs 37.36 cfs

EROSION AND SEDIMENT CONTROL

An erosion and sedimentation control plan was reviewed and approved by the Town of Burlington Conservation Commission. The plan complies with the Town of Burlington Bylaw, the Massachusetts Department of Environmental Protection’s Stormwater Management Policy and the Environmental Protection Agency (EPA) National Pollutant Discharge Elimination System (NPDES) requirements. The Erosion and Sedimentation Control Plan was developed based on the anticipated construction of the proposed project. In the event that the proposed construction sequence changes, the erosion and sedimentation control plan will be adjusted to ensure proper measures are in place to protect downstream locations.

ANTICIPATED CONSTRUCTION SEQUENCE

The proposed project is expected to proceed in the following sequence of activites:

o Installation of Haybales with Silt Fence

o Clear and Grub Trees

o Remove Topsoil and Subsoil

o Install Temporary Sedimentation Basins

o Earthwork operations;

o Construct Proposed Buildings


o Install Utilities

o Install Pavement, Landscaping, and final Site Improvements

PROPOSED EROSION AND SEDIMENTATION CONTROLS

The following erosion and sedimentation control measures will be implements on the project site:

o Installation of Haybales with Silt Fence at the perimeter of construction activities as shown on the design plans;

o Installation of sediment bags at existing catch basins;

o Installation of a temporary construction entrance where vehicles will enter and exit the project site;

o Installation of temporary sedimentation basins and drainage swales to collect and treat runoff from exposed surfaces; and

o Installation of temporary stabilization methods for soil stockpiles.

TEMPORARY SEDIMENTATION BASINS

The temporary sedimentation basins have been sized to pass the 2-year 24 hour storm event in accordance with the applicable requirements. The discharge from the temporary sedimentation basins is controlled by temporary outlet structure which is specifically designed to minimize the intrusion of sediment into the outlet from the temporary basin. Regular inspection of the temporary sedimentation basins will identify the need for sediment removal or cleaning of outlet devices to ensure proper operation.


APPENDIX ONE HYDROLOGIC ANALYSIS

1S

Existing Subcatchment-1

Overland East

1SB

Existing Subcatchment 1B East MHD Land

3S

Existing Subcatchment-3 (To

UG Det.) 7S

Existing Subcatchment-2

Overland MHD

1R

Design Point 1

2R

Existing Offsite Flow Design Point 2

3UP

Existing Underground Recharge

Drainage Diagram for 14023 - 400 Wheeler Road-ExPrepared by {enter your company name here}, Printed 5/7/2014HydroCAD® 9.10 s/n 00853 © 2010 HydroCAD Software Solutions LLC

Subcat Reach Pond Link

14023 - 400 Wheeler Road-Ex Printed 5/7/2014Prepared by {enter your company name here}

Page 2HydroCAD® 9.10 s/n 00853 © 2010 HydroCAD Software Solutions LLC

Soil Listing (selected nodes)

Area(acres)

SoilGroup

SubcatchmentNumbers

0.000 HSG A8.487 HSG B 1S, 1SB, 7S

13.637 HSG C 1SB, 3S, 7S7.368 HSG D 1S, 1SB, 7S1.810 Other 3S

31.302 TOTAL AREA

Type III 24-hr 2 YR Rainfall=3.20"14023 - 400 Wheeler Road-Ex Printed 5/7/2014Prepared by {enter your company name here}


Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 pointsRunoff by SCS TR-20 method, UH=SCS

Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method

Runoff Area=393,879 sf 0.00% Impervious Runoff Depth=0.88"Subcatchment 1S: Existing Flow Length=420' Tc=15.4 min CN=71 Runoff=6.24 cfs 0.662 af

Runoff Area=137,005 sf 0.00% Impervious Runoff Depth=0.48"Subcatchment 1SB: Existing Tc=5.0 min CN=62 Runoff=1.23 cfs 0.126 af

Runoff Area=113,853 sf 69.25% Impervious Runoff Depth=2.17"Subcatchment 3S: Existing Tc=5.0 min CN=90 Runoff=6.61 cfs 0.472 af

Runoff Area=16.501 ac 0.00% Impervious Runoff Depth=0.64"Subcatchment 7S: Existing Flow Length=2,710' Tc=19.5 min CN=66 Runoff=6.79 cfs 0.884 af

Avg. Flow Depth=0.15' Max Vel=32.68 fps Inflow=7.11 cfs 0.788 afReach 1R: Design Point 199.0" Round Pipe n=0.010 L=1.0' S=1.0000 '/' Capacity=12,871.01 cfs Outflow=7.11 cfs 0.788 af

Avg. Flow Depth=0.17' Max Vel=35.40 fps Inflow=9.72 cfs 1.357 afReach 2R: Existing Offsite Flow 99.0" Round Pipe n=0.010 L=1.0' S=1.0000 '/' Capacity=12,871.01 cfs Outflow=9.72 cfs 1.357 af

Peak Elev=215.76' Storage=4,021 cf Inflow=6.61 cfs 0.472 afPond 3UP: Existing Underground Recharge Outflow=2.93 cfs 0.472 af

Total Runoff Area = 31.302 ac Runoff Volume = 2.144 af Average Runoff Depth = 0.82"94.22% Pervious = 29.492 ac 5.78% Impervious = 1.810 ac



Summary for Subcatchment 1S: Existing Subcatchment-1 Overland East

Runoff = 6.24 cfs @ 12.24 hrs, Volume= 0.662 af, Depth= 0.88"

Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrsType III 24-hr 2 YR Rainfall=3.20"

Area (sf) CN Description217,933 77 Woods, Good, HSG D66,549 77 Brush, Fair, HSG D87,744 55 Woods, Good, HSG B21,653 56 Brush, Fair, HSG B

393,879 71 Weighted Average393,879 100.00% Pervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

8.5 50 0.0500 0.10 Sheet Flow, Sheet FlowWoods: Light underbrush n= 0.400 P2= 3.20"

0.8 60 0.0600 1.22 Shallow Concentrated Flow, SCFWoodland Kv= 5.0 fps



15.4 420 Total

Subcatchment 1S: Existing Subcatchment-1 Overland East

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

6

5

4

3

2

1

0

Type III 24-hr 2 YRRainfall=3.20"

Runoff Area=393,879 sfRunoff Volume=0.662 af

Runoff Depth=0.88"Flow Length=420'

Tc=15.4 minCN=71

6.24 cfs



Summary for Subcatchment 1SB: Existing Subcatchment 1B East MHD Land

[49] Hint: Tc<2dt may require smaller dt



Area (sf) CN Description86,255 55 Woods, Good, HSG B12,622 70 Woods, Good, HSG C33,954 77 Woods, Good, HSG D4,174 70 Woods, Good, HSG C



5.0 Direct Entry,

Subcatchment 1SB: Existing Subcatchment 1B East MHD Land

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

1

0



Runoff Depth=0.48"Tc=5.0 min

CN=62

1.23 cfs



Summary for Subcatchment 3S: Existing Subcatchment-3 (To UG Det.)




Area (sf) CN Description25,861 70 Woods, Good, HSG C9,148 74 >75% Grass cover, Good, HSG C

78,844 98 Paved parking & roofs113,853 90 Weighted Average35,009 30.75% Pervious Area78,844 69.25% Impervious Area


5.0 Direct Entry,

Subcatchment 3S: Existing Subcatchment-3 (To UG Det.)

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

7

6

5

4

3

2

1

0




CN=90

6.61 cfs



Summary for Subcatchment 7S: Existing Subcatchment-2 Overland MHD



Area (ac) CN Description7.349 70 Woods, Good, HSG C0.349 70 Brush, Fair, HSG C0.052 77 Woods, Good, HSG D0.119 56 Brush, Fair, HSG B3.710 55 Woods, Good, HSG B3.495 70 Woods, Good, HSG C0.166 55 Woods, Good, HSG B0.006 77 Woods, Good, HSG D1.255 70 Woods, Good, HSG C

16.501 66 Weighted Average16.501 100.00% Pervious Area


3.2 50 0.0800 0.26 Sheet Flow, Sheet FlowGrass: Short n= 0.150 P2= 3.20"

7.1 843 0.0800 1.98 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps


1.3 461 0.0150 5.81 3.17 Pipe Channel, 10.0" Round Area= 0.5 sf Perim= 2.6' r= 0.21'n= 0.011 Concrete pipe, straight & clean


19.5 2,710 Total



Subcatchment 7S: Existing Subcatchment-2 Overland MHD

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

7

6

5

4

3

2

1

0


Runoff Area=16.501 acRunoff Volume=0.884 af

Runoff Depth=0.64"Flow Length=2,710'

Tc=19.5 minCN=66

6.79 cfs



Summary for Reach 1R: Design Point 1

[52] Hint: Inlet/Outlet conditions not evaluated

Inflow Area = 12.187 ac, 0.00% Impervious, Inflow Depth = 0.78" for 2 YR eventInflow = 7.11 cfs @ 12.23 hrs, Volume= 0.788 afOutflow = 7.11 cfs @ 12.23 hrs, Volume= 0.788 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrsMax. Velocity= 32.68 fps, Min. Travel Time= 0.0 minAvg. Velocity = 21.86 fps, Avg. Travel Time= 0.0 min

Peak Storage= 0 cf @ 12.23 hrsAverage Depth at Peak Storage= 0.15'Bank-Full Depth= 8.25', Capacity at Bank-Full= 12,871.01 cfs

99.0" Round Pipen= 0.010Length= 1.0' Slope= 1.0000 '/'Inlet Invert= 201.00', Outlet Invert= 200.00'

Reach 1R: Design Point 1

InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

7

6

5

4

3

2

1

0

Inflow Area=12.187 acAvg. Flow Depth=0.15'

Max Vel=32.68 fps99.0"

Round Pipen=0.010

L=1.0'S=1.0000 '/'

Capacity=12,871.01 cfs

7.11 cfs

7.11 cfs



Summary for Reach 2R: Existing Offsite Flow Design Point 2






Reach 2R: Existing Offsite Flow Design Point 2

InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

10

9

8

7

6

5

4

3

2

1

0



Round Pipen=0.010

L=1.0'S=1.0000 '/'


9.72 cfs

9.72 cfs



Summary for Pond 3UP: Existing Underground Recharge

Inflow Area = 2.614 ac, 69.25% Impervious, Inflow Depth = 2.17" for 2 YR eventInflow = 6.61 cfs @ 12.07 hrs, Volume= 0.472 afOutflow = 2.93 cfs @ 12.26 hrs, Volume= 0.472 af, Atten= 56%, Lag= 11.2 minPrimary = 2.93 cfs @ 12.26 hrs, Volume= 0.472 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrsPeak Elev= 215.76' @ 12.26 hrs Surf.Area= 2,750 sf Storage= 4,021 cf

Plug-Flow detention time= 15.9 min calculated for 0.472 af (100% of inflow)Center-of-Mass det. time= 15.9 min ( 821.9 - 806.0 )

Volume Invert Avail.Storage Storage Description#1 214.30' 11,000 cf Custom Stage Data (Pyramidal) Listed below

Elevation Surf.Area Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft)

214.30 2,750 0 0 2,750218.30 2,750 11,000 11,000 3,589

Device Routing Invert Outlet Devices#1 Primary 214.10' 10.0" Vert. Orifice/Grate C= 0.600 #2 Primary 216.90' 12.0" Vert. Orifice/Grate C= 0.600

Primary OutFlow Max=2.93 cfs @ 12.26 hrs HW=215.76' (Free Discharge)1=Orifice/Grate (Orifice Controls 2.93 cfs @ 5.37 fps)2=Orifice/Grate ( Controls 0.00 cfs)



Pond 3UP: Existing Underground Recharge

InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

7

6

5

4

3

2

1

0

Inflow Area=2.614 acPeak Elev=215.76'

Storage=4,021 cf

6.61 cfs

2.93 cfs

























15.4 420 Total


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0




Tc=15.4 minCN=71

13.42 cfs










5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

4

3

2

1

0




CN=62

3.78 cfs










5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

11

10

9

8

7

6

5

4

3

2

1

0




CN=90

10.16 cfs














19.5 2,710 Total




Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0




Tc=19.5 minCN=66

17.09 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0



Round Pipen=0.010

L=1.0'S=1.0000 '/'


15.68 cfs

15.68 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

23222120191817161514131211109876543210



Round Pipen=0.010

L=1.0'S=1.0000 '/'


21.06 cfs

21.06 cfs









214.30 2,750 0 0 2,750218.30 2,750 11,000 11,000 3,589






InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

11

10

9

8

7

6

5

4

3

2

1

0

Inflow Area=2.614 acPeak Elev=216.80'

Storage=6,876 cf

10.16 cfs

3.97 cfs











Peak Elev=218.09' Storage=10,412 cf Inflow=15.86 cfs 1.183 afPond 3UP: Existing Underground Outflow=8.09 cfs 1.183 af














15.4 420 Total


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0




Tc=15.4 minCN=71

26.76 cfs










5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

10

9

8

7

6

5

4

3

2

1

0




CN=62

9.06 cfs










5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0




CN=90

15.86 cfs














19.5 2,710 Total




Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

40

38

36

34

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0




Tc=19.5 minCN=66

37.43 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

34

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0



Round Pipen=0.010

L=1.0'S=1.0000 '/'


31.91 cfs

31.91 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

50484644424038363432302826242220181614121086420



Round Pipen=0.010

L=1.0'S=1.0000 '/'


45.38 cfs

45.38 cfs









214.30 2,750 0 0 2,750218.30 2,750 11,000 11,000 3,589


Primary OutFlow Max=8.05 cfs @ 12.21 hrs HW=218.07' (Free Discharge)1=Orifice/Grate (Orifice Controls 4.95 cfs @ 9.08 fps)2=Orifice/Grate (Orifice Controls 3.10 cfs @ 3.95 fps)




InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w (

cfs)

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Inflow Area=2.614 acPeak Elev=218.09'Storage=10,412 cf

15.86 cfs

8.09 cfs

1S

Off Site

1SP

Existing Subcatchment

1B East MHD Land

7P

Existing

Subcatchment-2

Overland MHD

30S

North Parking Area

40S

Northeast Parking Area

60S

Access Road

71S

Proposed Building

Rooftop

72S

Tributary to Pond

(south)

73S

Tributary to Pond (NE)

1R

Design Point 1

2R

(new Reach)

3UP

Existing Underground

Recharge

20P

Detention Basin 1

40UP

Proposed UG Recharge

70UP

Proposed UG Recharge

Routing Diagram for 15062 - 400 Wheeler Road-PrPrepared by {enter your company name here}, Printed 7/16/2015

HydroCAD® 10.00-13 s/n 00853 © 2014 HydroCAD Software Solutions LLC

Subcat Reach Pond Link

15062 - 400 Wheeler Road-Pr Printed 7/16/2015Prepared by {enter your company name here}

Page 2HydroCAD® 10.00-13 s/n 00853 © 2014 HydroCAD Software Solutions LLC

Soil Listing (all nodes)

Area

(acres)

Soil

Group

Subcatchment

Numbers

0.000 HSG A

6.303 HSG B 1SP, 30S, 40S, 71S, 72S, 73S

9.276 HSG C 1SP, 7P

4.675 HSG D 1S, 1SP, 30S, 40S, 60S, 72S, 73S

9.538 Other 7P, 40S, 72S, 73S

29.792 TOTAL AREA

Type III 24-hr 2 YR Rainfall=3.20"15062 - 400 Wheeler Road-Pr Printed 7/16/2015Prepared by {enter your company name here}


Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 pointsRunoff by SCS TR-20 method, UH=SCS, Weighted-CN


Runoff Area=58,549 sf 0.00% Impervious Runoff Depth=1.40"Subcatchment 1S: Off Site Tc=5.0 min CN=80 Runoff=2.19 cfs 0.157 af

Runoff Area=112,307 sf 0.00% Impervious Runoff Depth=0.56"Subcatchment 1SP: Existing Tc=5.0 min CN=64 Runoff=1.29 cfs 0.120 af

Runoff Area=9.140 ac 2.74% Impervious Runoff Depth=0.88"Subcatchment 7P: Existing Subcatchment-2 Flow Length=1,126' Tc=27.6 min CN=71 Runoff=5.01 cfs 0.669 af

Runoff Area=73,360 sf 85.64% Impervious Runoff Depth=2.54"Subcatchment 30S: North Parking Area Tc=5.0 min CN=94 Runoff=4.84 cfs 0.357 af

Runoff Area=61,893 sf 88.29% Impervious Runoff Depth=2.64"Subcatchment 40S: Northeast Parking Area Tc=5.0 min CN=95 Runoff=4.19 cfs 0.313 af

Runoff Area=15,395 sf 0.00% Impervious Runoff Depth=1.40"Subcatchment 60S: Access Road Tc=5.0 min CN=80 Runoff=0.58 cfs 0.041 af

Runoff Area=74,601 sf 100.00% Impervious Runoff Depth=2.97"Subcatchment 71S: Proposed Building Tc=5.0 min CN=98 Runoff=5.35 cfs 0.424 af

Runoff Area=344,210 sf 67.55% Impervious Runoff Depth=2.17"Subcatchment 72S: Tributary to Pond Tc=5.0 min CN=90 Runoff=19.98 cfs 1.428 af



Avg. Flow Depth=0.17' Max Vel=34.82 fps Inflow=9.27 cfs 3.319 afReach 2R: (new Reach)99.0" Round Pipe n=0.010 L=1.0' S=1.0000 '/' Capacity=12,871.01 cfs Outflow=9.27 cfs 3.319 af


Peak Elev=211.02' Storage=58,069 cf Inflow=28.90 cfs 2.062 afPond 20P: Detention Basin 1 Outflow=1.20 cfs 1.564 af

Peak Elev=229.32' Storage=6,968 cf Inflow=4.19 cfs 0.313 afPond 40UP: Proposed UG Recharge Outflow=0.35 cfs 0.309 af





Summary for Subcatchment 1S: Off Site



Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.05 hrsType III 24-hr 2 YR Rainfall=3.20"

Area (sf) CN Description

58,549 80 >75% Grass cover, Good, HSG D

58,549 100.00% Pervious Area


5.0 Direct Entry,

Subcatchment 1S: Off Site

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

2

1

0

Type III 24-hr

2 YR Rainfall=3.20"

Runoff Area=58,549 sf

Runoff Volume=0.157 af

Runoff Depth=1.40"

Tc=5.0 min

CN=80

2.19 cfs



Summary for Subcatchment 1SP: Existing Subcatchment 1B East MHD Land





61,225 55 Woods, Good, HSG B12,622 70 Woods, Good, HSG C34,286 77 Woods, Good, HSG D4,174 70 Woods, Good, HSG C



5.0 Direct Entry,

Subcatchment 1SP: Existing Subcatchment 1B East MHD Land

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

1

0

Type III 24-hr

2 YR Rainfall=3.20"



Runoff Depth=0.56"

Tc=5.0 min

CN=64

1.29 cfs



Summary for Subcatchment 7P: Existing Subcatchment-2 Overland MHD



Area (ac) CN Description

5.046 70 Woods, Good, HSG C0.349 70 Brush, Fair, HSG C3.495 70 Woods, Good, HSG C

* 0.250 98 IMPERVIOUS

9.140 71 Weighted Average8.890 97.26% Pervious Area0.250 2.74% Impervious Area


7.8 50 0.2500 0.11 Sheet Flow, Sheet FlowWoods: Dense underbrush n= 0.800 P2= 3.20"

18.0 330 0.0150 0.31 Shallow Concentrated Flow, Forest w/Heavy Litter Kv= 2.5 fps



27.6 1,126 Total



Subcatchment 7P: Existing Subcatchment-2 Overland MHD

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

5

4

3

2

1

0

Type III 24-hr

2 YR Rainfall=3.20"

Runoff Area=9.140 ac


Runoff Depth=0.88"

Flow Length=1,126'

Tc=27.6 min

CN=71

5.01 cfs



Summary for Subcatchment 30S: North Parking Area





62,827 98 Paved parking, HSG B6,036 61 >75% Grass cover, Good, HSG B4,497 80 >75% Grass cover, Good, HSG D

73,360 94 Weighted Average10,533 14.36% Pervious Area62,827 85.64% Impervious Area


5.0 Direct Entry,

Subcatchment 30S: North Parking Area

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

5

4

3

2

1

0

Type III 24-hr

2 YR Rainfall=3.20"



Runoff Depth=2.54"

Tc=5.0 min

CN=94

4.84 cfs



Summary for Subcatchment 40S: Northeast Parking Area





* 54,644 98 All Impervious Area5,322 80 >75% Grass cover, Good, HSG D1,927 61 >75% Grass cover, Good, HSG B


54,644 88.29% Impervious Area


5.0 Direct Entry, Direct

Subcatchment 40S: Northeast Parking Area

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

4

3

2

1

0

Type III 24-hr

2 YR Rainfall=3.20"



Runoff Depth=2.64"

Tc=5.0 min

CN=95

4.19 cfs



Summary for Subcatchment 60S: Access Road








5.0 Direct Entry,

Subcatchment 60S: Access Road

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

0.6

0.55

0.5

0.45

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

0

Type III 24-hr

2 YR Rainfall=3.20"



Runoff Depth=1.40"

Tc=5.0 min

CN=80

0.58 cfs



Summary for Subcatchment 71S: Proposed Building Rooftop





74,601 98 Paved parking, HSG B



5.0 Direct Entry, Rooftop Runoff

Subcatchment 71S: Proposed Building Rooftop

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

5

4

3

2

1

0

Type III 24-hr

2 YR Rainfall=3.20"



Runoff Depth=2.97"

Tc=5.0 min

CN=98

5.35 cfs



Summary for Subcatchment 72S: Tributary to Pond (south)





76,572 80 >75% Grass cover, Good, HSG D35,129 61 >75% Grass cover, Good, HSG B

* 232,509 98 All Impervious Surfaces



5.0 Direct Entry,

Subcatchment 72S: Tributary to Pond (south)

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr

2 YR Rainfall=3.20"



Runoff Depth=2.17"

Tc=5.0 min

CN=90

19.98 cfs



Summary for Subcatchment 73S: Tributary to Pond (NE)










5.0 Direct Entry,

Subcatchment 73S: Tributary to Pond (NE)

Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

9

8

7

6

5

4

3

2

1

0

Type III 24-hr

2 YR Rainfall=3.20"



Runoff Depth=2.08"

Tc=5.0 min

CN=89

8.91 cfs







Peak Storage= 0 cf @ 12.09 hrsAverage Depth at Peak Storage= 0.11'Bank-Full Depth= 8.25' Flow Area= 53.5 sf, Capacity= 12,871.01 cfs

99.0" Round Pipen= 0.010 Concrete pipe, straight & cleanLength= 1.0' Slope= 1.0000 '/'Inlet Invert= 201.00', Outlet Invert= 200.00'


InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

4

3

2

1

0

Inflow Area=4.276 ac

Avg. Flow Depth=0.11'

Max Vel=28.38 fps

99.0"

Round Pipe

n=0.010

L=1.0'

S=1.0000 '/'


4.04 cfs

4.04 cfs



Summary for Reach 2R: (new Reach)


Inflow Area = 25.517 ac, 49.74% Impervious, Inflow Depth > 1.56" for 2 YR eventInflow = 9.27 cfs @ 12.42 hrs, Volume= 3.319 afOutflow = 9.27 cfs @ 12.42 hrs, Volume= 3.319 af, Atten= 0%, Lag= 0.0 min




Reach 2R: (new Reach)

InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

10

9

8

7

6

5

4

3

2

1

0



Max Vel=34.82 fps

99.0"

Round Pipe

n=0.010

L=1.0'

S=1.0000 '/'


9.27 cfs

9.27 cfs







Volume Invert Avail.Storage Storage Description

#1 214.30' 11,000 cf Custom Stage Data (Pyramidal) Listed below


214.30 2,750 0 0 2,750218.30 2,750 11,000 11,000 3,589

Device Routing Invert Outlet Devices

#1 Primary 214.10' 10.0" Vert. Orifice/Grate C= 0.600 #2 Primary 216.80' 12.0" Vert. Orifice/Grate C= 0.600





InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

5

4

3

2

1

0


Peak Elev=215.32'

Storage=2,814 cf

4.84 cfs

2.36 cfs



Summary for Pond 20P: Detention Basin 1



Plug-Flow detention time= 487.6 min calculated for 1.564 af (76% of inflow)Center-of-Mass det. time= 403.2 min ( 1,210.5 - 807.3 )


#1 207.00' 154,313 cf Custom Stage Data (Prismatic) Listed below (Recalc)

Elevation Surf.Area Inc.Store Cum.Store(feet) (sq-ft) (cubic-feet) (cubic-feet)

207.00 10,128 0 0208.00 12,199 11,164 11,164209.00 14,369 13,284 24,448210.00 16,641 15,505 39,953211.00 19,013 17,827 57,780212.00 21,485 20,249 78,029213.00 24,058 22,772 100,800214.00 26,731 25,395 126,195215.00 29,506 28,119 154,313


#1 Primary 207.50' 5.0" Vert. Orifice/Grate C= 0.600 #2 Primary 211.00' 4.0" Vert. Orifice/Grate C= 0.600 #3 Primary 212.40' 3.0" W x 24.0" H Vert. Orifice/Grate C= 0.600

Primary OutFlow Max=1.19 cfs @ 15.24 hrs HW=211.02' (Free Discharge)1=Orifice/Grate (Orifice Controls 1.19 cfs @ 8.76 fps)2=Orifice/Grate (Orifice Controls 0.00 cfs @ 0.42 fps)3=Orifice/Grate ( Controls 0.00 cfs)



Pond 20P: Detention Basin 1

InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0


Peak Elev=211.02'

Storage=58,069 cf

28.90 cfs

1.20 cfs



Summary for Pond 40UP: Proposed UG Recharge






Elevation Surf.Area Voids Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (%) (cubic-feet) (cubic-feet) (sq-ft)

227.00 10,000 0.0 0 0 10,000232.00 10,000 30.0 15,000 15,000 12,000






Pond 40UP: Proposed UG Recharge

InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

4

3

2

1

0


Peak Elev=229.32'

Storage=6,968 cf

4.19 cfs

0.35 cfs




Inflow Area = 1.713 ac,100.00% Impervious, Inflow Depth = 2.97" for 2 YR eventInflow = 5.35 cfs @ 12.07 hrs, Volume= 0.424 afOutflow = 0.69 cfs @ 12.60 hrs, Volume= 0.421 af, Atten= 87%, Lag= 31.8 minPrimary = 0.69 cfs @ 12.60 hrs, Volume= 0.421 af






227.00 9,000 0.0 0 0 9,000231.00 9,000 30.0 10,800 10,800 10,518


#1 Primary 227.00' 4.0" Vert. Orifice/Grate C= 0.600 #2 Primary 230.00' 48.0" W x 6.0" H Vert. Orifice/Grate C= 0.600





InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

5

4

3

2

1

0


Peak Elev=229.89'

Storage=7,804 cf

5.35 cfs

0.69 cfs































5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

4

3

2

1

0

Type III 24-hr

10 YR Rainfall=4.50"



Runoff Depth=2.46"

Tc=5.0 min

CN=80

3.88 cfs











5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

3

2

1

0

Type III 24-hr




Runoff Depth=1.27"

Tc=5.0 min

CN=64

3.54 cfs















27.6 1,126 Total




Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

11

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=1.75"

Flow Length=1,126'

Tc=27.6 min

CN=71

10.67 cfs











5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=3.82"

Tc=5.0 min

CN=94

7.10 cfs














Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=3.92"

Tc=5.0 min

CN=95

6.08 cfs











5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

1

0

Type III 24-hr




Runoff Depth=2.46"

Tc=5.0 min

CN=80

1.02 cfs













Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=4.26"

Tc=5.0 min

CN=98

7.58 cfs












5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

34

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0

Type III 24-hr




Runoff Depth=3.40"

Tc=5.0 min

CN=90

30.73 cfs













5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=3.30"

Tc=5.0 min

CN=89

13.89 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

9

8

7

6

5

4

3

2

1

0



Max Vel=33.66 fps

99.0"

Round Pipe

n=0.010

L=1.0'

S=1.0000 '/'


8.43 cfs

8.43 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0



Max Vel=43.27 fps

99.0"

Round Pipe

n=0.010

L=1.0'

S=1.0000 '/'


18.73 cfs

18.73 cfs










214.30 2,750 0 0 2,750218.30 2,750 11,000 11,000 3,589







InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

7

6

5

4

3

2

1

0


Peak Elev=215.92'

Storage=4,452 cf

7.10 cfs

3.11 cfs










207.00 10,128 0 0208.00 12,199 11,164 11,164209.00 14,369 13,284 24,448210.00 16,641 15,505 39,953211.00 19,013 17,827 57,780212.00 21,485 20,249 78,029213.00 24,058 22,772 100,800214.00 26,731 25,395 126,195215.00 29,506 28,119 154,313



Primary OutFlow Max=2.00 cfs @ 14.81 hrs HW=212.57' (Free Discharge)1=Orifice/Grate (Orifice Controls 1.45 cfs @ 10.62 fps)2=Orifice/Grate (Orifice Controls 0.50 cfs @ 5.70 fps)3=Orifice/Grate (Orifice Controls 0.06 cfs @ 1.32 fps)




InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

48

46

44

42

40

38

36

34

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0


Peak Elev=212.57'

Storage=90,698 cf

44.61 cfs

2.00 cfs










227.00 10,000 0.0 0 0 10,000232.00 10,000 30.0 15,000 15,000 12,000







InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

6

5

4

3

2

1

0


Peak Elev=230.34'

Storage=10,013 cf

6.08 cfs

0.95 cfs










227.00 9,000 0.0 0 0 9,000231.00 9,000 30.0 10,800 10,800 10,518







InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

8

7

6

5

4

3

2

1

0


Peak Elev=230.37'

Storage=9,110 cf

7.58 cfs

3.68 cfs































5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=4.33"

Tc=5.0 min

CN=80

6.81 cfs











5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=2.70"

Tc=5.0 min

CN=64

8.05 cfs















27.6 1,126 Total




Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=3.39"

Flow Length=1,126'

Tc=27.6 min

CN=71

21.23 cfs











5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

11

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=5.89"

Tc=5.0 min

CN=94

10.69 cfs














Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=6.01"

Tc=5.0 min

CN=95

9.10 cfs











5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

2

1

0

Type III 24-hr




Runoff Depth=4.33"

Tc=5.0 min

CN=80

1.79 cfs













Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

12

11

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=6.36"

Tc=5.0 min

CN=98

11.16 cfs












5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

50

45

40

35

30

25

20

15

10

5

0

Type III 24-hr




Runoff Depth=5.43"

Tc=5.0 min

CN=90

47.95 cfs













5.0 Direct Entry,


Runoff

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Type III 24-hr




Runoff Depth=5.32"

Tc=5.0 min

CN=89

21.88 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0



Max Vel=41.73 fps

99.0"

Round Pipe

n=0.010

L=1.0'

S=1.0000 '/'


16.58 cfs

16.58 cfs










InflowOutflow

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

40

38

36

34

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0



Max Vel=53.11 fps

99.0"

Round Pipe

n=0.010

L=1.0'

S=1.0000 '/'


37.36 cfs

37.36 cfs










214.30 2,750 0 0 2,750218.30 2,750 11,000 11,000 3,589







InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

11

10

9

8

7

6

5

4

3

2

1

0


Peak Elev=216.98'

Storage=7,373 cf

10.69 cfs

4.26 cfs










207.00 10,128 0 0208.00 12,199 11,164 11,164209.00 14,369 13,284 24,448210.00 16,641 15,505 39,953211.00 19,013 17,827 57,780212.00 21,485 20,249 78,029213.00 24,058 22,772 100,800214.00 26,731 25,395 126,195215.00 29,506 28,119 154,313



Primary OutFlow Max=4.70 cfs @ 13.48 hrs HW=214.39' (Free Discharge)1=Orifice/Grate (Orifice Controls 1.70 cfs @ 12.44 fps)2=Orifice/Grate (Orifice Controls 0.75 cfs @ 8.64 fps)3=Orifice/Grate (Orifice Controls 2.25 cfs @ 4.52 fps)




InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

75

70

65

60

55

50

45

40

35

30

25

20

15

10

5

0


Peak Elev=214.39'

Storage=136,727 cf

69.83 cfs

4.70 cfs










227.00 10,000 0.0 0 0 10,000232.00 10,000 30.0 15,000 15,000 12,000







InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

10

9

8

7

6

5

4

3

2

1

0


Peak Elev=231.03'

Storage=12,088 cf

9.10 cfs

4.20 cfs










227.00 9,000 0.0 0 0 9,000231.00 9,000 30.0 10,800 10,800 10,518







InflowPrimary

Hydrograph

Time (hours)3029282726252423222120191817161514131211109876543210

Flo

w

(cfs

)

12

11

10

9

8

7

6

5

4

3

2

1

0


Peak Elev=230.89'

Storage=10,504 cf

11.16 cfs

8.47 cfs


APPENDIX TWO STORMWATER CALCULATIONS

SYMMES, MAINI & McKEE ASSOCIATES, INC.

CLOSED DRAINAGE SYSTEM CALCULATIONS

10-YEAR FREQUENCY

Project: Burlington Summit Notes: n= 0.013 for reinforced concrete pipe

Proj. #: 15062.00 n= 0.010 for high density polyethylene pipe (smooth interior)

Date: 7/15/15 c= 0.95 impervious areas

By: SEB c= 0.20 for lawn/planting areas

Ckd by:

Line Length Area Imp. Area Perv. CA SUM Time of Rainfall Req. Cap. Pipe Slope Flow Full Design Vel. Rim Inv. Elevations Pipe Cover Time in

From To (ft) (acres) (acres) CA Concen. I (in./hr.) Qd (cfs) (in) (ft/ft) Qf (cfs) Vf (fps) Vd (fps) Comments Elev.(ft) Upper Lower Q/Qf Pipe

CB 1-12 DMH 1-9 59 0.63 0.09 0.61 0.61 5.00 5.70 3.49 12 0.050 10.35 13.18 10.1 233.00 227.92 224.97 0.34 4.08 0.10

CB 1-13 DMH 1-9 35 0.19 0.03 0.18 0.18 5.00 5.70 1.04 12 0.050 10.35 13.18 7.1 230.60 226.72 224.97 0.10 2.88 0.08

DMH 1-9 DMH 1-8 80 0.00 0.79 5.10 5.70 4.53 30 0.005 37.81 7.70 4.4 230.84 224.87 224.47 0.12 3.47 0.31

CB 1-11 DMH 1-8 65 0.19 0.13 0.21 0.21 5.00 5.70 1.18 12 0.050 10.35 13.18 7.4 231.76 227.72 224.47 0.11 3.04 0.15

CB 1-10 DMH 1-8 25 0.14 0.02 0.14 0.14 5.00 5.70 0.80 12 0.050 10.35 13.18 6.6 230.40 225.72 224.47 0.08 3.68 0.06

DMH 1-8 DMH 1-7 72 0.00 1.14 5.41 5.70 6.52 30 0.005 37.81 7.70 4.8 230.00 224.37 224.01 0.17 3.13 0.25

CB 1-9 DMH 1-7 34 0.26 0.04 0.25 0.25 5.00 5.70 1.43 12 0.050 10.35 13.18 7.8 228.44 225.71 224.01 0.14 1.73 0.07

CB 1-8 DMH 1-7 35 0.26 0.07 0.26 0.26 5.00 5.70 1.49 12 0.050 10.35 13.18 7.9 230.20 225.76 224.01 0.14 3.44 0.07

CB 1-7 DMH 1-7 23 0.44 0.12 0.44 0.44 5.00 5.70 2.50 12 0.050 10.35 13.18 9.1 229.20 225.16 224.01 0.24 3.04 0.04

DMH 1-7 DMH 1-6 126 0.00 2.09 5.65 5.70 11.94 30 0.005 37.81 7.70 5.8 228.32 223.91 223.28 0.32 1.91 0.36

CB 1-6 DMH 1-6 40 0.30 0.02 0.29 0.29 5.00 5.70 1.63 12 0.019 6.38 8.13 5.7 227.56 225.28 224.52 0.25 1.28 0.12

CB 1-5 DMH 1-6 30 0.54 0.04 0.52 0.52 5.00 5.70 2.98 12 0.019 6.38 8.13 6.8 229.48 224.78 224.21 0.47 3.70 0.07

CB 1-4 DMH 1-6 27 0.55 0.09 0.54 0.54 5.00 5.70 3.09 12 0.019 6.38 8.13 6.9 229.04 224.63 224.12 0.48 3.41 0.07

DMH 1-6 DMH 1-5 126 0.00 3.44 6.02 5.70 19.63 36 0.008 75.34 10.66 7.6 227.96 223.18 222.24 0.26 1.78 0.28

CB 1-3 DMH 1-5 28 0.72 0.12 0.71 0.71 5.00 5.70 4.02 12 0.050 10.35 13.18 10.5 229.04 223.63 222.23 0.39 4.41 0.04

CB 1-2 DMH 1-5 28 0.45 0.02 0.43 0.43 5.00 5.70 2.47 12 0.050 10.35 13.18 9.1 226.72 223.63 222.23 0.24 2.09 0.05

DMH 1-5 DMH 1-4 52 0.00 4.58 6.30 6.70 30.70 36 0.019 119.91 16.96 12.0 227.84 222.13 221.14 0.26 2.71 0.07

CB 1-1 DMH 1-4 28 0.34 0.22 0.36 0.36 5.00 5.70 2.08 12 0.050 10.35 13.18 8.7 229.33 222.50 221.10 0.20 5.83 0.05

DMH 1-4 WQU 1 139 0.00 4.95 6.37 5.70 28.20 36 0.008 75.34 10.66 8.4 229.93 221.04 220.00 0.37 5.89 0.28

WQU 1 DMH 1-3 87 0.00 4.95 6.64 5.70 28.22 36 0.008 75.34 10.66 8.4 231.40 219.90 219.25 0.37 8.50 0.17

DMH 1-3 DMH 1-2 199 0.00 4.95 6.82 5.70 28.22 36 0.008 75.34 10.66 8.4 232.40 219.10 217.61 0.37 10.30 0.40

DMH 1-2 DMH 1-1 288 0.00 4.95 7.21 5.70 28.22 36 0.008 75.34 10.66 8.4 230.00 217.50 215.34 0.37 9.50 0.57

CB 3-8 DMH 3-7 45 0.39 0.10 0.39 0.39 5.00 5.70 2.22 12 0.052 10.56 13.44 9.0 233.00 229.00 226.56 0.21 3.00 0.08

CB 3-7 DMH 3-7 34 0.10 0.21 0.14 0.14 5.00 5.70 0.78 12 0.010 4.63 5.90 3.7 231.00 227.00 226.56 0.17 3.00 0.15

DMH 3-7 DMH 3-6 108 0.00 0.53 5.08 5.70 3.01 18 0.010 13.67 7.74 5.2 232.50 226.66 225.38 0.22 4.34 0.34

CB 3-6 DMH 3-6 38 0.26 0.00 0.25 0.25 5.00 5.70 1.41 12 0.050 10.35 13.18 7.7 235.80 227.38 225.48 0.14 7.42 0.08

CB 3-5 DMH 3-6 39 1.23 0.34 1.24 1.24 5.00 5.70 7.06 12 0.050 10.35 13.18 12.3 234.00 227.44 225.48 0.68 5.56 0.05

DMH 3-6 DMH 3-5 200 0.00 2.01 5.43 5.70 11.48 18 0.010 13.67 7.74 7.7 235.40 225.48 225.38 0.84 8.42 0.43

TD DMH 3-4 10 0.06 0.00 0.05 0.05 5.00 5.70 0.30 12 0.010 4.63 5.90 2.8 239.00 225.75 225.56 0.07 12.25 0.06

DMH 3-4 DMH 3-3 58 0.00 0.05 5.06 5.70 0.30 12 0.020 6.55 8.34 3.6 242.00 225.46 222.54 0.05 15.54 0.27

DMH 3-5 DMH 3-3 99 0.00 2.01 5.86 5.70 11.48 18 0.008 11.84 6.70 7.0 238.50 223.28 222.54 0.97 13.72 0.24

DMH 3-3 DMH 3-2 48 0.00 2.07 6.10 5.70 11.78 18 0.008 11.84 6.70 7.0 234.00 222.44 222.08 1.00 10.06 0.11

CB 3-4 DMH 3-2 53 0.28 0.22 0.31 0.31 5.00 5.70 1.75 12 0.010 4.63 5.90 4.7 232.00 224.73 222.08 0.38 6.27 0.19

DMH 3-2 DMH 3-1 205 0.00 2.37 6.21 5.70 13.53 36 0.008 75.34 10.66 6.8 232.00 221.98 220.44 0.18 7.02 0.50

CB 3-3 DMH 3-1 53 0.19 0.11 0.20 0.20 5.00 5.70 1.17 12 0.050 10.35 13.18 7.3 228.40 223.09 220.44 0.11 4.31 0.12

DMH 3-1 WQU 94 0.00 2.58 6.72 5.70 14.70 36 0.010 85.68 12.12 7.6 228.75 220.34 219.43 0.17 5.41 0.21

CB 3-2 WQU 30 0.06 0.08 0.08 0.08 5.00 5.70 0.44 12 0.050 10.35 13.18 5.5 233.20 220.93 219.43 0.04 11.27 0.09

CB 3-1 WQU 22 0.05 0.01 0.05 0.05 5.00 5.70 0.28 12 0.050 10.35 13.18 4.8 233.10 220.55 219.43 0.03 11.55 0.08

WQU DMH 1-1 81 0.00 2.70 6.92 5.70 15.42 36 0.010 85.68 12.12 7.7 232.40 219.33 215.30 0.18 10.07 0.17

DMH 1-1 FES 170 0.00 7.65 7.78 5.70 43.63 36 0.036 166.14 23.50 16.7 222.00 215.20 209.00 0.26 3.80 0.17

DCB WQU 2-1 110 1.32 0.16 1.29 1.29 5.00 5.70 7.33 12 0.010 4.63 5.90 7.1 234.30 230.00 229.20 1.58 3.30 0.26

OCS 2-2 DMH 2-6 247 0.00 1.29 5.26 5.70 7.33 18 0.020 19.33 10.94 8.6 235.60 224.90 222.40 0.38 9.20 0.48

DMH 2-6 OCS 2-1 155 0.00 1.29 5.74 5.70 7.33 18 0.015 16.74 9.47 7.8 239.90 222.30 219.94 0.44 16.10 0.33

RD DMH 2-5 28 1.71 1.62 1.62 5.00 5.70 9.26 18 0.035 25.57 14.47 11.3 243.00 232.00 231.00 0.36 9.50 0.04

DMH 2-5 DMH 2-4 121 0.00 1.62 5.04 5.70 9.26 18 0.050 30.57 17.30 12.8 236.70 230.90 226.00 0.30 4.30 0.16

OCS 2-1 DMH 2-3 194 0.00 2.91 6.07 5.70 16.59 24 0.010 29.47 9.38 8.3 241.30 219.84 217.90 0.56 19.46 0.39

DMH 2-3 DMH 2-2 246 0.00 2.91 6.46 5.70 16.59 24 0.010 29.47 9.38 8.3 233.80 217.80 215.30 0.56 14.00 0.49

DMH 2-2 DMH 2-1 117 0.00 2.91 6.95 5.70 16.59 24 0.010 29.47 9.38 8.3 217.40 215.20 213.40 0.56 0.20 0.23

Page 1

V

INSTRUCTIONS: Version 1, Automated: Mar. 4, 2008

1. In BMP Column, click on Blue Cell to Activate Drop Down Menu

2. Select BMP from Drop Down Menu

3. After BMP is selected, TSS Removal and other Columns are automatically completed.

Location:

B C D E F

TSS Removal Starting TSS Amount Remaining

BMP1

Rate1

Load* Removed (C*D) Load (D-E)

Deep Sump and Hooded

Catch Basin 0.25 1.00 0.25 0.75

Stormceptor - 77% 0.77 0.75 0.58 0.17

0.00 0.17 0.00 0.17

0.00 0.17 0.00 0.17

0.00 0.17 0.00 0.17

Total TSS Removal = 83%

Separate Form Needs to

be Completed for Each

Outlet or BMP Train

Project: Burlington Summit

Prepared By: SMMA *Equals remaining load from previous BMP (E)

Date: 2/25/2014 which enters the BMP

TS

S R

em

ov

al

Calc

ula

tio

n W

ork

sh

ee

t

Non-automated TSS Calculation Sheet

must be used if Proprietary BMP Proposed

1. From MassDEP Stormwater Handbook Vol. 1 Mass. Dept. of Environmental Protection

Stormceptor Design Summary - 1/2

Stormceptor Design SummaryPCSWMM for Stormceptor

Project InformationDate 7/16/2015Project Name Burlington SummitProject Number 15062.00Location Burlington, MA

Designer InformationCompany SMMAContact N/A

RainfallName BOSTON WSFO AP

State MA

ID 770

Years of Records 1948 to 2005

Latitude 42°21'38"N

Longitude 71°0'38"W

Notes

WQU 1

Water Quality ObjectiveTSS Removal (%) 80

Drainage AreaTotal Area (ac) 6

Imperviousness (%) 83.2

The Stormceptor System model STC 7200 achievesthe water quality objective removing 81% TSS for aFine (organics, silts and sand) particle size distribution.

Upstream StorageStorage Discharge(ac-ft) (cfs)

0 0

Stormceptor Sizing Summary

Stormceptor Model TSS Removal

%STC 450i 56STC 900 67STC 1200 67STC 1800 67STC 2400 72STC 3600 73STC 4800 77STC 6000 78STC 7200 81STC 11000 85STC 13000 85STC 16000 87

jhowe

Rectangle


Particle Size DistributionRemoving silt particles from runoff ensures that the majority of the pollutants, such as hydrocarbons and heavymetals that adhere to fine particles, are not discharged into our natural water courses. The table below lists theparticle size distribution used to define the annual TSS removal.

Fine (organics, silts and sand)

Particle Size Distribution SpecificGravity

SettlingVelocity Particle Size Distribution Specific

GravitySettlingVelocity

µm % ft/s µm % ft/s20 20 1.3 0.001360 20 1.8 0.0051150 20 2.2 0.0354400 20 2.65 0.21232000 20 2.65 0.9417

Stormceptor Design NotesStormceptor performance estimates are based on simulations using PCSWMM for Stormceptor.Design estimates listed are only representative of specific project requirements based on total suspendedsolids (TSS) removal.Only the STC 450i is adaptable to function with a catch basin inlet and/or inline pipes.Only the Stormceptor models STC 450i to STC 7200 may accommodate multiple inlet pipes.Inlet and outlet invert elevation differences are as follows:

Inlet and Outlet Pipe Invert Elevations Differences

Inlet Pipe Configuration STC 450i STC 900 to STC7200

STC 11000 toSTC 16000

Single inlet pipe 3 in. 1 in. 3 in.

Multiple inlet pipes 3 in. 3 in. Only one inletpipe.

Design estimates are based on stable site conditions only, after construction is completed.Design estimates assume that the storm drain is not submerged during zero flows. For submergedapplications, please contact your local Stormceptor representative.Design estimates may be modified for specific spills controls. Please contact your local Stormceptorrepresentative for further assistance.For pricing inquiries or assistance, please contact Rinker Materials 1 (800) 909-7763www.rinkerstormceptor.com






State MA

ID 770




Notes

WQU 2-1


Drainage AreaTotal Area (ac) 1.48


The Stormceptor System model STC 900 achieves thewater quality objective removing 81% TSS for a Fine(organics, silts and sand) particle size distribution.


0 0










µm % ft/s µm % ft/s20 20 1.3 0.001360 20 1.8 0.0051150 20 2.2 0.0354400 20 2.65 0.21232000 20 2.65 0.9417




STC 11000 toSTC 16000









State MA

ID 770




Notes

WQU 3-1


Drainage AreaTotal Area (ac) 3.7


The Stormceptor System model STC 4800 achievesthe water quality objective removing 83% TSS for aFine (organics, silts and sand) particle size distribution.


0 0




jhowe

Rectangle







µm % ft/s µm % ft/s20 20 1.3 0.001360 20 1.8 0.0051150 20 2.2 0.0354400 20 2.65 0.21232000 20 2.65 0.9417




STC 11000 toSTC 16000





APPENDIX THREE OPERATION & MAINTENANCE PLAN

1

Operation & Maintenance

Plan

Project:

Burlington Summit

400/600 Wheeler Road

Burlington, MA

July 17, 2015

Prepared by,

Symmes Maini & McKee Associates

Cambridge, MA

SMMA No. 15062

2

OPERATION AND MAINTENANCE PLAN

This Operation and Maintenance (O&M) Plan has been developed in accordance with the

Massachusetts DEP Stormwater Management Standard No. 9 to ensure that the stormwater

management system functions as designed.

Owner and Responsible Party

As the owner, the Gutierrez Company shall be the party responsible for adherence to the DEP

Stormwater Management Policy and the Approved Erosion and Sedimentation Control Permit after

completion of construction. The Gutierrez Company shall designate a Site Supervisor who shall

assume responsibility for this maintenance plan post construction.

If the property owner changes, it shall be the responsibility of The Gutierrez Company to notify the

future owner of the stormwater management system and its components, as well as the requirements

for operation and maintenance.

Maintenance Activities

The following site maintenance activities are required to maintain optimal pollutant attenuation by the

drainage system. A maintenance schedule follows in the next section.

Catch Basins and Manholes

Proper maintenance includes inspection of all grates, sumps, oil absorbent pillows, and outlets. Any

debris or obstructions should be removed. Structural damage should be recorded and reported. The

amount of sediment in each structure should be recorded. The catch basin sumps shall be cleaned

when they are half full of sediment or debris (approximately 2 feet below outlet pipe.) Oil absorbent

pillows shall be utilized in all catch basins and shall be monitored and maintained according to

manufacturer’s recommendations.

Stormceptor® Water Quality Units

After construction, the Stormceptors® should be inspected to determine the rate of sediment

accumulation. Once the rate has been determined, the units shall be inspected periodically to check

for the depth of sediment accumulation. The Water Quality Units should be cleaned once the

sediment depth reaches 15% of the unit’s capacity.

Snow Removal

Maintenance activities during the winter months are primarily limited to snow removal activities and

removal of debris and trash throughout the site.

Snow removal operations will adhere to the Massachusetts Department of Environmental Protection –

Bureau of Resource Protection Guidelines (dated March 8, 2001). Snow storage is allowed in wetland

buffer zone areas that provide proper conveyance to stormwater treatment best management

practices. Snow may not be stored in wetland resource areas. Snow will be stockpiled as far away

from resource areas as possible and removed as necessary under larger snow events. Stockpiling

3

snow in this manner will allow meltwater to enter the drainage system and thereby receive

pretreatment prior to discharging to receiving resource areas. Snow and ice that has accumulated

around catch basin grates will be removed.

Winter Salt & Sand Use

There shall be no use of sodium chloride (rock salt) on any paved surfaces. Other de-icing chemicals

approved by the zoning bylaws may be used with the prior written approval of the Conservation

Commission.

For concrete walkways and plaza areas, no binary chloride compounds shall be applied, i.e. calcium

chloride, for a minimum of 6 months after concrete installation is complete. This allows the concrete

to cure to its optimal strength. For the first year, an aggressive snow removal process through

mechanical means or hand shoveling followed by the use of sand or fine gravel mixtures optimal for

the life of the sidewalks and plaza systems.

MAINTENANCE SCHEDULE

Site Component Required Action Frequency

Detention Basins

Inspect basin At least twice per year and during

and after major storm events

Examine outlet structure for evidence of

clogging or outflow release velocities that

are greater than design flow

At least twice per year

Mow the upper-stage, side slopes, and

embankment At least twice per year

Remove trash and debris At least twice per year

Remove sediment from basin At least once every 5 years

Inspect unit to determine oil and sediment

accumulation rate

Quarterly for the first year of

operation

Inspect for depth of sediment, oil and

sediment accumulation rate, obstructions,

structural damage, or other malfunction

Quarterly in first year, at least twice

per year after

Stormceptor Units

Cleaning accumulated oils and sediment

Once sediment depth reaches 15%

of storage capacity

Sweep areas

Minimum four times per year: after

final snow melt, final leave fall, and

as needed during summer months

4

Pavement Areas Clean areas After any chemical release equal to

or greater than 5 gallons

Remove accumulated trash, litter, and

discarded materials throughout the site Weekly

Grass Areas Inspect depth of sediment, obstructions,

structural damage, or other malfunction Four times per year

Catch Basins and Drain

Manholes

Clean sumps of accumulated sediment,

document amount of sediment observed

(inches below outlet pipe)

When sumps are 1/2 full of

sediment/ debris (approx. 2-feet

below outlet pipe)

REPORTING & DOCUMENTATION

The Site Supervisor shall be responsible for maintaining an accurate Site Maintenance Log. The Site

Maintenance Log shall be located in a convenient location and made available to the Burlington

Conservation Commission upon request.

The Site Maintenance Log shall:

Document the completion of planned maintenance tasks.

Identify the person responsible for the completion of tasks.

Identify any outstanding problems, malfunctions or inconsistencies identified during the

course of routine maintenance.

The Site Supervisor shall be responsible for ensuring that the scheduled tasks are appropriately

completed as described in this plan and the Site Maintenance Log accurately represents activities

carried out as described in this plan.

Site Maintenance Log

A Site Maintenance Log shall be completed as described above and shall, at a minimum, include the

following items:

Date of activity performed

Specific maintenance task

Structural components maintained, as identified on the O & M Plan

Staff person or contractor performing activity

Supervisor verification of maintenance activity

Recommended additional maintenance task(s)

5

Areas of concern, erosion or systems discrepancies requiring attention

Drainage Operation and Maintenance Agreement

The property own shall submit yearly maintenance records to the Board of Health pursuant to the

Order of Conditions (Mass DEP #122-439) for a Drainage Operation and Maintenance Plan

Agreement.

The agreement indicates that all on-Site drainage structures shall be inspected and cleaned and all

paved areas will we swept and maintained at least four times annually and immediately after any

chemical release equal to or greater than five gallons.

The property owner shall submit information that confirms all street sweepings and catch basin

sediments have been disposed in accordance with state and local requirements. The Board of Health

shall be provided with the name and contact information of the Site Manager responsible for

scheduling the Operation and Maintenance requirements.

Public Safety Features

On-site public safety features include the following:

Treatment of stormwater runoff to remove 80% of Total Suspended Solids (TSS).

Heavy-duty covers and grates on all manholes and catch-basins designed to withstand

H20 loading.

Maintain or reduce peak runoff rates from pre-development to post-development.

Creation and implementation of Operations & Maintenance Plan to ensure the ability of

the stormwater management system to continue to operate as designed.

Documents

UPDATED SITE DESIGN NARRATIVE AND CALCULATIONS · 2017-08-07 · UPDATED SITE DESIGN NARRATIVE AND CALCULATIONS Burlington Summit The Gutierrez Company One Wall Street, Burlington,