17B-010 (11) 408 Bridge Road 05/29/01
Northampton, Massachusetts
Proposed
Stormwater Management System
Operation & Maintenance Plan
During Construction
The Contractor shall be responsible for inspection and maintenance during
construction.
At all times, siltation fabric fencing, stakes and hay bales sufficient to construct a
sedimentation control barrier a minimum of 50 feet long will be stockpiled on the
site in order to repair established barriers which may have been damaged or
breached.
An inspection of all erosion control and stormwater management systems shall be
conducted by the Contractor at least once a week and during all rainstorms until
the completion of construction. In case of any noted breach or failure, the
Contractor shall immediately make appropriate repairs to any erosion control
system and notify the engineer of any problems involving stormwater
management systems.
A rainstorm shall be defined as all or one of the following:
• Any storm in which rain is predicted to last for twelve consecutive hours or
more.
• Any storm for which a flash flood watch or warning is issued.
• Any single storm predicted to have a cumulative rainfall of greater than one-
half inch.
• Any storm not meeting the previous three thresholds but which would mark a
third consecutive day of measurable rainfall.
The Contractor shall also inspect the erosion control and stormwater management
systems at times of significant increase in surface water runoff due to rapid
thawing when the risk of failure of erosion control measures is significant.
In such instances as remedial action is necessary, the Contractor shall repair any
and all significant deficiencies in erosion control systems within two days.
The Conservation Commission shall be notified of any significant failure of
stormwater management systems and erosion and sediment control measures and
shall be notified of any release of pollutants to a water body(stream, brook,pond,
etc.).
1
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tormceptor 1 r esign
r ,
y Quantity Control Material
0 Controlled 0 Concrete ; :
' 5 Uncontrolled Fiberglass
s e
rr u
62 `
a , z
.28 = b: .. ;tormcepto Annual Annual }
r � Model Flow TSS
r,N 900 100.0 90.4
1200 100.0 91.2
1800 100.0 91.7
2400 100.0 93.3
3600 100.0 94.2
4800 100.0 95.6
6000 100.0 96.0
7200 100.0 96.7
i
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Location Address or Lot No. 408 Bridge Road, Northampton
On-site Review
Deep Hole Number 2 Date: 5/17/01 Time: 8:50 Weather Cloudy
Location (identify on site plan)
Land Use Woods Slope (%) 2-3 Surface Stones <5%
Vegetation
Landform Outwash Plain
Position on Landscape (sketch on back)
Distances from:
Open Water Body >100 Feet Drainage way >100 Feet
Possible Wet Area >100 Feet Property Line <100 Feet
Drinking Water Well Feet Other
DEEP OBSERVATION HOLE LOG
Depth from Soil Horizon Soil Texture Soil Color Soil Other
Surface(Inches) (USDA) (Munsell) Mottling (Structure,Stones,Boulders,
Consistency,%Gravel
0-7" Ap SL 10YR3/2 non
7"-23" Bw SL 10YR4/6 non Fine sand
23"-36" C1 S 10YR5/3 non GR coarse sand
36"- C2 Fine SL 10YR4/3 10%@38" Massive, friable, very fine
7.5YR5/6
7.5YR6/2
'MINIMUM OF 2 HOLES REQUIRED AT EVERY PROPOSED DISPOSAL AREA
Parent Material(geologic) Glacial Outwash Depth to Bedrock: non
Depth to Groundwater: Standing Water in the Hole: 103 Weeping from Pit Face: 87"
Estimated Seasonal High Ground Water: 38"
DEP APPROVED FORM- 12/07/95
Location Address or Lot No. 408 Bridge Road, Northampton
On-site Review
Deep Hole Number 1 Date: 5/17/01 Time: 8:30 Weather Cloudy
Location (identify on site plan)
Land Use Woods Slope (%) 2-3 Surface Stones <5%
Vegetation
Landform Outwash Plain
Position on Landscape (sketch on back)
Distances from:
Open Water Body >100 Feet Drainage way >100 Feet
Possible Wet Area >100 Feet Property Line <100 Feet
Drinking Water Well Feet Other
DEEP OBSERVATION HOLE LOG
Depth from Soil Horizon Soil Texture Soil Color Soil Other
Surface(Inches) (USDA) (Munsell) Mottling (Structure,Stones,Boulders,
Consistency,%Gravel
0-6" Ap SL 10YR3/2 non
6"-22" Bw SL 10YR4/6 non Fine sand
22"-48" C1 S 10YR5/3 10%@40" GR coarse sand
7.5YR5/6
7.5YR6/2
48"-96 C2 Fine SL 10YR4/3 Massive,friable, very fine
MINIMUM OF 2 HOLES REQUIRED AT EVERY PROPOSED DISPOSAL AREA
Parent Material(geologic) Glacial Outwash Depth to Bedrock: non
Depth to Groundwater: Standing Water in the Hole: non Weeping from Pit Face: 87"
Estimated Seasonal High Ground Water: 40"
DEP APPROVED FORM- 12/07/95
MWEEMENNEMOrmw
Area 13
Total Sq Ft = 136658
Tatal Acres = 3.13
Walkways: 1358.78 Sq Ft (0.03 Ac`
Rooftops: 5471.08 Sq Ft (0.13 Ac)
Ledge: 4791.02 Sq Ft (0.11 Ac)
_ Woods: 97371.88 Sq Ft (2.24 Ac)
Green: 27665.24 Sq Ft (0.64 Ac'
RIM 9SMH 7.98
8'IO= 92.64
12'OUT 92.64 I �OE DITCH
MEAN
1 0 DERINC WIRE FENCE REMN4NTS FOUND 00
FOUOD FOR L 0
M I 1
1 1 D
RNNAGE DITCH
' ' \\ WIRE FENCE REMNAM
5
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RIM=98.]4
10'10 =95.88 n I
4'I0 96.62
12'OUT=95.82 N ` o
RIM=99.02 4'I0=97.1 7.1♦
J10'OUT=97.14
II 200.29'I.P.TO I.P.
(200'DEED)
SMH
RIM=99.55
8'IN a 94.45
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Area 12
"i.
Total Sq Ft = 14880.12 /' / �
Total Acres = 0.34 ^V ��r •
/. , ! Area 14 (woods)
Roadway: 11509.01 Sq Ft (0.26 Ac)'�' �, R;41""�* DE
■ Tot al Sq Ft = 5923.33
RIM Walkways: 529.67 Sq Ft (0.01 Ac) _ '/ i p;.l."!� ... Total Acres = 0.14
RIM 100.52 Green: 2801.44 Sq Ft (.06 Ac) ■ .. ;.�
Area S Post Developed
Total Sq Ft = 19405.51 � '
Total Acres = 0.45
Roadway: 10332.23 Sq Ft (0.24 Ac
walkways: 1571.70 Sq Ft (0.04 Ac) Drainage Area
Rooftop: 1275 Sq Ft (.03 Ac)
Green: 6226.58 Sq Ft (.14 Ac)
Figure 4 408 Bridge Road
0 100 200 400 600
Northampton,MA
II
II
Total Sq Ft = 164061.36
Total Acres = 3.77
Impervious: 1197.73 Sq Ft (0.03 Ac)
Grass: 10409.84 Sq Ft (0.24 Ac)
Woods: 136614.45 Sq Ft (2.88 Ac)
iLedge: 26985.87 Sq Ft (0.62 Ac)
0
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PRO—A
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200.29'I.P.TO I.P. \ _
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197. 0 COMPUTED
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■}■T\ I� .'/:' NI � , . � / �l �/( --100—_ _ / .'// toe �•r� i
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,.'.'. Area 2
Total Sq Ft = 12755.63
— Total Acres .1 0.29
Sq Pre - Developed
Ledge: 6477.14 Sq Ft (0.15 Ac)
Woods: 6278.49 Sq Ft (0.14 Ac)
Drainage Area
Figure 3 408 Bridge Road
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USDA of Hampshire County,Central Part
=_ -- The
Berkshire General Soils Map
Gro pIu nC. 408 Bridge Road
' Northampton, Massachusetts
TSS Removal 80% 80%
Storm Water Rechargel 0.015 ac.-ft. 0.08 ac.-ft.
1.See HydroCAD calculation for pund 13 for the 10 year storm event.
Legend:
Required
Provided
6
Page 2 of 2
408 Bridge Road
Northampton, Massachusetts
Stormwater Management
Water Quality
TSS Removal
BMP technology TSS removal Cumulative TSS
removed
BMP 1 Parking lot sweeping 10% 10%
BMP 2 Stormwater treatment chamber 78% 70%
Total TSS removal 80%
Water Qualfty Volume
WQV=water quality volume
ReV= recharge volume
I = total impervious area (including rooftop)
Ir= rooftop impervious area
RR= rooftop runoff
Total Site I = 0.74 acres
Ir= 0.15 acres
" Stormwater to be treated for water quality is equal to:
0.5 inch of runoff x total impervious area of post development site for discharge to a non critical areas.
WQV=0.5"x I (acres)/ 12 0.031 acre-feet
Stormwater Recharge
Group A= 0.40
Group B= 0.25
Group C= 0.10
Group D= waived
Volume to recharge Re t cre-
I (acres) (in) feet)
100% of impervious area, soil group"B" 0.74 0.25 0.015
ReV= I x Volume to recharge/ 12 1 0.015 acre-feet
Exfiltration at the proposed underground basins were utilized in the calculation, provided that the soil at this
location is from hydraulic group"B". A conservative value of percolation rate of 10 minutes per inch was used.
Ignoring the recharge volume at the wetlands, the exfiltration volume for the entire of post-development site
during a 10 year storm is 0.08 acre-feet. (See HydroCAD calculation for pond 13 for the 10 year storm)
5
Stormwater Management Summary
Page 1 of 2
408 Bridge Road May 28, 2001
Drainage Report
incorporated into the design return the peak runoff conditions to the pre developed
conditions and ensure that the project will not generate an increase in the peak
runoff leaving the site.
Special care was taken in this design to incorporated recharge stormwater as much
as possible. Pond # 10 (HydroCAD calc.) shows the volume (in acre-feet) of
stormwater that will be recharge into the ground for each storm event
The storm water management system has been designed so that peak flows for the
2, 10, 100-year storms are attenuated to practical levels. The major objective of
the stormwater management system is to control volumes being discharged to the
receiving areas. Special care has been taken to treat runoff with a series of best
management practices to maintain water quality. These practices include, catch
basins equipped with a storm water treatment chamber, which are capable of
removing 80% of the total suspended solids, and to remove oil from stormwater
runoff.
5
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uthwester) onion
Reach 14 proposed 0.15 0.01 0.32 0.03 0.56 0.04
VI. Summary
In summary, although the development of the project will generate an increase in
the amount of storm water runoff, the storm water mitigation measure
4
408 Bridge Road May 28, 2001
Drainage Report
Area 1 represents the watershed on the northeastern section of the site, which
consists of approximately 83% of wooded area, and approximately 9.5% of
exposed bedrock. The reminder of area is comprised of residential home and
associated landscape area. Stormwater runoff from this watershed flows northerly,
overland into the wetlands.
Area 2 represents the watershed on the southern area of the site. This area consists
of mainly exposed bedrock with some light wooded and underbrush. Stormwater
runoff from this area flows southerly overland and offsite.
IV. Post-Developed (Proposed) Conditions
After the proposed construction, the drainage patterns will mimic the existing
conditions. Stormwater infiltration has been incorporated into the design to help
mimic existing drainage and recharge patterns and to manage total volumes of
runoff. Stormwater controls include, catch basins equipped stormwater treatment
chamber, dispersed overland flow, and underground infiltration basin with outlet
control structure. Discharge pipes will be equipped with flared ends and rip rap
pads.
Figure 4 shows the areas that comprise the post condition model. Areas 11, 12,
and 13 are the watersheds areas correspond to existing Area 1, and it includes the
proposed roadway, walkways and 13 residential units. Area 14 is the proposed
watershed area that corresponds to existing Area 2.
Area 11 is comprised of the southeasterly portion of the proposed roadway and the
associated parking spaces, rooftops, and walkways. This watershed area drains
into CB #1 via a stormwater treatment chamber and into an underground basin.
Area 12 is comprised of the northeasterly portion of the proposed roadway and the
associated parking spaces, and walkways. This watershed area drains into CB #2
via a stormwater treatment chamber and into an underground basin.
Area 13 is comprised of mainly the undeveloped area and some the rooftop of the
proposed building, walkways around the building, and some landscaped areas.
Stormwater runoff from this area, which is not expected to be contaminated, will
sheet flow downgrade into the wetland.
The underground basin systems will be equipped with an outlet control structure
that will attenuate flow rate and encourage infiltration and groundwater recharge.
To avoid erosion at the discharge points, outfall runoff will discharge into the
wetland by flared end outlets equipped with a riprap pads.
3
408 Bridge Road May 28, 2001
Drainage Report
I. Introduction
This report presents an analysis of the stormwater management system for the
proposed home units located on 408 Bridge Road in Northampton, Massachusetts.
The proposed construction will consist of a 24-foot paved roadway, paved
parking, 13 home units, and associated stormwater management controls.
The purpose of this analysis is to determine the 2, 10, and 100-year peak flow
rates and quantity for current site conditions, and subsequently, to design a
stormwater management system that will equalize any increased peak runoff from
the proposed site. The stormwater management system is designed to provide a
best management practice, which addresses stormwater peak flow rates, quantity,
and quality.
II. Site Soils
The USDA "Soil Survey of Hampshire County, Massachusetts, report classifies
the site soils to be "Charlton" (CrQ and has hydrologic group `B" designation,
(see the attached soil survey and USGS maps Fig. 2). The above soils of the site
area consist of some exposed bedrock mainly on the tops of the ridges and sandy
loam, and loamy sand on the lower elevations. In addition, two test pits were
performed on May 17, 2001 to determine the subsurface soils and high seasonal
groundwater on site (see location of TP on Plan N1 and attach Deep Observation
Hole Log).
III. Pre-Developed (Existing) Conditions
The proposed project site is located on 408 Bridge Road between Hatfield Street
and Chestnut Street. The site is situated on 4.1 acres of wooded parcel and it
includes 1,370 square feet of single family home, which is adjacent to Bridge
Road, and a 1.5 acres of wetlands. The topography on the site is varying from
steep slopes on the southerly portion of the parcel along the ridgeline to a
moderate slope on the northerly portion at the wetlands area. The site is divided
into two watersheds, the northeastern watershed (Area 1), and the southwestern
watershed (Area 2).
The boundaries for the drainage analysis were determined by current drainage
patterns and by the limits of the proposed work. Figure 3 shows the drainage area
(subcatchments) designated for the existing conditions analysis. The contributing
watershed includes areas to the southwest that are outside of the property bounds.
The highest point of the watershed is located on site. Therefore, there is no offsite
contribution of stormwater runoff to the project site.
2
DRAINAGE REPORT FOR:
PROPOSED
I �ID HO. UN.� ,
408 BRIDGE ROAD
NORTHAMPTON, MASSACHUSETTS
MAY 281, 2001
Prepared by:
The
Berkshire
Design
Group, Inc.
4 Allen Place - Northampton,MA 01060