Conservation Commission Regular Meeting Materials (linked)

CROSS RD
HARTFORD TURNPIKE
WATERFORD, CONNECTICUT SEPTEMBER 23, 2021
COMMUNITY
WATERFORD APARTMENT 
969 HARTFORD TURNPIKE
PROPOSED RENDERING
Copyright SLR International Corporation - 2021
99 REALTY DRIVE
CHESHIRE, CT 06410
203.271.1773
SLRCONSULTING.COM

CHD
Mon
IPIN
w/Punch
Mon
w/Disk
Mon
w/Disk
Mon
w/Disk
DH
in Rock
DH
in Rock
DH
DH
DH
CHD
Mon
CHD
Mon
CHD
Mon
IPIN
HARTFORD  TURNPIKE  (ROUTE 85)
CROSS   ROAD
Gravel
SNET 5
Support Pole
Conc
Headwall
Benchmark
Disk in Rock
Elev.=128.00'
N/F
Stonington Partners, LLC
N/F
Richard T. Morgan
N/F
Hendels Hartford Road, LLC
Benchmark
Disk in Headwall
Elev.=117.11'
Drainage R.O.W.
In Favor of
The State of Connecticut
(See Note 5A)
N/F
Connecticut
Light & Power
Company
N/F
Connectic
Light & Po
Company
CHD
Mon
Billboard
Approx. Slope Limits
(See Note 5A)
Ledge
HARTFORD TURNPIKE (ROUTE 85)
Approximate Limit
of Inland Wetlands
N/F
Connecticut
Light & Power
Company
N/F
Richard T.
Morgan
wr1
wr2
wr3
wr4
wr5
wr6
wr7
wr8
wr9
wr10
wr11
wr12
wr13
wr14
wr15
wr16
wr17
wr18
wr19
wr20
wr21
wr22
wr23
wr24
wr25
wr26
wr27
wr51
wr52
wr53
wr54
wx101
wx102
wx103
wx104
wx105
wx106
wx107
wx109
wx110
wx111
wx112
wx113
wx114
wx115
wx116
wx117
wx84
wx85
wx86
wx-1
wx-2
wx-3
wx-4
wx-5
wx-6
wx-7
wx-8
wx-9
wx-10
wx-11
wx-12
wx-13
wx-21
wx-22
wx-23
wx-24
wx-50
wx-51
wx-52
wx-53
wx-54
wx-55
wx-56
wx-57
wx-58
wx-59
wx-80
wx-81
wx-82
wx-83
Ledge
12" FES
INV.=113.0
D
CCB
SILTED
24" RCP
15" FES
INV.=99.0
15" FES
INV.=129.7
15" FES
INV.=129.1
S
116
118
114
112
110
114
50'
75'
50'
75'
100'
100' INLAND WETLAND UPLAND REVIEW AREA
100' INLAND WETLAND UPLAND REVIEW AREA
100'
100'
100' INLAND WETLAND
UPLAND REVIEW AREA
75'
Approximate Limit
of Inland Wetlands
TP1
TP2
TP3
TP4
TP5
TP6
TP7
TP8
TP9
TP10
TP11
TP12
TP13
TP14
TP15
TP16
TP17
TP18
TP19
TP20

CHD
Mon
IPIN
w/Punch
Mon
w/Disk
Mon
w/Disk
Mon
w/Disk
DH
in Rock
DH
in Rock
DH
DH
DH
CHD
Mon
CHD
Mon
CHD
Mon
IPIN
HARTFORD  TURNPIKE  (ROUTE 85)
CROSS   ROAD
Gravel
SNET 5
Support Pole
Conc
Headwall
Benchmark
Disk in Rock
Elev.=128.00'
Benchmark
Disk in Headwall
Elev.=117.11'
Drainage R.O.W.
In Favor of
The State of Connecticut
(See Note 5A)
CHD
Mon
Billboard
Approx. Slope Limits
(See Note 5A)
Ledge
HARTFORD TURNPIKE (ROUTE 85)
Approximate Limit
of Inland Wetlands
wr1
wr2
wr3
wr4
wr5
wr6
wr7
wr8
wr9
wr10
wr11
wr12
wr13
wr14
wr15
wr16
wr17
wr18
wr19
wr20
wr21
wr22
wr23
wr24
wr25
wr26
wr27
wr51
wr52
wr53
wr54
wx101
wx102
wx103
wx104
wx105
wx106
wx107
wx109
wx110
wx111
wx112
wx113
wx114
wx115
wx116
wx117
wx84
wx85
wx86
wx-1
wx-2
wx-3
wx-4
wx-5
wx-6
wx-7
wx-8
wx-9
wx-10
wx-11
wx-12
wx-13
wx-21
wx-22
wx-23
wx-24
wx-50
wx-51
wx-52
wx-53
wx-54
wx-55
wx-56
wx-57
wx-58
wx-59
wx-80
wx-81
wx-82
wx-83
Ledge
12" FES
INV.=113.0
D
CCB
SILTED
24" RCP
15" FES
INV.=99.0
15" FES
INV.=129.7
15" FES
INV.=129.1
S
116
118
114
112
110
114
100' INLAND WETLAND UPLAND REVIEW AREA
100' INLAND WETLAND UPLAND REVIEW AREA
100' INLAND WETLAND
UPLAND REVIEW AREA
Approximate Limit
of Inland Wetlands
FF=175.5
FF=170.5
W/O=160.5
FF=179.0
FF=177.0
FF=181.5
FF=171.5
FF=187.5
FF=177.5
116
118
120
122
126
130
122
124
120
W/O=160.5
FF=170.5
164
164
174
174
170
170
172
174
168
172
170
174
176
176
178
178
176
146
152
158
168
176
184
190
196
202
178
184
190
180
184
164
168
172
170
164
176
164
174
166
178
178
174
178
174
172
174
FF=172.0
170
170
172
174
176
174
172
172
142
146
150
158
174
172
159
164
164
161
112
170
172
174
176
174
162
166
164
162
164
156
154
156
154
166
153
168
166
109
110
112
112
120
130
114
109
170
174
174
172
170
174
174
160
174
170
168
166
162
172
172
170
170
168
168
160
162
158
156
154
152
150
148
146
144
142
140
138
136
134
132
130
128
126
124
122
120
118
116
114
154
146
142
138
134
130
126
122
150
154
176
188
192
174
124
136
116
150
146
142
160
111
118
114
140
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
MH 16
T.F.=177.90
INV.=170.25(S)
INV.=170.50(E)
INV.=170.50(NW)
CCB 17
T.F.=176.00
INV.=172.60(SE)
CLCB 38
T.F.=175.00
INV.=166.00(NE)
INV.=166.00(W)
CLCB 23
T.F.=175.10
INV.=171.70(E)
CLCB 23.1
T.F.=174.90
INV.=171.40(N)
OCS 140
T.F.=174.80
INV.=166.70(SW)
INV.=166.70(N)
OVFW RG 2
15" RISER HDPE WITH DOME GRATE
T.F.=175.20
INV.=171.00(W)
CCB 21
T.F.=173.60
INV.=168.25(NE)
INV.=168.00(SE)
CLCB 37
T.F.=173.20
INV.=165.20(S)
INV.=165.20(E)
CCB 14
T.F.=172.70
INV.=166.20(NE)
INV.=166.20(SE)
INV.=166.45(NW)
CCB 36.1
T.F.=172.50
INV.=169.00(SW)
OCS RG 3
15" RISER HDPE WITH DOME GRATE
T.F.=173.00
INV.=169.00(SW)
DBLCLCB 36
T.F.=171.50
INV.=164.40(N)
INV.=164.40(NE)
INV.=164.20(S)
CCB 10.4
T.F.=171.60
INV.=168.10(NW)
CASCADE CS-4 (MH 31)
T.F.=170.10
INV.=159.30(N)
INV.=159.30(SW)
DBLCCB 13
T.F.=169.80
INV.=165.80(NW)
INV.=166.50(NE)
INV.=165.80(S)
OVFW RG 1
24" RISER HDPE WITH DOME GRATE
T.F.=171.50
INV.=167.00(SE)
CCB 32
T.F.=169.40
INV.=160.50(NW)
INV.=160.50(S)
CCB 35
T.F.=169.70
INV.=163.50(N)
INV.=163.50(S)
INV.=164.00(NE)
CCB 33
T.F.=169.90
INV.=162.00(SE)
INV.=162.50(W)
DBLCCB 34
T.F.=169.00
INV.=163.25(N)
INV.=163.25(E)
CCB 10.3
T.F.=168.80
INV.=165.20(S)
INV.=165.45(SE)
CCB 130.1-4' SUMP AND HOOD
T.F.=168.10
INV.=162.00(E)
INV.=164.50(SW)
CCB 12
T.F.=167.80
INV.=163.50(N)
INV.=157.00(S)
INV.=157.25(E)
CCB 10.2
T.F.=167.40
INV.=163.95(N)
INV.=163.70(SE)
CCB 12.1
T.F.=167.80
INV.=158.50(W)
INV.=158.50(E)
CCB 10.1
T.F.=165.90
INV.=160.50(NW)
INV.=154.75(E)
INV.=155.25(NE)
CCB 11
T.F.=161.80
INV.=153.00(N)
INV.=152.50(SW)
CCB 10-5' dia
T.F.=161.70
INV.=151.00(NE)
INV.=151.00(SE)
INV.=151.00(W)
OVRW RG 4
18" RIDER HDPE WITH DOME GRATE
T.F.=163.30
INV.=160.30(N)
CDS 2020-5-C W/ GRATE TOP (CCB 9 )
T.F.=153.00
INV.=146.50(NE)
INV.=145.00(SW)
INV.=145.50(NW)
CCB 9.1
T.F.=153.00
INV.=149.60(SW)
CCB 6-4' SUMP
T.F.=126.70
INV.=121.50(NE)
INV.=121.50(SE)
CCB 7-4' SUMP
T.F.=126.80
INV.=122.00(SW)
INV.=122.50(N)
CCB 2-4' SUMP AND HOOD
T.F.=116.40
INV.=113.00(N)
INV.=113.00(SW)
CCB 3-4' SUMP AND HOOD
T.F.=116.40
INV.=113.35(S)
OCS 130
OCS 120
OCS 110
FES 130
T.F.=161.36
INV.=161.00(W)
FES 120.2
INV.=142.0
FES 110
T.F.=121.71
INV.=119.50(NW)
FES 100
INV.=112.0
FES 130.1
INV.=159.0
SAN MH 9
T.F.=178.40
INV.=167.70(NW)
INV.=167.60(S)
SAN MH 10
T.F.=177.00
INV.=170.20(SE)
SAN MH 8
T.F.=176.10
INV.=164.90(N)
INV.=164.80(S)
SAN MH 11
T.F.=174.60
INV.=166.80(SE)
SAN MH 7
T.F.=172.90
INV.=163.90(N)
INV.=163.80(S)
INV.=163.90(NW)
SAN MH 12
T.F.=172.50
INV.=164.60(NW)
INV.=164.50(S)
SAN MH 13
T.F.=172.00
INV.=165.50(N)
INV.=165.40(SE)
SAN MH 14
T.F.=170.10
INV.=165.90(S)
SAN MH 6
T.F.=167.00
INV.=162.00(N)
INV.=161.90(S)
SAN MH 5
T.F.=162.20
INV.=157.00(N)
INV.=156.90(SW)
SAN MH 4
T.F.=156.90
INV.=150.60(NE)
INV.=150.50(S)
INV.=150.60(N)
SAN MH 3A
T.F.=126.70
INV.=118.50(N)
INV.=118.40(S)
SAN MH 2
T.F.=129.00
INV.=116.90(N)
INV.=112.50(S)
EXSAN MH 1
T.F.=114.51
INV.=102.90(N)
ENDWALL
INV.=117.0(N)
TP1
TP2
TP3
TP4
TP5
TP6
TP7
TP8
TP9
TP10
TP11
TP12
TP13
TP14
TP15
TP16
TP17
TP18
TP19
TP20
142'-15" HDPE
S=0.56%
117'-12" HDPE
S=1.45%
42'-24" HDPE
S=3.57%
112'-24" HDPE
S=4.91%
42'-12" HDPE
S=7.38%
42'-30" HDPE
S=7.14%
143'-15" HDPE
S=0.87%
286'-18" HDPE
S=1.12%
92'-24" HDPE
S=4.08%
33'-15" HDPE
S=3.03%
57'-18" HDPE
S=2.19%
27'-12" HDPE
S=5.56%
109'-18" HDPE
S=3.67%
117'-12" HDPE
S=1.20%
12'-15" HDPE
S=1.67%
55'-15" HDPE
S=8.36%
183'-18" HDPE
S=1.26%
42'-30" HDPE
S=1.19%
68'-30" HDPE
S=2.94%
39'-12" HDPE
S=0.90%
91'-12" HDPE
S=0.88%
58'-18" HDPE
S=10.34%
72'-12" HDPE
S=1.04%
17'-12" HDPE
S=1.76%
130'-12" HDPE
S=1.62%
135'-15" HDPE
S=0.59%
126'-18" HDPE
S=0.56%
66'-24" HDPE
S=1.14%
75'-18" HDPE
S=0.67%
78'-18" HDPE
S=0.51%
99'-15" HDPE
S=1.57%
297'-24" HDPE
S=0.51%
95'-24" HDPE
S=1.26%
67'-12" HDPE
S=3.96%
47'-24" HDPE
S=0.64%
56'-15" HDPE
S=2.23%
58'-18" HDPE
S=0.43%
82'-30" HDPE
S=0.61%
26'-15" HDPE
S=1.92%
3'-18" HDPE
S=3.33%
7'-12" HDPE
S=2.86%
57'-15" HDPE
S=6.14%
3'-18" HDPE
S=3.33%
170'-8" PVC
S=1.47%
270'-8" PVC
S=0.67%
100'-8" PVC
S=4.90%
116'-8" PVC
S=5.43%
114'-8" PVC
S=10.09%
90'-8" PVC
S=1.67%
98'-8" PVC
S=9.80%
66'-8" PVC
S=0.61%
136'-8" PVC
S=0.59%
203'-8" PVC
S=4.73%
170'-8" PVC
S=1.71%
244'-8" PVC
S=1.11%
70'-8" PVC
S=1.29%
119'-8" PVC
S=1.76%
CONNECT TO
EXISTING 12" WATER
MAIN
6" SEWER SERVICE LATERAL (TYP.)
S=2.08% MIN.
WATER SERVICE LATERAL
(TYP.)
FIRE HYDRANT
(TYP. OF 4)
FES 120.1
INV.=142.5
OVFW RG 5
18" RISER HDPE WITH DOME GRATE
T.F.=154.700
CONTRACTOR TO COORDINATE
CONSTRUCTION OF GAS MAIN
WITH EVERSOURCE
MH 12.2
T.F.=166.80
INV.=160.00(S)
INV.=160.00(W)
INV.=160.00(E)
YD 12.3
T.F.=167.00
INV.=164.00(W)
CDS 2015-4-C (140)
T.F.=177.90
INV.=170.00(S)
INV.=169.75(N)
INV.=170.00(W)
INV.=169.50(E)
YD 13.1
T.F.=171.90
INV.=168.20(SW)
86'-12" HDPE
S=1.98%
88'-15" HDPE
S=1.70%
51'-12" HDPE
S=7.84%
28'-24" HDPE
S=10.54%
MH 7.1
T.F.=138.00
INV.=131.50(N)
INV.=125.45(S)
99'-15" HDPE
S=0.81%
80'-15" HDPE
S=0.87%
YD 38.2
T.F.=172.30
INV.=167.50(SW)
MH 38.1
T.F.=174.00
INV.=166.80(SW)
INV.=166.80(NW)
INV.=166.80(NE)
90'-12" HDPE
S=5.56%
CCB 35.1
T.F.=173.70
INV.=169.00(SW)
YD 17.2
T.F.=180.70
INV.=177.00(N)
YD 17.1
T.F.=174.50
INV.=172.25(W)
INV.=172.25(S)
52'-12" HDPE
S=9.13%
94'-12" HDPE
S=1.86%
8-INCH HDPE
S=0.5% MIN.
10-INCH HDPE
S=0.5% MIN.
12-INCH HDPE
S=0.5% MIN.
10-INCH HDPE
S=0.5% MIN.
12-INCH HDPE
S=0.5% MIN.
10-INCH HDPE
S=0.5% MIN.
10-INCH HDPE
S=0.5% MIN.
12-INCH HDPE
S=0.5% MIN.
12-INCH HDPE
S=0.5% MIN.
10-INCH HDPE
S=0.5% MIN.
10-INCH HDPE
S=0.5% MIN.
15-INCH HDPE
S=0.5% MIN.
6" PERFORATED
UNDERDRAIN W/
CLEANOUT (TYP.)
6" PERFORATED
UNDERDRAIN W/
CLEANOUT (TYP.)
6" PERFORATED
UNDERDRAIN W/
CLEANOUT (TYP.)
EMERGENCY RIPRAP
SPILLWAY
CREST ELEV.=123.0
- SEE DETAIL
RIPRAP FILTER BERM
(TYP.)
RIPRAP OVERFLOW SPILLWAY
CREST ELEV.=110.5
- SEE DETAIL
STORMWATER BASIN 140
120-4'HX8'X8' OPEN BOTTOM RETAIN-IT MODULES
BOTTOM OF STONE = 166.3
BOTTOM OF STRUCTURE = 166.8
INSIDE TOP = 170.8
OUTSIDE TOP = 171.5
WATER QUALITY
BASIN 1
STORMWATER
BASIN 110
STORMWATER
BASIN 120
STORMWATER
BASIN 130
WATER QUALITY
BASIN 2
WATER QUALITY
BASIN 3
WATER QUALITY
BASIN 6
WATER QUALITY
BASIN 5
WATER QUALITY
BASIN 4
GRAPHIC DEPICTION OF WATER MAIN
GRAPHIC DEPICTION OF GAS MAIN
GRAPHIC DEPICTION OF WATER MAIN
GRAPHIC DEPICTION OF GAS MAIN

SLR International Corporation, 99 Realty Drive, Cheshire, CT  06410 
203.271.1773            slrconsulting.com
September 20, 2021 
Ms. Maureen Fitzgerald 
Environmental Planner 
Town of Waterford 
15 Rope Ferry Road 
Waterford, CT  06385 
Re: 
Multifamily Residential Development 
969 Hartford Turnpike (Route 85) 
Waterford, Connecticut 
SLR #141.15901.00004 
Dear Maureen, 
SLR International Corporation (SLR) is in receipt of a memorandum dated July 20, 2021, addressed to Darin 
L. Overton, PE, of SLR from Maureen Fitzgerald, Environmental Planner of the Town of Waterford,
regarding the above-referenced project. We offer the following responses to the comments contained
therein.
Preliminary Comments 
C1. 
The application fee is $160.00 for commercial developments. 
R1. 
The application fee will be provided. 
C2. 
Activities to be reviewed/licensed also include the proposed discharge of treated stormwater to 
inland wetlands. 
R2. 
Comment noted. 
C3. 
The wetland delineation report indicates no watercourses were delineated on the site, yet the 
topographic survey plan shows an intermittent watercourse. This should be addressed in the 
wetland evaluation and impact assessment. Surface water flows into the wetland across the 
Eversource right-of-way and is fed by treated stormwater discharge from a portion of the 
Waterford Commons retail center. Approximately 26 acres of drainage area is treated by the 
stormwater basin easterly of the utility right-of-way and discharged thru a level spreader to the 
easement. 
R3. 
We acknowledge that a watercourse exists on site. Watercourses were not specifically 
delineated on site because all are located entirely within the wetland boundary. 

September 20, 2021 
Ms. Maureen Fitzgerald 
Page 2 
 
 
 
SLR International Corporation            slrconsulting.com
 
C4. 
The proposed project stormwater discharge point to the wetland appears to be a narrow swale 
area along the Rte 85 embankment. The potential impacts of the velocity of the concentrated 
discharge to this location and any need for stabilization measures to prevent erosion, flooding of 
existing vegetation or measures to promote diffusion of flow through the receiving wetland 
should be addressed. 
 
R4. 
The flared end section (FES) 100 discharges to a riprap splash pad into a proposed narrow swale. 
The narrow swale then discharges into Water Quality Basin #6. However, we will revise to 
provide a permanent erosion control product, in addition to the splash pad, that facilitates 
vegetation and combats erosion in high-flow applications. As there is a reduction in peak flows 
to the narrow swale beyond Water Quality Basin #6 with similar discharge characteristics to 
existing conditions, we do not anticipate any erosion control problems. Any flooding of existing 
vegetation should be similar to existing conditions. 
 
C5. 
Does the project stormwater discharge, in combination with the existing discharge from 
Waterford Commons pose issues to the capacity of the 18 inch culvert under Rte. 85? 
 
R5. 
The cross culvert under Route 85 is 36 inches in diameter, not 18 inches. The proposed project 
will reduce the existing peak-discharge rates to the culvert under Route 85 and will pose no 
issues regarding capacity. 
 
C6. 
The receiving wetland of the Jordan Brook mainstem are of very high functional value and support 
a cold-water trout fishery sensitive to water quality impacts and surface water temperatures. 
Marbled salamanders have been recorded in the small detention area at this culvert outlet west 
of the project. Provide a summary of pollutant removal effectiveness of the stormwater treatment 
train proposed for the development. Is the stormwater anticipated to be detained in the slope 
wetland prior to discharge downstream of Rte. 85 where additional renovation of temperature 
may occur?  What is the relative elevation difference between the culvert at 99.0 and the adjacent 
wetland surface? 
 
R6. 
A simple method for estimating pollutant export from urban development sites has been 
performed to determine the pollutant removal effectiveness of the proposed stormwater 
treatment train. The attached results demonstrate that the proposed system will achieve 87 
percent Total Suspended Solids (TSS) removal and considerable reductions in the total proposed 
pollutant loading for nutrients and metals. 
 
 
 
After discharging from the detention basins, stormwater will meander toward the 36-inch 
reinforced concrete pipe (RCP) culvert under Route 85 like existing conditions. Stormwater 
would only be detained should the existing 36-inch RCP capacity be exceeded. The wetland 
elevation varies as you move upgradient. 
 

September 20, 2021 
Ms. Maureen Fitzgerald 
Page 3 
 
 
 
SLR International Corporation            slrconsulting.com
 
 
The proposed detention basins detain the first inch of stormwater runoff (Water Quality 
Volume {WQV}, also referred to as the “first-flush”) and, therefore, allow stormwater runoff 
from a hot surface to sit and cool within the basin before discharging. Stormwater will not 
infiltrate either as the basins are redesigned with permanent pools. Per the Connecticut 
Department of Energy & Environmental Protection (CTDEEP), 2004 CT Stormwater Quality 
Manual, use of wetland plants and trees for shading and increased pool depths are means to 
reduce thermal impacts. The detention basins are planted with New England Wetmix, New 
England Erosion Control/Restoration Mix, Autumn Brilliance Apple Serviceberry trees, and 
Cherokee Chief Dogwoods to reduce sun exposure. The southern sun exposure of Stormwater 
Basin 110 is further reduced by the existing mature tree line. 
  
C7. 
The use of rain gardens to treat the water quality volume from the building roof area is an 
encouraged LID practice. The stormwater management plan will need a maintenance and 
inspection schedule for these practices. 
 
R7. 
A maintenance and inspection schedule for the proposed stormwater practices have been 
provided on Sheet UT-2. 
 
C8. 
Upon review of the sizing of WQ basin 3 bottom elevation and the outlet elevation. It appears it 
holds 0.3 feet of runoff which may not meet the WQ volume from building #3. Is the bottom 
deeper than it appears on the utility and grading plan? 
 
R8. 
The top of frame elevation of the overflow outlet riser has been corrected to an elevation of 
173.0 feet to match the sizing computations. The bottom is correctly shown at an elevation of 
172.0 feet. 
 
C9. 
Provide the total impervious area of the proposed development and the calculated water quality 
volume. I found only the computations for the roof areas and the sizing of the rain gardens. What 
is the WQV from the roadways and parking areas and how much is treated by the stormwater 
detention areas? Please provide details on the retention storage volumes & water quality storage 
volumes provided in basins 110, 120 and 130. 
 
R9. 
The calculations for the required WQV from the roads and parking areas as well as the total 
provided retention volume in each of the detention areas is provided on the first and second 
pages of Attachment E. The calculations do not include the impervious areas from the building 
rooftops as those areas are treated separately by the proposed water quality basins.  
 

September 20, 2021 
Ms. Maureen Fitzgerald 
Page 4 
 
 
 
SLR International Corporation            slrconsulting.com
 
C10. 
Provide information on the anticipated stormwater treatment function and performance of 
stormwater basins. 
 
R10. 
Basins 110 and 120 are to be Micropool Extended Detention (ED) ponds while Basin 130 is to be 
a pocket pond. Both are stormwater ponds and considered primary stormwater treatment 
practices in the CT Stormwater Quality Manual. These treatment practices can provide high-
levels of water quality treatment by capturing and treating the WQV and removing at least 80 
percent of the average annual total suspended solids (TSS) load. These basins will maintain a 
permanent pool of water and extended detention. The permanent pool of water in these 
systems enhances pollutant removal through mechanisms such as sedimentation, biological 
uptake, microbial breakdown, gas exchange, volatilization, and decomposition. Micropool ED 
ponds and pocket ponds were selected due to limited contributing drainage area. The basins 
will maximize the permanent pool depth to 100 percent of the WQV as explained in R6 to reduce 
thermal impacts. Table 11-P1-2 of the Stormwater Quality Manual outlines the percent of water 
quality volume allowed for pond designs. 
 
C11. 
Are the forebays sized to treat 10% of the WQV from the contributing impervious surface areas? 
 
R11. 
The size of forebays has been verified, and they have a storage volume that is equal to at least 
10 percent of the WQV. See attached for revised calculation. 
 
C12. 
The drainage report indicates the basins will retain stormwater and create a water quality feature, 
the details indicate they will be lawn. Have wet basin designs per the CT DEEP Manual been 
considered for additional stormwater renovation? 
 
R12. 
The detail will be revised to refer to the landscaping plan for planting the basins. In addition, 
see R10 above. 
 
C13. 
Basins 110 and 120 are in 10 ft. +/- cuts, exceeding the depth of the test pits performed in those 
areas. If they end up maintaining permanent pools, will this potentially impact the storage 
volumes and water quality treatment of the basins? 
 
R13. 
We will design these basins with permanent pools as Micropool ED ponds as explained in R10. 
This will not impact the storage volumes and water quality treatment of the basins as these are 
primary treatment practices. 
 
C14. 
The sequence and timing for conversion of the rain gardens and basins from temporary sediment 
traps to the permanent stabilized stormwater control and treatment features needs to be 
included in the stormwater management report and plan detail notes. 
 
R14. 
This will be added to the E&S plans as this is where the future contractor will see the 
instructions. 

September 20, 2021 
Ms. Maureen Fitzgerald 
Page 5 
 
 
 
SLR International Corporation            slrconsulting.com
 
 
C15. 
A construction phasing plan is recommended to minimize the extent and length of site exposure. 
The plan should indicate the extent of clearing and grading for each phase, the temporary 
sediment controls, construction stormwater management controls and stabilization measures. 
 
R15. 
The title sheet has the construction sequence while Sheets SE-1 and SE-2 are phased sediment 
and erosion control plans that indicate the clearing and grading for the two phases as well as 
the temporary sediment controls. The construction manager, when selected, will be required 
to generate a construction phasing plan to execute the work. 
 
Please feel free to contact me should you need any further information. 
 
Sincerely, 
 
SLR International Corporation 
 
 
 
 
Darin L. Overton, PE 
Principal Civil Engineer 
 
Enclosures 
 
141.15901.00004.s2021.ltr.docx