HomeMy WebLinkAbout20140715 stormwater review response - Stormwater Report - 500 GREAT POND ROAD 6/20/2014 Enright, Jean
From: Kathy Molina <Kathy@ morincameron.com>
Sent: Friday,June 20, 2014 11:02 AM
To: Enright,Jean; Hughes,Jennifer, lira@egglestonenvironmental.com; peter vandegraaf,
'S Koh r@northandovercc.com'; Ross Forbes; Chris Downer;Willis, Gene
Cc: Scott Cameron
Subject: North Andover Country Club - 500 Great Pond Road
Attachments: NAPB NACC Response Ltr 6-20-14.pdf, Revised Plans 6-20-14.pdf
Good morning,
Please find attached the stamped plans (revised per Planning Et Conservation review) as well as our response letter.
Hard copies are being delivered to Planning and Conservation this morning; all others are in today's mail.
If you have any questions please do not hesitate to contact our office.
Kathy Molina
THE MORIN-CAMERON GROUP, INC. 447 Boston Street, US Route 1, Topsfield, MA 01983
p I 78-887-85 6 f 1 97 -687-3480 w I www.morincameron.com
Please note the Massachusetts Secretary of State's office has determined that most emails to and from municipal offices and officials are public records.For more
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Please consider the environment before printing this email
1
The,
Morin-Cameron
June 20, 2014
North Andover Planning Board
North Andover Conservation Commission
1600 Osgood Street
North Andover, MA 01845
Attn: Mr. Curt Bellevance, Director of Community Development
RE: Response to Stormwater Review
North Andover Country Club Parking Lot Expansion
Dear Board Members:
This letter is in response to the review comments provided by Ms. Lisa D. Eggleston, P.E. of
Eggleston Environmental in a letter dated May 14, 2014 and Mr. Gene, Willis Division of Public
Works, in memos dated May 23, 2014 and June 11, 2014. We have repeated the comments of
Ms. Eggleston and added our responses in bold following each comment. The responses to Mr.
Willi's memos are shown following Ms. Eggleston's.
1. Comment
The entire project site is located within the Watershed Protection District (WPD). It is my
understanding that the lot(s) was/were created prior to Oct. 24, 1994 and is therefore not
subject to the "Conservation Zone" requirements of the Watershed Protection District
regulations. However, the Non-Disturbance Zone should be shown on the plan as
extending 100 feet from the edge of all wetland resource areas within the watershed
district. Likewise, the Non-Discharge Zone should be shown to include all of the area
within 325 feet of the edge of all wetland resource areas within the watershed district. I
believe, therefore, that all of the proposed work falls within one of these two protection
zones. The proposed uses are allowed by Special Permit within these zones; however the
construction of a new permanent structure within the Non-Disturbance Zone also
requires a variance from the Zoning Board of Appeals. It is unclear whether any of the
proposed facilities (parking lot, golf cart parking, practice greens or paddle tennis court)
would constitute a permanent structure under the Zoning Bylaw.
Response
The 100' buffer zone note was modified to reference the Non-Disturbance zone.
The entirety of the plan is within the 325' non-discharge zone, therefore, a Line
cannot be shown. A note was added to the existing conditions plan to clarify the
non-discharge zone.
CIVIL ENGINEERS • LAND SURVEYORS • ENVIRONMENTAL CONSULTANTS • LAND USE PLANNERS
447 Boston Street (U.S. Route 1), Topsfield, MA 01983 978.887.8586 FAX 978.887.3480
Providing Professional Services Since 1978
www.morincameron.com
North Andover Planning & Conservation Page 2
June 20, 2014
2. Comment
In accordance with the Special Permit Requirements of the Watershed Protection District
(Section 4.136 (4) of the Zoning Bylaw) the application must include written certification
by a Registered Professional Engineer or other qualified scientist stating that there will
not be any significant degradation of the quality or quantity of water in or entering Lake
Cochichewick as a result of the project, as well as proof that there is no reasonable
alternative location outside the Non-Disturbance and/or Non-Discharge ones for any
discharge, structure or activity associated with the proposed use to occur. Neither of
these items was included in the materials I reviewed.
Response
We certify that there will be no degradation of the quality or quantity of water in
or entering Lake Cochichewick as a result of the project.
3. Comment
Data available from Mass GIS indicates that a significant portion of the project site is also
within the Zone A for the Lake Cochichewick public water supply; this boundary should
be shown on the plan as well. Zone A is defined by the Massachusetts Drinking Water
Regulations (310 CMR 22.02) as including:
(a) the land area between the surface water source and the upper boundary of the
bank;
(b) the land area within a 400 foot lateral distance from the upper boundary of the
bank of a Class A surface water source, as defined in 314 CMR 4.05(3)(a); and
(c) the land area within a 200 foot lateral distance from the upper boundary of the
bank of a tributary or associated surface water body.
The bordering vegetated wetland immediately northeast of the project area is a tributary
wetland; hence Zone A includes the land within 200 feet of that wetland.
Response
No response required.
4. Comment
It should be noted that Standard 6 of the Massachusetts Stormwater Standards
specifically prohibits the discharge of stormwater within Zone A, as is called for on the
proposed plan. I believe that some allowance can be made for this project since the
drainage from the existing parking lot currently discharges within Zone A with minimal
treatment, but only if it can be demonstrated that there will be a net improvement in the
water quality of the discharge as a result of the project. For the reasons outlined herein I
do not believe that has been accomplished with the proposed plan. I also recommend
against allowing the stormwater discharge(s) to be moved closer to the tributary
wetland.
Response
The proposed design calls for the discharge of stormwater into a Zone A. There has
always been discharge of stormwater into Zone A under existing conditions,
therefore, the applicant is required to demonstrate that there will be a net
North Andover Planning & Conservation Page 3
June 20, 2014
Improvement over existing conditions as a result of the project. Presently, the
existing condition of the site provides negligible treatment or mitigation of
stormwater runoff from paved areas. The proposed design will incorporate the
following:
• Deep sump catch basins and sediment forebays to provide a minimum 44%
Total Suspended Solids (TSS) removal ahead of the primary treatment
systems.
• A wet water quality swale was added to the treatment train for the lower
parking area and a portion of Great Pond Road. The rain garden was
revised to a pocket wetland/bio retention basin. The treatment train for
discharge from the entire parking area on the plan will provide 44% pre-
treatment and will exceed 80% overall TSS removal as demonstrated in the
attached TSS calculations.
• The pocket wetland/bioretention basin construction will include the
removal of existing HSG D soil in the upper C-layer which is restrictive to
groundwater recharge in the existing condition. This will create a
hydrological connection between the treatment basin and a better drained
Lower C-layer to improve recharge to groundwater at the site. Recharge
credit in the post-development mitigation calculations was conservatively
omitted. Recharge will also occur in the wet water quality swaleby
constructing a retention volume below the outlet.
• ALL primary treatment best management practices have been designed to
treat 1" of runoff over the tributary pavement area.
• All paved surfaces, both existing and proposed, will pass through the
treatment system so 100% of the runoff will be treated in the constructed
condition.
• The existing site has the capacity to provide only 17% average adjusted TSS
removal over the total impervious area for 1,840 cubic feet of total runoff
based on a 1" storm. The upper parking area is somewhat treated while the
lower parking area receives no treatment. If the above BMP's are
Implemented at the site, there will be an average adjusted TSS removal of
85% over the entire parking area for 277 cubic feet of total runoff based on
a 1" storm. It is not realistic to estimate TSS removal in parts per million
since empirical data for the runoff for the existing or proposed site
conditions is not available. However, examining the TSS removal as a
quantity based on treatment per volume of runoff quantifies the significant
Improvement to water quality In the proposed condition. 17% TSS X 1,840
CF results in 1,491 CF of "untreated" runoff in the existing condition.
Contrastingly, there will only be 42 CF of untreated flow leaving the site in
the constructed condition. This represents a 97% improvement to water
quality based on TSS removal applied to the volume of runoff.
North Andover Planning & Conservation Page 4
June 20, 2014
5. Comment
While I understand that the detailed design of the proposed practice greens are to be
done by others the plan needs to show the approximate elevation of the greens and the
limits of side slope grading, particularly next to the wetland.
Response
Grading of the proposed practice green and grading to the wetlands is now shown.
6. Comment
The plan should also include the limit of work or of vegetation clearing per the Special
Permit requirements.
Response
A Limit of Work line has been added to the plan wherever a Siltation Fence is not
shown.
7. Comment
Both the Site Plan Review requirements (Sections 8.3(5) and (6) of the Zoning Bylaw) and
the Massachusetts Stormwater Management Standards require that the rate of runoff
from the post-development site be mitigated to pre-development rates. Stormwater
management needs to be accomplished on the project site, before the runoff leaves the
property. Based on the proposed grading, all of the runoff from the Phase 1 parking area
and much of the Phase 2 parking area would drain directly onto Great Pond Road,
bypassing the detention (and treatment) Best Management Practices (BMPs) on the site.
This is both inconsistent with the requirements/regulations and a potential public safety
hazard.
Response
Discharge from both parking phases does not discharge onto Great Pond Road. It
travels through the gutter and a swale into two (2) sediment forebays and
subsequently to the wet water quality swale. 6 inch contours have been added
along Great Pond Road and the end of the pavement area to clarify flow paths.
44% pretreatment is achieved prior to flows entering the wet water quality swale.
A grading detail was also added to clarify how the catch basins will capture the
runoff from the upper parking area.
8. Comment
Soils in the project area are mapped as being Hydrologic Soil Group B and C, however
the application states that the soils are more characteristic of HSG D soils based on four
soil test pits excavated to the northeast of the existing parking area which indicated
shallow depth to groundwater and bedrock. The proposed design therefore provides
minimal recharge of stormwater runoff from the site. It is my opinion that shallow
groundwater and ledge is not inconsistent with the mapped soil types, and that the
limited soil testing conducted does not meet the parameters for soil reclassification
outlined in Volume 3, Chapter 1 of the DEP Stormwater Handbook. Absent such data, a
North Andover Planning & Conservation Page 5
June 20, 2014
waiver of the groundwater recharge requirement under DEP Stormwater Standard #3
should not be granted.
Response
We did not perform extensive testing throughout the entire area due to the
impacts from test hole excavations on the daily golf course use. However, the test
results were all generally consistent within the proposed work area and
corroborated our observations of a perched or shallow groundwater condition.
The perched water table is the result of an impermeable (till) soil Layer that
restricts the recharge of surface runoff into the better drained Lower soil layers.
The steep topography results in a condition where surface runoff flows at the
ground surface or just below it between the B horizon subsoil and C Layer. At the
point where the slope flattens, breakout is observed at the wetland or in other
micro pockets, depressions or irregularities in the hit[ slope. Areas of shallow
Ledge can also be observed in the parking area. Based on the above ground
observations, consistent soil conditions throughout the work area and other above
ground observations, it is our opinion that the soils classification most
appropriate for design was HSG D. The SCS Soils classification of mainly HSG C
soil with a small area of HSG B soil seem to be representative of the Lower C Layer
which becomes more gravelly/sandy around an approximate 48" depth.
9. Comment
On page 5 of the submittal letter the application also states that the Town's Watershed
Protection District regulations "do not promote groundwater recharge in order to insure
protection of the groundwater entering the lake." To the contrary, Section 4.136(4)(g) of
the Zoning Bylaw specifically stipulates that within the Non-Disturbance Zone and Non-
Discharge Zone any runoff from impervious surfaces shall, to the extent possible, be
recharged onsite. I would also point out that the discharge of stormwater runoff to a
surface water tributary of the lake is significantly less protective of the water quality in
the lake than recharging the runoff to the groundwater would be, since the travel time
through the groundwater is considerably longer and provides additional filtration of the
runoff.
Response
No response required.
10. Comment
Based on the four soil test pits excavated on the site, the estimated seasonal high
groundwater (ESHGW) elevation is at approximately elevation 142 in the vicinity of the
proposed bioretention basin, or about a foot above the floor of the basin. The
hydrologic analysis should therefore include no storage below ESHGW and should not
include any exfiltration from the basin.
Response
Storage below ESHGW has not been utilized in the hydrologic analysis and
exfiltration from the basin has conservatively been removed from the analysis.
North Andover Planning & Conservation Page 6
June 20, 2014
However, in reality, the pocket wetland and wet water quality swaLe will achieve
the 0.1" of groundwater recharge by establishing the recharge volume below the
outlets for these BMP's. The design complies with the recharge requirements for D
soils/bedrock to the maximum extent practicable and will result in an overall
improvement to the recharge capacity of the site by slowing down the time of
concentration and rate of stormwater runoff.
11. Comment
Since the water quality treatment in a bioretention basin is provided in large part
through filtration and pollutant uptake in the subsoil, the proximity to groundwater
would also render the proposed bioretention basin ineffective in providing the required
treatment of runoff flow to the basin. The DEP Stormwater Handbook calls for two to
four feet of soil media between the floor of the basin and ESHGW to achieve the
necessary treatment, and an additional two feet of separation if the basin is also
designed to exfiltrate. Given the shallow groundwater on the site, I suggest that
alternative BMPs such as constructed stormwater wetlands may be more suitable
measures to treat the runoff.
Response
The bioretention basin was revised to function as a Pocket Wetland/bioretention
basin. As mentioned above, the existing parent soil below the pocket wetland will
be removed down to a well-drained soil layer to allow for some recharge (even
though no credit was taken for recharge in the calculations). The basin will be
deepened by 2 feet to further ensure that it has a direct connection with the
groundwater to support wetland plantings during wet periods. It is understood
that during dry months, the pocket wetland may function more like a bioretention
basin. The "wet zone" will be seeded with a New England wetland seed mix to
ensure that regardless of hydrologic conditions in the basin, a dominant wetland
plant or plants will thrive. The sediment forebay/detention basin remained in the
design so it can function as pretreatment and as a mitigation system. The sizing of
the sediment forebay/detention basin was revised to provide the required water
quality volume below the outlet. A deep sump catch basin and the sediment
forebay will ensure 44% pretreatment prior to discharge to the pocket wetland. A
Wet Water Quality Swale was added to replace the proprietary treatment system
for the lower parking area. Two cascading sediment forebays will provide the
required 44% pretreatment prior to the wet water quality swaLe. The swaLe will be
Located within the 25 foot buffer and may require a waiver, however, it should be
noted that we are replacing an existing grassed area with a planted wet water
quality swaLe. This is an improvement to the 25' buffer to the bordering wetland.
12. Comment
Per the DEP Stormwater regulations, proprietary devices such as the proposed CDS unit
are to be used for pretreatment of stormwater runoff only, and then only if they are
placed in an off-line configuration and sized in accordance with the recent DEP
guidelines. In order to meet both Standard #4 (TSS removal) and Standard #6 (Critical
Areas) of the Massachusetts Stormwater Standards it must be demonstrated that the first
North Andover Planning & Conservation Page 7
June 20, 2014
inch of runoff from all new pavement areas on the project site will undergo treatment in
one of the Treatment BMPs identified in Table CA-2 of the Stormwater Handbook as
being suitable for use in a Critical Area. In order to demonstrate a net improvement in
water quality, existing pavement areas should also be treated.
Response
The CDS Water Quality unit was removed from the design. Runoff from the
proposed new pavement will be treated by the use of two (2) cascading sediment
forebays and the proposed wet water quality swale. A grading detail was added to
the transition between the upper and lower parking areas to ensure that all flows
are captured by the catch basins. This discharge will travel through a deep
sump/hooded catch basins and the sediment forebay/detention basin where it will
be pretreated prior to discharging to the pocket wetland. 44% pretreatment and
at least 85% total suspended solids removal will result from the proposed
stormwater system.
13. Comment
The TSS removal calculations should include all proposed treatment trains for pavement
runoff and should account for any flow that bypasses the treatment BMPs altogether.
Unless it has been confirmed that the existing catchbasin on the site is equipped with a
deep-sump and a hooded outlet it should not be included in the TSS removal
calculations.
Response
TSS removal calculations have been updated. All flows have been taken into
account and there is no bypassing of the BMPs. The existing catch basin includes a
4'sump and hood (tee) outlet.
14. 1 have the following additional comments on the hydrologic analysis submitted in
support of the application:
■ Comment
The hydrologic analysis should include the 1-year storm, as is required by the North
Andover Wetlands Bylaw.
Response
The hydrologic analysis of the 1 year storm is included.
• Comment
The model should account for all drainage onto the project site, including that to the
south and east of the interior lot lines.
Response
The model accounts for all drainage onto the project site. A swale was added
along the parcel perimeter to ensure than offsite tributary area (not surveyed)
does not enter the treatment train for the parking area stormwater system.
North Andover Planning & Conservation Page 8
June 20, 2014
■ Comment
The model should include control points at all locations where runoff leaves the
project site, e.g. Great Pond Road,
Response
Runoff does not leave the site.
■ Comment
All vegetative cover on the existing site should be assumed to be in "good"
condition, not "fair" or "poor".
Response
The model has been changed to show good soil conditions.
■ Comment
In the post-development hydrologic model, Subcatchment P113 should be routed to
P3A, or the two combined. Based on the proposed grading it should not be routed
through the detention basin and bioretention basin.
Response
A grading detail was added to clarify how the catch basins will capture the
runoff from P1113.
15. Comment
As is indicated in the Stormwater Checklist and identified on the plans, the proposed
project entails more than an acre of land disturbance and is subject to the requirements
of EPA's Construction General Permit (CGP). It will require filing for coverage under the
CGP and the preparation and implementation of a Stormwater Pollution Prevention Plan
(SWPPP) prior to construction. The SWPPP should be prepared in conjunction with the
site contractor and should include a construction sequence aimed at minimizing the
duration of exposure of unstabilized soils on the project site. it should also address
stabilization/covering of soil stockpiles and any anticipated dewatering measures. The
SWPPP should be reviewed and approved by the Planning Board and/or Conservation
Commission prior to any disturbance on the site, and the board(s) may want to request
documentation of coverage under the CGP and copies of the monitoring reports.
Response
No response necessary.
Responses to North Andover Division of Public Works comments in memo from Mr. Gene Willis
dated 5/23/14.
1. Culvert to the northeast of WF C9 will be removed and replaced with regraded
swale and shoulder.
2. Volume and velocity of runoff will be added to report. Swale along Great Pond
Road will be shown with 6" contours and is sized to carry the design flows.
3. The driveway entrances are designed to DPW standards with a negative pitch away
from Great Pond Road.
4. There is a negative pitch leaving Parking Phase 1; 100 % of stormwater runoff is
captured in the gutter, swale and wet water quality swale.
North Andover Planning &Conservation Page 9
June 20, 2014
Responses to North Andover Division of Public Works comments in memo from Mr. Gene Willis
dated 6/11/14.
1. The sewer connects to the pump station for the country club. The discharge from
the pump station goes to the municipal sewer. A note was added to the plan to
require the contractor to notify DPW to inspect the sewer cLeanouts.
2. The water service was marked out on the premise. The service is metered by the
town.
3. Not applicable.
4. Not applicable.
5. Cross section references were added to the plan and details.
6. Not applicable.
7. A detail was added illustrating the road/parking space cross section.
B. A detail was added illustrating the swaLe at the culvert removal along the road.
We trust these responses satisfy the questions and concerns about the project. If you have any
additional questions or comments, please do not hesitate to contact our office at (978) 887-
8586 or speak with us at the next public hearing for the project.
Sincerely,
jTheMorl eron oup, Inc. N OF MqSSCOTT P.CAMERON
IVIL
mero P.E. 0 No 47601
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cc: North Andover Country Club
Eggleston Environmental
Gene Willis, PE NA DPW
X:\NACC\3006\Docs\Drainage\North Andover Country Clubresponse to review.docx