HomeMy WebLinkAbout- Consultant Review - 1600 OSGOOD STREET 10/3/2019 LANSAN Memorandum
361 Newbury Street,5th Floor Boston,MA 02115 T:800.952.6426
To: Monica Gregoire- Horsley Witten Group
From: Timothy O'Neill
Nathan Kirschner
Copied: Jean Enright-Town of North Andover
Sean O'Brien- Hillwood
John Smolak- Smolak &Vaughn
Date: October 3, 2019
Re: Stormwater Review
Proposed Redevelopment
1600 Osgood Street- North Andover, MA
Langan Project No.: 140182701
This memorandum addresses comments raised by your office in your September 10, 2019
memorandum to Ms. Monica Gregoire. Each question/comment is followed by Langan, Smolak
and Vaughan and Hillwood's response in bold and italics font and is stated below:
Stormwater Management Design Peer Review Comments:
HW offers the following overall comments concerning the stormwater management design as
per the Massachusetts Stormwater Handbook (MSH) dated February 2008, the North Andover
Stormwater Management and Erosion Control Regulations (Stormwater Regulations) adopted
February 5, 2011, and the North Andover Stormwater Management and Erosion Control Bylaw
(Bylaw).
The comments below correlate with the MSH standards and where the more stringent Town
requirements are applicable additional comments are noted. More than 50% of the proposed
development can be considered redevelopment. The area that is currently pervious must be
treated as new development.
1. Standard 1 states that no new stormwater conveyances may cause erosion in wetlands
of the Commonwealth.
a. The Applicant will utilize existing discharge points from the site and create no new
discharges. The Applicant has not demonstrated that there is sufficient outlet
protection at the existing culvert locations to withstand projected velocities from
the 2-year storm event. HW recommends that the Applicant provide these
calculations and if necessary, calculations for the sizing of riprap aprons.
MEMO Langan Project No. 140182701
September 11, 2019- Page 2 of 7
Comment Response: Under existing conditions, large grated concrete bulk head
discharge structures exist at 3 of the four discharge locations. The fourth discharge
location is an existing 42 inch RCP that runs beneath the rail road and discharges
directly to the Merrimack River.All of the proposed discharge locations were visual
inspected by our office on October 25,2019 and showed no signs of erosion. In the
proposed condition the existing discharge location will remain unaltered as the
stormwater management design reduces or matches peak flows to each discharge
location and will not result in an increased risk of erosion. Additionally, given the
proximity to existing inland wetland features it was agreed upon by both Langan
and Epsilon, the project's wetland consultant, that given the condition of the
outfalls and their proximity to existing wetlands any work at these locations would
have an adverse impact. Photos of the existing discharge locations have been
included in Attachment A of this document.
2. Standard 2 requires that post-development runoff does not exceed pre-development
runoff off-site. For a redevelopment project per MassDEP this standard must be met to
the maximum extent practicable.
a. Based on review of the Hydraflow Report and drawings, HW has the following
comments:
• Pond D-1 does not reflect infiltration basin D-1 on Sheet GC103. The 10"
overflow pipe on the drawing has an invert of 41.5', whereas in Hydraflow
it is listed at 41.55'. The length of the 10" pipe also does not reflect the
length in the model. The model shows an 8" outlet structure at elevation
41.25 and a weir at elevation 42.5' marked as inactive which are not shown
on Sheet GC103. HW recommends that the Applicant reconcile the model
with the drawings.
Comment Response: The outlet structure of Infiltration Basin D-1 has
been revised to be consistent with the Hydraflow model.
• Pond A-1.2 does not reflect raingarden A-1.2 on Sheet CG106. The
drawings show a 4" underdrain at elevation 47.50 with a zero percent
slope, whereas the model shows an 8" pipe at elevation 47.50 with a 2%
slope.
Comment Response: The outlet structure of Infiltration Basin A-1.2
has been revised to be consistent with the Hydraflow model.
Pond A-1.4 does not reflect extended dry detention basin A-1.4 on Sheet
CG105. The drawing shows a 4" orifice at elevation 40' and a 4"underdrain
at invert elevation 47.5'. The model shows a 4" orifice at elevation 41, 8-
inch orifice at elevation 39'.
Comment Response: The outlet structure of Infiltration Basin A-1.4
has been revised to be consistent with the Hydraflow model.
L,ANGAN
MEMO Langan Project No. 140182701
September 11, 2019- Page 3 of 7
• Pond A-1.5 does not reflect raingarden A-1.5 on Sheet CG106. The
drawings show a 4" underdrain at elevation 41.0 with a zero percentslope,
whereas the model shows an 8" pipe with a 1 % slope.
Comment Response: The outlet structure of Infiltration Basin A-1.5
has been revised to be consistent with the Hydraf/ow model.
• Sheet CG107 labels the wet pond as "A-S", which should be labeled "A-
2".
Comment Response: The label for Wet Pond A-2 has been corrected.
• The emergency spillway invert elevation is not labeled for Pond B-1 on
Sheet CG108. The leader for the outlet structure (OCS B-1) has a conflict
with the wetland limit lines, which blocks the invert elevation for the (2)
24" pipes.
Comment Response: The emergency spillway elevation for Extended
Dry Detention Pond B-1 has been labeled and the label for OCS B-1
has been shifted to avoid text conflicts.
• Pond C-2, Sheet CG105 indicates that the top of the pond is at elevation
39.70', whereas the model shows 39.50'. The leader for OCS C-2 and
associated orifices and pipes do not match what is in the Hydraf low model.
Comment Response: The outlet structure and top of pond elevation
of Infiltration Basin C-2 has been revised to be consistent with the
Hydraflow model.
HW recommends that the Applicant reconcile the model with the drawings.
b. The Applicant provides flared end sections and outlet protection for all pipes
discharging into ponds or raingardens; however, calculations and associated size
of the stone has not been provided. HW recommends that the Applicant provide
the size of the stone and supporting calculations.
Comment Response: The MassDOT standard detail for "Stone Pipe Ends for
Pipes 24 inches and less in Dia." has been included in the GC500 series
sheets of the design set. The detail "Preformed Scour Hole for Pipes Larger
than 24 Inches"has been included in the GC500 series sheets of the design
set.
C. The Applicant provided sizing calculations for Grass Swale A-1.2 and indicates that
the swale should be 2-feet deep with 1-foot of freeboard; however, the swale is
modeled as 1-foot deep. HW recommends that the Applicant revise the model to
accurately reflect the design.
L,ANGAN
MEMO Langan Project No. 140182701
September 11, 2019- Page 4 of 7
Comment Response:Grass Swale A-1.2 was intended to be 1 foot deep with
an additional 1 foot of freeboard. The report has been revised to state this.
d. In both the existing condition and proposed condition subcatchment areas,
potential run-on to the project area from adjacent properties of the parcel is not
captured in the calculations. HW recommends that the Applicant extend the
watershed boundaries beyond the limit of work and property lines to quantify
potential run-on to the project.
Comment Response: Based on discussions with your office on September
23' 2019, catchment areas where reviewed and found to appropriately
capture the extents of the project watershed. The discussion identified
curbing and catch basins placed at site entrances along the Osgood Street
frontage that divert run off into Osgood Street drainage system.
e. The Applicant has not included test pit information including groundwater
elevation and infiltration rates under each of the proposed infiltration systems in
the Stormwater Management Report. On page 12 of the Stormwater
Management Report, the Applicant indicates that additional testing will be
required to confirm groundwater elevation and infiltration rates. HW recommends
that if the Board approves this Applicant, they include a condition that requires
the Applicant to provide estimated seasonal high groundwater elevation and
infiltration rates in the proposed location of the infiltration systems for the Board
to review, prior to construction of these practices.
Comment Response: The applicant has been made aware of this comment.
3. Standard 3 requires that the annual recharge from post-development shall approximate
annual recharge from pre-development conditions.
a. The Applicant indicates that an Activity Use Limitation (AUL) for portions of the
site prohibits groundwater recharge. Therefore, recharge in areas where an AUL
exists has been compensated for through infiltration practices located in areas
outside of the AUL. Proposed practices within the AUL have been lined to prevent
infiltration. The Applicant has provided enough groundwater recharge to meet
Standard 3.
Comment Response:Noted.
4. Standard 4 requires that the stormwater system be designed to remove 80% Total
Suspended Solids (TSS) and to treat 0.5-inches of volume from the impervious area for
water quality.
a. The site is considered a Land Use of Higher Potential Pollutant Load (Standard 5),
therefore the Applicant is required to treat 1.0-inches of the impervious area for
water quality. The Applicant has elected to treat 1.0-inch for the parking areas and
L,ANGAN
MEMO Langan Project No. 140182701
September 11, 2019— Page 5 of 7
0.5-inch for rooftops. The Applicant has provided practices to manage the water
quality volume to meet the requirements under Standard 4.
Comment Response:Noted.
b. TSS calculations are provided in the Stormwater Management Report and indicate
that all proposed BMPs meet the 80% reduction in TSS except for Pond A-1.4
(72%). Since the project is a redevelopment, the Applicant needs to meet this
standard to the maximum extent practicable. Based on review of the information
presented, it appears that the Applicant has met the requirement to the maximum
extent practicable.
Comment Response:Noted.
5. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads
(L UHPPL).
a. The Applicant has stated that because the project will generate more than 1,000
vehicle trips per day for both Lot A and Lot B, the site is considered a high
pollutant load generator. Therefore, the Applicant has increased the WQv
(Standard 4) for the parking associated with Lots A and B from 0.5 inches to 1.0
inches. Further, any proposed rain gardens within the AUL zone have been lined
to prevent infiltration.
Comment Response:Noted.
6. Standard 6 is related to projects with stormwater discharging into a critical area, a Zone
II or an Interim Wellhead Protection Area of a public water supply.
a. The project site does not discharge into a critical area therefore Standard 6 is not
applicable to this project.
Comment Response:Noted.
7. Standard 7 is related to projects considered Redevelopment.
a. The project site is considered a redevelopment. Therefore the Applicant 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.
Once the Applicant addresses the comments in this letter, HW believes that the
proposed project will comply with Standard 7.
L,ANGAN
MEMO Langan Project No. 140182701
September 11, 2019- Page 6 of 7
Comment Response:Noted.
8. Standard 8 requires a plan to control construction related impacts including erosion,
sedimentation or other pollutant sources.
a. HW recommends that the Applicant include a construction sequence on the Plan
Set, specifically noting the methods to control erosion as required in Section 8.2
of the North Andover Stormwater Management and Erosion Control Regulations.
Comment Response: The soil erosion &sediment control plans have been
separated into three phases. The three phases roughly cover the following
activities:
Phase 1:Initial construction staging and site demolition
Phase 2.Mass earthwork, retaining wall construction and pad preparation
Phase 3: Utility installation, building construction,paving and Landscaping.
As discussed with your office, the intent of this phasing is to give a general
overview of the project but allow the contractor to refine the work within each
phase to accommodate the overall project schedule. Further construction
sequencing and phasing is to be coordinated with the contractor and property
owners.
9. Standard 9 requires a Long-Term Operation and Maintenance (O&M) Plan to be provided.
a. The Applicant has provided an O&M Plan with a Log Form and budget. HW
recommends that the Applicant provide a BM P Location Map (with snow storage
locations) and that the O&M Plan be signed by the property owner.
Comment Response: A stormwater management location figure identifying the
responsible parties for maintenance has been included in appendix G of the
Stormwater Management Report. Based on our discussions with your office and
town staff it is anticipated that the final signatures on this plan will be required as
a condition of approval.
b. HW requests that the Applicant clarify how solid waste will be removed from the
property. Is there a need for dumpsters?
Comment Response: A trash compactor will be installed at the new loading bay
along the north western face of existing building 20 on Lot A. Lot B manages all solid
waste internal to the building. Both facilities will contract with waste disposal
companies to truck waste off site in compliance with local and state regulations.
L,ANGAN
MEMO Langan Project No. 140182701
September 11, 2019- Page 7 of 7
10. Standard 10 requires an Illicit Discharge Compliance Statement to be provided.
a. The Applicant provided an Illicit Discharge Compliance Statement as Appendix I in
the Stormwater Management Report; however, the owner, address, telephone
number and signature are missing. HW recommends that the Applicant provide a
complete illicit discharge statement signed by the property owner prior to any land
disturbance.
Comment Response:Illicit discharge compliance statements have been included for
Lot A and Lot B. Based on our discussions with your office and town staff it is
anticipated that the final signatures will be required as a condition of approval
11. Miscellaneous Comments:
a. Sheet CG103 shows a sump pump at MH4 which ultimately discharges to the
closed storm drain network. It is unclear what the sump pump will be used for.
HW recommends that the Applicant provide additional information on the use of
the sump pump and the nature of the water to be pumped to the storm drain
network.
Comment Response: The sump pump is required to elevate stormwater runoff from
the small catchment area (±0.1 ac) contributing to the truck well. The newly
proposed truck well drainage structure invert was required to be at an elevation
that would not accommodate gravity conveyance to the retention system.
b. In accordance with Town Regulations, the Applicant should include the names of
the abutters on the plan set. HW recommends that the Applicant include the
abutters names per Section 7.1 d) of the North Andover Stormwater Management
and Erosion Control Regulations.
Comment Response: Immediate abutter information for each parcel can be found
on sheet VL 101 "AL TA/NSPS Land Title Survey-
C. In accordance with Town Regulations, the Applicant should compare total volume
of discharge at each control point for the design storms. HW recommends that
the Applicant include the total volume pre- and post-development per Section
7.2.B.f of the North Andover Stormwater Management and Erosion Control
Regulations.
Comment Response: A volume discharge comparison table has been included in
section 2.6 of the revised stormwater management report.
L,ANGAN
MEMO Langan Project No. 140182701
September 11, 2019— Page 8 of 7
Conclusions
HW recommends that the Planning Board require that the Applicant address these
comments as part of the Board's review process. The Applicant is advised that provision
of these comments does not relieve him/her of the responsibility to comply with all Town
of North Andover Codes and By-Laws, Commonwealth of Massachusetts laws, and
federal regulations as applicable to this project. Please contact Renee Bourdeau at 774-
413-2900 ext. 402 or at rbourdeau@horsleywitten.com if you have any questions
regarding these comments.
Comment Response:Noted
We trust these responses and revised materials adequately address your comments and
concerns. Please feel free to contact me at (203) 562-5771 with any questions or should you
require additional information.
\\langan.corr\data\NH\data7\140182701\Project Data\Correspondence\Comment Response Letters\2019-09-10 Horsely Whitten Stormwater\2019-10-03 HW Stormwater
Comment Response 1600 Osgood Street.docx
LANGAN
MEMO Langan Project No. 140182701
September 11, 2019— Page 9 of 7
APPENDIX A
Existing Outfall Images
L,AN AN
MEMO Langan Project No. 140182701
September 11, 2019— Page 10 of 7
Southwest Discharge to Concrete Channel (Watershed A)
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MEMO Langan Project No. 140182701
September 11, 2019— Page 11 of 7
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September 11, 2019— Page 12 of 7
Southwest Concrete Channel Discharge Structure at Property Line
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Westerner Discharge Structure at Property Line from Field
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MEMO Langan Project No. 140182701
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Northwestern wetland Discharge Structure at Property Line
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Onsite Discharge from Eastern Parking Lot to Remain on Lot A to
Wetlands along Lot C Osgood Frontage
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