HomeMy WebLinkAbout2024-08-13 Stormwater Review Refiling WITHDRAWN Horsley Witten Group
Sustainable ,environmental Solutions
112 Water Street•V Floor•Boston,MA02109 �h
857-203.8193 horsteywMen.com
January 12, 2024
Ms. Jean Enright, Planning Director
North Andover Planning Board
120 Main Street
North Andover, Massachusetts 01845
Ref: Initial Stormwater Peer Review
189 Willow Street
North Andover, Massachusetts
Dear Ms. Enright and Board Members:
The Horsley Witten Group, Inc. (HW) is pleased to provide the North Andover Planning Board
with this letter report summarizing our initial review of the stormwater management for the
proposed Office Building at 189 Willow Street in North Andover, Massachusetts. Hayes
Engineering, Inc. has submitted an application on behalf of Vincent J. Grasso (Applicant). The
project involves the construction of a commercial 6,667 square foot (sf) single story building on
a 3.34-acre parcel. The site is currently undeveloped and includes a large bordering vegetated
wetland (BVW) and bordering land subject to flooding (BLSF). The proposed area of
disturbance includes filling a portion of an isolated vegetated wetland (IVW) and creating 610 sf
of IVW and 4,438 sf of BVW. The development will require an Order of Conditions from the
North Andover Conservation Commission. The Applicant is applying to the Planning Board for a
Special Permit pursuant to Section 195-8.13.8 and Site Plan Review pursuant to Section 195-
8.11.A (1) of the North Andover Zoning By-Laws. The proposed stormwater management
includes a sediment forebay, a water quality swale, and an extended detention basin which
overflows to the BVW via an 8-inch pipe with a level spreader.
The following documents and plans were received by HW:
• q
Application for Permits at 189 Willow Street in the Town of North Andover,
Massachusetts, prepared by Hayes Engineering, Inc., dated November 8, 2023, includes
Stormwater Management Report, dated November 6, 2023 (244 pages);
o Exterior Building Elevations, Sheet A2.00, prepared by Finlo Architects, dated November
6, 2023; and
• Special Permit Site Plan, #189 Willow Street, North Andover, Mass., prepared by Hayes
Engineering, Inc., dated November 7, 2023, including:
o Cover Sheet C1
o Existing Conditions C2
o Erosion Control C3
o Proposed Site Plan C4
o Landscaping C5
o Detail Sheet C6
HorsleyWitten.com PHorsloyWittenGroup Horsley Witten Group, Inc.
Town of North Andover
January 12, 2024
Page 2 of 6
Stormwater Management Design Peer Review
In accordance with the North Andover Zoning Bylaw §195-8.14. E. (8) A Stormwater
management plan is required for all site plan review applications. The stormwater management
plan shall be prepared in accordance with the latest version of the Massachusetts Stormwater
Handbook (MSH) and demonstrate full compliance with the Massachusetts Stormwater
Standards and the North Andover Stormwater Management and Erosion Control, Chapter 165
of the Town Bylaws. Chapter 165 further references Chapter 250. Stormwater Management and
Erosion Control.
HW offers the following comments concerning the stormwater management design. We have
used the Massachusetts Stormwater Standards as the basis for organizing our comments.
However, in instances where the additional criteria established in §250-27 of the North Andover
Code requires further recommendations; we have referenced these as well.
1. Standard 1: No new stormwater conveyances (e.g., outfalls) may discharge untreated
stormwater directly to or cause erosion in wetlands or waters of the Commonwealth.
a. The revised application dated November 2023 did not include watershed maps.
However, the plans submitted in April 2023 did. The Pre-Development Conditions
Watershed Map dated November 21, 2022, does not include any elevations. The
Applicant has stated that the site drains to the adjacent BVW and has defined the
catchment area using the edge of the large BVW as the design point. The Existing
Conditions plan revised March 23, 2023, Sheet C2, includes some elevations but it is
difficult to confirm the contour lines drawn with the elevations listed. The Existing
Conditions Plan dated November 7, 2023 includes some elevations and no spot grades.
The site appears to include elevations between 235 and 238, however there are many
contours that are not labeled and many spot grades that do not appear to correlate with
the adjacent contour line drawn. HW is not able to confirm the Pre-Development
Watershed area with the information provided and we recommend that the Applicant
clarify the contours on the site specifically the contour associated with elevation 237. HW
further notes that the Applicant appears to use the edge of the property boundary as a
catchment area divide lint?. HW recommends that the Applicant clarify if any offsite runoff
from the roadway or from an adjacent property is flowing onto the site and should be
managed by the proposed stormwater system.
b. HW notes that there is an IVW in the center of the upland area. As noted above it is
difficult to understand the elevations on the Existing Conditions plan but it would be
reasonable to assume that a portion of the site drains towards this IVW or rainwater that
falls on the IVW may not flow out of it. HW recommends that the Applicant clarify the
watershed flowing towards and within the IVW.
c. HW recommends that the Applicant label the level spreader on the Proposed Site Plan
and provide calculations to confirm the size of the level spreader is adequate to prevent
erosion in the wetlands.
2. Standard 2: Stormwater management systems shall be designed so that post-development
peak discharge rates do not exceed pre-development peak discharge rates.
a. In accordance with §250-22 B. (6) a summary of pre- and post-development peak rates
and volumes of stormwater demonstrating no adverse impacts should be provided as
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part of the narrative, The Applicant has provided the peak flows but not the peak
volumes for the 2-year, 10-year, 25-year, and 100-year storm events in the Stormwater
Management Report. HW recommends that the Applicant include a table with peak
volumes as required.
b. In accordance with §250-22 B. (5) (a) a summary of proposed land area to be disturbed
and existing and proposed impervious area should be provided as part of the narrative.
HW recommends that the Applicant include the proposed land area to be disturbed and
the existing and proposed impervious area in the narrative.
c. The Applicant has included subcatchment area P.1 that is called Driveway to CB. It
appears that this small area of the site will be directed towards Willow Street and the
municipal drainage system. HW recommends that the Applicant confirm that the
additional driveway apron to Willow Street has been modeled under Pre- and Post-
development conditions. HW also recommends that the Applicant confirm why this area
is modeled towards the Design Point (BVW) if it is being captured by the municipal
system in the roadway.
d. The Applicant has included subcatchment area P.2 called Roof to Rain Garden. The
total area is 7,089 sf, however the building is only 6,667 sf. It is not clear why the
catchment area is larger than the building footprint. It is also not clear where the rain
garden is. HW recommends that the Applicant clarify subcatchment P.2.
e. The Applicant has included a spillway from the JVW Storage Pond at elevation 237.00 in
the HydroCAD model. The plan set does not appear to include a spillway. HW
recommends that the Applicant confirm that the HydroCAD model and plans are
consistent.
f. It appears that the Applicant has included the volume of the treatment swale in the
HydroCAD model of the Detention Basin. HW recommends that the Applicant confirm
that the storage volume in the Detention Basin does not include the volume in the swale.
g. The Applicant has used precipitation values equal to or greater than the values provided
by National Oceanic and Atmospheric Administration (NOAA) Atlas 14 for the 24-hour
storm events, as outlined in §250-23 E. (19). No further action required.
3. Standard 3 requires that the annual recharge from post-development shall approximate
annual recharge from pre-development conditions.
a. The Applicant has stated that because the existing site consists of Hydrologic Soil Group
(HSG) D it has only provided recharge to the maximum extent practicable. HW agrees
that groundwater is high and the HSG of D makes recharge difficult. However, the
exfiltration rate of the soil should be considered. The Applicant is including the storage
within the treatment swale for potential recharge meeting the requirements for HSG D.
However, the Applicant has not provided any soil test logs to indicate where ground
water has been observed beneath the treatment swale. HW recommends that the
Applicant provide soil test logs to confirm the depth to Estimated Seasonal High
Groundwater (ESHGW) and the soil texture. The soil test logs may indicate soil with a
higher infiltration rate than the 0.05 inches per hour assumed.
b. The Applicant has provided a drawdown calculation using the required recharge volume
of 147 cf. The value used should be the total volume that can be contained prior to
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flowing out of the treatment swale, which appears to be 428 cf based on the Treatment
Swale Sizing Calculation. HW recommends that the Applicant revise the drawdown
calculations to confirm that water will not be sitting in the treatment swale for an
extended period of time.
4. Standard 4 requires that the stormwater system be designed to remove 80% Total
Suspended Solids (TSS) and to treat 9-inch of volume from the impervious area for water
quality.
a. HW recommends that the Applicant provide a detail for the Treatment Swale, including
the check dams and weir if applicable at the northern edge.
b. HW recommends that the Applicant provide a detail for the forebay with clear
dimensions and materials. HW was not able to confirm the size of the forebay with the
information provided.
c. Per§250-23 B (1) the Applicant is required to remove 90% of the average annual load of
Total Suspended Solids (TSS) and 60% of the average annual load of Total
Phosphorus. This can be achieved by "retaining the volume of runoff equivalent to, or
greater than, one (1.0) inch multiplied by the total post-construction impervious surface
area on the new development site". The Applicant has provided water quality volume
calculations demonstrating that the treatment swale retains '/2-inch multiplied by the
impervious surface. HW recommends that the Applicant demonstrate that it is complying
with §250-23 B (1).
5. Standard 5 is related to projects with a Land Use of Nigher Potential Pollutant Loads
(LUHPPL).
a. The multi-tenant office building is not considered a LUHPPL. Standard 5 is not
applicable.
6. Standard 6 is related to projects with stormwater discharging into a critical area, a Zone 11, or
an Interim Wellhead Protection Area of a public water supply.
a. The site is not within a critical area. Standard 6 is not applicable.
7. Standard 7 is related to projects considered Redevelopment.
a. The project is not considered a redevelopment. Standard 7 is not applicable.
8. Standard 8 requires a plan to control construction related impacts including erosion,
sedimentation, or other pollutant sources.
a. The Applicant has proposed a 12-inch straw wattle for erosion protection. The limit of
work is within the 25-foot no disturb zone of the adjacent resource area. HW
recommends that the Applicant propose a much more robust erosion control barrier for
this project. HW suggests that the Applicant consider using a 12-inch compost sock with
a siltation fence instead of a straw wattle.
b. HW recommends that the Applicant add a note stating, prior to any land disturbance
activities commencing on the site, the contractor shall physically mark the limits of no
land disturbance with tape, signs, or orange construction fence, so that workers can see
the areas to be protected. The physical markers shall be inspected daily.
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c. HW recommends that the Applicant include a construction entrance detail.
d. It appears that there may be trees located within the limit of work. HW recommends that
the Applicant provide protection for any trees proposed to remain and clarify the extent
of trees to be removed as part of the proposed development.
9. Standard 9 requires a Long-Term Operation and Maintenance (O & M) Plan to be provided.
a. The Applicant has provided a Long-Term Operations and Maintenance Plan in Appendix
E of the Application. HW recommends that the Applicant provide an O&M Plan as a
standalone document to be signed by the owner, which includes the following:
i. Parties responsible for operation and maintenance;
ii. An example maintenance log or checklist for each stormwater practice that the
homeowner can use to log maintenance;
iii. A schedule for implementing routine and non-routine maintenance tasks to be
undertaken after construction is complete;
iv. An estimated operations and maintenance budget;
v, A simple sketch that is drawn to scale and shows the location of all stormwater
practices requiring Inspections and long-term maintenance; and
vi. Locations for snow storage.
10. Standard 10 requires an Illicit Discharge Compliance Statement be provided.
a. HW recommends that the Applicant provide a signed Illicit Discharge Compliance
Statement prior to land disturbance. The Planning Board may choose to consider
requesting receipt of this signed statement as a condition of approval.
11. Isolated Vegetated Wetland (IVW)
a. The Applicant is proposing to fill approximately 3,730 sf of IVW in the center of the
upland while retaining 1,493 sf and creating 610 sf. It is not obvious on the plan set the
depth of this wetland area. However, the spot grades range from 236.78 to 237.85,
Assuming the area has a potential to pond to 6 inches it would have a storage capacity
of 2,610 cf. The Applicant has provided an area to replicate the IVW with a surface area
of 2,100 sf and a storage volume of 1,188 cf. HW recommends that the Applicant clarify
the volume of IVW under existing and proposed conditions and confirm it is modeling the
IVW in a similar manner under pre- and post-development conditions.
12. 100-year Flood Plain
a. The Federal Emergency Management Agency (FEMA) has designated the entire parcel
as Zone A. The definition of a Zone A is `Areas with a 1% annual chance of flooding and
a 26% chance of flooding over the life of a 30-year mortgage. Because detailed analyses
are not performed for such areas; no depths or base flood elevations are shown within
these zones." The Applicant has included Letters of Map Amendment (LOMA) for two
adjacent properties dated 2014 and 2016, stating that the 100-year flood elevation for
189 Willow Street should be based on these adjacent LOMAs. Both LOMAs specifically
state that the flood elevation is subject to change. HW is not confident that the flood
elevation for 189 Willow Street in 2024 should be based on a flood elevation determined
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in 2014 by approximate methods. HW recommends that the Applicant apply for a
property specific LOMA to verify the actual flood elevation for this site.
b. HW notes that during the various storm events in January 2024, Willow Street had
flooding issues. HW is concerned that filling the IVW which may provide flood storage
may create additional flooding downstream of the site.
c. The Existing Conditions plan includes a reference which states "Approx. Extent of Zone
AIBLSF (El. 263.5) —See Note 4." HW was not able to locate Note 4 and believes that
the elevation listed is not accurate.
d. The Applicant has included in its application a table illustrating the Bordering Land
Subject to Flooding (BLSF) Fill and Created volumes. HW was not able to confirm these
values with the information provided on the plan set. As noted previously the contours
are difficult to read and need further clarification. For example, there is a spot grade of
elevation 236.45 near wetland flag WF B7 which is not included in the shaded area
designated as BLSF noted in the narrative as being elevation 236.5.
Conclusions
HW recommends that the Planning Board require that the Applicant provide a written response
to 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 Janet Bernardo at 508-833-6600
or at jernardo@horsleywitten.com if you have any questions regarding these comments.
Sincerely,
HORSLEY WITTEN GROUP, INC.
Janet Carter Bernardo, P.E.
Associate Principal
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1/16/24,8:59 AM Town of North Andover Mail-RE: 189 Willow Street-updated letter
._. ......._....
NORTH ANI)OVER
Massachusrlks Jean Enright <jenright@ north an dove rma.gov>
RE: 189 Willow Street - updated letter
Janet Bernardo <jbernardo@hors]eywitten.com> Tue, Jan 16, 2024 at 8:55 AM
To:Jean Enright <jenright@northandoverma.gov>
Cc:Amy Maxner<amaxner@northandoverma.gov>
HI Jean,
While working on the North Andover Mall flood plain I went back to the flood plain for Willow Street. The Feb
2023 preliminary plan has expanded the flood plain in the area. Please see attached,
Thanks, Janet
Janet Carter Bernardo,RE.
Horsley Witten Group
Office:857-263-8193
From:Jean Enright<jen rig ht@northandoverma.gov>
Sent: Friday,January 12, 2024 8:21 AM
To:Janet Bernardo<jbernardo a horsleywitten.com>
Subject: Re: 189 Willow Street- updated letter
Hi Janet,
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