HomeMy WebLinkAbout2019-06-04 Stormwater Review 0
Horsley Wiffen Group
Sustainable Environinental Solutions
294 Washtn9ton Street-Suite 801•Boston,NIA 02108
857-263-8193 horaleywitten.com
May 1, 2019
Ms. Monica Gregoire, Staff Planner
Planning Department
Town of North Andover
120 Main Street
North Andover, Massachusetts 01845
Ref: 2nd Stormwater Review
Enterprise Bank, 247 Chickering Road
North Andover, MA
Dear Ms. Gregoire and Board Members:
The Horsley Witten Group, Inc. (HW) is pleased to provide the North Andover Planning Board
with this letter report summarizing our second review of the Stormwater Management Report
and permitting plans for the proposed Enterprise Bank facility and associated parking at 247
Chickering Road, North Andover, MA. The plans were prepared for Enterprise Bank (Applicant)
by MHF Design Consultants, Inc. A portion of the project is located within the 100-foot buffer of
an adjacent wetland resource area and therefore is within the jurisdiction of the North Andover
Conservation Commission. Incorporating LID practices is an important criteria to the
Conservation Commission and particularly relevant in meeting the requirements of North
Andover's municipal separate storm sewer systems (MS4) permit.
The following additional documents and plans were received by HW in response to our initial
peer review letter dated March 28, 2019:
• Letter to North Andover Planning Board in response to peer review comments, prepared by
MHF Design Consultants, Inc., dated April 24, 2019;
• Stormwater Management Report, Proposed Site Re-Development, 247 Chickering Road,
North Andover, MA, prepared by MHF Design Consultants, Inc., revised April 24, 2019; and
• Site Re-Development Plans for Assessors Map 46 Lot 4, 247 Chickering Road, North
Andover, Massachusetts 01845, prepared by MHF Design Consultants, Inc., revised April
15, 2019, which include:
o Title Sheet 1 of 11
a Existing Conditions Plan 2 of 11
• Demolition Plan 3 of 11
o Site Plan 4 of 11
o Grading & Drainage Plan 5 of 11
o Utilities Plan 6 of 11
o Erosion & Sediment Control Plan 7 of 11
a Landscape Plan 8 of 11
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Town of North Andover
May 1, 2019
Page 2 of 7
o Detail Sheet 9 of 11
o Detail Sheet 10 of 11
• Detail Sheet 11 of 11
• Lighting Proposal (LSi) 1 of I
• Truck Turn Plan (MHF Design) 1 of 1
• Building Elevations (Cube 3) 1 of 1
Stormwater Management Design Peer Review
The following comments correlate with the HW initial peer review dated March 28, 2019.
Additional comments are added in bold font.
1. Standard 1 states that 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 Applicant is proposing to discharge stormwater to a closed drainage system in
Chickering Road. Under existing conditions, the runoff from the site appears to sheet
flow onto Chickering Road and there are no obvious catch basins. HW recommends that
the Applicant clarify the final discharge point and verify that the stormwater conveyance
will not cause erosion in wetlands of the Commonwealth.
The Applicant is reducing the impervious area currently sheet flowing off the site
and discharging onto the state roadway. The final discharge point will be
permitted through MassDOT. As currently designed this project will likely not
create erosion in a wetland.
b. Route 125/133 is a State Highway. HW recommends that the Applicant confirm that
MassDOT will allow the property to discharge into the state stormwater system. The
Applicant has noted on the plans that the drainage improvements in the public right-of-
way are to be done per Plan Reference#2 and coordinated with MassDOT. HW was not
able to verify Plan Reference#2, Therefore, we further recommend that the Applicant
provide the Planning Board with the appropriate documentation.
The Applicant has stated that it is in discussions with MassDOT. HW is aware that
in other communities MassDOT is not receptive to allowing private property
owners to discharge stormwater onto state roadways. The Planning Board may
choose to condition this approval requiring the Applicant to provide the approval
from MassDOT prior to any land disturbance or to design a stormwater system
that will not discharge to Route 125/133.
2. Standard 2 states that stormwater management systems shall be designed so that post-
development peak discharge rates do not exceed pre-development peak discharge rates.
a. The Applicant has provided data for two test pits; however, the location of the test pits is
not indicated on the plans. According to NISH Vol. 2, Ch. 2, p. 104 each infiltration
system requires at least 2 test pits within the approximate location of the infiltration
structure. HW recommends adding the location of the test pits to the plans to verify that
they are within the vicinity of the subsurface infiltration system.
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May 1, 2019
Page 3 of 7
The Applicant has provided the two test pits on Sheet 5 of 11 as requested. The
tests pits are located within 50 feet of the infiltration system and indicate very
similar soils and depth to groundwater. The test pits indicate that the bottom of
the system will maintain a minimum of 2 feet of separation from the ESHGW table.
HW is satisfied.
b. The Applicant has used time of concentration (Tc) values in the HydroCAD modeling
calculations of less than 5 minutes. Standard engineering practice utilizes a minimum of
5 or 6 minutes, HW recommends that the Applicant adjust the Te values to be a
standard minimum. Furthermore, under existing conditions it appears that the longest Tc
path would be over the landscaped island at the front of the property. HW recommends
that the Applicant confirm that the chosen flow path is the longest.
The Applicant has adjusted the Tc values as requested.
c. The Applicant has provided HydroCAD modeling calculations that verify that the post-
development discharge rate and volume do not exceed the pre-development discharge
rate or volume.
No further comment needed. The Applicant complies with Standard 2.
3. Standard 3 states that the annual recharge from post-development shall approximate the
annual recharge from pre-development conditions based on soil type.
a. The Applicant has shown that through the reduction of impervious surface and the
installation of a subsurface infiltration system, the annual recharge requirement has
been met.
No further comment needed. The Applicant complies with Standard 3.
b. The Applicant has not provided drawdown calculations. HW recommends adding the
appropriate calculations to the stormwater report.
The Applicant has provided the requested drawdown calculations in Section 3 of
the Stormwater Management Report. HW is satisfied.
c. The Applicant has provided the depth to the estimated seasonal high groundwater
(ESHGW)for the two test pits. However, neither the ground elevation nor the exact
location of the test pits are included in the stormwater report. In order to judge whether
the design provides the minimum two feet of separation between the bottom of the
infiltration system and the ESHGW, HW recommends adding the location and ground
elevation of the test pits to the stormwater report. If the separation is less than 4 feet a
mounding analysis is required in accordance with the MSH Vol. 3, Ch. 1, p 28.
The Applicant has provided the two test pits on Sheet 5 of 11 as requested. The
tests pits are located within 50 feet of the infiltration system and indicate very
similar soils and depth to groundwater. The test pits indicate that the bottom of
the system will maintain a minimum of 2 feet of separation from the ESHGW table.
A mounding analysis is required when the vertical separation from the bottom of
an exfiltration system to seasonal high groundwater is less than four(4) feet and
the recharge system is proposed to attenuate the peals discharge from a 10-year
or higher 24-hour storm. As designed the Applicant is not attenuating the 10-year
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24-hour storm event therefore a mounding analysis is not required. HW is
satisfied.
4. Standard 4 states that the stormwater management system shall be designed to remove
80% of the average annual postconstruction load of Total Suspended Solids (TSS) and is
sized to treat 0.5-inches of volume from the impervious area for wafer quality.
a. The Applicant has stated in its Operations and Maintenance (O&M) Plan that fall, and
spring sweeping will be conducted on site. According to MSH Vol. 2, Ch. 1, p. 9 in order
to achieve 5%TSS removal credit the area needs to be swept on a quarterly average
with a high efficiency vacuum sweeper. HW recommends adding the type and average
timing of the sweeping program to the O&M Plan.
The Applicant has included the type and timing to the sweeping program in the
O&M Plan as requested. The Planning Board may choose to include a special
condition requiring annual documentation of the sweeping program conducted.
b. The Applicant indicates 75%TSS removal rates to the First Defense hydrodynamic
separator. However, no TSS removal evaluation or documentation for appropriate sizing
have been submitted. To address this standard HW recommends that the Applicant add
the proper documentation to the stormwater report.
The Applicant has provided the requested documentation. HW is satisfied.
c. The Applicant has not provided any calculations for Water Quality Volume to assure that
0.5-inches of volume from the impervious area is treated for water quality. HW
recommends providing these calculations.
The Applicant is providing water quality for two of the proposed catchment areas
within the parking lot by utilizing Filterra tree box filters and a First Defense High
Capacity proprietary separatory for the remainder of the lot. The subsurface
infiltration system is recharging the roof runoff which is considered clean. The
Applicant has provided the documentation and calculations for the First Defense
system however HW did not receive the documentation for the Filterra tree box
filters. The Filterra tree box filters are considered an acceptable low impact design
(LID) practice. HW recommends that the appropriate documentation be provided
to the Planning Board.
5. Standard 5 is related to projects with a Land Use of Nigher Potential Pollutant Loads
(LUHPPL).
a. The proposed project is not considered a LUHPPL and therefore Standard 5 is not
applicable.
No further comment needed.
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 proposed project is not located within a critical area therefore Standard 6 is not
applicable.
No further comment needed.
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May 1, 2019
Page 5 of 7
7. Standard 7 states that a redevelopment project 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 9 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.
a. The proposed development is considered a redevelopment and the Applicant is reducing
impervious cover. Please refer to the applicable comments for Standards 2-6 noted
above.
No further comment needed.
b. The narrative provided by the Applicant in Section 3 of the Stormwater Report for
Standard 7 is not accurate. HW recommends that the Applicant revise the narrative.
The narrative has been revised as requested. No further comment needed.
c. As a redevelopment project the Applicant is required to improve existing conditions and
to demonstrate that it has made a complete evaluation of possible stormwater
management measures, including environmentally sensitive site design and low impact
development (LID)techniques that minimize land disturbance and impervious surfaces."
HW recommends that the Applicant demonstrate to the Town that it has conducted a
complete evaluation of LID techniques that were consider in the design phase of this
project. It appears that it may be feasible to install a bioretention area or vegetated swale
within the landscaped area parallel to Chickering Road.
The Applicant has included two Filterra tree box filters. The Filterra tree box filters
are considered an acceptable LID practice.
8. Standard 8 requires a plan to control construction related impacts including erosion,
sedimentation or other pollutant sources.
a. The Applicant has mentioned a detention basin in the construction sequence. HW
recommends changing that language to"subsurface infiltration structure."
The construction sequence has been revised as requested.
b. HW recommends that the Applicant include the location of temporary and permanent
seeding, vegetative controls, and other temporary and final stabilization measures to the
Erosion Control Plan.
The Applicant has included additional stabilization measures as requested.
c. HW recommends that the Applicant include the following conditions to the Sediment and
Erosion Control Plan:
• Sediment shall be removed once the volume reaches 114 to 1/2 the height of a hay
bale. Sediment shall be removed from silt fence prior to reaching the load-bearing
capacity of the silt fence which may be lower than 114 to 112 the height;
• Sediment from sediment traps or sedimentation ponds shall be removed when it
reaches a depth of six inches;
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May 1, 2019
Page 6 of 7
• Topsoil shall be stripped from disturbed areas, stockpiled in approved areas and
stabilized with temporary vegetative cover if it is to be left for more than 30 calendar
days;
• Soil stockpiles must be stabilized or covered at the end of each workday. Stockpile
side slopes shall not be greater than 2:1; and
• Dust shall be controlled at the site.
The Applicant has included the requested notes to Sheet 7 of 11. The Applicant
complies with Standard 8.
9. Standard 9 states that a long-term operation and maintenance (O&M)plan shall be
developed and implemented to ensure that stormwater management systems function as
designed.
a. To comply with this standard, HW recommends adding the following information to the
O&M Plan:
• Instructions on how future property owners will be notified of the presence of the
stormwater system and the requirements for proper operation and maintenance;
• A simple sketch that is drawn to scale and shows the location of all stormwater
practices; and
• An estimated operations and maintenance budget.
The Applicant has provided information for the property owner as well as a simple
sketch to illustrate the location of the various stormwater practices that require
routine maintenance. The Planning Board may choose to require that a budget be
provided prior to construction.
b. MSH Vol. 2, Ch. 2, p. 106 requires mosquito control measures for subsurface structures
to be included in the O&M Plan.
HW agrees that these controls are not needed for this system.
c. The Applicant has added inspection reports for the Hydrodynamic Separator to the O&M
Plan. HW recommends adding inspection reports for the remaining stormwater
practices.
HW was not able to locate the additional inspection reports for the various
stormwater practices.
d. The Applicant has indicated a maintenance schedule for the Hydrodynamic Separator
which does not align with the manufacturer's instructions. HW recommends adding the
following provisions:
• Inspect the unit regularly during the first year of installation;
• Remove oil and floatables once per year, with sediment removal;
• Remove oil and floatables following a spill in the drainage area; and
• Remove sediment following a spill in the drainage area.
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Page 7of7
The requested information has been added Vs the O&M Plan.
8. HVV recommends adding the following items to the O&M Plan:
° The aignotuna(s) nf the property Ovvner(m).
mThe names and addresses of the perGon(8) responsible for operation and
maintenance. If responsibility is to be contracted to o third party, a copy of the
maintenance aQree0oent(s) must beprovided.
� A plan or map showing the location nfthe systems and facilities, including easements,
catch basins, O8@Oh0|eS/8C0ene lids, 0@iO' and ntVrn1vvet*rdovicae.
• A list of easements with the purpose and location of each. Easements shall be
recorded with the Essex North Registry of Deeds prior to issuance of a certificate of
completion by the Planning Board.
* Provisions for the Planning Board or its designee to enter the property at reasonable
times and ina reasonable manner for the purpose Ofinspection.
The requested information has been added tm the O&M Plan.
1O. Standard YO requires 8D Illicit Discharge Cmnvn&gnCe Statement b7b8provided.
8. The Applicant has provided a signed Illicit Discharge Compliance Statement signed by
the engineer. HW recommends that the statement be signed by the Applicant to verify
that iiis fully aware of the requirement.
No further comment needed.
Conclusions
HW is satisfied that the Applicant has responded adequately to our comments. The Planning
Board and or the Conservation Commission may choose to include special conditions as noted
above for any approvals granted. 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. P|8oseCOntaCtJ@netBernBnJO8t(5OB) 833-O600O,8t
jbernardo@horsleywitten.com if you have any questions regarding these comments.
SiDCe[8|y'
HORSLEYVV|TTEN 8Fl{)UP, INC.
{l «
Janet Carter Bernardo, P.E.
Senior Project K8anmQor
CC: Jennifer A. HUgheS, Conservation Administrator
NOMMUNNINOMMW Onk1w am VAIM
INNOW OW .-AMWAVA
fi� A ORW NNNW�
44 Stiles Road -Suite One - Salem, New Hampshim 03079
TEL (603) 893-0720 - FAX (603) 893-0733
MHF Design Consultants, Inc. www.mhfdesign.coin
April 24,2019
North Andover Planning Board
Town of North Andover
120 Main Street
North Andover, MA 01845
Attn. Ms. Monica Gregoire, Staff Planner
Re: Enterprise Bank
247 Chickering Road
North Andover, MA
Sub: Horsley Witten Group Response
to Comments
Dear Ms. Gregoire:
Please find criclosed a revised set of plans and supporting documentation regarding the above
referenced project located at 247 Chickering Road. The plans have been revised to address the comments
in the Horsley Witten Group review letter,dated March 28, 2019. Based on those comments we offer the
following:
Stormwater Management Design Peer Review
Standard 1:
a. The predevelopment runoff from the existing development drains towards Chickering Road as
sheet and shallow concentrated flows. The proposed development consists of capturing onsite
runoff with a closed drainage system and connecting into the Chickering Road closed drainage
system,which will be constructed as part of the MassDOT roadway improvements. Based on the
reduction in both peak rate of runoff and peak volume in comparison to the existing conditions,
there should be no negative impacts to downstream tributaries or wetland areas as part of the
proposed development.
b. Discussions between MassDOT and the projeetteam are ongoing and once final approval is
obtained by MassDOT we will forward to the Town accordingly.
Standard 2:
a. Test pits locations have been added to the Grading&Drainage Plan.
b. The minimum time of concentration has been revised to a 6 minutes as requested. MHF verified
that the currently shown Tc path in the pre-development analysis is the longest hydraulic flow
path &no changes were made to the Tc.
c. Comment acknowledged,no action required.
Standard 3:
a. Comment acknowledged, no action required.
ENGINEERS PLANNERS SURVEYORS
HW Response Comments
Apri124,2019
/ e A
Page 2 of 3 .f �
MHF t�aalgn Consultants, Inc.
b. Drawdown calculations have been provided as requested.
e. Test pit locations have been added to the Grading&Drainage Plan. The proposed design is not
attenuating runoff but is providing static storage for groundwater recharge therefore in.
accordance with the Stormwater Handbook a mounding analysis is not required and therefore not
provided.
Standard 4:
a, The O&M has been revised to account for quarterly street sweeping by a high efficiency vacuum.
Once a third-party maintenance company has been engaged,the type and average timing of the
street sweeping will be established and provided to the Town as needed prior to construction.
b. Additional documentation has been provided regarding the TSS removal rates for the First
Defense hydrodynamic separator,
c. Water Quality Volurne calculations have been provided as requested.
Standard 5:
a. Comment acknowledged, no action required.
Standard 6:
a. Comment acknowledged, no action required.
Standard 7:
a. Comment acknowledged, no action required.
b. The narrative within Section 3 of the Stormwater Report has been revised as needed.
c. The site stormwater design was revised to include two(2)Filterra tree box filters as discussed
with the Conservation Commission at the recent meeting held on 4/10/19. The addition of the
Filterra units, onsite drainage system, O&M plan and reduction in impervious coverage
demonstrates an improvement over existing conditions.
Standard 8:
a. Language in the construction sequence.has been revised as suggested.
b. Temporary seeding and vegetation is shown in accordance with the Erosion Control& Sediment
Control Plna and final stabilization, seeding and landscaping is shown in accordance with the
Landscape Plan. Additionally,temporary erosion control BMP's and details are shown on the
plans and details sheets.
c. The five(5) recommended conditions have been added to the Erosion Control Plan as suggested.
Standard 9:
a. The requested information has been added to the O&M Plan as follows:
• The Order of Conditions will be recorded as pant of the approvals through the
Conservation Commission, The O&M will be referenced as part of the OOC which will
provide the required information needed for future owners regarding notification for
proper operation and maintenance.
• A plan has been added to the O&M Plan indicating locations of the stormwater BMP's
required for maintenance.
• Once a third-party maintenance company has been engaged a maintenance budget will be
provided to the Town as needed prior to construction.
I-IW Response Comments
April 24, 2019 MOMMMEMMMOW NNOWW Em now
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Page 3 of 3
MHF Deslgn- "n's-u-l-t'a'n-ts",-'"[n—c.
b. Mosquito control measures for the Subsurface structures are not provided for the proposed
underground infiltration system since it is a closed drainage system with inlet provided via roof
drains from the proposed facility with no direct access for mosquitos.
c. Inspection report logs have been added to the O&M as requested.
d. The additional provisions requested have been added to the O&M Plan &the maintenance
schedule for the Hydrodynamic Separator has been revised consistent with the manufacturer's
instructions.
e. The recommended itents have been including as follows:
• Owner's Signature will be added to the O&M and provided prior to construction.
• Once a third-party maintenance company has been established,a copy of the maintenance
agreement will be sent to the Town as needed prior to construction.
• A plan has been added to the O&M Plan indicating locations of the storinwater BMP's
required for maintenance.
• All easements are shown on the Existing Conditions Plan with deed references shown as
appropriate.
• Additional information has been added to the O&M Plan indicating the allowance of
Town representatives to enter the site upon authorization of the property owner.
Standard 10:
a. The applicants' signature will be added to the Illicit Discharge statement as requested and
provided prior to construction.
Please review the attached revised information and should you have any questions,please feet free to
call out-office at your convenience.
Sincerely yours,
MI I.- esi it Consultants,Inc.
Cirf y
Project Manager
CR 457019
cc: Janet Carter Bernardo, PE, Horsley Witten Group
Jennifer Hughes,North Andover Conservation Administrator
Luke Bouchard,Enterprise Batik
\\MFS\Coinpatiy_Data\Pi-oLjects\Eiig\457019\4570-HW Response Letter.docx
Horsley Wifhen Groin
tistaitiablc: rivironmental Solution
294 Washington Street•Surte 801»Boston,MA 02108
857-2618193•horsleywrtten.corn
March 28, 2019
Ms. Monica Gregoire, Staff Planner
Planning Department
Town of North Andover
120 Main Street
North Andover, Massachusetts 01845
Ref: Enterprise Sank
247 Chickering Road
North Andover, MA
Dear Ms. Gregoire 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 Report and
permitting plans for the proposed Enterprise Bank facility and associated parking at 247
Chickering Road, North Andover, MA. The plans were prepared for Enterprise Bank (Applicant)
by MHF Design Consultants, Inc. HW understands that the Applicant is proposing to raze the
existing 2-story veterinary building and demolish the associated paved parking and site features
and construct a new 3,250 square foot (sf) building with drive-thru along with associated paved
driveways, access aisles, 23 parking spaces, a new trash enclosure and a new stormwater
management system. The proposed stormwater system includes four deep sump catch basins,
a water quality unit, and a subsurface infiltration system. A portion of the project is located within
the 100-foot buffer of an adjacent wetland resource area, identified by Norse Environmental on
January 30, 2019 and therefore is within the jurisdiction of the North Andover Conservation
Commission. Incorporating LID practices is an important criteria to the Conservation
Commission and particularly relevant in meeting the requirements of North Andover's municipal
separate storm sewer systems (MS4) permit.
The following documents and plans were received by HW:
• Special Permit—Site Plan Review Application for property at 247 Chickering Road, North
Andover, MA;
• Certified Town of North Andover Abutter List, dated March 6, 2019;
• Stormwater Management Report, Proposed Site Re-Development, 247 Chickering Road,
North Andover, MA, prepared by MHF Design Consultants, Inc., dated March 13, 2019; and
• Site Re-Development Plans for Assessors Map 46 Lot 4, 247 Chickering Road, North
Andover, Massachusetts 01845, prepared by MHF Design Consultants, Inc., dated March
13, 2019, which include:
• Title Sheet 1 of 11
o Existing Conditions Plan 2 of 11
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Town of North Andover
March 28, 2019
Page 2 of 6
o Demolition Plan 3 of 11
o Site Plan 4 of 11
o Grading & Drainage Plan 5 of 11
o Utilities Plan 6 of 11
o Erosion & Sediment Control Plan 7 of 11
o Landscape Plan 8 of 11
o Detail Sheet 9 of 11
o Detail Sheet 10 of 11
o Detail Sheet 11 of 11
a Lighting Proposal (LSi) 1 of 1
o Building Elevations (Cube 3) 1 of 1
Stormwater Management Design Peer Review
HW offers the following overall comments concerning the stormwater management design as
per the Zoning Bylaw for the Town of North Andover, last amended May 16, 2017 and the
Massachusetts Stormwater Handbook (MSH) dated February 2008 as well as standard
engineering practice. The North Andover Stormwater Management and Erosion Control
Regulations adopted February 5, 2011 and the North Andover Stormwater Management and
Erosion Control Bylaw are not applicable as the land disturbance is less than 43,560 sf.
In accordance with Article 8.3, section 5.e)viii) of the Zoning Bylaw, all applications for Site Plan
Review must demonstrate full compliance with the Massachusetts Stormwater Standards.
Therefore, the comments below correlate with the MSH standards. In accordance with
Massachusetts Department of Environmental Protection (MassDEP) the project is considered a
redevelopment which allows for some standards to be met to the maximum extent practicable.
1. Standard 1 states that 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 Applicant is proposing to discharge stormwater to a closed drainage system in
Chickering Road. Under existing conditions, the runoff from the site appears to sheet
flow onto Chickering Road and there are no obvious catch basins. HW recommends that
the Applicant clarify the final discharge point and verify that the stormwater conveyance
will not cause erosion in wetlands of the Commonwealth.
b. Route 125/133 is a State Highway. HW recommends that the Applicant confirm that
MassDOT will allow the property to discharge into the state stormwater system. The
Applicant has noted on the plans that the drainage improvements in the public right-of-
way are to be done per Plan Reference#2 and coordinated with MassDOT. HW was not
able to verify Plan Reference #2. Therefore we further recommend that the Applicant
provide the Planning Board with the appropriate documentation.
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March 28, 2019
Page 3 of 6
2. Standard 2 states that stormwater management systems shall be designed so that post-
development peak discharge rates do not exceed pre-development peak discharge rates.
a. The Applicant has provided data for two test pits; however, the location of the test pits is
not indicated on the plans. According to MSH Vol. 2, Ch. 2, p. 104 each infiltration
system requires at least 2 test pits within the approximate location of the infiltration
structure. HW recommends adding the location of the test pits to the plans to verify that
they are within the vicinity of the subsurface infiltration system.
b. The Applicant has used time of concentration (Tc)values in the HydroCAD modeling
calculations of less than 5 minutes. Standard engineering practice utilizes a minimum of
5 or 6 minutes, HW recommends that the Applicant adjust the Tc values to be a
standard minimum. Furthermore, under existing conditions it appears that the longest Tc
path would be over the landscaped island at the front of the property. HW recommends
that the Applicant confirm that the chosen flow path is the longest.
c. The Applicant has provided HydroCAD modeling calculations that verify that the post-
development discharge rate and volume do not exceed the pre-development discharge
rate or volume.
3. Standard 3 states that the annual recharge from post-development shall approximate the
annual recharge from pre-development conditions based on soil type.
a. The Applicant has shown that through the reduction of impervious surface and the
installation of a subsurface infiltration system, the annual recharge requirement has
been met.
b. The Applicant has not provided drawdown calculations. HW recommends adding the
appropriate calculations to the stormwater report.
c. The Applicant has provided the depth to the estimated seasonal high groundwater
(ESHGW)for the two test pits. However, neither the ground elevation nor the exact
location of the test pits are included in the stormwater report. In order to judge whether
the design provides the minimum two feet of separation between the bottom of the
infiltration system and the ESHGW, HW recommends adding the location and ground
elevation of the test pits to the stormwater report. If the separation is less than 4 feet a
mounding analysis is required in accordance with the MSH Vol. 3, Ch. 1, p 28.
4. Standard 4 states that the stormwater management system shall be designed to remove
80% of the average annual postconstruction load of Total Suspended Solids (TSS) and is
sized to treat 0.5-inches of volume from the impervious area for water quality.
a. The Applicant has stated in its Operations and Maintenance (O&M) Plan that fall, and
spring sweeping will be conducted on site. According to MSH Vol. 2, Ch. 1, p. 9 in order
to achieve 5% TSS removal credit the area needs to be swept on a quarterly average
with a high efficiency vacuum sweeper. HW recommends adding the type and average
timing of the sweeping program to the O&M Plan.
b. The Applicant indicates 75% TSS removal rates.to the First Defense hydrodynamic
separator. However, no TSS removal evaluation or documentation for appropriate sizing
have been submitted. To address this standard HW recommends that the Applicant add
the proper documentation to the stormwater report.
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Town of North Andover
March 28, 2019
Page 4 of 6
c. The Applicant has not provided any calculations for Water Quality Volume to assure that
0.5-inches of volume from the impervious area is treated for water quality. HW
recommends providing these calculations.
5. Standard 5 is related to projects with a Land Use of Nigher Potential Pollutant Loads
(LUHPPL).
a. The proposed project is not considered a LUHPPL and therefore Standard 5 is not
applicable.
6. Standard 6 is related to projects with stormwater discharging into a critical area, a Zone 1I or
an Interim Wellhead Protection Area of a public water supply.
a. The proposed project is not located within a critical area therefore Standard 6 is not
applicable.
7. Standard 7 states that a redevelopment project 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.
a. The proposed development is considered a redevelopment and the Applicant is reducing
impervious cover. Please refer to the applicable comments for Standards 2-6 noted
above.
b. The narrative provided by the Applicant in Section 3 of the Stormwater Report for
Standard 7 is not accurate. HW recommends that the Applicant revise the narrative.
c. As a redevelopment project the Applicant is required to improve existing conditions and
to demonstrate that it has made a complete evaluation of possible stormwater
management measures, including environmentally sensitive site design and low impact
development (LID)techniques that minimize land disturbance and impervious surfaces."
HW recommends that the Applicant demonstrate to the Town that it has conducted a
complete evaluation of LID techniques that were consider in the design phase of this
project. It appears that it may be feasible to install a bioretention area or vegetated swale
within the landscaped area parallel to Chickering Road.
8. Standard 8 requires a plan to control construction related impacts including erosion,
sedimentation or other pollutant sources.
a. The Applicant has mentioned a detention basin in the construction sequence. HW
recommends changing that language to "subsurface infiltration structure."
b. HW recommends that the Applicant include the location of temporary and permanent
seeding, vegetative controls, and other temporary and final stabilization measures to the
Erosion Control Plan.
c. HW recommends that the Applicant include the following conditions to the Sediment and
Erosion Control Plan:
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Town of North Andover
March 28, 2019
Page 5 of 6
• Sediment shall be removed once the volume reaches 1/4 to 112 the height of a hay
bale. Sediment shall be removed from silt fence prior to reaching the load-bearing
capacity of the silt fence which may be lower than 114 to 112 the height;
• Sediment from sediment traps or sedimentation ponds shall be removed when it
reaches a depth of six inches;
• Topsoil shall be stripped from disturbed areas, stockpiled in approved areas and
stabilized with temporary vegetative cover if it is to be left for more than 30 calendar
days;
• Soil stockpiles must be stabilized or covered at the end of each workday. Stockpile
side slopes shall not be greater than 2:1; and
• Dust shall be controlled at the site.
9. Standard 9 states that a long-term operation and maintenance (O&M)plan shall be
developed and implemented to ensure that stormwater management systems function as
designed.
a. To comply with this standard, HW recommends adding the following information to the
O&M Plan:
• Instructions on how future property owners will be notified of the presence of the
stormwater system and the requirements for proper operation and maintenance;
• A simple sketch that is drawn to scale and shows the location of all stormwater
practices; and
• An estimated operations and maintenance budget.
b. MSH Vol. 2, Ch. 2, p. 106 requires mosquito control measures for subsurface structures
to be included in the O&M Plan.
c. The Applicant has added inspection reports for the Hydrodynamic Separator to the O&M
Plan. HW recommends adding inspection reports for the remaining stormwater
practices.
d. The Applicant has indicated a maintenance schedule for the Hydrodynamic Separator
which does not align with the manufacturer's instructions. HW recommends adding the
following provisions:
• Inspect the unit regularly during the first year of installation;
• Remove oil and floatables once per year, with sediment removal;
• Remove oil and floatables following a spill in the drainage area; and
• Remove sediment following a spill in the drainage area.
e. HW recommends adding the following items to the O&M Plan:
• The signature(s) of the property owner(s).
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Town (f North Andover
March 28. 2O10
Page GofO
» The names and addresses of the pe[enn/a\ responsible for operation and
maintenance. If responsibility is to be contracted to a third pmrty, a copy 0fthe
maintenance agnee[nenK:\ must beprovided.
• A plan or map showing the location of the systems and facilities, including easements,
catch basins, manholes/access |ids, main, and a|orrnvV8te[devicem.
w A list of easements with the purpose and location of each. Easements shall be
recorded with the Essex North Registry of Deeds prior to issuance of a certificate of
completion by the Planning Board.
• Provisions for the Planning Board or its designee to enter the property at reasonable
times and ino reasonable manner for the purpose Ufinspection.
10. Standard 10 requires an Illicit Discharge Compliance Statement to be provided.
8. The Applicant has provided a signed Illicit Discharge Compliance Statement signed by
the engineer. HVVrecommends that the statement be signed by the Applicant toverify
that it is fully avv8r8 of the requirement.
Conclusions
HW recommends that the Planning Board and or the Conservation Commission require that the
Applicant address these comments an part of the review process. The Applicant ie advised that
provision of these ConDrneDts does not relieve him/her ofthe responsibility to comply with all
Town of North Andover Codes and By-Laws, Commonwealth of Massachusetts laws, and
federal regulations os applicable to this project. P|eaoeoon(ao1JanetBern8rdoai /5O8\ 833-
00OOn[mt 'bm[nerdo@hors|eywit[mn.00rnifyouhewaanyquesUonsre0anjiUgtheeeco0[Dents.
Sincerely,
HDR5LEYVV|TTEN GROUP' INC.
Janet Carter Bernardo, P.E. K8mrimPozirnaN
Senior Project yWanoger Staff Planner
CC: Jennifer A. Hughes, Conservation Administrator