HomeMy WebLinkAbout20140805 ENGINEER RESPONSE COMMENTS POLA
34 Main Street,Suite 201
Plymouth, MA 02360
Phone:617-689-1010
Fax:617-689-3010
July 8, 2014
Curt Bellavance, AICP
Director, Community Development
Town of North Andover
1600 Osgood Street
North Andover, MA 01845
RE: Fire Station—North Andover, Massachusetts
Civil Engineering Review Comments June 30, 21.04
50% Construction Document Comment Responses
Dear Mr. Bellavance:
At the request of our client, Donham & Sweeney Architects, we are writing this letter in response
to Eggleston Environmental's stormwater review letter dated June 30, 2014. Our response to
each of the numeric comments is provided below.
I. Polaris Consultants concurs with their determination that the project is not subject to the
North Andover Stormwater Management and Erosion Control Regulations. We
understand that the project needs to provide for mitigation of the 100-year storm event
(8.6 inches of rain over a 24-hour period) and have designed for this requirement.
In response to the comment concerning the Massachusetts Storrnwater Regulations, we
understand that the Town will be pursuing a formal Request for Determination of
Applicability(RDA) from the North Andover Conservation Commission.
2. In regard to the use of porous pavers, we have discussed the load rating of the fire
apparatus with Lisa Eggleston and it's limiting the use of porous pavers to the visitor's
parking area. Since there would be several maintenance issues associated with using two
types of paving over a contiguous area, we believe there is limited benefit to using porous
pavers at this Site. The overall integrity of the larger parking should be considered and
we would not recommend the limited use of the porous pavers.
3. Design details for the proposed subsurface infiltration system have been provided to the
North Andover Planning Board on Sheet C6.0.
4. The pre- and post-construction drainage calculations provided to Lisa Eggleston are based
on the Rational Method and are adequate for a one-acre Site. The calculations indicate
that there will be no net impact to the downstream sources from the 2-, 10-, 25- and 1.00-
Curt Beilavance
July 8, 2014
Page 2 of 2
year storm events. The RDA decision may have an impact as to how stormwater is
managed. Therefore, once the RDA decision is made, the drainage calculations will be
revisited for the specific sub watershed areas, and detailed pipe sizing calculations will be
provided.
5. Two to four feet of clean granular fill is being placed across the Site, as
indicated in the infiltration calculations provided to Eggleston Environmental and the
subsurface infiltration system design details provided to the Town. The estimated wetted
area of the infiltration system extends to a depth of about 3.5 feet. Based on the amount of
clean granular fill bought to the Site and the depth of the infiltration system, we do not
believe the proposed galleys will negatively impact abutters and we recommend a
minimum setback of 5 feet from the property line.
6. The water quality treatment goals for the proposed Oil Water Separator (OWS) systems
will"depend on if the Site needs to meet the Massachusetts Stormwater Management
regulations. Therefore, once the RDA decision is made, we will work with Eggleston
Environmental on the appropriate OWS requirement.
7. The proposed catch basin detail shown on Sheet C7.0 has a minimum 4-foot-deep sump,
and includes a requirement for a hooded outlet to control potential oil and gas migration
off proposed pavement.
8. We concur with the comment concerning the catch basin located at the Site entrance to
Chickering Road. The proposed catch basin will meet the detail shown on Sheet C7.0 (a
minimum 4-foot-deep sump and the requirement for a hooded outlet to control potential oil
migration). With these safe guards in place, we recommend discharging the overflow to
the nearby Swale.
9. There is limited new additional flow directed to the swale and the flow to this area is
restricted by a 24-inch diameter reinforced concrete pipe located upstream at the
intersection of Chickering Road and Prescott Street. We have discussed the use of a box
culvert with the Town Engineer and the preference is to use an oversized 36-inch diameter
reinforced concrete pipe. Should the Town prefer the use of a box culvert, we would
recommend a standard 3-foot and 2-foot section.
We appreciate the opportunity to work with you on this project, and should you have any
questions,please do not hesitate to contact me at 617-750-8135.
Very Truly Yours,
Paul G. Costello, P.E.
Principal-In-Charge
Cc: Chris Logan, Donham and Sweeney Architects
POLARIS CONSULTANTS LLC
'
,
POLARIS
J4 Main Street,Suite 201
Plymouth,NAD23GO
Phone:617-689-1010
Fax:617-689-3010
July 29' 2O14
Jennifer Hughes, Adudoistcuk)c
Conservation Commission
Town of North Andover
l6D0 Osgood Street, Suite 2O35
North Andover, MAOlK45
RE: Fire Station —North Andover, Massachusetts
5D96 Construction Documents
Request for Determination oƒApplicability Application
Dear Ms. Hughes:
At the request of our client, Donham & Sweeney Architects, we are writing this letter tnupdate
you on the atuCun of the yJorib Andover Fire S(udoo Civil Site design, myncifioa|1y as it oo|uies to
the awa|o located u6UoceoL to Cbiobodog Road. The lofbrrnut|on is being provided in support of
anegaiive Determination of Applicability for the Site.
Project Background
The existing site conditions were surveyed by Sullivan Engineering Group LLC (p[oo dated
February 7` 2014 and amended h8arnb 25' 2014). The Site is located at the corner of
Chickerin8Itood and Prescott Street and encompasses an area of46'ZMg square feet. The
Site has been used as ubuaobu|l field and is generally open soil grass land with msoil ioƒlc]d.
The topography ia generally flat (from E} lhO {n the south west corner io ]B.. l64io the north
east corner). The immediate area around the Site is foucoJ and there is u2,331 square foot
paved uooeau area on the Site from uo existing curb cut ouPrescott Street. The west side of
the Site is marked by a 3-foot-wide exdboo svvo}e that slopes 1.5% from u 24-ich-diazotcr
»niofwznod cmnon:ie pipe that omnsnos Prescott Street at the oodb (El. 160) to a lnvv point of
El. 157 located 200-feet south, The svvale has become overgrown with vegetation, and was
not delineated ny wetlands by Sullivan Engineering Group,
The proposed plans are to construct an 8,323 square foot footprint Central Fire Station. The
yluoa are for o two-story structure for housing of administrative facilities and D,o apparatus,
up to 37-fecL-long and with u25-fbot interior turning radius. Access to the Site will befrom
a new curb cut on Prescott Street and the construction of a new curb cut on Chickering Road
(over the existing 8n/ulo). The proposed Site Plan includes 14.245 square feet of open
Jennifer Hughes
July 29, 2014
Page 2 of 3
landscaped space and 23,721 square feet of asphalt, grass pavers and concrete surface. The
access from Chickering Road will require the filling of the man-made swale over a distance
of about 109 feet.
Stormwater Design and Best Management Practices
Polaris Consultants has been working with the Town and Eggleston Environmental to develop
the best management practices for controlling stormwater at the Site and for protecting the
overall integrity of the existing earthen swale, Based on the Existing Conditions Plan provided
by Sullivan Engineering, it has been determined that the project is not subject to the North
Andover Stormwater Management and Erosion Control Regulations. However, the project
needs to be protective of the swale and provide for mitigation of the 100-year storm event (8.6
inches of rain over a 24-hour period). The design calls for no additional flow to be directed to
the existing swale or any off-site areas. In short, the net run-off will be stored on-site and
recharged via underground storage chambers.
An estimated 155 feet of erosion control barriers (silt fence and haybales) will be placed in the
vicinity of the earthen swale to protect areas that will remain undisturbed, It has been agreed to
install a 109-foot long, 3-foot-wide by 2-foot-deep box culvert at the Chickering Road access in
order to best mimic the cross-sectional area of the swale being disturbed. The box culvert will
be capable of handling twice as much flow as the upgradient 2-foot-diameter pipe.
The pre- and post-construction drainage calculations provided to Eggleston Environmental are
based on the Rational Method and we believe are adequate for a one-acre Site. The calculations
indicate that there will be no net impact to the swale or downstream sources from the 2-, 10-,
25- and 100-year storm events. Clean granular fill is being placed across the Site, as indicated
in the infiltration calculations provided to Eggleston Environmental, and the subsurface
infiltration system design details have been provided to the Town.
For water quality management, three Oil Water Separator (OWS) systems have been proposed
for the Site, all proposed catch basins shall have a minimum 4-foot-deep sump, and all catch
basins shall be equipped with a hooded outlet to control potential oil and gas migration. One
proposed catch basin on Chickering Road will meet the detail shown on Sheet C7.0 (a minimum
4-foot-deep sump and the requirement for a hooded outlet to control potential oil migration).
With these safe guards in place, we recommend discharging the overflow to the nearby swale.
The quantity of flow will be no more than the existing flow being directed to the Swale.
POLARIS CONSULTANTS LLC w
Jennifer Hughes
July 29,2014
Page 3 of 3
Summary
In closing, we believe the following items need to be considered when assessing the suitability
of the proposed work at the Site:
I. Sullivan Engineering Group LLC has not delineated any wetlands at the Site. The
information they have provided to the Town and subsequently to Donham and Sweeney
and Polaris is provided on Sheet C1.0.
2. An estimated 109-feet of Moot by 2-foot of box culvert, at a 1.5% slope will be placed
below the Chickering Road access ramp. It has been determined that this cross-section
is best to mimic the functionality of the swale and to provide for more than twice the
capacity of the upgradient 2-foot-diameter pipe(Sheet C5.0).
3. Prior to conducting any construction activity, 155-feet of erosion control barriers will be
placed in the vicinity of the swale to protect the undisturbed, downslope areas, and to
maintain the functionality of the existing Swale during construction (Sheet C6.0).
4. Calculations submitted to the Town indicate that there will be no net additional flow to
the swale or any off site area from the 2-, 10-, 25- and 100-year storm events. Clean
granular fill is being placed across the Site and over 220 pre-cast 4-foot- by 4-foot
leaching galleys will be used. The subsurface galleys will be rated for H-20 loads. The
subsurface infiltration system design details have been provided to the Town on Sheet
c6.0.
5. To improve upon the overall water quality of the Site, three Oil Water Separator(OWS)
systems have been proposed and all proposed catch basins shall have a minimum 4-foot-
deep sump. All catch basins shall also be equipped with a hooded outlet to control
potential oil and gas migration from potential on-site spills (Sheet C7.0).
We appreciate the opportunity to work with you on this project, and should you have any
questions, please do not hesitate to contact me at 617-750-8135.
Very Truly Yours,
Paul G. Costello, P.E.
Principal-1'n-Charge
Cc: Curt Bellavance, North Andover Community Development
Brett Donham, Donham and Sweeney Architects
Chris Logan, Donham and Sweeney Architects
POLARIS CONSULTANTS LLC