Tighe DPW correspondence 2012-05-170-106-3-10
April 16, 2012
Mr. James Laurila, P.E.
City Engineer
_ .. Department of PublicWork!?"" .. ~.~ .. "",, __ " __ ,,""_"."_."._ .. _ .. _
Locust Street
Re: Kollmorgen -Stormwater Permit -Remaining Co liance .l.iD;::,U'::'::'
Northampton, MA 01060 1r
Dear Mr. Laurila: ' "
The purpose of this correspondence is to respond to your le\er dated January 30, 2011
which detailed the Department of Public Workfs remaining complian issues with the
Kollmorgen stormwater system. Each of. the outstanding ite s is add below under
the same headings provided in your previous letter.
Recharge Volume Inadequate
On December 2, 2011 we provided the Department of Public V\ orks with a table that
detailed the proposed design water quality volumes and the a -built r quality volumes
for the bioretention areas located on the Kollmorgen site. Th tab.le that while the
as-built volumes provided are si~nificantly less t~an the orig(naldesig I the total volume
was still above the water quality volume required by thel current 'Io.r''\l''n',\\Al:::>ror Policy.
However, based on site inspections during and after rains s by staff, It has been
determined that the bioretention area associated with CB-retains water for periods
longer than 72 hours and cannot /:Ie utilized asa portion f the quality volume
requirement for the site.,
In order to make up for the loss of volume from the CB-19 iprea, it is proposed that the
catchbasin grates located in the bioretention area in the nortMiast co of the site (CB-17
and CB-18) be raised' 8-inches to provide additional water ,: uality ume in this area.
Based on ~ as-built survey information, raising these two catch bas ns will provide an
g7q f additional~cubic feet of volume. This will result in a total ume of 264 cubic feet for
the site which is above the required water quality volume 0 3, 2 cubic Attached is a
revised table showing the proposed volumes for each of the ar ::1/6
Erosion and Sediment Control
Small erosion gullies within the parking lot swales and some flaccumu on of sediment fn
the bioretention areas were noted during our September 2011 Ii Isp1ect:IOn of the stormwater
system. It is anticipated that as the vegetation becomes furt er establ ed this spring in
the bioretention areas and swales, the root systems from the lants will id in retaining the
soil and mulch. The contractor for the project is planning to r move sediment that has
migrated into the bioretention areas. In addition, rounded st e may placed in some of
the larger erosion gullies to prevent continued erosion in th swales. The use of stone
instead .of mulch in small areas of the stormwater collection wales s uld not affect the
functionality of the stormwater· management system which appears be operating as
designed;
19 II· 2 I) II 53 Southampton Road • Westfield, MA 01085 • ., 1413
.
• Fax 413.562.5317
Record Plans
A revised stamped Grading and 'Drainage record plan (SheeL of 17) will be prepared and
forwarded to the DPW following the completion of work to rise catch asin grates CB-17
and CB-18. No other structural changes to the stormwat r manag ment system are
proposed.
Next Steps
As noted previously, the catchbas·in grates located in the bior ention ar a in the northeast
corner of the site (CB-17 and CB-18) will be raised 8-inches 0 provide additional volume
necessary to meet the Stormwater Policy requirements for the ite.
The approved operation and maintenance agreement for the ol/morge drainage system
requires remedial action be taken when any of the bioretentio areas uti ized for infiltration
begin to hold water for more than 72 hours following a r instorm. The first step in
attempting to restore the infiltration properties of the fai d area s the removal of
accumulated sediment. If this does not work the vegetatio is to be removed and the
bioretention area soils are to be loosened by tilling, harrowing, r overtur ing.
In the future, if a bioretention area at the Kollmorgen site fail due to cl gging and removal
of vegetation and loosening of the soil is necessary, the grade of the re abilitated area will
be left lower durin the reconstru' ocess to provide add ional vol me as proposed in
the original design for t e stormwater system. The attac ed table shows the design
volumes that will be targeted during the reconstruction work. On avera e the bioretention
areas will need to be left approximately 6-inches lower to mee the origin I design volumes.
If you have any questions regarding the actions proposed in t is corresp ndence, please do
not heSitate to contact the undersigned at 413-57 -3281 r via email at
j pviamari@tighebond.com.
Very truly yours,
TIGHE & BOND, INC.
fvi{; P:E., ~~D AP
Uaf5I;r Project Manager
Copy: Andrew Crystal (w/encl)
John Weatherwax (w/encl)
J:\O\OOl06\Drainage\4-16-12 Letter To Jim Laurila.Doc
Tighe&Bond
Tlghe&Bond
TABLE 1
Water Quality Volume Provided
I __ .4re:;!~~:U"f~L_~I~ ~::,~:;~:':!i Jt~ ~_ater Quali~y_
Volur l1e Provided
I Provided
•
•
! CB-5 220 CF
i
!
CB-6 389 CF I
• CB-7 389 CF 106 CF
! CB-8 389 CF 151 CF
I CB-9 389 CF 122 CF
• CB-10 395 CF 102 CF
I
CB-11 320 CF 64 CF
I
CB-12 1,058 CF 1,038 CF
• CB-13 1,058 CF i 1,038 CF
CB-17/18 826 CF 1,234 CF
CB-19
CB-21 291 CF 15 CF
CB-22 493 CF i. 34 CF
Area in CB-7 Row : 92 CF
· Area in CB-8/CB-1O Row 94 CF
:
Total 6,878 CF 4,264 Cf
I 13,630 CF 3,630 CI
!
All volumes calculated for volume below the elevation of thE catch basi n grate.
J:\O\OOl06\Drainage\Srormwater Report rev 04-2012.doc
Kollmorgen Stormwater Report
CITY OF NORTHAMPTON, MASSAC USETTS
DEPARTMENT OF PUBLIC ORK
125 Locust Street
Northampton, MA 0106
Edward S. Huntley, P.E.
Director
May 17, 2012
Mr. Jay P. Viamari, P.E.
Project Manager
Tighe & Bond
53 Southampton Road
Westfield, MA 01085
413-587-1570
Fax 413-587-1576
Re: Kollmorgen -Stormwater Permit -Remaining Compliance ssues
Dear Mr. Viamari:
The Northampton Department of Public Works (DPW) has received our April 16, 2012 letter and
attached Table 1, Water Quality Volume Provided describing how outstan g items for compliance
with the Storm water Management Permit for the project will be corr cted. The PW has the following
comments:
Recharge Volume
The proposal to raise the grates for catch basins 17 and 18 is an acc table sol tion to provide capacity
that meets minimum water quality volume for the project in compli ce with S dard 3 of the
Massachusetts Stormwater Management Standards. In addition the PW requ sts that during future
maintenance and reconstruction of the bioretention areas, the water uality vol es of these structures
be maintained in accordance with the "Actual Water Quality Vol "specifie in Table 1, Water
Quality Volume Provided (rev. 04-2012) prepared by Tighe & Bon. For ex pIe, if the bioretention
areas require additional mulch or stone or full reconstruction inelu . g replace ent of soil media and
plants, the reconstructed volume of each of the bioretention areas 1 be no Ie s than the Actual Water
Quality Volume Provided in Table 1.
Erosion and Sediment Control
The site was inspected on September 22 and 23,2011 by Jay Viam
Weatherwax, Kollmorgen and documented in 2011 Inspection and
that erosion repair and/or sediment removal was required in many
In the April 16, 2012 letter from Jay Viamari, PE, it was noted that
planning to remove the sediment that has migrated into the biorete
migrated into the bioretention systems must be removed as soon as
these systems and avoid costly reconstruction if they fail. The DP
the maintenance work on the swales and bioretention areas has bee
Pg.1/2
., P.E., Ti e & Bond and John
aintenan e Review. It was noted
the swal and bioretention areas.
The contr ctor for the project is
. on areas.' Sediment that has
ossible to maintain the function of
requests . tten confirmation that
complete.
II
/1
The swales and bioretention areas have experienced numerous issues ! th erosia and ineffectiveness of
the wood mulch. Part of the problem may be that the original design C~led for gr s swales which were
constructed with plantings and mulch instead of grass. The mulch that FilS install d may not be
appropriate for use in swales. The use of stone and further estab1ishme~t of the ve etation will certainly
improve the problem, but erosion and sediment control in the S\\rales r bioreten ion areas must
continue to be monitored and corrected in a timely way. .
Record Plans and Next Steps ,I
At the completion of work proposed to raise the catch basin grates, pI se submi final Record Plans for
DPW approval that include all changes made to the stormwater syste that were dertaken to address
the issues described above. Record Plans must include a professional gineer st p with signatures
and dates that are consistent with the latest revision dates on the recor . plans.
Please'n~tify Doug McDonald at the DPW (587-1582) regarding the J.,nstructio
are questions. . Ii
Sincerely,
J q es Laurit .. P .E.
C;E meer
c.c. Charlene Pellegrino, VP, Kollmorgen Electro Optical
Andrew Crystal, LEED AP, Western Builders
John Weatherwax, Kollmorgen
Louis Hasbrook, Northampton Building Department
Pg.212
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