HomeMy WebLinkAboutConsultant Review - 1600 OSGOOD STREET 6/24/2005 EGGLESToNE Nisi RONMENTAL
June 24, 2005
North Andover Conservation Commission
400 Osgood Street
North Andover,MA 01845
Attn: Alison McKay L E C
RE: Stormwater Management Review
1600 Osgood Commerce Center
Dear Alison and Commission Members:
Per your request, I have conducted an initial technical review of the Notice of Intent (NOI)
submittal package for the proposed parking lot improvements at 1600 Osgood Street, (the Lucent
Technologies site) in North Andover, with respect to stormwater management. The materials I
have received and reviewed to date include the following:
• Notice of Intent Application, Proposed Parking Lot and Drainage Improvements, 1600
Osgood St,North Andover prepared by Epsilon Associates Inc. and dated May 26, 2005.
• Drainage Report for 1600 Osgood Commerce Center Building 20 & 21 Parking Lot,
prepared for 1600 Osgood St LLC by Marchionda & Associates, L.P. and dated May 20,
2005. (Drainage calculations for 1-year storm event provided separately)
• Notice of Intent Site Plans, 1600 Osgood Commerce Center, North Andover, MA, 6
Sheets, prepared by Marchionda & Associates, L.P. and Huntress Associates, Inc. and
dated May 25, 2005.
In addition, Mike Howard of Epsilon Associates has provided me with a copy of the Applicant's
June 21, 2005 response to comments made by the Planning Board's consultant, VHB Inc.,
portions of which address drainage issues.
My primary focus in this review is on the overall stormwater management approach and design
concepts used in the project, as well as its compliance with the stormwater management and
flood storage standards (Section IV) of the North Andover Wetlands Bylaw and with the
Massachusetts Wetlands Protection Act and Stormwater Management Policy. My comments are
outlined below.
Overall Stormwater Management Approach and System Design
The project area is an approximately 7-acre portion of the 160-acre site formerly occupied by
Lucent Technologies. The Applicant is proposing to construct a new 190,000 sf parking lot in the
front of the property between the existing buildings and Osgood Street. The area is currently
comprised of a paved access driveway and manicured turf and is relatively level.
55 OLD COACH ROAD SUDBURY MA 01776 TELIFAx978.443.9262
1600 0s,(,,00(l. Tectiiiical RevAll",
Jtinc� 24. 2005
Under existing conditions, approximately two-thirds of the project area drains overland in a
northerly direction to an on-site closed drainage system, and is subsequently discharged to an
onsite wetland system located to the north of the project area. Drainage from the remainder of
the.project area is in a southerly direction to another closed drainage system, with discharge to a
wetland located in the southwest portion of the site.
As proposed, drainage from 90 percent of the new parking lot would be collected in deep sump
catchbasins and conveyed through a Stormceptor treatment unit and then an extended detention
basin before being discharged to the northern wetland area. A small portion of the parking area
would drain directly to the detention basin via deep sump catchbasins, Another small area of the
parking lot and the existing site driveway would drain through deep sump catchbasins to the
southern wetland. Groundwater recharge would be accomplished by diverting a portion of the
flow from the Stormceptor unit to the detention basin to a subsurface infiltration system located
immediately adjacent to the detention basin.
My primary concern with the proposed stormwater management plan is that while the rate of
peak runoff flow is mitigated by the proposed detention structures, the impact of changes in the
volume of runoff flow to the two onsite wetland resource areas has not been addressed. In
addition, I believe that more information is needed to document the groundwater recharge and
water quality improvements provided by the project. My specific comments on these and other
issues as they relate to the project's compliance with the nine North Andover and State
Stormwater Standards follow.
Standard#1. Untreated Stormwater
Standard #1 prohibits any new discharges of untreated stormwater to wetland resource areas of
the Town of North Andover, whereby treated stormwater is defined to the stormwater that meets
the requirements in Standards 2 through 9. As currently proposed, most of the runoff flows from
the paved areas of the project site would be routed through deep sump catchbasins, a
Stormceptor unit and an extended detention pond prior to discharge. The remaining paved areas
would be routed through at least one of these BMPs prior to discharge. The adequacy of the
treatment provided by these BMPs is addressed under Standard#4.
Standard#2. Post-Development Peak Discharge Rates
The North Andover regulations require that post-development peak discharge rates for the 1, 10
and 100-year storm events do not exceed pre-development peak discharge rates. The state
standards require this of the 2 and 10-year 24-hour storm events, with evaluation to determine
that the 100-year event does not cause increased flooding impacts offsite. The North Andover
regulations also call for a sub-watershed delineation of the site, including the peak flow rate,
time of peak flow and the volume of runoff at each discharge point, to be used as a basis for the
hydrologic analyses.
"lie NOI package includes a hydrologic analysis based on modeling conducted using the
i iydraflow model for the 1, 2, 10 and 100-year design storms, which indicates that the peak rate
1600 Osgood, Tcch7iic<il Rcv ic�,N; w;
hiiie 24, 2005
of runoff from the site would not exceed pre-development rates. I have the following comments
on the hydrologic analysis:
1. As indicated above, the analysis needs to address the net impact on the volume of flow
discharged to each of the two onsite wetland systems, not just the rate of flow. As
proposed the project would divert runoff flow from approximately 1.93 acres that
currently drains to the on-site wetland to the south of the project area and add it to the
drainage area to the northern wetland area. Based on the model, the total volume of flow
discharged from the project area to the southern wetland would be reduced by 25 to 50
percent from existing conditions, while the volume discharged to the wetland system to
the north of the project area would be increased by up to 140 percent. The impact of these
changes on the hydrology and potential flooding of the wetlands should be evaluated in
the context of the total flow to each of the wetland systems.
2. It is not clear how the infiltration system is being modeled, as the maximum elevation
reached and the associated storage volumes listed in the model output are not consistent
with the design plans.
Standard#3. Recharge to Groundwater
Standard #3 requires that the annual groundwater recharge from the post-development site
should approximate the annual recharge from the pre-development site, based on pre-
development soil conditions.
The NOI submittal includes infiltration volume calculations based on 138,600 acres of net
impervious area being added to the site in areas of HSG A and C soils. The calculated recharge
volume required is 2,888 cubic feet.
1. Additional information is needed to support the recharge calculations. Specifically, the
calculation of net impervious area needs to be clarified and should include tabulations of
the total pre-development drainage area and total post-development drainage area. In
addition, if the landscaped islands in the 190,000 sf parking lot are to be excluded from
the impervious area calculations, design details need to be provided demonstrating that
these areas are graded and surfaced to recharge naturally.
2. The storage calculations for the proposed Stormtech infiltration system are based on
utilizing the entire system depth. Given that the invert of the 8-inch pipes into the system
is 14 inches below the top of stone and the outlet invert from DMH-7 to the detention
basin is less than 10-inches above that, it appears that the system will back up and
overflow before the top several inches of storage are utilized. The calculations should be
revised accordingly.
3. Site specific soil testing data is needed to confirm infiltration rates, depth to groundwater,
depth to bedrock, and general suitability for infiltration at the proposed recharge system
location, and also to support the assumption of 50 percent HSG A and 50 percent HSG C
soils used in the calculations. The drainage report indicates that soil testing has been
1000 OSgood, 'I,cchnical Rcvicw 4
June 241 200
conducted, but the soil logs and test pit locations were not included in the materials I
reviewed.
4. The applicant needs to provide calculations demonstrating that recharge facilities will be
totally dewatered within 72 hours following a storm event.
5. DEP design guidelines for subsurface infiltration systems call for a setback of 100 feet
from slopes greater than 20 percent. The proposed recharge area is immediately adjacent
to the detention pond embankment with a slope of 33 percent, thus there is significant
potential for breakout into the detention pond. While this may not negatively impair the
detention pond functioning (assuming the slope is adequately stabilized), it does defeat
the purpose of groundwater recharge if the infiltrated flow is subsequently discharged as
surface flow.
Standard#4. 80% TSS Removal
Standard #4 stipulates that stormwater management systems be designed to remove 80% of the
average annual load of total suspended solids (TSS) from the post-development site. It is
presumed to be met when suitable BMPs are implemented, sized appropriately to treat the
prescribed runoff volume, and properly maintained.
The stormwater management system proposed for this project would utilize a combination of
deep sump catchbasins with outlet hoods followed by treatment through a Stormceptor treatment
unit and an extended detention pond to reduce the total suspended solids (TSS) load from most
of the pavement runoff from the new parking lot. The remaining areas would undergo treatment
in at least one of these BMPs. My comments are as follows:
1. It is not clear why the treatment areas are not consistent with the runoff subareas
modeled, and why the total treatment area (7.04 acres) differs from the total runoff area
modeled (6.82 acres). Treatment areas are not shown on the plan, so it is difficult to
determine which areas are included in the calculations.
2. The TSS removal calculations assume 10 percent TSS removal for pavement sweeping in
all of the treatment areas. The DEP Stormwater Policy states that granting of this 10
percent credit is discretionary on the part of the Commission. The O&M Plan for this
project calls for pavement sweeping at least four times per year, therefore granting of this
credit may be appropriate provided that adherence to the O&M Plan can be ensured.
3. As proposed, the TSS removal in the drainage area discharging to the southern wetland
would only be 32.5 percent. While the DEP guidelines do allow for averaging of removal
rates among multiple treatment trains, it is only when the discharges are within the same
subbasin. Additional treatment needs to be provided for the runoff discharged to this
wetland.
1600 Osgood. Te.cllrnical RcvICy' 5
Jurnc 24, 2005
4. Calculations should be provided demonstrating that the Stormceptor unit is designed to
treat the entire tributary flow generated by 0.5-inches of runoff to the level of treatment
stated (71 percent)without bypassing.
5. Additional information is needed to demonstrate that the proposed extended detention
basin would provide adequate detention to achieve the stated pollutant removals.
Specifically, the basin should provide a minimum of 24 hours detention for the range of
storms that would occur over a year (not just the one year storm) and should empty
within a 48 to 72-hour period following a storm to provide storage capacity for the next
event. A low flow channel should be incorporated in the basin design and the flow path
through the basin should be maximized. As currently proposed the 4-inch outlet, with its
invert at grade, would provide no detention for low flow conditions, and most of the
basin would be short-circuited by the flows discharged through FES-02.
6. Soil testing data at the proposed detention pond location is needed to verify that the basin
will be above the high groundwater elevation.
7. Although it is not included in the calculations provided, additional TSS removal credit
can be taken for infiltrated flows.
Standard#5. Higher Potential Pollutant Loads
The proposed project does not constitute a land use with higher potential pollutant loads.
Standard#6. Protection of Critical Areas
The project site is not located in a critical area as defined by the Stormwater Management Policy.
Standard#7. Redevelopingnt
The proposed project is not a redevelopment project as defined in the Stormwater Management
Standards since it represents a net increase in impervious surface.
Standard#8. Erosion and Sediment Control
Erosion and sediment control measures to be undertaken during project construction are
addressed in Section 8.0 of the NOI narrative and depicted on the project plans.
1. The plan should also include provisions to prevent heavy equipment from compacting
soils in the planned infiltration area during construction.
2. The proposed project will be subject to NPDES permit compliance and will require
preparation of a construction Stormwater Pollution Prevention Plan (SWPPP). The
Commission should be provided the opportunity to review and approve the SWPPP as it
is developed. Provision for construction monitoring of the site should also be established.
1000..0s',"Ood. 'FeG11111cal RRC:VMN' 6
J tine 24, 2005
Standard#9. Operation and Maintenance Plan
The applicant has submitted an O&M plan outlining measures for maintaining the structural
water quality controls on the site. The plan identifies the owner and party responsible for O&M
as being Ozzy Properties, Inc or any successor thereof.
1. Appropriate locations for snow storage on the site should be designated and a description
of the proposed snow management procedures in accordance with the DEP Bureau of
Resource Protection snow disposal guidelines should be added to the O&M Plan.
I appreciate the opportunity to assist the North Andover Conservation Commission with the
review of this project, and hope that this information is suitable for your needs. Please feel free
to contact me if you or the applicants have any questions regarding the issues addressed herein.
Sincerely,
EGGLESTON ENVIRONMENTAL
Lisa D. Eggleston, P.E.
C: Mike Howard & Julie Vondrak, Epsilon Associates
Matt Leidner, Marchionda& Associates
29 05 04: 36p Eggleston Environmental 9704439262 p02
EGGLESTON ENVIRONMENTAL
June 29, 2005
North Andover Conservation Commission
400 Osgood Street RECEIVED
North Andover, MA 01845
Attn: Alison McKay JUN 2 9 2005 Pi
RE: Stormwater Management Review NORTH ANDOVER
1600 Osgood Commerce Center CONSERVATION COMMISSION
Dear Alison and Commission Members:
I am submitting this letter in follow-up to my previous letter of June 24, 2005 regarding
the stormwater management review of the proposed parking lot improvements at 1600
Osgood Street, (the Lucent Technologies site) in North Andover, Since that time I have
received and reviewed the June 28, 2005 letter from Matthew Leidner, RE, of
Marchionda & Associates L.P. responding to my June 24, 2005 review comments and
including the Stormceptor sizing program output, test pit logs, revised O&M Plan and
site plan revisions through 6/28/05. 1 have also had several telephone conversations with
Matthew Leidner to discuss my comments. At this point, I believe that all of the issues
raised in my June 24, 2005 letter have been satisfactorily addressed. My comments are
summarized below:
1. In the revised plans, the infiltration system has been lowered slightly in order to
utilize the entire storage volume prior to overflow. In conjunction with the highly
permeable soils facilitating vertical flow, this will help to reduce the potential for
breakout on the detention basin slope. In addition, I have suggested to Mr. Leidner
that an impermeable barrier (e.g. polyethylene) be placed along the side of the
infiltration system facing the detention basin to prevent lateral flow toward the basin.
2. 1 also recommend that several low berms or a shallow winding channel be added in
the bottom of the detention basin to minimize short circuiting and enhance the time of
travel through the basin for small storm events.
Once again, I appreciate the opportunity to assist the North Andover Conservation
Commission with the review of this project, and hope that this information is suitable for
your needs. Please feel free to contact me if you or the applicants have any questions
regarding the issues addressed herein,
Sincerely,
ECOLESTONENVIRONMENTAL
11�I Q) ��61 4
CXJ VIt(—
Lisa D. Eggleston,P.E.
C: Mike Howard&Julie Vondrak,Epsilon Associates
Matt Leidner, Marchionda&Associates
55 0LD CoAcHRoAD SuDwRYAM 01776 TELIFAx978.443.9262
min
COPY
29 05 04: 36p Eggleston Environmental 9704439262 p42
EGGLESTONENV[RONMENTAL
June 29, 2005
North Andover Conservation Commission
400 Osgood Street RECEIVED
North Andover, MA 01845
Attn: Alison McKay JUN 2 9 2005 YA)
RE Stormwater Management Review NORTH ANDOVER
1600 Osgood Commerce Center CONSERVATION COMMISSION
Dear Alison and Commission Members:
I am submitting this letter in follow-up to my previous letter of Julie 24, 2005 regarding
the stormwater management review of the proposed parking lot improvements at 1600
Osgood Street, (the Lucent Technologies site) in North Andover. Since that time I have
received and reviewed the June 28, 2005 letter from Matthew Leidner, P.E. of
Marchionda & Associates L.P. responding to my June 24, 2005 review comments and
including the Stormceptor sizing program output test pit logs, revised O&M Plan and
site plan revisions through 6/28/05. 1 have also had several telephone conversations with
Matthew Leidner to discuss my comments. At this point, I believe that all of the issues
raised in my June 24, 2005 letter have been satisfactorily addressed. My comments are
summarized below:
1. In the revised plans, the infiltration system has been lowered slightly in order to
utilize the entire storage volume prior to overflow, In conjunction with the highly
permeable soils facilitating vertical flow, this will help to reduce the potential for
breakout on the detention basin slope. In addition, I have suggested to Mr. Leidner
that an impermeable barrier (e.g. polyethylene) be placed along the side of the
infiltration system facing the detention basin to prevent lateral flow toward the basin.
2. 1 also recommend that several low berms or a shallow winding channel be added in
the bottom of the detention basin to minimize short circuiting and enhance the time of
travel through the basin for small storm events.
Once again, I appreciate the opportunity to assist the North Andover Conservation
Commission with the review of this project, and hope that this information is suitable for
your needs. Please feel free to contact me if you or the applicants have any questions
regarding the issuer,addressed herein.
Sincerely,
EGGLFSTON ENVIRONMENTAL
C>61
Lisa D. Eggleston,P.E.
C: Mike Howard& Julie Vondrak,Epsilon Associates
Matt Leidner, Marchionda& Associates
55 OLD COACH ROAD SuDBuRYA4A 01776 TELIFAx978.443.9262
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