Hinckley Street Reconstruction-DPW Memo_December 2015CITY OF NORTHAMPTON, MASSACHUSETTS
DEPARTMENT OF PUBLIC WORKS
125 Locust Street
Northampton, MA 01060
413-587-1570
Fax 413-587-1576
Edward S. Huntley, P.E.
Director
Pg.1/9, M:\Hinckley Street\Permits\NOI\Memo_NCC_response12092015.doc
Memorandum
To: Northampton Conservation Commission
From: James R. Laurila, P.E. City Engineer
Nicole Sanford, Senior Environmental Scientist
Date: December 9, 2015
Re: City of Northampton Department of Public Works
Hinckley Street Reconstruction Project - Notice of Intent
DEP File Number: 246-0683
Additional Supporting Information
The memorandum provides additional information and discussion regarding the proposed
construction of a drainage outfall as part of the Hinckley Street Reconstruction Project. This
additional information is provided as a follow-up to the last Conservation Commission hearing
on July 23, 2015.
1.0 Proposed Project and Project Purpose
A Notice of Intent (NOI) has been submitted to the Northampton Conservation Commission
(NCC) for the construction of a new stormwater management system including a 36- inch
diameter outfall located within 200 feet of the Mill River. The project includes a 14-foot wide
gravel access road leading to the new outfall. This new outfall and drainage system is proposed
to replace an existing outfall pipe that is undersized, in disrepair and eroding the existing
embankment adjacent to Riverside Drive. The “Project Purpose” as defined in the regulations
(310 CMR 10.04), is to construct a new stormwater management system to help mitigate
flooding in the Elm Street Brook area, improve street drainage in the Hinckley Street and
Riverside Drive area, and to replace an existing outfall that is undersized and in disrepair.
Reduction in stormwater flow to the Elm Street Brook will be accomplished by rerouting
drainage from upper Hinckley Street, upper Warner Street, and Maplewood Terrace to the new
proposed outfall. Rerouting drainage from the Elm Street Brook drainage system to the new
outfall will help alleviate flooding on lower Elm Street during heavy rain events, providing a
public safety benefit beyond the outfall project site discussed in the NOI.
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Stormwater modeling was completed by CDM Smith to quantify the reduction in flow to the Elm
Street Brook resulting from the proposed project. The modeling revealed the following flows
into Elm Street Brook and what the proposed flow and percent reduction would be if the new
outfall is constructed:
Storm Event Existing
Discharge
(cfs)
Proposed
Discharge(cfs)
Percent Flow
Reduction
Flow
Reduction
(cfs)
Flow
Reduction
(gpm)
2- year 123.6 117.1 5.3 6.5 2,917
10-year 261 244.4 6.4 16.6 7,450
25-year 376.8 350.9 6.9 25.9 11,625
50-year 485.6 462.6 4.7 22.8 10,233
100-year 664.3 636.7 4.1 27.6 12,388
The construction of the new outfall will provide important relief to the undersized Elm Street
Brook Drainage system, as this table illustrates. This current project is a cost-effective means to
make drainage improvements that will benefit many properties in this area of the City.
The project was filed as a new development project. During the hearing for this NOI, a NCC
member noted that the project was filed under new development and not redevelopment. The
regulations state that the issuing authority may allow work to redevelop a previously developed
riverfront area (RA), provided the proposed work improves existing conditions (310 CMR 10.58
(5) Redevelopment Within Previously Developed Riverfront Area: Restoration and Mitigation).
A previously developed riverfront is defined as an area that contains areas degraded prior to
August 7, 1996 by impervious surfaces from existing structures or pavement, absence of topsoil,
junkyards, or abandoned dumping grounds. The existing outfall may be considered degraded,
but is located outside of the riverfront area. Additionally, the bike jumps may be considered
degraded, but they were constructed in 2013. Based on these definitions, we have considered the
construction of the new outfall a new development in the Riverfront Area and 310 CMR 10.58
(4) and not (5) applies to the project.
2.0 Proposed Project - Performance Standards (310 CMR 10.58(4))
Where a proposed activity involves work within the riverfront area, the regulations state the
issuing authority shall presume that the area is significant to protect the eight interests of the
MWPA listed below (310 CMR 10.58 (3)):
Protection of public and private water supply;
Protection of groundwater supply;
Flood control;
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Storm damage prevention;
Prevention of pollution;
Protection of land containing shellfish;
Protection of fisheries; and
Protection of wildlife habitat.
Although the RA in the project location has been altered in the past as described above, we have
not attempted to rebut the presumption of the interests of the Wetlands Protection Act (WPA) in
this location (that is that we have not rebutted that the eight interests exist at the project site). By
proposing some mitigation to flood control in Elm Street Brook the interests of the act are
enhanced by the proposed changing of drainage areas with the new outfall. Because the
presumptions above were not rebutted, we proceeded in the NOI by presenting the outfall project
and detailed the project impacts in the RA. General performance standards are established in the
regulations for projects located in the RA. These are briefly discussed below.
310 CMR 10.58(4) Riverfront Area – General Performance Standard- The Applicant shall prove
that there are no adverse effects on interests in MWPA and that work, including proposed
mitigation, will have no significant adverse impact on riverfront area to protect interests in the
act, and that there are no practicable and substantially equivalent economic alternatives.
In a subsequent section we discuss alternatives to the project that we believe are no better than
the project proposed. We believe that the interests of the WPA are enhanced by the proposed
project because of the provision of some flood relief and public safety improvements for the Elm
Street Brook area. In addition, the replacement of the failed existing outfall will prevent future
storm damage and erosion of the existing embankment thereby preventing excess eroded
sediments from entering the Mill River.
310 CMR 10.58(4)(a) Protection of other resource areas – As previously presented, the project
work within the resource area meets the performance standards for all other resource areas within
the RA.
310 CMR 10.58(4)(b) Protection of rare species – The project area is not located within mapped
Priority or Estimated Habitat for rare species. This performance standard does not apply to the
project site.
310 CMR 10.58(4)(c) Practicable and Substantially Equivalent Economic Alternatives - A
detailed discussion of alternatives is presented in Section 3.1.
310 CMR 10.58(4)(d) No significant adverse impact – The outfall project as proposed meets the
standard of no significant adverse impact defined in the regulations. As stated in the regulations,
“within 200 foot riverfront areas, the issuing authority may allow the alteration of up to 5,000 SF
or 10% of the riverfront area within the lot, whichever is greater…” The WPA regulations also
state: “the calculation also shall exclude areas used for structural stormwater management
measures, provided there is no practicable alternative to siting these structures within the
riverfront area…” There is approximately 783,000 SF of RA on the parcel and the outfall
project will impact 3% (19,380 SF) of RA, significantly less than the 10% allowed. This
disturbance is all work within the RA.
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The majority of impact to RA will occur in the outer riparian zone except for 200 SF of impact
necessary for grading for the access road. All other impact is temporary, resulting in the
majority of the inner riparian zone remaining vegetated and undisturbed.
Under the Massachusetts Stormwater Management Standards, the project is considered a
redevelopment project because it is a roadway improvement project. A stormwater report has
been prepared for this project by CDM Smith and is located in Section 8 of the NOI.
Given that the RA is already a highly altered area of this site (former canal, BMX tracks and
footpath to the Mill River) and the proximity to a paved road and residential area, it is unlikely
that this project will impair the capacity of the riverfront area to provide important wildlife
habitat functions. The majority of the inner riparian zone will remain undisturbed and once the
stormwater outfall and associated structures are installed the area will remain mostly
undeveloped, but better stabilized with the existing failed outfall removed.
The proposed work will not impair groundwater or surface water quality as the purpose of the
stormwater outfall is to dissipate energy during storm events to prevent downstream erosion.
Sedimentation barriers will be in place to prevent erosion during construction.
3.0 Practicable and Substantially Equivalent Economic Alternatives (310 CMR 10.58(4)(c)
The regulations state there must be no practicable and substantially equivalent economic
alternative with less adverse effects on interests of MWPA.
Definition of Practicable (310 CMR 10.58 (4)(c)1) –An alternative is practicable and
substantially equivalent economically if it is available and capable of being done after taking into
consideration costs, existing technology, proposed use and logistics in light of the overall
“project purpose”.
The four factors to be considered regarding whether an alternative is practicable are as follows:
1. Costs –whether costs are reasonable or prohibitive to the owner; higher or lower costs
will not determine whether an alternative is practicable; evaluation should consider the
financial capability reasonably expected from the type of owner rather than the personal
or corporate financial status of that particular owner; and documentation of costs may be
required.
2. Existing technology – alternatives use best available measures or engineering practices
that have been developed and are commercially available
3. Proposed use –The item is related to the concept of “Project Purpose”. A practicable and
substantially equivalent economic alternative includes alternatives which are
economically viable for the proposed use from the perspective of site location, project
configuration within a site, and the scope of the project. In the context of publically
financed projects, the proposed use includes consideration of legitimate governmental
purposes (e.g. protection of health and safety of public, etc…).
4. Logistics – presence or absence of physical or legal constraints
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The “Project Purpose” is to construct a new stormwater management system to help mitigate
flooding in the Elm Street Brook area, improve street drainage in the Hinckley Street and
Riverside Drive area, and to replace an existing outfall that is undersized and in disrepair.
Reduction in stormwater flow to the Elm Street Brook will be accomplished by rerouting
drainage from upper Hinckley Street, upper Warner Street, and Maplewood Terrace to the new
proposed outfall. Rerouting drainage from the Elm Street Brook drainage system to the new
outfall will help alleviate flooding on lower Elm Street during heavy rain events, providing a
public safety benefit beyond the outfall project site discussed in the NOI.
Scope of Alternatives (310 CMR 10.58 (4)(c)2) – The regulations state the scope of alternatives
shall be commensurate with the type and size of the project. The issuing authority or another
party may overcome the presumption by demonstrating the practicability of a wider range of
alternatives, based on cost, and whether the cost is reasonable or prohibitive to the owner;
existing technology; proposed use; and logistics in light of the overall project purpose. The area
under consideration for practicable alternatives extends to the original parcel and the subdivided
parcels, any adjacent parcels, and any other land which can reasonably be obtained with the
municipality for activities conducted by municipal government.
3.1 Evaluation of Alternatives
Evaluation of Alternatives (310 CMR 10.58 (4)(c)3 – the applicant shall submit information to
describe site locations and configurations sufficient for a determination by the issuing authority
under 310 CMR 10.58(4)(d) – No significant adverse impact. The level of detail of information
shall be commensurate with the scope of the project and the practicability of alternatives. Where
an applicant identifies an alternative which can be summarily demonstrated to be not practicable,
an evaluation is not required. The issuing authority shall not require alternatives which result in
greater or substantially equivalent adverse impacts. If an alternative would result in no
identifiable difference in impact, the issuing authority shall eliminate the alternative.
Alternatives to the proposed project were considered that met the defined “project purpose” as
described above. Based on the requirements of the regulations also described above, the
following alternatives were considered.
Four alternatives were considered:
1) New 10-in outfall: Replacement of the existing outfall would result in similar RA impacts
because it would be necessary to extend the outfall to the old canal in the RA so that drainage
discharge would not scour the steep embankment. This alternative requires the installation of
drain manholes and additional pipe to a discharge point at the canal, such that the exit velocity
could be reduced to acceptable levels. The configuration would be similar to the project that is
proposed. The Proposed Use criteria is not met to make this a practicable alternative because this
smaller outfall would not improve drainage for Hinckley Street or reduce the flooding impacts on
Elm Street Brook.
2) Elm Street Brook Master Plan: In a report in May 2012, CDM proposed a Master Plan of
infrastructure improvements for the Elm Street Book drainage area. Among the
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recommendations were 1,900 feet of new 48-inch diameter pipe and 1,600 feet of 7 ft x 4 ft box
culvert. Other improvements included about 15,000 linear feet of new drainage pipe ranging in
size from 12-72 inches in diameter. The total projected cost of the improvements was about $19
million. The improvements were designed to manage Elm Street Brook flood impacts for up to a
10-year storm. Although this alternative involves construction work in other locations it is
included because it is consistent with one of the main “Project Purposes”, to aid with flodd
control in Elm Street Brook. However, the Proposed Use criteria is not met to make this a
practicable alternative because the scope of the project would not improve drainage for Hinckley
Street or provide for a new outfall to replace the one in disrepair. In addition, the cost criteria are
not met because the project cost for this alternative is substantially greater than the proposed
project.
3) New 36-in outfall with a temporary access road: This alternative is the same as the proposed
project with the exception that a temporary construction road would be used. This temporary
road would be removed at the end of construction. The removal of the road would be
accomplished by reducing the grade, making it less steep, from the edge of Riverside Drive to
the south side of the temporary access road. By removing the road, any future maintenance and
repair of the system would require that the road be built again, thus requiring future RA
disturbance. This Alternative meets the “proposed use” criteria. However, it would increase the
cost of the project by adding the work necessary to remove the road. This alternative would have
the same RA impacts.
According to the regulations (310 CMR 10.58(4)(a)3.: “The issuing authority shall not require
alternatives which result in greater or substantially equivalent adverse impacts.”
4) New 36-inch outfall with a road width of 10-feet: This alternative is similar to 3, in that the
access road that is left will be narrower than the proposed 14-ft. The narrowing of the road
would be accomplished by reducing the grade, making it less steep, from the edge of Riverside
Drive to the north side of the 10-ft wide permanent access road. Narrowing the road may hinder
the ability and movement of equipment that may be necessary for any future maintenance and
repair of the system. The narrow road poses some increase in safety hazards during any future
maintenance and repair activity. This Alternative meets the “proposed use” criteria. The cost of
the project would essentially be the same. This alternative would have the same RA impacts as
the proposed project.
According to the regulations (310 CMR 10.58(4)(a)3.: “The issuing authority shall not require
alternatives which result in greater or substantially equivalent adverse impacts.”
4.0 Other Project Related Information
Smith College – Paradise Road Housing and Outfall Replacement: Since the last Conservation
Commission hearing for this project, it was suggested that DPW look at the details of the
replacement outfall that was constructed recently by Smith College as part of new Student
Housing at the end of Paradise Road. The design plans do not show a road being needed to
construct the drain outfall and no road was proposed as part of that outfall construction. The new
outfall is a 15-inch diameter HDPE pipe installed on steep slope to the Mill River. The DPW
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required that an armorflex articulated block mat or other armoring be installed on the sewer
easement to prevent damage to the sewer interceptor line.
The peak flow for a 100-yr storm for the Paradise Road outfall project was 5.8 cubic feet per
second. The project engineer selected a larger diameter ribbed plastic pipe to aid in reducing
pipe velocity. (By comparison the 100-yr storm flow for the Hinckley Street outfall project is
90.2 cfs, or about 15 times more flow.)
As was requested, DPW recently went back and reviewed the design plans and calculations
completed by Berkshire Design Group. The project required a stormwater permit from DPW
and had been previously reviewed and approved. We determined that the project was constructed
by Geeleher Enterprises. On December 2, 2015, DPW met with Ryan Geeleher to discuss
construction methods used to construct the outfall. Mr. Geeleher said that he did not need to
build an access road because there was already a sewer easement with a gravel path at the
discharge end of the outfall. He said without the existing easement he would have needed to
build a road from the top of the slope. He said that he used a large excavator at the top of the
slope to install some of the drain pipe and a light weight tracked excavator from the bottom of
the slope for the remainder of the project.
Hinckley Street Outfall Constructability Review: During the December 2, 2015, meeting with
Ryan Geeleher we provided him with a copy of the proposed design plan for the outfall. Mr.
Geeleher said that because of the drainage manholes, size of the pipe and outfall that a large
excavator would be needed during construction and that a road as shown would be necessary to
complete construction. Without prompting, he added that the City would want to maintain the
road for maintenance and any repair work once the project is completed. The need to get
equipment to drain manholes, the outfall and channel would require a road.
Elm Street Brook Flooding September 30, 2015 storm event:
The flooding of Elm Street that occurred on September 30, 2015 on Elm St and Milton Street
followed the same pattern as past flood events. A storm event with periods of more intense
rainfall pushed the brook, the high school culverts and the street drainage systems beyond their
capacity and resulted in flooding in Elm Street from approximately 225 feet west of Nutting
Avenue to Milton Street and flooding in Milton Street from Elm Street to Ormond Drive. Elm
Street was closed for a period of time because of the flooding.
The rainfall totals for September 30, 2015 from nearby gauges were:
3.19 inches (Behind Stop & Shop, KMANORTH44)
2.97 inches (Northampton, Old Ferry Rd, KMANORTH66)
2.92 inches (DPW, Flood Control Station)
2.33 inches (Smith College, KMANORTH55)
Most of the rainfall fell between 1 am and 9:30 am with two short periods of more intense rain at
around 6:15 am and 8:45 am. The rainfall rates peaked at 0.64 inch per hour at 6:07 am and 0.83
inch per hour at 8:40 am at the rain gauge Behind Stop and Shop. According to TP-40, this
storm event would be considered a 2-year 24 hour storm (3 inches) and just under a 1-year, 1
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hour rainfall (0.95 inches). Below are two photos from the most recent flooding event of Elm
Street Brook that shows Elm Street being closed (Photo credit: Daily Hampshire Gazette).
5.0 Summary
As requested, additional information about the project and project alternatives has been provided
in accordance with the WPA regulations. Given the analyses above, none of the alternatives
reviewed meets the regulatory definition of Practicable and Substantially Equivalent Economic
Alternatives.
In addition, the amount of RA disturbance for the proposed projects falls well below the amount
of RA disturbance allowed under the regulations. As stated in the regulations, “within 200 foot
riverfront areas, the issuing authority may allow the alteration of up to 5,000 SF or 10% of the
riverfront area within the lot, whichever is greater…” The WPA regulations also state: “the
calculation also shall exclude areas used for structural stormwater management measures,
provided there is no practicable alternative to siting these structures within the riverfront area…”
There is approximately 783,000 SF of RA on the parcel and the outfall project will impact 3%
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(19,380 SF) of RA, significantly less than the 10% allowed. This disturbance is all work within
the RA.
The DPW requests that an Order of Conditions be issued for this proposed project.