RITST Hayner/Swanson, Inc.
Civil Engineers/Land Surveyors
May 24. 2022
Daniel Hudson, P.E.
City Engineer
9 Riverside Street
Nashua. NH 03062
Dear Mr. Hudson:
Hayner/Swanson, Inc. (HSI) is pleased to submit this proposal to perform professional services
in support of the City of Nashua’s investigation, evaluation and resolution of concerns with the
sewer and wastewater collection systems.
These services will be performed on an on-call basis and may include assignments throughout
the City.
As a first assignment, we understand that the City wants HSI to evaluate the feasibility of
implementing changes to the existing drainage and combined sewer system in the area of Factory
Street and Water Street. Presently, a number of upstream pipes carrying stormwater tic into the
combined sewer system. The goal is to disconnect these drainage pipelines from the combined
system and have the separated stormwater outlet at the river.
HSI proposes to perform an initial evaluation of alternatives. This evaluation will build on
studies which are presently underway by the City Engineering Department. We will work
closely with City staffas we perform our evaluation.
We understand that there are several concerns which we will be mindful of during our work:
e The City is planning a project to reconstruct sidewalks and repave Factory Street. Some
alternatives which we will evaluate would require work in Factory Street. The City needs
to know if work will be recommended in Factory Street as soon as reasonably possible.
e There are two existing stormwater outfalls at the river. One is 48-inch diameter and the
other is 30-inch diameter. While directing the separated stormwater, flow to the 48-inch
outfall would be preferable, this may not be feasible due to various constraints.
e While it may be advantageous to direct the flow to the 30-inch outfall. this pipe may not
have sufficient capacity. If additional capacity is needed, adding another pipe adjacent to
the 30-inch outfall may be recommended. Although this would normally be a significant
permitting hurdle, we note that the City Riverfront Project has submitted a wetland
permit for the area in question. This application already includes reconstructing the
entire riverbank in the vicinity of the outfall. Amending this application might be a
reasonable approach to permitting a proposed twin pipe outfall.
3 Congress St. Nashua, NH 03062 - (603) 883-2057
131 Middlesex Turnpike, Burlington, MA 01803 - (781) 203-1501
www. hayner-swanson.com
