To:
From:
Re:
G. Motion:
Discussion:
City of Nashua, Public Works Division
Board of Public Works Meeting Date: February 29, 2016
Stephen Dookran, P.E., City Engineer
Engineering Department
Citywide Infiltration/Inflow Analysis
To approve the engineering contract for the Citywide Infiltration/Inflow
Analysis to Wright-Pierce of Manchester, NH in an amount not to exceed
$168,893. Funding will be through: Department: 169 - Wastewater; Fund:
Wastewater; Activity: Inflow and Infiltration .
From the large volumes of wastewater being treated by the wastewater facility during
times when the total flow is expected to be low, the City suspects that about 25 to 30 %
of extraneous infiltration and inflow (I/I) are coming into the plant. In addition, the new
discharge permit for the treatment plant requires ongoing efforts to reduce 1/I in the sewer
system.
Extraneous flows including infiltration and inflow reduces the capacity of the wastewater
collection system and increase costs to treat the extraneous water at the Nashua
Wastewater Treatment Facility (NWTF). Also, the discharge at the NWTF is reaching
the flow limit where planning of facility improvements and/or expansion may be
required. The purpose of this phase of this I/I Analysis is to provide citywide metering of
the sewersheds during the spring season which typically has higher groundwater and wet
weather events. Results for this will analysis will identify sewersheds with high
infiltration and inflow and provide recommendations for further investigations and
removal of infiltration and inflow.
A request for proposal was emailed to three engineering consulting firms on December
31, 2015 and posted on the City’s website. Four proposals were received on January 26,
2016 from the following firms:
Weston & Sampson of Portsmouth, NH $ 206,980
Wright-Pierce of Manchester, NH $ 168,893
Hazen of Boston, MA $ 257,527
Woodward & Curran of Andover MA $ 279,000
All four firms are qualified to complete the work. The proposal by Wright Pierce was
thorough and they can complete the required tasks for the least proposed cost. The
Selection Committee recommends Wright Pierce for this study.
