To:
From:
Re:
A. Motion:
Discussion:
City of Nashua, Public Works Division
Board of Public Works Meeting Date: June 7, 2016
Stephen Dookran, P.E., City Engineer
Enginecring Department
Citywide Infiltration/Inflow Analysis
Change Order No. 2
To approve Change Order No. 2 for the Citywide Infiltration/Inflow Analysis to Wright-
Pierce of Manchester, NH in an amount of $23,709. Funding will be through:
Department: 169 - Wastewater; Fund: Wastewater; Activity: Inflow and Infiltration.
On February 29, 2016, this board approved the Citywide Infiltration/Inflow Analysis to
provide citywide metering of the sanitary sewer network for eight weeks during the
spring season which typically has higher groundwater and wet weather events for the
purpose of identifying extraneous infiltration and inflow (I/I) in the wastewater collection
system. Data from the flow metering will identify sewer subareas with high infiltration
and inflow and will allow the consultant to provide recommendations for further
investigations and removal of I/I.
To get enough data to analyze, rainfall in amounts of a half inch or more is needed.
During the eight week metering period which ended on May 27, 2016, only one rain
event occurred that had one half inch of rain. For this reason, Change Order No. 1 for
$9,882 was issued extending the metering period for 14 days. While one additional rain
event above one half inch has occurred, four rain events are needed for reliable results.
This request for Change Order No.2 is to extend the metering period until July 1 to
acquire the best results possible to complete the I/I analysis. The meters can be
withdrawn prior to July 1 for a cost savings if the necessary rain events occur.
The total contract value with Change Order No. 1 is $178,775. With Change Order No.
2, the total contract value is $202,484.
