HomeMy WebLinkAboutNorth Andover Interceptor Capacity Memo-revised - Woodard & Curran - Miscellaneous - 0 Prescott Street 4/21/2026
MEMORANDUM (Revised 4/22/26)
TO: Tim Willett, Town of North Andover
Jean Enright, Town of North Andover
SUBMITTED BY: Kenneth W. Carlson, PE
DATE: April 21, 2026
RE: Zero Prescott Street Development
Sewer Capacity Analysis
Background and Purpose
Woodard & Curran was retained by the Town of North Andover (Town) to evaluate downstream sewer
capacities under both existing peak dry and wet weather flows and the addition of future flows from the
planned development at Zero Prescott Street, including building a hydraulic model of a portion of the East
Side Interceptor Sewer downstream of the planned development. The purpose of this memo is to
summarize the anticipated impact on sewer capacity of the East Side Interceptor as a result of peak
wastewater flow from the proposed Zero Prescott Street development. A detailed Technical
Memorandum will follow.
Existing Peak Flow
Two temporary flow meters were installed on February 10, 2026 by Flow Assessment Services, LLC (FAS) in
order to measure existing wastewater flow in the East Side Interceptor Sewer downstream of the proposed
Zero Prescott Street development Meter Site #1 at MH 11002 on the East Side Interceptor Sewer before
it reaches Sutton Street, and Meter Site #2 at MH 09088 on Sutton Street. The locations of the flow meters
are shown in Figure 1. Meter Site #1 has experienced a metered peak flow of 4.1 mgd. This peak flow
occurred on March 11, 2026 as a result of significant rainfall and snow melt in the area. Metering is
scheduled to continue for several more weeks in order to meter flows in the East Side Interceptor Sewer
during the traditional spring high groundwater season when wastewater flows are typically at their peak.
The additional meter data will be used in future capacity analyses of the East Side Interceptor and to
calibrate the model used in assessing future sewer capacity.
significant part of Town, as well as the East Side Interceptor Sewer. In addition, significant flow from a large
part of Town is introduced into the East Side Interceptor Sewer at Main Street prior to the GLSD Meter.
Accordingly, the focus of this capacity evaluation is on the East Side Interceptor Sewer from the Zero
Prescott Street development to Sutton Street, since the remaining portion of the East Side Interceptor Sewer
serves a signifcant part of the Town such that assessing the impacts of the Zero Precscott Street
development on the remaining sections of the interceptor sewer would be unreasonable.
Future Flow From Zero Prescott Street
Based on the Comprehensive Permit Application Package dated October 21, 2025, the future development
at Zero Prescott Street is anticipated to have 296 units with a total of 457 bedrooms. Massachusetts Title
5 Guidelines recommend using 110 gpd/bedroom to estimate future wastewater generation. This would
result in an average dry weather flow (ADWF) of 50,270 gpd. Using a typical dry weather diurnal curve
Town of North Andover (0234962.12) Page 1 of 3 Woodard & Curran, Inc.
North Andover Interceptor Capacity Memo-revised April 21, 2026
peaking factor of 1.87, the resulting peak dry weather flow (PDWF) is estimated to be 98,549 gpd, or
approximately 0.1 mgd.
Total Peak Flow and Model Results
Based on the peak flow experienced at Meter Site #1, and the anticipated future peak wastewater flow from
Zero Prescott Street, the interceptor is anticipated to experience a peak flow of approximately 4.2 mgd
upstream of MH 09100 at Sutton Street, including the large volume of wastewater from areas served by the
portion of unmodeled sewer upstream of the development. It should be noted that no significant
wastewater flow is contributed to the interceptor sewer from Meter Site #1 at MH 11002 to MH 09100 on
Sutton Street. A portion of the East Side Interceptor Sewer from the proposed development to Sutton Street
was modeled using InfoWorks ICM Sewer Software to determine the impact of the additional wastewater
flow from the proposed development on the existing interceptor sewer. Only the East Side Interceptor Sewer
from MH 12001 (the future loading location of Zero Prescott Street) to MH 09100 in Sutton Street was
modeled since the remaining portion of the East Side Interceptor Sewer serves a signifcant part of the Town
in addition to the Zero Prescott Street proposed development. The 4.2 mgd peak flow was simulated in the
modeled portion of the East Side Interceptor Sewer to assess impacts on the hydraulic grade line (HGL), an
indicator of capacity based on how full the interceptor would be under peak flow conditions. The result of
the model run showed a maximum peak HGL depth to diameter (d/D) value of 0.54 in one section of sewer
with the flattest slope between MH 11008 and MH 11007 in High Street, meaning that the East Side
Interceptor Sewer would be flowing only about half full in that section of the interceptor with the lowest
capacity. Therefore, it can be concluded that the East Side Interceptor Sewer would have sufficient
capacity to carry the additional flow from the Zero Prescott Street proposed development from
connection point to the interceptor to Sutton Street without surcharging the interceptor, and no
increase in capacity is required at this time.
As stated earlier, a Technical Memorandum will be submitted presenting the detailed technical data
supporting the recommendation herein.
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North Andover Interceptor Capacity Memo-revised April 21, 2026
Figure 1: EAST SIDE INTERCEPTOR SEWER PLAN AND PROFILE
HYDRAULIC GRADE LINE (HGL) AT METER SITE #1
ESTIMATED PEAK FLOW CONDITION
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