Inflow and Infiltration Investigations

Infiltration and inflow (I/I) is excess water that flows into sewer pipes from groundwater and stormwater.

Groundwater (infiltration) seeps into sewer pipes through holes, cracks, joint failures, and faulty connections.  

Stormwater (inflow) rapidly flows into sewers via roof drain downspouts, foundation drains, storm drain cross-connections, and through holes in manhole covers.

Most I/I is caused by aging infrastructure that needs maintenance or replacement.

CURRENT PROJECTS - Updated on April 27, 2021

2021 Inflow & InfiltrationInflow and Infiltration Work Photo

The Town's consultants, Weston & Sampson, and contractor, National Water Main Cleaning Company, began daytime cleaning and inspection of sewer lines on Monday, March 29, 2021 They have completed the manhole inspection and nighttime flow isolation portion of the project and are continuing the hydraulic cleaning and closed-circuit television inspection (CCTV) work.


Daytime: cleaning/television of sewer pipelines and inspection on sewer manholes will be conducted between 7 am -5 pm. During these routine inspections, the sewer pipelines are cleaned hydraulically with a pressurized water truck and a sewer-jetting nozzle and television inspected with a closed-circuit television inspection (CCTV) camera. The vacuum pressure created by the cleaning may cause air to escape through the traps and drains of your plumbing fixtures such as toilets and sinks. These inspections are conducted between 7 am and 5 pm. Weston & Sampson may need to access your property to conduct the investigations in sanitary sewer easements operated and maintained by the Town. 

Nighttime: flow measurements are also being performed as part of the investigations between midnight (12 am) and 6 am. Flow measurements only require work crews to access sewer manholes and does not require cleaning. Work crews will have police officer detail with them at all times during nighttime flow isolation.

These investigations are being conducted as part of Shrewsbury’s 2021 Infiltration Investigations Project. The purpose of the investigations is to locate sources of groundwater entering the sanitary sewer. By removing this extra flow, Shrewsbury will reduce the amount of wastewater it sends to the regional Westborough Wastewater Treatment Plant.

Where & When


Daytime work will be ongoing in the following areas: Barnard Street, Browning Road, Bunker Hill Road, Deerfield Road, Forest Hill Drive, Longfellow Road, Main Street (between Gage Lane and I-290), Old Mill Road, Rawson Place, Straw Hollow Lane, Tanglewood Drive, Wachusett Circle, Wadsworth Road.

This project will be ongoing and work will take place in the following areas:

Subarea 3C – Longfellow Road / Browning Road / Deerfield Road Area.  Click here for a map of this area.

Subarea 7B – Westview Avenue / Ireta Road / Old Mill Road / Minuteman Way Area. Click here for a map of this area. 

Subarea 7D – O’Donnell Avenue / Thestland Drive / Audubon Drive Area. Click here for a map of this area.

Please Note

We apologize for any inconvenience you may experience during this work and appreciate your continued cooperation while we strive to improve our sanitary sewer system. If you have any questions or experience any inconvenience related to the inspection work described above, please contact the Department of Public Works - Water and Sewer Division at (508) 841-8502 or