West Parish Filters in November

The following projects have progressed over the months of November:

• Clearwell & Backwash Pump Station - CH Nickerson worked on troubleshooting the new domestic water system in November, while also demolishing equipment in the existing backwash pump room. The new backwash pumps have been online for several weeks. In early December the new domestic water system was brought online and the contractor was able to make the final transmission main connection, disconnecting the old Clearwell from the system.

• New Water Treatment Plant - Hazen, the Commission's design engineer, is working on completion of 100% design documents, incorporating Commission comments and input provided through a 90% design peer review completed in November.

In November, the contractor worked to optimize the new domestic water system. The system supplies potable water to the West Parish campus and consists of two pumps, a UV disinfection system, and a sodium hypochlorite system to provide a chlorine residual throughout the campus distribution system. 

When the domestic water system was first brought online, the sodium hypochlorite pumps were not providing a consistent dose after sudden changes in water flow velocity. This system meets instantaneous water demands, which happen frequently throughout the day when staff use sinks, bathrooms, and other connections.  

The design build team spent the month of November troubleshooting the system, changing out the chemical metering pumps and other equipment, and making changes to the programming for the pumps. By the end of the month they had made enough progress to bring the system online again.

The domestic water system was a critical path step, and the old existing Clearwell could not be taken out of service until this system was online.   

Liz Stich with CHN and Chief Operator Pete Thayer troubleshoot the domestic system

(SWSC photo, 11/08/2023)

While working on the domestic system, the contractor also made progress with demolishing the existing process water and backwash pumps in the existing pump room. The contractor is required to demolish the existing pump systems as part of the contract.   

Lifting backwash pump out of the pump room

(SWSC photo, 11/08/2023)

Demolishing the process water pumps

(photo by AECOM, 11/14/2023)

Pulling out backwash elbow

(photo by AECOM, 11/15/2023)

Remaining piping connection awaiting tie-in in December

(SWSC Drone photo, 11/02/2023)

The new Clearwell and Backwash Pump Station facility ("Backwash Facility") will replace the existing clearwell and backwash, domestic, and process water pumps. The existing clearwell was originally constructed as a slow sand filter in the 1920s and the roof leaked into the clearwell until we installed the temporary tarp cover. Failure of this clearwell would require the Rapid Sand Filter Plant to be shut down entirely. The existing backwash pumps were installed in the 1970s with the construction of the Rapid Sand Filter Plant and need to be replaced. Parts for these pumps are no longer available should they require repair. This new Clearwell and Backwash Pump Station structure will provide the reliability and redundancy needed for the water treatment process and will be utilized with both the existing and new treatment plant.

New Water Treatment Plant - Highlights

Hazen is currently completing the 100% design documents, and is addressing Commission comments and peer review comments on the 90% document submitted in September. Bid opening for this project is planned for mid-2024.

New WTP Progress Rendering

(Hazen rendering, October 2023)

Why are we building a new plant?

The Commission currently relies on our 1970s era dual media filtration rapid sand filters to treat most of the system's water, and uses the slow sand filters, which date back to the 1920s, to augment water production when needed.

In 2012 the U.S. Environmental Protection Agency (EPA) and Massachusetts Department of Environmental Protection (MassDEP) updated its regulations related to disinfection byproducts (DBPs).

DBPs form when chlorine (required for safe disinfection) reacts with dissolved natural organic matter (NOM) found in surface water bodies such as the Commission’s Cobble Mountain Reservoir, the main source of the drinking water supply. Data indicate that the more intense and extreme precipitation patterns observed in recent years can cause increases in the amount of NOM in the reservoir.

The 1970s-era rapid sand filters are not capable of removing the amount of NOM necessary to consistently meet the DBP regulations. In addition, many other components of the plant are at or beyond the end of their useful life, increasing the risk of failure. Therefore, in 2015 the Commission initiated a comprehensive planning process to modernize the drinking water treatment plant.

The new plant will include the use of Dissolved Air Flotation (DAF) to treat the water by using rising bubbles to push flocculated particles up into a floating mat. The floating mat is collected at the end of a long tank. This process removes particulates and organics upstream of the filters and will enable the Commission to reduce DBPs in the distribution system to meet regulatory compliance for decades to come.

On November 9^th the SWSC hosted a Friends & Family Open House to celebrate the completion of the Backwash Facility at West Parish Filters. The event drew over 100 visitors and allowed us to showcase the final product of everyone’s hard work over the last couple years. We were happy to provide everyone who worked on this project as well as Water Operations staff the opportunity to see the results of their hard work and see the facility in operation!

Friends & Family Open House.

(SWSC photo, 11/09/2023)

West Parish Filters Labor staff repaired an old sand line at Slow Sand Filters 11-14. This sand line is used to send mucked sand out of the slow sand filters and into sand bins for storage. Staff also built a new set of stairs and platform to make access into the Influent Control Structure (ICS) easier and safer for our operators.

Water Operations staff repair sand piping at SSF 11-14

(SWSC Drone Photo, 11/02/2023)

New stairs to ICS Structure built by SWSC Labor staff

(SWSC photos, 12/11/2023)

Nature moment...

Coyote pups spotted at Provin Mountain Reservoir

(SWSC photo, 06/12/2023)