Water Archives - Tata & Howard

PFAS Mitigation, Shrewsbury, MA

A PFAS Journey to Determine Effective Management and Treatment Options

Tata & Howard is working with the Town of Shrewsbury, MA to address perfluoroalkyl and polyfluoroalkyl substances (PFAS) in the groundwater. The Town of Shrewsbury water system serves a population of approximately 38,300. The system consists of about 200 miles of main, nine active groundwater wells from three well sites, three pressure zones, six storage tanks, and one water treatment plant. The 7.0 million gallon per day (mgd) Home Farm Water Treatment Facility utilizes biological treatment for removal of manganese.

In 2020, Shrewsbury detected PFAS in the wells. Sampling has indicated that PFAS is present in most of the wells operated by the Town but under the maximum contaminant level (MCL) of 20 nanograms per liter (ng/L) for PFAS6 as regulated by the Massachusetts Department of Environmental Protection (MassDEP) which includes the sum of concentrations for PFOS, PFOA, PFHxS, PFNA, PFHpA, and PFDA. Raw water from one well site, the Sewell Well, has been consistently higher than 20 ng/L; but the finished water from all wells after treatment at the Home Farm Water Treatment Plant has been in compliance and consistently less than 16 ng/L. Most of the PFAS is in the form of PFOA and PFOS which are the two compounds for which the EPA has developed a proposed MCL. The PFOA indicated by the green bar in Table 1 is higher than the proposed Federal MCL of 4 ng/L.

Currently, the Town has been managing the sources to improve water quality and stay under the current MCL of 20 ng/L for PFAS6. A mass balance is utilized to estimate finished water PFAS concentrations based on updated sample results and changes in the operation of the sources. Tata & Howard created the base tool which can be used to see how changes to PFAS levels or flow rates can affect the finished water concentration.

Table 2 represents existing conditions. The numbers used for PFAS are the highest results from each individual well observed in a year of sampling data, showing the finished water level is about 16 ng/L. As long as the PFAS concentrations in the wells remain consistent, the Town will remain in compliance. If sample results change and they see an increase in PFAS concentration at Sewell, the Town will make adjustments using the mass balance to manage the sources to remain in compliance.

The Town cannot manage sources like this indefinitely. They decided to move forward with reviewing PFAS treatment options and pilot testing to determine the best course of action if/when treatment is required.

Tata & Howard and the Town considered three treatment options. The first option is anion exchange, which uses a resin with positively charged ions. These are typically single use resins and require one to three minutes of empty bed contact time. The next option is Granular Activate Carbon (GAC) which uses adsorption. This media can be made from different types of carbon sources that can be recycled through thermal reactivations and requires a ten minute empty bed contact time. There are limitations with GAC on some of the short chain PFAS. The third type is novel media, which includes other types of media that do not fall into the first two categories. The novel media piloted uses an adsorption process that is classified as a single use resin and has a two to three minute empty bed contact time.

Shrewsbury’s pilot testing utilized three anion exchange resins from two suppliers (one of which was regenerative), a coal-based GAC, and a novel media. The novel media selected works like GAC since it is not as sensitive to chlorine and chlorides, which can impact the effectiveness of anion exchange resins.

The GAC pilot test utilized two 6-inch columns in series rather than one very tall column to give more flexibility for installation and backwashing. A total of 10 gallons of media were installed with a loading rate of 7.5 gal/ft2 and an empty bed contact time of approximately ten minutes. The anion exchange and novel medias each utilized one 6-inch column with five gallons of media installed, a loading rate of 11.25 gal/ft2, and an empty bed contact time of approximately two minutes.

The water source was a tap on the effluent line from the existing filters using finished water that had been treated for manganese removal but not any of the chemical additions of KOH, phosphate, chlorine, and fluoride. There were control valves so the water only came through the unit when the treatment plant was online, which is typically more than 20 hours per day.

There was an initial baseline water quality sampling event at the start, at the end of week 20, and at the end of piloting. PFAS samples were taken day one, day seven, and then monthly for the duration of the pilot. Samples were taken from the 25% sample tap until breakthrough (50% of the raw water PFAS levels, so between 6 and 7 ppt), then at the 50% tap.

Table 3 shows the result from the different taps at the end of the pilot. The anion exchange results are from the best performing anion exchange resin. GAC was first detected in week 8 with breakthrough in the 25% tap in week 16 and the 50% tap in week 44. There was a detected amount in the final sample tap in week 64, which was the final week of the testing.

Anion exchange had the longest time to first detect but the 25% breakthrough for all anion exchange and novel media were all within a sample event or so of each other and occurred between weeks 44 and 52. The novel media had breakthrough of the 50% tap at week 60 and was detected in the 100% tap at the final week while the anion exchange was ND in the 100% tap at the end of the pilot.

Table 4 is a summary as to what the permanent filter system may look like. The filters are similar in size but the number of recommended filters differs for each resin. The overall building footprint is similar as well. The anion exchange did perform slightly better than the novel media, however, the overall PFAS removal results over the duration of the pilot was similar. Because of this, construction costs, long term media replacement costs, and operational considerations were included as part of the media selection process.

The Town has not yet made a final decision on media type, but it appears that the novel media may be the best fit for the Town’s needs. Specifically, the novel media allows for some backwashing and chlorination, reducing the potential of biofilm buildup and potential capacity loss due to increased headloss through the media. Additionally, the novel media has a smaller footprint in comparison to GAC. The Town of Shrewsbury’s current PFAS levels do contain mostly PFOS and PFOA at concentrations higher than the proposed Federal regulations for those two compounds. Also, based on reviewing the data of the PFAS6 compounds, PFOA was the compound first detected for all media; also, the majority of the detected PFAS6 concentrations in the effluent throughout the pilot were PFOA.

One additional challenge moving forward is the design of the facility so the water goes through the manganese treatment first, the new PFAS treatment next, and finally utilizes the existing clearwell for chlorine contact, with finished water pumping into the system, all while keeping the existing treatment online during construction and start up. Tata & Howard is currently completing a preliminary design to better estimate costs before completing the final design, permitting, and ultimately construction.

Four Water Storage Tanks, Westfield, MA

Tata & Howard provided engineering services to the City of Westfield for its water tanks, most recently the Provin Tank. For background, the City of Westfield water system consists of 242 miles of water main ranging in size from under 4-inches up to 24-inches and has one main service area. There are also four small high service areas, each of which utilizes a booster pump station. There are nine groundwater supply sources and one active surface water supply source, the Granville Reservoir, and there are interconnections with the City of Springfield at three locations. The system has a total of four tanks with a total capacity of 11.2 million gallons (mg). In 2014, a Condition Assessment Report was completed for each of the City’s four prestressed concrete tanks in order to evaluate condition of each tank and provide recommendations for required rehab work.

The site of the East Mountain Tank, a 2.7 mg tank constructed in 1961, was deemed a “hard hat zone” due to its declining condition. The dome and dome cap were determined to be in fair to poor condition, showing significant deterioration of concrete, and it was further determined that the dome would need to be completely replaced. Due to the significant rehabilitation required, the City decided to construct a new tank. Tata & Howard started the design of the new East Mountain Road Tank in 2017, and the new tank was constructed and operative by 2020.

Wanting to be proactive and avoid the deterioration found at the old East Mountain Road Tank, the City contracted Tata & Howard in 2020 to design and bid the rehab of the City’s three other tanks: the Northwest Road Tank, Sackett Tank, and Provin Mountain Tank.

Rehab work required on the Northwest Road Tank, which was constructed in 1975, consisted of exterior cleaning and coating, repairing of concrete patches, replacing access hatches, replacing the dome vent, and installation of a new overflow screen.

The Sackett Tank, which was more recently constructed in 1991, only required exterior cleaning and coating and replacement of an access hatch.

The Provin Mountain Tank, which is located in the southeastern corner of City, is a 5.0 mg prestressed concrete tank originally constructed in 1967. Measuring 148 feet in diameter and standing 40 feet high, it connects to the system via a 16-inch line. The original scope of the rehab work needed was as follows:

Exterior cleaning and coating
Concrete patch repairs
Injecting a polyurethane grout into a crack
Replace dome hatch and dome vent
Install new overflow screen
Evaluate and repair exposed and broken prestressed wires

With all of these tanks being prestressed concrete, prestressed wires are wrapped tightly around the dome ring as reinforcement to hold the weight of the water. In October 2021, the contractor arrived on site to complete the rehab work on the Provin Mountain Tank. When they started chipping away at loose concrete, it was discovered just how bad the condition of the dome ring was. Each day, more wires were found broken, with more than one third of the total wires found to be broken. The dome was in danger of potential collapse.

The team reconvened to discuss next steps on the project. During rehab work, the contractor surveyed the surrounding area to see if any residents were potentially in the path of the tank if it were to collapse. The tank level was lowered to about 25% capacity, and it was decided to complete repairs on the tank to act as a temporary fix. Temporary repair work began in October 2021 and was completed in April 2022, consisting of the following:

Remove all loose gunite material and broken wire by hand
Apply shotcrete to the dome ring face and provide a uniform surface
Install prestressing strand, Teflon shims, and anchors
Apply shotcrete to fully encapsulate the prestressing strand
Repeat for subsequent layers (estimate 3-4 layers, 17 strands total, 0.6 inch each)
Pressure-wash top surface and face of dome ring
Seal surface cracks on the top surface of the dome ring with Sika 55
Apply a waterproof coating on the dome ring apron and face (Tamoseal)

This repair work extended the useful life of the tank by 2-5 years. The question then was whether to abandon the existing tank or replace it with a new tank. To evaluate if a replacement tank was needed, a storage evaluation was completed. US Census trends and ASR data used to estimate service populations and demands to 2041 showed that the future MDD was estimated at 10.7 mgd. Emergency storage, equalization storage, and fire flow storage were calculated and totaled for current and future demand conditions, showing that the future required storage for the system was approximately 2.77 mg. While having a water storage surplus may initially sound like a positive, too much of a surplus can lead to water quality issues such as water age and disinfection byproducts. This data indicated a replacement tank was not needed based on needed system storage alone.

Hydraulic impact was also studied. Pressure decreased 2-4 PSI depending on which sources were running, and the available fire flow decreased up to 600 gpm, but was limited to the area around the tank which is mostly residential. Resultant flows were sufficient for the residential area.

While storage and hydraulics showed that the tank was not needed, it was determined that there would be significant lack of fire protection in much of the system if the Sackett Tank was offline for repairs or other issues in addition to elimination of the Provin Mountain Tank. Due to the lack of fire protection under this scenario, it was ultimately recommended to replace the tank.

EPS modeling was used to evaluate change in water age for various size replacements. It was ultimately decided to construct a 2 mg tank with the recommendation that the City change the operation of their wells to increase fluctuation in tank levels. Overflow was decided to match the old tank at 428 feet, and the inside diameter of the new tank would be 79 feet compared to 148 feet of the existing tank. The new Provin Tank is currently in design with an anticipated bid this fall, with site work expected to begin by late fall. Given that temporary repairs were completed in April 2022, we are on track to replace the tank within the 2-3 year time frame based on the lifespan of the temporary repairs.

The existing tank will be demolished after the new tank is in service.

Water Treatment Plant, Amherst, MA

Tata & Howard contracted with the Town of Amherst for design, permitting, and bidding of the 1.5 million gallon per day (MGD) Centennial Water Treatment Plant, to treat surface water from the Pelham Reservoir System. The existing Centennial WTP, located in the Town of Pelham but supplying the Amherst Public Water System, has a history of issues with turbidity, color, and disinfection byproducts in the form of total trihalomethanes (TTHM) and haloacetic acids (HAA5) because of high levels of organics in the Pelham Reservoir System. Due to the age and condition of the existing WTP, the filters which were the primary treatment process at the existing WTP were no longer effective at removing organics, leading to a decrease in finished water quality and total WTP capacity. The existing Centennial WTP has been offline since 2018 due to water quality, as well as infrastructure concerns related to a lightning strike which impacted pumping equipment and communications at the Centennial Water Treatment Plant’s raw water pump station.

Based on the results of the pilot study performed by the Town of Amherst, Tata & Howard completed design of the new Centennial Water Treatment Plant including dissolved air flotation (DAF) clarifiers and granular activated carbon (GAC) filtration for treatment of organics, color, turbidity, and low levels of iron and manganese. The DAF system includes polyaluminaum chloride for coagulation, two rapid mix chambers, and three package DAF units which each include two high rate flocculation chambers, two low-rate flocculation chambers, a saturation tank, effluent collection system, discharge weir, mechanical skimmers and beach, and associated appurtenances and controls. Three dual media filter chambers with a silica sand/course garnet base layer and GAC above are located downstream of the DAF units, prior to final chemical addition.

Additional chemical feed includes a gaseous chlorine system for 4-log inactivation of viruses, gaseous ammonia for chloramine formation, sodium fluoride for dental health, and sodium hydroxide for pH adjustment and corrosion control. The new facility also includes an advanced Supervisory Control and Data Acquisition (SCADA) system for automated control of the water treatment plant. Operators for the Town of Amherst will be able to remotely monitor and control operation of the Centennial WTP, through a recently extended town fiber optic cable network.

The design of the Centennial WTP included provisions to maintain the Amherst water distribution system, as even with the Centennial WTP offline, the clearwell of the existing facility also serves to maintain pressure in a small portion of the water distribution system between the Centennial WTP and a booster pump station. The Centennial WTP feeds the majority of the water system (excluding the portion between the WTP and the booster pump station) by gravity. Since the existing WTP including the clearwell will be demolished prior to construction of the new WTP, design and construction of the new WTP will include a temporary water storage tank to maintain pressure and keep all connections active in the high service area of the Amherst Public Water System.

Permitting for this project included a BRP WS 24 New Treatment Plant application with MassDEP, Site Plan Review with the Pelham Zoning Board of Appeals, and a Request for Determination of Applicability (RDA) with Pelham Conservation Commission.

The Centennial Water Treatment Plant was recently bid and awarded to R.H. White Construction Co. of Auburn, MA for a contract amount of $18,876,000. This project received funding though the Drinking Water State Revolving Fund program, and construction is expected to be completed by the summer of 2025.

Steele Street Pump Station, New Britain, CT

Tata & Howard provided engineering services for modifications to the Steele Street Pump Station including installation of a new constant-run type pump station with variable frequency drives; and design and installation of a new permanent outdoor diesel generator and automatic transfer switch.

In addition, T&H provided construction administration and resident observation services for the modifications to the pump station.

Steele Street Pump Station Standby Generator

Water Infrastructure and Conservation Adjustment (WICA) Water Mains, Hazardville, CT

Tata & Howard provided design, bidding, and construction administration services for approximately 2,600 linear feet of new water main in Enfield, CT.

Approximately 500 linear feet of existing 10-inch asbestos cement water main on Hazard Avenue was replaced with new 12-inch HDPE water main. This water main crosses a ConnDOT 48-inch culvert and the replacement was completed using horizonal directional drilling. Approximately 2,100 linear feet of existing 2-inch steel and 6-inch asbestos cement water main was replaced with new 8-inch ductile iron water main. Wetlands permitting and coordination with the ConnDOT were required to cross the existing 48-inch culvert on Hazard Avenue.

Bidding services and construction administration services with full-time resident project representation and site visits were also provided.

Bargh Replacement Raw Water Pipeline, CT

Tata & Howard was retained by Aquarion Water Company of CT for the Bargh Replacement Raw Water Pipeline Project. The project consisted of assisting Aquarion Water Company of CT with sizing a new diversion pipeline from the Bargh Raw Water Pumping Station in to the Putnam Reservoir, both in Greenwich, CT, preparing design plans and specifications for the new 24-inch water main, assisting Aquarion with permit acquisition for the project, and performing field testing to identify the ledge profile along the main.

Construction administration and resident observation services were also performed. Stake out the pipeline, review clearing limits with Contractor, Landscape Architect, Arborist, Stamford and Greenwich, observe CCTV storm drain inspections, accompany Contractor and subs on pre-blast surveys and document, and arrange for Archeologist to delineate sensitive areas to protect.

Godfrey Brook Water Treatment Plant

Today’s volume and demand for daily water use may have changed since the town incorporated in 1881, but one goal remains constant to this day: safe water.

Team T&H continues to deliver safe, potable water through engineering excellence of precision, collaboration, feedback, and commitment between all team members, water department operators, and project managers. The Godfrey Brook WTP project scope involves construction administration and resident project representative services. Process elements of the project include biological iron and manganese pressure filters, a packed tower aerator, and chemical addition for the purpose of pH adjustment, corrosion control, and disinfection. The new WTP includes a clearwell to achieve 4-Log inactivation of viruses prior to the distribution system. The WTP also includes HVAC, plumbing, electrical, and advanced SCADA systems for monitoring and control of the new treatment plant and the wells. Site work includes new raw and finished water mains, stormwater controls in the form of a sub-grade stormwater infiltration system, and residuals storage tanks for solids handling after backwashing the biological filters, and electrical including a new electrical standby generator. The project also includes site upgrades to the wells and access road, including an RCP culvert replacement to improve drainage of Godfrey Brook (a tributary stream into the Charles River), submersible well pumps and motors for the seven wells, and a precast concrete raw water metering vault for flow control. Currently, the biological filters are in the acclimation phase, the final step prior to a performance test to confirm effectiveness of removing iron and manganese.

Located to the left of the Godfrey Brook WTP’s exterior stands a packed tower aerator (shown above). The tower aerator removes carbon dioxide to increase pH in a more cost effective manner than chemical addition, and adds dissolved oxygen before the biological manganese filters, which is critical to biological filtration.

Biological manganese filters (above) come after the packed tower aerator for efficient removal of manganese. Biological iron filter is upstream of the packed tower to optimize the performance of all downstream processes.

The project included a culvert reconstruction to replace a damaged pipe. Culverts are trench-like constructs designed to allow free-flowing water beneath a road or railway, whether stormwater or a stream. Pictured is the finished culvert over Godfrey Brook, a tributary to the Charles River.

T&H team members Matt O’Dowd, Juliette Burcham, Mitch Garon, and Barry Pociask review the electrical connection for the disconnect of the submersible well pump for well 1A. The Godfrey Brook Wellfield features seven total gravel packed wells: five rehabilitated and two newly installed.

The newly installed chemical feed system includes skid-mounted chemical metering pumps used for potassium hydroxide; here, chemical addition occurs for pH adjustment, along with the addition of sodium hypochlorite for disinfection and zinc orthophosphate for corrosion control prior to entering the water distribution system.

Maine Water – Hydraulic Modeling & Fire Flow Analysis

Tata & Howard completed the Water Distribution System Comprehensive System Facility Plan for the Maine Water Company – Biddeford/Saco Division in 2013. This plan included updating and verifying the system’s hydraulic model and was utilized to develop distribution system recommendations for existing and future demand conditions. Prioritized recommendations were developed for future implementation. The recommendations included distribution system operation and maintenance practices and water main improvements to strengthen transmission capabilities, promote looping and mitigate fire flow deficiencies.

Based on Tata & Howard’s knowledge and experience with the Maine Water hydraulic model, and the regional increase in residential development, T&H has recently been retained to provide hydraulic modeling and fire flow analysis for several proposed subdivisions or areas of critical concern including:

Sumter Landing – Old Orchard Beach, ME
West Saco Development – Saco, ME
Portland Avenue – Old Orchard Beach, ME
Breakwater Retirement Community – Rockland, ME

Another task requested by Maine Water was identified based on historic concerns for fire flows in the system’s low service area in Biddeford, ME. Tata & Howard produced model iterations to identify the most appropriate location for a pressure reducing valve (PRV) vault from the high service area to allow additional flow in case of a fire. Several locations were identified and modeled with the Pike Street boundary location determined to be the most appropriate from a constructability standpoint. Subsequently, Maine Water negotiated a design contract to prepare bid documents for the PRV structure and appurtenances.

Finally, due to historic water quality concerns in the Pine Point area of Saco, ME, Maine Water retained Tata & Howard to run an Extended Period Simulation (EPS) for the Pine Point service area, and in particular, the Pine Point Storage Tank. During low demands in the off-season (winter) months, the Pine Point tank SCADA historically had indicated no changes in level. The EPS was developed using systemwide data and historic demands. Alternatives were evaluated including transmission line modifications/replacements, taking the tank off-line during the off-season, and evaluating a booster pump station to force cycling of the tank. Based on the results as well as factoring in operation and maintenance costs associated with the alternatives, design of a booster pump station was recommended.

Capital Improvements and Asset Management Plan, Gardner, MA

Tata & Howard prepared a Capital Improvements and Asset Management Plan (CIP) for the existing water, wastewater, and stormwater systems. The purpose of the CIP is to develop a complete inventory of all assets with replacement costs and useful life to assist the DPW in identifying areas in need of rehabilitation, repair, or replacement and prioritize improvements to make the most efficient use of the DPW’s budget.

The CIP was divided into three parts, water, wastewater, and stormwater systems. Buried and above ground infrastructure was evaluated for the water and wastewater systems and the stormwater evaluation included drainage pipes and structures. The stormwater asset evaluation including a field inspection of every outfall. The outfalls were mapped and a condition assessment performed. Water and wastewater above ground infrastructure included all supply, treatment, pumping, and storage components. Equipment, including vehicles, lawn mowers, and construction equipment was not included in the inventory.

As part of the water and wastewater pipe asset management evaluation, each segment of pipe was evaluated based on material, age, diameter, soil conditions, break history, and system specific concerns such as static pressure, potential water hammer, infiltration and inflow (I/I) concerns, and known operation and maintenance issues. The stormwater outfalls were evaluated based on condition, catchment size, pipe size and material, size compromised and soil conditions.

The asset management plan for above ground infrastructure included an inventory and evaluation of all above ground facilities, including the water supplies, water and wastewater treatment facilities, pump stations, and storage tanks. The evaluation was used to develop a prioritized list of assets and a replacement schedule. The DPW now has a working database that can be updated as new information becomes available and can be reviewed when reviewing selection of yearly capital projects. Also, by reviewing the water, wastewater, and stormwater system together, the study can be used to make more efficient use of funds by potentially addressing water, wastewater and stormwater needs together on a street.

New Hampton Road Water Main Project

Tata & Howard completed design, funding, and construction phase services in the City of Franklin, NH for the $3.5M New Hampton Road Water Main Project. The new 16-inch and 12-inch ductile iron water mains replaced a 1940s era unlined cast iron water main (approximately 14,000 linear feet) with a history of main breaks and extends over three miles from the Babbitt Road Booster Station to the Sanbornton Wellfield.

The water main was identified as a priority in the 2016 Capital Efficiency Plan prepared by Tata & Howard and will provide improved water quality, distribution pressure, and fire protection.

Tata & Howard assisted the City with maximizing the NHDES SRF Loan with the City’s paving program funds to fully reconstruct 9,000 linear feet of New Hampton Road as part of the project.

Project Category: Water