Projects Archive - Tata & Howard

Wading River Pilot Study — Attleboro, MA

At the Wading River Water Treatment Plant, pilot testing, conducted by Blueleaf, Inc. and consulted by Tata & Howard, Inc., was performed to evaluate the removal of natural organic material for the reduction of disinfection byproduct formation in the distribution system, the reduction of manganese concentrations, and the removal of PFAS compounds. The removal of organic carbons by magnetic ion exchange (MIEX®), the removal of manganese by GreensandPlus™ filtration, and the removal of PFAS by FLOURO-SORB®-200 media, were found to be the most effective treatment processes.

Scaled satellite imagery of the existing Wading River Water Treatment Plant

Project Background

The City of Attleboro, Water Department (AWD) operates the Wading River Water Treatment Plant (WTP), located in Mansfield, MA, which includes two gravel packed supply wells and submersible well pumps, each pumping from a filter sand bed. The Wading River provides additional water to the filter sand basins via a steel pile dam and intake structure, and is considered a surface water source. The wells pump to the WTP where water is chemically treated with sodium hydroxide for pH adjustment, sodium hypochlorite for disinfection, polyphosphate for corrosion control, and hydrofluorosilicic acid for dental hygiene. Treated water flows through a 630,000-gallon, baffled concrete contact tank prior to being pumped into the water distribution system.

The Wading River source is historically a high source of organic matter, which act as disinfection byproduct (DBP) precursors in the distribution system. Despite efforts by the City to optimize existing treatment to reduce the formation of trihalomethanes (TTHMs), a class of DBPs, test results have indicated levels above the maximum contaminant level (MCL) of 80 micrograms/liter (µg/L) in some quarters, with locational running annual averages (LRAA) up to almost 85 µg/L at some sampling locations. To reduce DBP precursors and operate the WTP year-round, targeted treatment for organics removal will be required.

Locational Running Annual Average (LRAA) of TTHMs at several locations in the Attleboro drinking water distribution system

The Massachusetts Department of Environmental Protection (MassDEP) published a new combined MCL of 20 nanograms/liter (ng/L) for six perfluoroalkyl and polyfluoroalkyl compounds (PFAS) in October 2020. Following the publication of the new standard, testing for PFAS was conducted at the Wading River supply wells and the Wading River WTP finished water in September 2020, October 2020, January 2021, and monthly from April 2021 to September 2021. Laboratory results indicated PFAS results over the limit, suggesting a need for targeted treatment.

MassDEP guidelines require the completion of a series of permit applications and an engineering study including a pilot test proposal, pilot testing, and a pilot test report to evaluate, optimize, and summarize the treatment results. In accordance with those guidelines, three seasons of pilot testing were conducted: Season I, from March to April of 2022, Season II, from August to September of 2022, and Season III, from July to August of 2023. Per the standards to conduct a pilot study on surface water sources, the pilot test included one cold weather season and one warm weather season.

Pilot Testing

Two systems for organics removal were tested: 1) dissolved-air flotation (DAF) followed by dual-media filtration, and 2) magnetic ion-exchange (MIEX®) followed by GreensandPlus™ filtration. The MIEX® & GreensandPlus™ filtration process train was added to the pilot test following the discovery of elevated manganese levels during Season I of testing.

DAF clarification is a process similar to clarification by sedimentation, except that particles formed by coagulation are floated to the surface by the injection of air through a recycle stream at the bottom of the clarifier tank, instead of being allowed to settle to the bottom. The recycle stream is injected through specially designed nozzles, resulting in the formation of bubbles which adhere to formulated flocc particles and float to the surface, effectively clarifying the source water. Depending on the system utilized, typical DAF systems can operate with a surface loading rate of between 4 and 8 gallons per minute per square foot (gpm/sf). Optimal coagulation and flocculation conditions for DAF can be predicted by standard jar tests, which were conducted prior to Season I of testing. Polyaluminum chloride (PACI) was selected as the coagulant.

Dual-media filtration is a gravity operated, rapid-flow process widely used in water treatment. It is necessary to follow the coagulation, flocculation, and clarification processes with filtration to remove excess turbidity. Dual-media filters contain a layer of anthracite on top of a layer of fine sand, which rapidly remove residual solids from the water, trapping larger particles in the anthracite and smaller particles in the fine sand. The filters can be backwashed on a schedule determined by differential pressure across the filter or at periodic time increments.

Pilot mixers, flocculators, and dissolved-air flotation clarifier during Season III of pilot testing at the Wading River WTP

MIEX® is a specialized treatment process targeted at the removal of organic carbon, specifially dissolved organic carbon (DOC). MIEX® resin consists of ion exchange beads that contain magnetized components to form agglomerates from negatively charged organic particles. The MIEX® system utilizes a stirred up-flow contactor, resin settler, and a regeneration/recycle loop to remove total organic compound (TOC) in an efficient manner. Batches of resin are periodically regenerated in a sodium chloride brine solution, replacing the TOC with target chloride anions and leaving a concentrated brine and organics waste stream. Freshly regenerated resin, as well as new resin to make up for carryover losses, is fed to the reactor to maintain a consistent ion exchange capacity. Depending on the system utilized, hydraulic loading rates can range from 6 to 12 gpm/sf. Residuals from MIEX® systems consist of waste from the regeneration process, and depending on the frequency of regenerations, are typically 0.02% to 0.06% of the treatment flow.

Schematic of a typical MIEX® treatment system

GreensandPlus™, the trade name for Inversand’s oxide-coated sand product, is a manufactured filter media used for the removal of iron, manganese, hydrogen sulfide, arsenic, and radium from water supplies. The GreensandPlus™ process utilizes a layer of anthracite which acts as a physical filter for the manganese precipitated by the addition of the chlorine oxidant. Below the anthracite top layer is the oxide-coated sand media, which acts as a catalyst in the oxidation of the manganese. Manganese that is oxidized in this part of the process is then removed via adsorption or physical filtration.

For PFAS removal, two treatments were compared: 1) granular activated carbon (GAC) and 2) an anion-exchange removal, clay bentonite media, FLOUROSORB®-200.

GAC filtration has proven to be effective in removal of PFAS from drinking water at many locations throughout New England. GAC removes PFAS by adsorption, which is a physical process of accumulating a substance at the interface between the liquid and solid media phases. The GAC used in this pilot study was Calgon FILTRASORB 400, which is made from select grades of bituminous coal through a process known as reagglomeration to produce a highly active, durable, granular product capable of withstanding the abrasion associated with repeated backwashing, hydraulic transport, and reactivation for reuse. The Calgon FILTRASORB 400 can be recycled and reused through thermal reactivation to restore its adsorptive capacity, which eliminates the costs and long-term liability associated with the disposal of spent media.

CETCO’s FLOURO-SORB®-200 is a proprietary, NSF-certified, bentonite-clay adsorption media that is proven to effectively treat multiple variants of PFAS. The removal mechanism is similar to anion-exchange resins. FLOURO-SORB®-200 adsorbent media binds the entire spectrum of PFAS compounds, is not negatively impacted by most other water quality parameters such as dissolved or total organic carbon and chlorine and requires short empty bed contact times of two to three minutes.

Removal of Organic Compounds and Manganese

As mentioned previously, manganese concentrations were found to be higher than expected during Season I of testing. The first organics removal process, DAF and dual-media filtration, was utilized to remove manganese by several oxidation strategies. The oxidation of manganese causes it to precipitate out of solution, allowing it to be removed by direct filtration through the dual-media filters. The oxidation strategies included the oxidation of manganese by potassium permanganate, sodium hypochlorite, and chlorine dioxide. While potassium permanganate was the most effective oxidation chemical for direct filtration of manganese, none of the oxidation strategies were able to consistently maintain manganese concentrations below the secondary maximum contaminant level (SMCL) of 0.05 mg/L. Additionally, DAF followed by dual-media filtration did not consistently reduce DBP precursors to maintain TTHMs below the MCL of 80 μg/L in simulated distribution system sampling.

Box Plot of Pilot Influent Manganese Concentrations Compared to Monthly Historical Data, from Blueleaf’s “Warm-Water Season Pilot Study Report (September-August 2022).”

While GreensandPlus™ is more effective than dual-media filtration for manganese removal, providing additional oxidation of manganese with its oxide-coated media, the coagulated particles formed by DAF can be problematic for GreensandPlus™ media, “gumming up” the small particles with coagulant and reducing filter run times. Therefore, MIEX®, which does not coagulate organic particles for removal, was provided as an alternate pretreatment for the removal of organic compounds prior to manganese removal. MIEX® followed by GreensandPlus™ filtration was found to be effective for both organics and manganese removal, maintaining manganese concentrations below the SMCL, and removing DBP precursors to reduce TTHMs below 80 μg/L in simulated distribution sampling.

Removal of PFAS

Since many media have been shown to remove PFAS to non-detect levels, one way to measure the relative effectiveness of PFAS removal by a particular media is in terms of empty bed volumes (EBVs) between media replacement. By measuring PFAS breakthrough (defined as PFAS being higher than non-detect levels) at sampling points located 25%, 50%, 75%, and 100% through the treatment beds, EBVs for each treatment option were estimated. After 16 weeks of PFAS testing, GAC had treated almost 14,000 EBVs, and was providing 23% PFAS removal at the 25% tap, 41% removal at the 50% tap, 69% removal at the 75% tap, and 90% removal at the 100% tap. At the same time, FLOURO-SORB®-200 had treated approximately 68,600 bed volumes, and was providing 87% removal at the 25% tap, 85% removal at the 50% tap, and 100% removal at the 100% tap. The FLOURO-SORB®-200 media was determined to have a higher treatment capacity than GAC for PFAS removal.

Empty Bed Volumes Treated and PFAS6 result, by PFAS-removal process and sampling point

Conclusions

The DAF and dual-media filtration treatment process was utilized throughout the study to evaluate TOC removal and manganese removal by coagulation, oxidation, clarification, and filtration. A MIEX® and GreensandPlus™ treatment process was added during Seasons II and III as an alternate for TOC and manganese removal. Both processes were found to be effective in removing TOC, however, the MIEX® & GreensandPlus™ process was more effective than the DAF & dual-media filtration process in removing TOC and reducing DBP formation. Additionally, the MIEX® & GreensandPlus™ process more consistently removed manganese to concentrations under the SMCL than the DAF & dual-media filtration process. FLOURO-SORB®-200 clay bentonite anion-exchange media was found to have a higher capacity for PFAS removal than GAC. FLOURO-SORB®-200 showed significantly more bed volumes treated before PFAS breakthrough at the 25% and 50% taps than GAC showed at breakthrough of the equivalent sample tap, making it a more effective treatment media for removal of PFAS.

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.

Manganese Filtration Using Biological Pressure Filtration Whitepaper

Abstract: Manganese levels of the Home Farm Wells in Shrewsbury have exceeded the Secondary Maximum Contaminant Levels and Health Advisory limits. Various treatment options were evaluated and based on loading rates, removal efficiencies, and estimated costs, biological pressure filtration was selected. This paper provides an overview of the results of the pilot testing, design criteria, and funding assistance.

First to Recycle Greensand Backwash Water in Massachusetts

Water Treatment Facility – Natick, Massachusetts

Due to contamination from Volatile Organic Compounds (VOCs) at two of the Town’s water supply wells, the Town of Natick took steps to construct a water treatment facility to treat the water from the contaminated wells. Tata & Howard conducted a water treatment facility siting evaluation and pilot study; and completed the design of the treatment facility, which utilizes air stripping and pressure filtration technology.

During the course of the design, it was determined that the backwash water would not be permitted by the MWRA to be discharged into the sewer system. Therefore, alternatives needed to be evaluated. One option was to provide holding tanks for the backwash water. This would enable the Town to recycle the supernatant to the head of the facility and therefore, minimize waste of the supply water. Since the area was not conducive for the installation of drying beds, the sludge collected at the bottom of the holding tank was removed by means of a septage hauler.

Tata & Howard proposed to recycle the backwash water, which required DEP approval as it had not been done before in the state. DEP gave approval and now recycled backwash water is used in numerous water treatment facilities in Massachusetts.

First Ultrafiltration with Preozonation in the Country

Spectacle Pond Water Treatment Facility Littleton, Massachusetts

The Spectacle Pond Water Treatment Facility removes iron and manganese from a 1.5 mgd source well, utilizing a combination of preozonation for oxidation followed by ultrafiltration membranes.

This combination of treatment processes provides secondary benefits for this well, which is under the influence of surface water from the adjacent Spectacle Pond. The secondary benefits include superior water quality, barrier protection from contaminants and microorganisms, significant reduction in chemical use, and minimal waste production. Because the water quality is superior, the Town was granted a waiver for chlorination from the MassDEP, which was the first such waiver in Massachusetts. The plant was the first of its kind in the United States and the first municipal application of ultrafiltration in Massachusetts.

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.

Archives: Projects