Holds our projects
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.
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.
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.
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.
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.
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.
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.
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.
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:
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.
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.