Adapting to supply chain issues
North Andover Sewer Extension Site Map
Woodard & Curran’s wastewater experts designed the sewer extension and pump station in two phases to adhere to critical deadlines established by Massachusetts Department of Transportation’s (MassDOT) Route 125 road and intersection reconstruction project and Amazon’s expected facility completion. The first phase consisted of 2,300 feet of force main in the middle of the project area. This phase of construction went to bid in April 2020 and was fast tracked for completion in November 2020 to make way for the road reconstruction project. The second phase consisted of 8,200 feet of force main and 6,200 feet of gravity sewer, as well as a new pump station. This phase of construction went to bid in October 2021 and was completed in December 2023, in time for Amazon’s opening of its new facility.
While Woodard & Curran’s engineering consultants take pride in designing with consideration for many variables, our team could not predict the supply chain issues and rising material costs that occurred because of the COVID-19 pandemic. Our collaborative approach with the town and contractors helped mitigate material and equipment delays and maintain cost estimates to ensure the project was delivered on time and on budget.
During the project’s second phase, the contractor proposed a night crew to focus on trench preparation and paving to keep the project on schedule and adhere to additional safety protocols. Woodard & Curran’s design team also fielded recommendations from the contractor when material and equipment delays arose. The bid package for Phase 2 included an alternate for the force main material because of rising costs and supply shortages. This approach allowed the town to select the force main material in the best interests of project budget, which ultimately ended up being ductile iron (DI) force main piping. This avoided potential for different hydraulic properties between Phase 1 and Phase 2 and any impact to pump station equipment. In another instance, the specified pump station control panel was significantly delayed. The contractor offered an alternative unit to adhere to the project schedule, and, although larger than specified, Woodard & Curran accepted the recommended alternative on the town’s behalf. A similar situation occurred with the pump station’s emergency generator fuel tank. The manufacturer offered a smaller alternative, which the design team accepted so as to keep the project moving forward.
Protecting water quality with the sewer extension
East of Route 125 is Lake Cochichewick, North Andover’s primary drinking water supply. To the west, the Merrimack River is a major recreational area and a drinking water source for the region. Adding public sewer collection to this area will improve the quality of surface water for both the lake and the river by eliminating the use of septic systems which do not provide enough protection from nutrients and bacteria entering the groundwater, and eventually, surface water. Wastewater collected from the service area is delivered to the Greater Lawrence Sanitary District for advanced biological treatment meeting strict environmental permit requirements prior to discharging clean effluent to the Merrimack River.
While extending the sewer system results in overall environmental improvement for the area, the project itself adhered to strict environmental protection controls during construction imposed by the North Andover Conservation Commission under state and local wetlands protection laws. Catch basins receiving surface water runoff and trench dewatering discharge in the project area were protected by silt sacks during construction while sensitive environmental areas were protected by straw waddles and silt fences.
The sewer extension required an additional pump station to be built on a site near the Merrimack River and a brook with an adjacent sensitive wetland area. The pump station’s emergency generator will keep the equipment running in the event of power failure to ensure untreated wastewater does not impact area groundwater or wetlands. Similarly, an emergency bypass will allow operators to conduct maintenance or repairs without impacting service.
In addition to the equipment design, the project team incorporated a stormwater retention and treatment system in the pump station design, as well as sediment and erosion control measures during construction to protect the sensitive environmental areas. The site was re-planted with native species and signs advising town staff and the public of the adjacent sensitive wetland areas were installed on the site fencing as directed by the North Andover Conservation Commission.
