CCSD Wastewater Conveyance

Chemung County Sewer Districts (CCSD) historically owned and operated two wastewater treatment plants (WWTPs) that serve the city of Elmira and the surrounding area: the Milton Street WWTP, constructed in 1987, and the Lake Street WWTP, constructed in 1962. Both facilities experienced significant aging infrastructure and regulatory compliance issues, including new disinfection requirements and nutrient discharge limits associated with the Chesapeake Bay Watershed mandates. To address these issues most cost-effectively, CCSD decided to pursue constructing a new conveyance system from the Lake Street facility to the Milton Street facility and expanding and updating the Milton Street facility into a regional treatment facility capable of treating the combined flows from the entire service area.

Larson Design Group (LDG) is a member of a team to undertake the CCSD wastewater treatment plant consolidation program, which consists of two separate engineering contracts: the conveyance project and the consolidation project.

The conveyance project consists of constructing a new conveyance system capable of conveying 30 MGD of wastewater from the Lake Street influent facility to the regional treatment facility at Milton Street. The conveyance system consists of rehabilitating 15,000 of existing 48-inch gravity sewer outfall to be repurposed as transmission main and constructing 3,500 linear feet of new 48-inch gravity sewer and a 1,000-foot siphon across the Chemung River. The conveyance infrastructure required extensive permitting, as much of the new infrastructure will be located within the floodplain and part of the new gravity sewer intersects a US Army Corps of Engineers levee. The Chemung River in the vicinity of the siphon crossing contains endangered mussel habitat and archeological sensitivities. LDG coordinated an extensive and fast-paced field investigation campaign including inspection for the existing 48-inch diameter outfall, a geotechnical investigation, topographic survey, wetlands delineation, and an archeological investigation. Streamlined regulatory interaction, including proactive pre-permitting discussions and consistent open communication, were key in securing permits in a timely manner, which was a critical path schedule item for the overall $200 million consolidation program.

A video investigation of the 48-inch gravity sewer was required to inform the rehabilitation design of this existing sewer. After a third-party contractor was unable to inspect this sewer due to high flows, LDG developed a novel video investigation rig to perform the inspection in-house.

To ensure accurate cost estimating, construction sequencing, and overall constructability of the design, specific feedback and input regarding construction cost estimating and scheduling was incorporated at key points along the design process. This activity helped to proactively address constructability issues before the project was bid. This level of detail was necessary, as the very tight regulatory timeline driving the overall consolidation program did not allow time for rebidding or construction delays.

Permitting included an Article 16 flood control permit, a SHPO cultural resources clearance, a NYDEC/USACE joint permit, a NYSDEC incidental take permit, a NYSDOT permit 32, a SWPPP, and easement and right-of-way coordination.

LDG also provided construction administration and inspection services to oversee the construction of the conveyance system.