New Rivanna Pump Station

In 2006 and 2007, a system-wide flow monitoring program was completed for RWSA as part of the Comprehensive Sanitary Sewer Study. The flow monitoring indicated that several interceptors experienced significant amounts of inflow and infiltration during wet weather events. Wet weather pumping capacities were established in consultation with the City and ACSA, with the Rivanna Interceptor to the Moores Creek Wastewater Treatment Plant (WWTP) to carry a peak wet weather flow rate equivalent to 53 million gallons per day (mgd). The City and ACSA also agreed to achievable milestones for reduction of inflow and infiltration sources within their system where cost-effective.

The existing Rivanna Pump Station is located at the corner of Chesapeake Street and Riverside Avenue within the City of Charlottesville, adjacent to the entrance of Riverside Park. The urban sewer service area for the pump station includes northern and eastern portions of the City, extending into Albemarle County within the urban ring north of the City. The existing pump station was built between 1979 and 1981. The pump station currently discharges into a 2,600-foot long, 36-inch force main, which carries the flow to the headworks of the wastewater treatment plant. The pump station is supplied back–up power through a diesel generator at a separate site, on Marchant Street, located between the pump station and the Moores Creek WWTP. The current firm pumping capacity of the Rivanna Pump Station is 24.5 mgd.

From 2010 to 2011, Hazen and Sawyer performed the evaluation of 5 preliminary concepts for the needed expansion of pumping capacity between the Rivanna Interceptor and Moores Creek WWTP, and received comment at several public meetings, including a full presentation of the three top concepts at a public meeting in October 2011. At the December 2011 RWSA Board Meeting, the Board selected Concept E for final design. The project includes the construction of approximately 1,620 linear feet of an 8-foot diameter curved tunnel and the construction of the New Rivanna Pump Station on the present Moores Creek WWTP site. The curved tunnel alignment accommodates most of the new tunnel within public right-of-way and existing RWSA sewer easements, thereby minimizing impacts to private property.

Geotechnical borings and testing were conducted and revealed that the tunnel can be excavated by a tunnel boring machine (TBM) in full face rock for its entire length and there was no need for surface jet grouting. Dynamite blasting was not used for the tunnel excavation. The vibrations resulting from the TBM had no impact on the surface structures, since the operation is based on grinding the rock face, as opposed to dynamite blasting or pounding of the rock face.

The preliminary engineering report was completed in mid-October 2012. The preliminary pump station design includes a self-cleaning wet well, four-350 horsepower pumps and two-200 horsepower pumps, channel grinders, screening, carbon scrubbers for odor control, generator backup power, and all related site, civil, electrical and instrumentation work. The total estimated project cost was $40,000,000. Project completion is anticipated in 2017.