New Rivanna Pump Station

New Rivanna Pump Station Tunnel

New Rivanna Pump Station Tunnel

Project History

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.

Increasing Our Capacity to Handle Wastewater

Few of us realize that most of the wastewater from our northern and eastern urban area (including Crozet) flows through this system to our Moores Creek campus. This wastewater infrastructure requires pipelines for transmission. The New Rivanna Pump Station project began in 2010 to provide increased capacity for wastewater in a much-needed area.  This project required a sophisticated tunnel boring machine (affectionately named Ms. Chelsea) to excavate over 6,000 cubic feet of rock so that crews could install a 5 feet diameter pipe.

This new pipe will increase the capacity from 17 to 37 thousand gallons per minute (or 53 million gallons per day) of wastewater coming from the northern and eastern portion of the City and the County.  With this upgrade in the wastewater system, sewer will no longer be at risk of overflowing into the Rivanna River during big storm events. Additional features of the New Rivanna Pump Station include a self-cleaning wet well design, influent channel grinders, six pumps, odor control, and an emergency generator.

 

Rivanna Pump Station Construction

Rivanna Pump Station Construction

Tunnel Complete!

Tunnel Complete!  Click on the image to watch a video of the tunnel breakthrough.  (Photo: Michelle Simpson)

 

front-of-pump-station-august-2016

Front of the New Rivanna Pump Station (August 2016)

Senior Principal Engineer Benjamin Alter, Hazen & Sawyer, and Michelle Simpson, RWSA Senior Civil Engineer at floor level. (Sept 2016)

Senior Principal Engineer Benjamin Alter, Hazen & Sawyer, and Michelle Simpson, RWSA Senior Civil Engineer at floor level. (Sept 2016)

Rivanna Pump Station Aerial Map

MORE PHOTOS:  Rivanna Pump Station Photo Gallery and Project photo log

Project Update Meeting for Woolen Mills Neighborhood

Adams Robinson (ARCO),  Hazen and Sawyer, and Rivanna Water and Sewer Authority hosted an update session on the project for the Woolen Mills community on Tuesday, December 6, 2016. Topics discussed were (Click here for pdfs of the information that were shown at the meeting.):

  • Our contractors will be returning to the site this month
  • January and February they will be connecting the old pipe with the new pipe (tunnel)
  • “Bypass pumping” will take place in Feb-Mar time frame but 24 hr pumping is anticipated to last only one-two weeks and will put into use critically silenced pumps to minimize noise and meet city noise ordinance.
  • Once the pipe connections are complete and we put into operation the new pump station, demolition of the old pump station will take place and the property will be restored to a flat, grass surface.
  • We appreciate the creative ideas to utilize the concrete shoring wall, but access to this area for regular operations and maintenance is of primary importance to serving the community’s wastewater treatment needs.

Adams Robinson (ARCO) has made extensive progress since the last community meeting in November 2014! The new pump station structure and tunnel construction are complete. Startup and testing of the new pump station and electrical gear at Moores Creek will be conducted over the next few months with official start up anticipated late April/early May 2017. As part of the preparation work to start up the new pump station, ARCO mobilized back into the existing pump station (adjacent to the Riverview Park entrance) in January 2017 and made the final structural modifications which will allow the sewer interceptor flow to be connected to the new tunnel and conveyed to the new pump station. Following successful startup of the new pump station, the existing pump station will be decommissioned and demolished in addition to the existing 36” force main.