David and Goliath – The Story of How a Small Town is Overcoming the Major Challenge of Bringing Their Sewer System into Compliance

The City of Brevard (City) is a small town nestled in the scenic mountainous region of western North Carolina. Established in 1861, the City is home to approximately 7,600 people within the 13.3 square kilometer (km2) (or 5.12 square mile [mi2]) boundary. The City’s Public Works Department maintains 89 kilometers (km) (or 55 miles) of gravity sewer, 10 km (6 miles) of force main, and 17 pump stations. The City has admirably maintained the system with funding available from a small municipality to provide their customers with quality service. However, like other municipalities across North Carolina, Father Time has unfortunately caught up with the system. The aging infrastructure, combined with rainfall amounts higher than any other location in North Carolina, over 2,540 millimeters (mm) (or 100 inches) of rainfall in each of the past two years), can no longer prevent excessive wet weather infiltration and inflow (I&I). The I&I has resulted in excessive system surcharging, with over 60 reportable sanitary sewer overflows (SSOs) in the past 3 years. In addition to the SSOs, the increased cost of operation and maintenance (O&M) at their Wastewater Treatment Plant (WWTP) from the elevated dry and wet weather flows further restricts the City’s limited available funding for performing needed maintenance in other areas of the their wastewater collection system.Instead of focusing on what band-aides can be used to keep the system afloat, the City has tackled the challenge of evaluating and improving the sanitary sewer system head-on. In 2009, the City began with a comprehensive sanitary sewer system evaluation survey (SSES) to identify I&I sources and determine at what level it is cost effective to treat and/or remove the I&I. In 2012, the City utilized the results of the SSES to initiate a system-wide flow monitoring study and modeling evaluation. The study divided the City’s sewershed into 11 sub-basins and prioritized rehabilitation and replacement efforts based on the high peaking factors and rain-derived (RD) I&I. The study also identified some inflow sources that could be identified and addressed via small point repairs, resulting in immediate reductions in dry and wet weather flows. In 2014, the City utilized the results of the flow monitoring study to perform a hydraulic model evaluation of the sewer system to perform improvement alternatives evaluations. The alternatives included rehabilitation only, upsizing only, and a combination of the two. The results of the evaluation determined that the most cost-effective approach was to perform rehabilitation of the upstream collection system as well as upsizing of the downstream primary conveyance system.Once the problems were identified and the recommended rehabilitation/upgrades were agreed upon, the City took on the challenge of implementing the improvements. The City’s dedicated staff have strategically combed through the City’s collection system to identify locations of significant inflow sources, several of which have been addressed and are providing immediate benefits to the collection system through a reduced number of SSOs (25 SSOs in 2013, 18 SSOs in 2014, and 10 SSOs in 2015 thus far) and an average daily dry-weather flow to the WWTP. The City is in the process of cured-in-place lining of approximately 7,925 meters (m) (or 26,000 feet) of 152.4 mm (6 inch) and 20.32 cm (8 inch) diameter gravity sewers within the highest priority sewersheds.The most significant of these improvement projects is the Neely Road Pump Station and Equalization Improvements project, which includes a new 31,823 cubic meters per day (m3/d) (or 7 million gallon per day [MGD]) submersible pump station, approximately 3,962 m (13,000 feet) of 508 mm (20 inch) diameter PVC force main, and a 12,113 m3 (3.2 million gallon [MG]) equalization storage tank at the WWTP.The project has presented several unique design challenges, including:The necessity for a unique operating scheme: the pump station was designed to operate efficiently at a dry weather flow of approximately 4,456 m3/d (1 MGD) up to a peak wet weather flow of 31,823 m3/d (7 MGD) – a significant range in flow that required an innovative solution.The navigation of environmental challenges: in addition to a majority of the force main being located under roads owned by the North Carolina Department of Transportation, the force main crosses the French Broad River which is an approximately 30.48 m (100 foot) wide water supply river that provides habitat for endangered species, such as the Elk Toe Mussel, which is immediately downstream of the proposed crossing.Significant location limitations: the 12,113 m3 (3.2 MG) equalization storage tank needed to be constructed on a 45.7 m by 45.7 m (150 ft by 150 ft) lot at the back of the WWTP where an existing police firing range is located. The site is bounded to the south by the Chlorine Contact Chamber, to the east by a mountain, and to the north and west by high quality wetlands (as determined by the U.S. Army Corps of Engineers).The Neely Road project is being funded through a Clean Water State Revolving Fund (CWSRF) loan, which is administered by the North Carolina Department of Environmental Quality – Division of Water Infrastructure. The CWSRF offers loans at an interest rate of one half the federal bond rate. For the Neely Road project, that resulted in a 1.84% interest rate on the $13,660,000 loan. A reduced interest rate such as this results in millions of dollars in savings to the City, as presented below:CWSRF Loan @ 1.84% over 20 years = $16,340,000Federal Bond @ 3.68% over 20 years = $22,580,000Federal Bond @ 3.68% over 30 years = $26,110,000The purpose of this presentation is to discuss how a small community like the City of Brevard is undertaking the goliath-like obstacle of evaluating its sewer system, prioritizing system improvements, and strategically implementing those improvements through use of City staff, limited funds, and state loans to position the City for long-term compliance with its state sewer system permit.