Background on Alexandria’s Combined Sewer System

The Clean Water Act requires cities operating combined sewer systems to develop a “Long Term Control Plan” for reducing untreated sewage discharges that violate water quality standards. The goal of the Plan is to implement additional treatment and storage of mixed stormwater and sewage that will lead to compliance with water quality standards. Cities like Alexandria typically have 20 years to implement the plan once it is approved by EPA. In other words, the city has 20 years to reduce sewage discharges to the point where they no longer cause exceedances of bacteria standards that are in place to protect public health when people are swimming or kayaking in a waterway (also known as “primary contact recreation.”)

In Virginia, the state has designated all waters in the state as suitable for fishing, swimming, or boating, and set enforceable water quality standards (regulations) that dictate how much bacteria can be present in a waterbody before it becomes unsafe for recreation and swimming.  Oronoco Bay, the receiving water into which Outfall 001 discharges, is Virginia state water, and is considered freshwater in this context.

Those standards are found here:

  • E.coli is used in Virginia’s standards as the indicator of bacterial pollution.
  •  Normally permits require compliance with a certain level of e.coli, measured by a 30 day geometric mean (average), based on 4 or 5 samples during the 30 day period.
  • However, since Alexandria is only required to sample Outfall 001 on a quarterly basis, every four years, then the following standard applies:

“If there are insufficient data to calculate monthly geometric means in freshwater, no more than 10% of the total samples in the assessment period shall exceed 235 E. coli CFU/100 ml.”

Alexandria’s combined sewer system has been operating under a 1999 Long Term Control Plan approved by EPA that only required the city to comply with the minimum “best management practices” for reducing CSOs. It appears the city proposed to EPA that this would lead to compliance with water quality standards, which all Control Plans have to achieve by law.

Outfall 001 on Oronoco Bay

In 2010, EPA and Virginia imposed new pollution limits for bacteria on Hunting Creek, a tributary of the Potomac into which Outfalls 002, 003 and 004 discharge. This resulted in a requirement that Alexandria update its Control Plan to reduce untreated sewage discharges from Hunting Creek to meet the much lower limits, but the update does not apply to Outfall 001, because it’s not in Hunting Creek.

As a result, Outfall 001 is still subject to the 1999 Control Plan, which still requires Alexandria to meet water quality standards. Outfall 001 accounts for approximately a third to a half of the entire volume of untreated sewage discharged by Alexandria into the Potomac and Hunting Creek, approximately 70 million gallons a year.

There is very little recent monitoring data for Outfall 001’s discharge into Oronoco Bay, because Alexandria’s permit only requires quarterly monitoring from one of the four outfalls each year. Outfall 001 was last monitored in 2014, and will be again in 2018. See the city's annual report on it's combined sewer system for 2014 report. Appendix A in the report has quarterly sampling data that shows e.coli counts much higher than the 235 standard.

Older water quality monitoring data for Oronoco Bay, collected by Alexandria under their previous 2007-2012 permit show results of weekly sampling at four locations in the Bay (as opposed to the quarterly sampling in 2014, which was done at Outfall 001).  This data shows frequent violations of the 235/100 ml e.coli standard, during both CSO events and ‘routine’ operations, which we assume to mean dry weather.

Under the current 2013-2018 permit, DEQ removed the water quality monitoring requirement for Oronoco Bay, so we only have ambient water quality data for 2007-2012. Given the fact that nothing has changed in the city’s sewer system, it’s likely that water quality in Oronoco Bay continues to be severely impacted by raw sewage, rendering it unsafe for swimming or boating.

The law requires, that Alexandria address the discharges from Outfall 001 in its current update to the Long Term Control Plan.  As it stands, based on the data we have, Outfall 001’s raw sewage discharges are violating state water quality standards for Oronoco Bay, and thus violating the terms of the 1999 Long Term Control Plan, which requires compliance with water quality standards.

It makes no sense to us for Alexandria to ignore this pollution, particularly given its high volume and the fact that it’s discharging into Oronoco Bay, a part of the Potomac that’s frequently used for recreation, including high school rowing teams’ practice. In order to protect public health and comply with federal and state environmental laws, Alexandria needs to include Outfall 001 in its plan to reduce sewage discharges from the city’s sewer system.