By Carla Branch and James Cullum
alexandrianews.org
Alexandria’s aging sewer system and limited sewage treatment capacity have already had a negative impact on proposed development and without a significant expenditure of funds, the situation will only get worse.
The city is divided into sewersheds. The 4600 acre Holmes Run Shed is the largest. The Department of Transportation and Environmental Services is currently conducting an evaluation of the Holmes Run sewer system to prioritize rehabilitation needs.
“We have meters throughout the Holmes Run sewershed that give us readings on the flow when the weather is dry and during rain events,” said Emily Baker, deputy director of TES. “We will look at the data from these meters to determine how much the sewer is leaking and where the most substantial of those leaks is occurring. That will allow us to prioritize the work that we need to do.”
That work will occur over the next five years at a projected cost of $25.9 million. “Like in other parts of the City, we hope that we can rehab these sewers by lining pipes so that we don’t have to dig up the sewer,” Baker said.
The rehabilitation project is important because leaking pipes allow rainwater to enter the system causing sewage to flow into Hoofs Run before it enters the Alexandria Sanitation Authority’s waste treatment plant. It also causes excess capacity for the plant. This summer, because of that excess capacity, ASA refused to issue an acceptance letter for the Department of Defense BRAC project at Mark Center.
TES Director Rich Baier explained the situation in a Sept. 9, memorandum to City Manager Jim Hartmann, the mayor and members of City Council. “Due to its age, the City’s sanitary sewer collection system (as is typical with older municipal sanitary sewer systems) has developed leaks and cracks that allow stormwater and groundwater to enter into the collection system. Because the ASA trunk sewer system was not designed for this excess water, water entering the City’s system during large storm events can contribute to un-permitted overflows into Hooff s Run, the terminal point of the Holmes Run Trunk Sewer.
“While wet weather capacity overflows currently only occur during extreme storm events, the City and ASA seek to implement proactive steps to address this issue. Accordingly, the City’s CIP includes an infiltration and inflow rehabilitation program in the Holmes Run sewershed as has already been done in the Four Mile and Commonwealth sewersheds and is now underway in the Taylor Run sewershed.
“This spring, ASA raised concerns about additional sanitary sewer connections in this sewershed further contributing to the potential for these un-permitted overflows. As a result of this concern, ASA indicated that it would not issue “Acceptance Letters” for developments in this sewershed unless the developments were able to provide storage for their sewer flows during rain events. Under State law, projects that generate a sanitary sewer flow greater than 40,000 gallons per day (gpd) (the equivalent of approximately 115 single family homes or townhouses, 135 multi-family units, or 200,000 square feet of commercial development), must apply for and receive a ‘Certificate to Construct’ from the Virginia Department of Environmental Quality. In order to issue the Certificate to Construct, VDEQ requires an Acceptance Letter from the owner of the receiving collection system and/or treatment works certifying that the systems have sufficient capacity. Without an Acceptance Letter from ASA, development projects that meet this threshold may not be able to move forward with construction.
“Several projects in the Holmes Run shed have been impacted by this ASA decision not to issue Acceptance Letters. One affected project was the Department of Defense BRAC project at Mark Center. As a result of this wet weather issue, City and ASA staff worked on this issue and the BRAC project is now designing a pump station and force main system to pump their flows into the segment of the City’s collection system that drains to the Arlington County wastewater treatment plant. Staff calculations indicate that there is sufficient capacity in the City’s allocation at the Arlington plant to accommodate the flows from the BRAC project. The Arlington authorized geographic boundary of the sewershed that drains to Arlington has been approved by Arlington for expansion across Seminary Road to include this BRAC project. As a result, ASA has indicated that it will now issue an Acceptance Letter for the Department of Defense BRAC project.
“Since ASA raised this wet weather issue, City staff has taken several steps to address their concerns about the City’s wet weather contributions in this shed. Staff is accelerating the Inflow & Infiltration (I&I) rehabilitation already scheduled and funded in the CIP for this sewershed.
Staff is evaluating water conservation measures such as recommending that new development projects in the Holmes Run shed install ultra-low flow plumbing fixtures, Staff is also studying options for providing wet weather storage in the Holmes Run shed. As a result of these commitments by the City, ASA has indicated that it will soon begin issuing Acceptance Letters for additional projects in the Holmes Run shed. Staff is currently evaluating the costs of these wet weather mitigation measures. A recommendation for calculating an equitable contribution by development projects in this sewershed to offset the costs of these mitigation measures is planned to be brought to Council in the fall,” the memorandum said.
A City Sewer Master Plan
TES is working on a citywide sewer master plan. “We had hoped to have it finished by next spring but because the Beauregard Small Area Plan has been fast-tracked, we may not meet that deadline,” Baker said. “We work very closely with the Planning and Zoning staff on all developments and we have all done a good job projecting our sewer needs to 2050, based on projected development. We will continue to work on the sewer master plan but will certainly have a list of priorities for the Holmes Run sewershed to Council very soon.”
TES staff projects that the City will need an additional 12 million gallons a day above the 21.6 millions gallons a day that is currently allocated to the city from the ASA facility. The need for this capacity is projected to begin in 2025 and increase over time. Capacity at the ASA treatment facility is now limited by two factors: nutrient discharge limitations (permitted pounds of nitrogen and phosphorus that can be discharged into the Potomac River by the ASA facility) and hydraulic capacity (volume of flow that can physically pass through the plant and its collection system).
The discharge of nutrients is constrained by a finite fixed limit to the number of pounds of nutrients (nitrogen and phosphorus) that can be discharged into the Potomac River and Chesapeake Bay. These nutrient limits (“caps”) have been applied to sanitary sewer plants statewide which discharge into the Chesapeake Bay watershed. The State has also implemented a “cap and trade” policy, whose details remain to be implemented. ASA is currently designing an upgrade to the treatment plant, which is why they acquired the Hooff-Fagelson site, that will address these new, stricter nutrient treatment requirements at the facility’s current capacity. The design of this upgrade is intended to result in the best available technology to meet these requirements, particularly for nitrogen.
The Sept. 9, memorandum concluded that, “while there are clear future capacity issues, in the short and medium term, there is no need for a moratorium. However, major land use upzonings coming forward will need to have conditions attached to fairly address capacity and nutrient issues…There are solutions to each of these challenges. The challenge is to identify the most cost-effective solution and optimum funding approach.”