Federal constraints derail $800m Potomac regional reservoir study, prompting utilities to weigh independent path

Federal constraints derail $800m Potomac regional reservoir study, prompting utilities to weigh independent pathStrict U.S. Army Corps of Engineers (USACE) feasibility study rules have eliminated large-scale secondary water storage options like the Trevilla Quarry from federal evaluation, pushing Washington-area water suppliers to consider self-funding the required studies to secure future federal backing.

USACE enforcement of the "3x3 rule" limits the secondary water source feasibility study to $3 million, a constrained timeframe, and a 35% engineering design requirement.

The constraints effectively remove the $800 million Trevilla Quarry and large-scale water reuse projects from the current federal study.

The revised USACE study will now focus on expanding the Dalecarlia Reservoir, which would add only 12 hours of emergency water supply to the Washington Aqueduct.

WSSC Water and regional partners are exploring Section 203 authority to conduct their own feasibility studies to keep major regional storage projects viable for federal construction funding.

Washington-area water suppliers are facing a major setback in securing long-term secondary water storage after new federal guidance severely restricted the scope of an ongoing U.S. Army Corps of Engineers (USACE) feasibility study. During a March 18, 2026, meeting of the Washington Suburban Sanitary Commission (WSSC Water), officials revealed that the USACE has enforced strict limitations on the study, which was originally scoped at $13 million over six years. Jackie Seiple, USACE Baltimore District lead planner, explained that the study must now conform to the "3x3 rule" enacted in the Water Resources Development Act of 2014. The rule caps the study at $3 million and requires completion within a constrained timeframe, which was extended to four years due to funding delays. Crucially, the guidance mandates that the study reach 35% engineering design. "This limits the options that we can look at because, for example, things like Trevilla that have miles of pipeline... we're going to have to do boreholes along that length, and it really adds and increases the cost," Seiple said. As a result, the $800 million Trevilla Quarry project in Montgomery County—long identified as a critical regional storage solution—and large-scale water reuse projects have been dropped from the federal study. Instead, the USACE is pivoting to smaller-scale alternatives, primarily the expansion of the Dalecarlia Reservoir. However, this expansion would only provide an additional 12 hours of water supply to the Washington Aqueduct. WSSC Water Commissioner Jeffrey Seltzer called the shift "alarming and incredibly disappointing," noting that an additional 12 hours of resiliency would not support WSSC Water's customer base. Despite the federal pivot, regional water suppliers are not abandoning large-scale solutions. A recent Interstate Commission on the Potomac River Basin study warned that the regional water supply is at risk of shortage in the immediate term during extreme drought conditions. To keep major projects like the Trevilla Quarry alive for potential federal construction funding, utilities are exploring the use of Section 203 authority. This would allow non-federal entities to fund and conduct their own feasibility studies with USACE assistance, ultimately producing a Chief's Report that could be submitted to Congress for authorization and appropriations. "We are still working together, just maybe in different ways," said WSSC Water General Manager and CEO Kishia L. Powell, emphasizing that the region remains focused on securing external funds to build a protected secondary water source.