Engineering firm: Dillard Creek could supply long‑term demand but has drought and permitting limits; test wells are cost‑effective alternative

Stephen Steele of CHA told the Nelson County Board of Supervisors on Oct. 14 that two primary options exist to serve projected buildout demand around the Larkin property: a surface-water intake on Dillard Creek or drilled groundwater wells.

CHA estimated the creek’s average daily flow at about 8.3 million gallons per day and noted Virginia rules permitting withdrawal of no more than 10 percent of daily flows, which would yield roughly 830,000 gallons per day under average conditions — comfortably above the Authority’s projected 30‑year additional demand of about 81,000 gallons per day. However, Steele emphasized that daily calculations are required and that drought periods can preclude withdrawals for extended stretches; CHA’s historical analysis showed days and multi‑day runs when withdrawals at the planned rate would not have been possible during known droughts.

Permitting for a stream withdrawal is complex and typically requires Virginia Water Protection and U.S. Army Corps of Engineers review, aquatic‑species studies (CHA identified the potential for mussel species in the corridor), intake screen design, and ongoing monitoring and reporting. CHA estimated initial permitting work for withdrawal authorization at roughly $40,000–$50,000, and islanded projects can have full capital costs in the multimillion‑dollar range (CHA cited comparable projects near $6.5 million), with annual operating and chemical costs in the range of $150,000–$250,000.

As an alternative or complement, CHA recommended test wells guided by resistivity surveys to locate fractures that yield groundwater. CHA identified three candidate well sites on the Larkin property (two ridge locations and one site nearer the school), explained VDH practice limits on usable yield (only 55 percent of a well’s measured yield is typically allocated to avoid excessive drawdown), and outlined next steps and costs: site preparation $10,000–$40,000 and test drilling and a 48‑hour drawdown test typically $15,000–$25,000 per well.

Board members discussed access challenges for ridge sites, the relative timeline for DEQ permitting (CHA estimated roughly a year largely driven by agency review), and the comparative long‑term maintenance burdens of impoundments. CHA recommended that the county consider a storage‑augmented approach if relying on stream withdrawal, or phased test‑well drilling if groundwater proves sufficient.

Next steps: CHA will refine cost estimates and permit scopes for the Board’s capital improvement planning meeting; staff and CHA expect to discuss results further at an upcoming work session.