Milestone Reservoir Tunnel & Shaft

Milestone Reservoir Tunnel & Shaft

Leesburg, Virginia

In Loudoun County, Virginia, crews converted an abandoned rock quarry into a reservoir as part of the Milestone Reservoir Tunnel & Shaft project. The reservoir provides one billion gallons of raw water storage to support the Trap Rock Water Treatment Facility during periods of reduced Potomac River flow caused by drought or contamination, offering an estimated 30 day supply of drinking water for the surrounding communities.

Our scope included providing steel pipe used to connect the pump station to the reservoir. The contractor excavated a 232 foot deep vertical shaft adjacent to the quarry, along with a 778 foot horizontal tunnel that meets the shaft approximately 232 feet below grade.

We furnished 42 inch steel pipe in 42 foot lengths with lifting lugs on the bell end, engineered to carry the full weight of the vertical pipe column as each section was lowered into the shaft. The contractor welded each bell and spigot joint at a welding station located at the shaft collar, with the final segment supporting the entire 232-foot pipe string until backfilling was completed.

At the bottom of the shaft, we supplied a 90 degree, 42 inch elbow fitted with a 42 by 36 inch reducer to transition to the 778 feet of 36 inch tunnel pipe also furnished. This 36 inch pipe was specifically designed to withstand backfilling of the 6 foot diameter tunnel and will remain at the base of the reservoir to enable raw water withdrawal to the treatment facility when required.