HRSD York River Outfall and Diffuser . Yorktown, VA.

The outfall and diffuser is designed to convey a peak hydraulic flow of 75 MGD.  The existing 48" diameter outfall pipe was extended across the Yorktown Power Station’s (YPS) property approximately 1,500 feet to the bank of the York River and approximately 3,500 feet into the York River to a new 320-foot long, 35-foot deep, multi-port diffuser with 32 diffuser ports.  The new 48" diameter outfall pipe crossed multiple structures on the YPS property including the cooling water canal, ponds, buried utilities, roads, and parking lots. The outfall pipe is supported above-grade on a 200-foot long, single span pipe bridge across the cooling water canal.

Total volume of dredged material was approximately 60,000 CY.  A portion of the subaqueous HDPE pipe was buried in a trench with stone bedding and backfill from the shoreline out to a point identified with borings as being soft silty material. The outfall and diffuser is pile supported with a single 12” square precast concrete pile with precast pile cap through the soft silty material to its termination approximately 3,800 LF into the York River.