Consultants recommend in‑lake approach for High Rock Lake dredging; cost estimates range widely

Consultants from Geosyntech told the Rowan County Board of Commissioners on Aug. 4 that High Rock Lake has accumulated roughly 1.6 million to 2.8 million cubic yards of sediment in its upper reaches and recommended an in‑water material relocation—pumping sediment into bermed island areas—as the most cost‑effective path forward.

Geosyntech presented sediment sampling and bathymetric survey results from three study reaches (upper lake, Swearing Creek reach and mid‑channel). The firm reported 22 sampling locations and described material types: sands in the upper reach and finer clay/silt deposits in the Swearing Creek and mid‑channel areas. Consultants said some dredged material could be amened and reused as topsoil in upland settings, but that finer sediments would likely require nitrogen‑type amendments before agricultural reuse.

The team identified practical alternatives—hydraulic dredging with in‑lake relocation (Scenario A), upland management using geotubes or geopools (Scenarios C/D), and mechanical removal options—and provided Class 4 AACE cost estimates. They said Scenario A would likely cost between about $15 million and $57 million depending on volume removed; upland options (e.g., Scenario C1) could range as high as $50 million–$160 million. Consultants cautioned the cost ranges include a contingency of –30% to +50% typical of class‑level estimates.

Consultants explained tradeoffs: in‑water relocation is a "single touch" that reduces handling and truck traffic but will require detailed permitting with the U.S. Army Corps of Engineers and state agencies. Geosyntech also flagged logistical constraints for upland disposal—site acreage, road access, truck‑traffic impacts and potential repaving—and noted one county parcel currently owned by Cube Hydro (Parcel 606004) was identified as a candidate dredge material management area (DMMA).

Commissioners asked about permitting timelines and ecological impacts. Consultants said permitting and additional seasonal studies could take time; a rough project schedule offered in the presentation estimated approximately one year for design and permitting followed by about two years of dredging operations for the volumes discussed. Consultants recommended county outreach to federal and state agencies and phased work (starting with high‑priority shoals) while pursuing grant and alternative funding sources.

The board did not vote on an alternative at the meeting; consultants asked commissioners to select a preferred scenario to begin formal permitting outreach and funding identification.