Town releases hydrologic study for Chipwood Lane dams; FEMA hazard‑mitigation grant eyed

Town staff told commissioners that a hydrologic and hydraulic (H&H) study completed for the Chipwood Lane dam system recommends constructing auxiliary spillways and upgrading culverts to reduce risk of overtopping and to comply with the North Carolina Dam Safety Law.

The study was submitted to the North Carolina Department of Environmental Quality (NCDEQ) for review; the town explained it will pursue design and construction options and attempt to secure a federal hazard‑mitigation grant administered via the state. The grant opportunity the town identified is structured as an 80/20 program (FEMA/state), and staff said the state has indicated it would cover the 20% local share in this program, which would leave no local out‑of‑pocket cost if the grant is awarded.

Study findings and estimated costs The H&H study recommended two concept options: a minimum “spillway” concept and a larger‑capacity option that includes larger culverts and a riser. The minimum design includes a 25‑foot wide auxiliary spillway for the upper pond and resetting of the existing 15‑inch RCP outfalls; construction for both dams under the minimum concept was estimated at about $656,000 (construction cost only). A larger concept that adds a larger culvert system and a five‑foot riser was estimated at roughly $1.2 million for construction. Design fees were estimated at $120,000–$270,000 depending on scope; the combined higher‑end total across both dams could approach $1.5 million including design and construction.

Alternatives and constraints Staff said the town also considered breaching the dams. Breaching both dams was estimated at about $730,000 and would remove the dams as amenities and eliminate ongoing dam maintenance, but it would change the site and likely require additional environmental review.

Why it matters: safety, compliance and cost The dams have experienced overtopping events that required activation of emergency action procedures and temporary pumping to protect the structures, staff said. The NCDEQ issued a Notice of Deficiency in September 2024 citing overtopping risk; the H&H study was completed in late June and submitted to NCDEQ for comment. Town staff proposed to advertise an RFQ for engineering design, to hire a grant writer to pursue the FEMA‑administered hazard mitigation grant, and to seek the state’s cooperation in funding the local match.

Timing and next steps Staff told the board it proposed a two‑year timeline for completing design and construction if grant funding is secured. If the town does not receive grant funds, staff outlined options including pursuing a future grant cycle, using stormwater fund surpluses for partial design, or financing through revenue bonds or general fund allocations. Commissioners asked staff to ensure the study considered upstream and adjacent dams and failure scenarios that could affect the town’s dams.