Beaver Brook Dam & Crossing, NRCS NH

Hollis, New Hampshire

Under D&K’s on-call contract for Soil Conservation services, the firm performed site investigation, design, and construction inspection services for the rehabilitation design of the Beaver Brook Dam, which required replacement of the principal spillway, outlet structure, and provided for vehicular crossing. The new spillway includes a precast concrete riser and outlet pipe. The new vehicular crossing is a 15-ft-wide, precast box culvert recessed into the streambed. An oversized “halo” style trash-rack was designed in recognition of historic beaver debris problems. The scope of services included: review of site information and NHDES Dam Bureau files, site reconnaissance and field survey, geotechnical investigation and laboratory testing of embankment material overview, wetlands delineation, preparation of supporting documentation for NHDES, Dam Reconstruction and Dredge and Fill Permit applications, a hydrologic study of contributing watersheds and spillway hydraulics, preliminary and final design drawings of improvements to spillway and vehicular crossing, preliminary and final construction cost estimates, bid and construction phase services, and an Operations & Maintenance Plan (O&M Manual). Wetlands in the project area were delineated, GPS’d, and analyzed for potential impacts associated with the project.