D&K designed the temporary breach of a failed spillway on an 800-foot-long earthen dam. D&K’s water resources staff completed the breach design and provided permitting assistance. D&K assisted the owner in choosing repair/reconstruction alternatives to restore the water body to its originally designed condition. The owner elected to pursue a permanent breach of the dam.
Pomainville Dam Removal
D&K provided evaluation, survey, and preparation of permit applications for an earthen dam. Vermont Agency of Natural Resources (VANR) personnel determined that the dam’s original 30-inch diameter metal spillway riser had been replaced with a 24-inch plastic pipe and the emergency spillway had been filled to the crest elevation of the dam. Presented three potential remedy options to bring the dam back into compliance with VANR dam safety regulations. The determination was made to remove the dam. D&K was responsible to provide hydrologic analysis of the watershed using HydroCAD, and prepare conceptual and final designs for removal of the dam and restoration of the stream. D&K completed the dam safety permit and coordinated with Vermont State wetlands and dam safety officials. D&K provided construction observation services.
Geer Dam Removal
DuBois & King designed a partial removal of the Geer Dam, a former hydroelectric, run-of-the-river dam on the Ompompanoosuc River. The combination concrete gravity and buttress dam was constructed by a private individual in the early 1980s (designed by DuBois & King). The dam has been identified as an obstruction to aquatic organism passage (AOP) and a source of local fluvial geomorphic instabilities evidenced by downstream channel incision and bank instability.
Removing a portion of the dam restored AOP and improved geomorphology. The D&K team performed a structural evaluation, developed a hydraulic model, and determined geomorphic compatibility to identify the effects of partial removal of the dam on the stream and the remaining section of the dam. Services also included a topographic survey of the dam and river reaches up- and downstream, wetland delineation, AOP evaluation, preliminary through final design, and construction observation.
Norwich Reservoir Dam Removal
The Norwich Reservoir Dam was a run-of-the-river, cyclopean gravity dam located on the Charles Brown Brook. The dam formerly impounded a reservoir, but had has no function and caused significant negative impacts to the brook and to downstream reaches. DuBois & King developed removal design to meet the objectives of restoring AOP and the natural functions of Charles Brown Brook through the reach occupied by the obsolescent dam and infilled impoundment.
The reach of the brook above the dam silted in and became a wetland, such that no aquatic organism passage was possible. As a part of the removal design, the project team chose to remove the high-nutrient silt in the impoundment. Services included topographic survey, wetland delineation, hydrologic and hydraulic modeling, geomorphic assessment, regulatory coordination (with the Army Corps of Engineers, State Dam Safety Program, and State Wetlands Program), and community outreach.
Eastman East Lake Road Drainage
The Eastman Community Association (ECA) selected DuBois & King to assess existing conditions (including stormwater patterns, drainage infrastructure, erosion areas, roadway conditions and subsurface conditions) to evaluate stormwater quality, erosion and roadway improvements to mitigate water quality impact to Eastman Lake. Located within the sub-association of the Eastlake Condominium Association (ELCA), DuBois & King collaborated with both stakeholders on developing improvement alternatives. The engineering study discussed roadway surface, stormwater collection and stormwater treatment options enhance water quality discharging to the lake. An engineering study recommending the preferred alternative, project phasing and anticipated construction costs has been approved by the ECA and ELCA project committee. A Public Hearing is scheduled to receive public feedback that will ultimately lead to the design/development phase of the project.
Construction of the recommended improvements are scheduled to be completed Summer 2017. DuBois & King staff are providing hydraulic and hydrologic (H&H) analysis, drainage system design, geotechnical engineering, wetland delineation, survey, and permitting assistance to advance the project from study phase to design phase and though construction.