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Sanderson Gulch Redesign

Matrix led the ecological design for restoration of a reach along Sanderson Gulch from the confluence with the South Platte River upstream past Lipan Street and Sanderson Gulch Park in Southwest Denver. Sanderson Gulch has a 9.7 square mile drainage area with 100-year flows exceeding 3,200 cubic feet per second (CFS). The drainageway was redesigned to remove nearly 100 homes and businesses from the FEMA regulated floodplain, improve ecological function of the channel and surrounding areas, and contribute to water quality improvements for the watershed. Additionally, local public infrastructure is better protected and public safety during storm events has been improved. The site is constrained by multiple road crossings and adjacent industrial and commercial development.. Part of the design included splitting stormflows between the open channel and a series of large-capacity box culverts below the open channel. For baseflow and storms smaller than 10-year events (954 CFS), all water in the creek remains in the open channel. Any flows greater than the 10-year event are diverted into the box culverts below the surface channel to convey large volumes of water to the South Platte River more effectively.

Matrix influenced the design of the open channel and wetland system to include overbank, vegetated bioswales that assist with water quality improvements in conjunction with the water quality vault. Our team implemented a pilot study of the use of wood chips as a weed control mechanism that alters soil chemistry to favor native species. The pilot study included a series of test plots to statistically demonstrate the effect and offer a new weed control tool to Denver Parks and Recreation that uses a forestry by-product to help establish native seeded areas. Matrix led the ecological stream and wetland design, planting plan and plant palette development, as well as maintenance strategies, construction administration support, and post-construction adaptive management monitoring.