Stormwater & Flood Control Planning & Design
Clean Water Service (CWS) is tasked with managing stormwater in portions of Washington County, OR that fall within the Urban Growth Boundary with the goal of protecting waterways and natural resources within stream and wetland corridors. When a new development is proposed, CWS works with the developer to meet regulatory requirements associated with increased runoff from impervious surfaces with the goal of maintaining discharges of stormwater to pre-development conditions. Traditionally, meeting these requirements consists of designing and constructing large, regional stormwater management facilities in upland areas adjacent to the new developments.
Client: Sempervirons Fund and Peninsula Open Space Trust
Mill Creek is the largest tributary of San Vicente Creek, in Santa Cruz County, an important stream for steelhead and coho salmon on the central California coast. Mill Creek drains a small, steep watershed containing a localized area of granitic rocks within the highly erosive marine sediments that dominate the Coast Range. Because of this, Mill Creek is an important source of resistant spawning gravel, which is limiting for fish in many watersheds in the central Coast Range. Within the recently-acquired San Vicente Redwoods Preserve, two dams on lower Mill Creek impound gravel and prevent fish passage.
Client: South Coast Habitat Restoration
Waterways was retained by South Coast Habitat Restoration to prepare designs for improving fish passage at five barriers along Gaviota Creek. The sites are located north of Gaviota and directly adjacent to Highway 101. Each barrier is composed of a concrete grade control structure, originally installed to keep the creek from undermining Highway 101. Design concepts range from structural modification of individual weirs to complete removal and channel realignment.
Waterways is supporting Central Coast Wetlands Group by leading the design team in development of plans to construct a 30 acre managed wetland to treat irrigation runoff within the Elkhorn Slough Watershed.