Sunset Lake Outfall Remediation
Stormwater Outfall Remediation and Bank Stabilization
Stormwater discharging from three degraded outfalls on private property located adjacent to 100 GBC Drive, coursed steep slopes to Sunset Lake. Over time, severe erosion occurred and caused sedimentation to enter the lake. This recreational body of water was created around 1900 with the construction of a dam in the Muddy Run tributary to the Christina River. Siemens, the property owner, is commended for their quick resolution to correct the situation with needed drainage improvements.
Landmark Science & Engineering was hired to perform the environmental permitting through state and federal agencies, obtain approvals and complete the design needed to eliminate sedimentation from reaching the lake and to stabilize the banks and shoreline. Stormwater remediation was successfully achieved through creative civil engineering site design performed by Landmark’s civil and water resources engineers, environmental scientists, landscape architect, and land surveyors.
Creative Gabion Basket/Mattress Design
Civil engineering design utilized gabion baskets and mattresses to construct facilities that, over time, will take on a very natural appearance and only be visible in the main channels. This will be achieved with a Reforestation Plan designed to provide native trees, shrubs, and groundcover that, along with naturally occurring vegetation, will begin to grow into the facilities.
Stormwater Management Facilities:
1) a unique, articulating, cascading weir with 9-degrees deflection in a 160-foot radius and 10 sections of gabions overcome 12 feet of fall from stormwater discharge to the lake outfall;
2) a dual-discharge headwall combines, directs and funnels stormwater from the relocated middle outfall and the northerly outfall through innovative, inverted V-notch weirs to 3) a long, curving chute. Bank protection and energy dissipation occurs before water reaches and enters the lake.
Sunset Lake Water Quality Improvements
These facilities slow the velocity of the stormwater, dissipating the energy before water reaches the lake. This reduces/eliminates erosion and sedimentation from entering the lake and improves the overall water quality.
Scope of Work
Landmark provided services for remediation of the three stormwater outfalls and restoration of the channels and banks leading to the lake and shoreline. The scope of work included:
- Land surveying,
- Environmental Services:
- Mapping of the Waters of the U.S. (WOTUS) and wetland delineation,
- Environmental permitting through the U.S. Army Corps of Engineers (USACE) and Dept. of Natural Resources and Environmental Control (DNREC),
- Applied for and received a NWP 13 from the USACE,
- Agency processing through New Castle County’s Engineering Section of the Department of Land Use,
- Civil engineering site design,
- Landscape and reforestation plans,
- Construction site plans, and
- Construction review on a periodic basis.