Raccoon Creek Bank Stabilization Project

Raccoon Creek Bank Stabilization Project Overview

Western Pennsylvania

GAI developed and prepared a bank restoration stabilization plan with necessary plan sheets to fulfill the Client’s obligations of restoring and monitoring approximately 435 linear feet of perennial streambank. After large rainfalls, streambank along a private landowner’s property had washed approximately 42 feet of land perpendicular to the bank causing a large unstable area along the property. To restore the bank and comply with all standards and permits associated with an adjacent pipeline, GAI worked with multiple local, state, and federal agencies to develop a plan for stabilization and acquire all necessary permits. Due to the instability of the bank, an emergency permit was acquired through the State, to temporarily stabilize the property from future erosion. Temporary stabilization included installing rip-rap streambank protection via dumped rock along the unstable and washed-out bank.

Once permanent restoration permits were received, permanent restoration was completed in November and December 2019. The riprap from the temporary stabilization was repositioned to construct a longitudinal peaked stone rock filter (LPSRF). The LPSRF was designed and installed for dual purposes, which included providing E&SC to divert flow away from the streambank work area, and to serve as a rock foundation for the restored toe of bank. A large woody debris (LWD) base (i.e., brush base layer), consisting of live and dead wood, was then installed on the rock foundation layer. A series of three geolifts (i.e., soil and seed wrapped in coir fabric), with live brush cuttings between geolifts, were then installed above the LWD base layer. Compacted backfill was then used on the landward side of the stabilization structure to restore the bank to its approximate pre-construction location. Rock keys and supplemental live trees and/or cuttings were installed to enhance the overall stability and protection of the structure. Rock steps were installed on three of the keys for access to the stream for recreational purposes.

GAI’s involvement in the project was from the initial site assessment to providing copies of the final set of drawings and specifications in the final construction package, coordinating directly with the agencies and third-party inspectors to comply with permits. GAI was considered the prime contractor for this project hiring a construction company to implement the design. GAI, therefore, managed overall construction being on-site one hundred percent of the time for construction observation services. GAI is currently leading bi-annual monitoring to prepare required reports for a minimum of five years after construction.

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