RECOVERY--Y--PROJECT NUMBER 122353, MT ST HELENS GRADE BUILDING STRUCTURES PILOT PROJECT

This contract action was accomplished using other than competitive procedures because a statute exists that expressly authorizes or requires that the acquisition be made from a specific source or through another agency (FAR 6.302-5); specifically, Sole source awards under the 8(a) Program. Per FAR 6.302-5 a J&A is not required for this award. The May 18 eruption of Mount Saint Helens in Washington in 1980 resulted in approximately 3.8 billion cubic yards of earth materials being released in a massive landslide. The resulting debris avalanche deposit has continued to erode and introduce sediment materials into the Toutle-Cowlitz-Columbia River system. This contract is for the construction of a pilot project consisting of Grade Building Structures in order to help alleviate the sediment problem that is occurring downstream. Grade Building Structures (GBS) in general are structures to be built in the sediment plain above the existing Sediment Retention Structure (SRS) for the purpose of increasing sediment deposition in the plain and decreasing the volume of sediment available for deposition in the Cowlitz River. The concept of Grade Building Structures was proposed as one of several potential measures for managing the sediment eroding from the debris avalanche on Mount Saint Helens and being transported through the North Fork Toutle, Main Stem Toutle and Cowlitz River systems. The purpose of the Pilot Project is to test the sediment retention performance of a few types of Grade Building Structures. The SRS sediment plain is currently an actively aggrading, predominantly unvegetated braided channel network. Channel locations change widely and rapidly during winter storm events but tend to stabilize during the drier summer months. It is theorized that as the valley slopes increase and sediment loads decline, the SRS sediment plain would transition fro m the current unvegetated braided network to a multi-channel and island network. The sediment plain is showing the beginnings of an ability to grow depositional islands and vegetate them near the SRS, however these islands are fragile and may quickly be eroded. This expected multi-thread channel system is also called an anastomosing river pattern. The anastomosing landform reengages the channel and the island overbank during high sediment laden flows, depositing material in a stabilized island environment where it is retained for a longer period. This is in contrast to the unvegetated braided system where the moving channel may mix the substrate stripping out the finer materials and move them downstream. In order for the river to become more stable in this pattern, island growth will need to be induced and potentially sustained with planted vegetation. This may be more quickly attained by the implementation of a system of structures that could help speed the timeline for the creation of this process. The goal of the overall Grade Building Structures is to help speed the forming of this anastomosing river pattern which would increase sediment capacity as the islands fill, sustain vegetation, become inundated, and fill again in a pattern the river naturally moves into. The objective is to allow the river to move towards this natural pattern in order to attain the goal of quickened sediment capacity, while maintaining fish passage, debris passage, and sustainable construction efforts.