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Q H <br />tH <br />rC C� <br />H0 <br />H 'a1 <br />CA H <br />xHx <br />ti! O <br />H U <br />OHt�jy <br />W 0 <br />CyZ <br />HH <br />O v Fi <br />n t7 C�/.' <br />H O En <br />watershed behind the rpographically lowest berm, using the SCS graphical peak discharge <br />method. The resulting estimated peak flow was approximately 1.8 cfs. A design pea': of 2.0 cfs <br />was then used to size spillways and erosion protection structures for each berm. The design <br />criteria indicated that minimum requirements, based on King County Surface Water Management <br />guidelines, were sufficient to design overflow spillways xnd erosion protection structures for each <br />berm. <br />1.1.3 Imolementation <br />The construction of the compensation wetland will occur concurrently with site <br />preparation and construction of the Recreation Center. The existing wetland will nct be cleared <br />and filled until these plans are approved and the permits received. The construction of the <br />compensation wetlands will proceed by clearing of the access and work areas, corstructirq the <br />I berms, preparing the soils to specifications, and planting. <br />lu <br />3.1.3.1 A"ess <br />MI <br />The access road will be the existing dirt road on the site with upgrading of the surface as <br />necessary to make it passable for the construction equipment. <br />1.1.3.2 Construction <br />(Please see the accompanying design drawings and specifications) <br />1.1.3.3 Topsoil <br />The topsoil in the wetlands will be imported from elsewhere on the Boeing Everett <br />property. It is a peaty soil from a former wetland in the vicinity of the south flightline. It has <br />been stockpiled in reserve, and will be placed in the wetland areas in depths of one to three feet. <br />M This will provide a good growth medium for wetland plants, a natural seed source for some <br />wetland plants, and a soil that will hold moisture well after water input to the wetland ceases in <br />the summer. The existing wetland was determined not to be a reliable source of soil material <br />because the organic topsoil in the wetland was found to be three feet or less in depth. However, <br />if that soil needs to be removed for engineering reasons and/or can be practicably retrieved, it <br />will be used in the new wetlands as well. <br />1.1.3.4 Erosion Control <br />(Erosion control measures are included in the construction specifications.) <br />1.1.3.5 Planting Plan <br />The planting design and specifications are given on the accompanying drawing L-1. The <br />disturbed areas will be seeded with either a wetland or a woodland seed mix, depending on <br />location, for erosion control immediately following completion of the earthwork. Western red <br />DAMES 9 MOORE <br />