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Amendment 2 proposes a drainage concept to use the capacity of the existing storm <br /> lift stations to fully convey the 100-year stormwater event from the Riverside Road <br /> and 8th Street right of ways, thereby avoiding an overflow outfall into the <br /> Snohomish River. It also proposes to use the large water quality pond 2 to treat the <br /> runoff from 8th Street. The elements necessary to accomplish the above drainage <br /> concept are as follows: <br /> • Interconnect the entire existing drainage gravity system in Riverside Road to <br /> balance the lift stations' pumping capacities (This concept was proposed in <br /> previous amendments to the hydraulic drainage report). <br /> • Rescind the allowable drainage flows from lots 4 and 5 to Riverside Road <br /> and the pervious area of lot 8. <br /> • Lot 5 will be provided with a 15-inch storm drainage stub to discharge flow <br /> directly into the Snohomish River via existing 8-and-12-inch outfalls <br /> retrofitted with an in situ liner. <br /> • Lots 4 and 5 have been raised to higher ground elevations than the perimeter <br /> roads and could drain easier to the Snohomish River, similarly to Lot 3 <br /> designs currently under permit review. <br /> • Eliminate storm surface runoff from the Riverside Road overpass, to above <br /> water quality pond 2 overflow elevation, from reaching Lift Station #1. <br /> • Update pump capacities based on as-built records. <br /> • Pump stormwater runoff collected in 8th Street to the Riverside Road gravity <br /> system for conveyance to the water quality pond. The future rail spur <br /> extension required 8th Street to remain near existing road elevations. The <br /> recent construction of the 42-inch Tulalip Tribe water main lessens the <br /> potential feasibility of gravity connectivity from 8th Street to the gravity <br /> system on the west side of Riverside Road. <br /> Amendment 2 uses the Amendment 1 figures with redlined modifications to <br /> preserve the continuity and to easier follow the proposed updates. New tables and <br /> additional figures are included to corroborate concepts not included in Amendment <br /> 1. <br /> Riverside Business Park <br /> Apri112,2017 <br /> KPFF,Amendment 2 P Page 4/If' <br />