2019-10-28-minutes-public-works-study-session

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Memorandum Information so they could better understand risks and continue the partnership with the County by sponsoring the project as a Fish Habitat project. The refined hydraulic model showed the Increase in flow from removing the NF Teanaway Road culverts as an obstruction has some effect on the water surface elevations through the private properties. The highest Increase in water surface elevation Is approximately 0.4 feet near the inlets of the private property culverts. This suggests that the private driveway culverts may have not been designed to convey the 100 -year flow without overtopping. The model also assumed all private crossings were operating at full capacity. Any blockages to these culverts would presumably raise the water surface elevations above those modeled. Design Decision The County and project team are continuing with the design of the new Lids Creek channel across DNR property as the preferred alternative. This is based on the Information In the attached documents and the points below: • Replacing the LJrck Creek culverts with a 40 -foot bridge on NP Teanaway Road, and leaving the creek in its existing channel, would result in increased flood risk to private properties. This risk would be exacerbated if the private crossings were blocked during a high-flow event. Property owners have Indicated their main concern Is to stop the continued flooding from Lick Creek. The new channel across DNR eliminates this flood hazard and risk. • Lick Creek is currently highly -channelized and constrained between NFTeanaway Road and private residences with little natural hydrologic function. A new lick Creek channel across DNR property would provide enhanced functions like sediment and debris movement, fish passage (eliminates passage need on three private crossings), fish and aquatic habitat, and restore natural channel dynamics and hydrologic function. • Leaving Lick Creek In the existing channel would require long -tern maintenance and management through the private properties. The new bridge and channel will be designed to provide natural channel functions and eliminate the need for on-going channel maintenance. The fish passage and habitat enhancement elements provided by the new channel continue the investment In the Teanaway River Basin by cooperative partners and agencies, Including WDFW, Kittitas County, DNR, US Forest Service, FHWA, National Marine Fisheries Service, and the Yakama Nation.