A status update meeting held on the proposed Black Horse at Whiskey Creek development was the subject of a presentation given by Kittitas County Department of Public Works Director Mark Cook on Tuesday.

Commissioners Brett Wachsmith, Laura Osiadacz and Cory Wright were in attendance along with representatives and counsel from D.R. Horton, the land developer. Other stakeholders present included representatives from Ellensburg Water Company, Washington Department of Fish and Wildlife and landowners who live close to the proposed development.

Director Cook’s presentation focused on the work his department has been doing with the developer, WDFW and Ellensburg Water Company to find a way to mitigate flood runoff from the development, located at Reecer Creek and Bender roads. An 18-foot box culvert that crosses the development is pending installation, which would replace the existing 48-inch metal culvert. The property, which has historically been used as a floodplain for Whiskey Creek has had numerous flooding issues over the years, most likely caused by high groundwater and a leaky stormwater conveyance system. Water backing up against the original culvert has also been identified as a culprit.

The most recent flooding event at the proposed development occurred during the spring runoff season of 2017. An investigation showed leaking stormwater pipes allowed high groundwater into the conveyance system, overwhelming the onsite stormwater storage ponds. The property has a history of flooding. According to an adjacent landowner, a retention pond overflow incident in February 2016 lasted for 46 days, causing the water to enter the Ellensburg Water Company canal. The company had to turn off their water supply upstream from the incident and ended up sending a cease and desist order to the county for the flooding. Certain water supply standards must be met by the water company, and runoff from the development compromises those standards.

As a result of the flooding incidents, Cook’s report said the developer is electing to redesign its stormwater ponds into ponds that allow the water to naturally evaporate. The existing retention ponds were designed to allow the water to naturally seep back into the water table, but they have had a history of not functioning correctly. Prior proposals included installing pumps to move the water in the retention ponds uphill, and a detention pond, a concrete-lined pond that allows the water to dissipate along with natural flow patterns. Concerns over further flooding or failure from those proposals resulted in them not being implemented.

Along with the pond redesign, Cook’s report included a revised plat map that displays a proposed flood channel that would be incorporated into the south edge of the development. Under the plan, 26 of the 354 lots on the property would be eliminated, along with the entrance from Bender Road.

The presentation also addressed work the Flood Control Zone District has undertaken to develop a two-dimensional flow model that is in the final state of FEMA acceptance for regulatory remapping the area floodplain. The model tests various flood alleviation alternatives at the proposed development. The report explains the flow models demonstrate that while some downstream flooding would be mitigated by the proposed channel, the current Whiskey Creek channel will still be incapable of alleviating downstream flooding on property adjacent to the development. The models also show a likely increase in downstream surface water depth if the flood channel and culvert are implemented.

“As you can see, there are numerous issues,” Cook said during his presentation. “We have not yet found a way to adjust them all satisfactorily. I think there is an answer, but I think the answer is probably going to take us down a path to something other than this. Whether or not that’s going to be acceptable or achievable to area residents or not, I can’t speak to that.”

In talks with the developer, WDFW and adjacent landowners, Cook said another idea surfaced that would have the potential to alleviate concerns from the water company and neighbors. The plan would include improving part of the creek channel near the proposed culvert to connect with an undershot that bypasses the water company canal and reconnect with the channel on the other side.

“You could imagine the difficulty in that,” he said. “It means we would be in a potential property acquisition mode. I only mention that because it looks to be our endpoint. If this is not acceptable to all parties in the room, I don’t know where we go next.”

As the developer has a land use entitlement, Cook said it is important that the county continues to work with the parties involved to come up with a solution that satisfies everyone involved. With the proposed improvements to the development, he said it looks that floodwater issues on that property will be mitigated, and so the next step is finding a way to address downstream flooding that impacts the water company and adjacent landowners.

“The reality is that once we get the onsite stormwater managed, we get a grip on the flooding impact, then (the developer’s) got a clear path to final plat,” he said. “That has always been the conversation we’ve had together. That is why you’ve seen us continue to work these alternatives to find that magic bullet that gets us to that.”

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