Two proposed locations for potential dams in the upper basin of the Chehalis River have been deemed suitable for construction but still present challenges, according to a report released Thursday by consultants tasked with researching the issue.

    The findings are the first to be released since the Chehalis River Basin Flood Authority voted to fund a second phase study into water retention at a cost of $250,000.

    The Lewis County Public Utility District initialized the project last year when it proposed the possibility of building two earthen dams to blunt the impact of chronic flooding in the Chehalis River Basin.

    Shannon and Wilson Consulting staff conducted the research, which included a visit to the site with a geophysicist, review of historical photos and the collection of geological data at the two sites.

    The proposed dam sites are located on the South Fork Chehalis River and the south end of the Boistfort Valley and on the main stem of the river about one mile south of Pe Ell, according to the report.

    In a preliminary conclusion of the findings, researchers wrote that their reconnaissance level study unearthed design challenges at the site including large, active landslides in and around the sites and a limited quantity of soils to use in construction.

    “However, in our opinion, none of these present a fatal flaw to dam construction,” the report’s conclusion reads. “The sites have many positive attributes, including the presence of strong rock for dam foundation and as a construction material, the apparent lack of active faults and a relatively thin overburden.”

    The report concluded that the general locations of the proposed dams “appear to be suitable, but future exploration and engineering study may identify a more favorable location and/or orientation for one or both structures.”

    Flood Authority Chairman Ron Averill, a Lewis County Commissioner and proponent of water retention, said the results were encouraging.

    The first half of the second phase study is expected to be completed soon, and Averill said he hopes to bring the issue before the full authority by November. The 11 member jurisdictions will then have to vote on whether or not to provide another $250,000 to finish the study into whether or not the projects are feasible.

    Initial estimates by the Lewis County PUD have placed the cost of the potential projects at well over $300 million.

    Averill said he hopes to have the support of the authority. The Confederated Tribes of the Chehalis Reservation initially opposed the study citing a lack of information, and others on the authority have been reluctant to throw their full support behind water retention.

    Thurston County Commissioner Karen Valenzuela said during an open house on flood programs Wednesday that the “jury is still out” on dams and that she had not decided whether or not to support the potential projects.

    “I don’t think we’ve gotten to the point to say whether it’s a ‘go’ or a ‘no go,’” said Valenzuela, Thurston County’s representative on the flood authority.

    The flood authority recently announced that it had obligated most of the $2.5 million it was allotted by the state Legislature in 2008 to research basin-wide flood control projects.

    Averill said money to fund the second half of the water retention study was included as an obligated expenditure and would be available should the flood authority choose to move forward on the project.