Hart Crowser, under contract to the USDA Forest Service, is conducting a peer review of engineering analyses related to remedial design of the Holden Mine site in Eastern Washington. One of the items to be reviewed is the hydrologic and hydraulic analysis of Holden Creek including HEC-RAS modeling, bridge designs, and site hydrology. Hart Crowser required high level technical support for these portions of the review.
Role/Services: WSE provided technical review of the hydrologic and hydraulic analysis including the following tasks:
- Review of the hydrologic analysis for the project, including HEC-1 hydrologic modeling;
- Regression based peak flow analyses;
- Gage data review and flood frequency analyses;
- Gage data transposition;
- Design peak flows for hydraulic analysis;
- Determine fish passage design flows;
WSE also conducted a review of the HEC-RAS hydraulic model, floodplain evaluation, and the Holden Bypass Road Bridge hydraulic analysis.
Outcome: WSE concluded that the project hydrologic data warrants further consideration to ensure that the design values chosen are acceptably conservative. Further, it was noted that any changes to the design peak discharges would necessitate additional review of the hydraulic and floodplain evaluations.