M200 Basin Retrofit

M200 Basin Retrofit, WA


Sustainable Design


Civil Engineering

Land Surveying


Identified hydrologic sub-basins that were primary contributors to sediment loading in the system

Identified hydrologic sub-basins that were primary contributors to sediment loading in the system

HDS units provide water quality benefits throughout entire basin and are easily maintained

Pre-treatment units improve water quality for 583 acres.

AHBL worked with the City of Wenatchee to improve water quality of runoff in the City’s stormwater conveyance system, which ultimately discharges to the Columbia River. The basin, identified as M200, is an 817-acre, highly urbanized area featuring residential, commercial, and industrial land uses. The project’s design goals were to provide pre-treatment distributed throughout the M200 basin per the Washington State Department of Ecology Stormwater Management Manual for Eastern Washington requirements.

AHBL began by identifying hydrologic sub-basins that were considered to be primary contributors to sediment loading in the system. We determined that pre-treatment would be the best approach. After analyzing the stormwater flows and turbidity throughout the M200 basin, AHBL chose to implement hydrodynamic separators (HDS) for pre-treatment. The location of the units are identified in the graphic above. The HDS units will provide the following benefits:

  • Site specific facilities target water quality benefits throughout the basin.

  • Ecology GULD approved for pre-treatment.

  • Can be installed on existing storm mains.

  • Allow for minimal disruption during construction and routine maintenance.

  • Can be easily maintained with existing equipment.

    Boundary and topographic surveys were conducted for Peachey Street Outfall and Columbia Street. AHBL obtained existing ground elevations for adjoining streets. Physical improvements located included roadways, paving, sidewalks, grade breaks, visible utilities, parking, curbing landscaping and other