Portland Wellhead Protection Ordinance Technical Committee

(Portland, OR)  Landau Associates participated in a technical committee convened to develop a wellhead protection ordinance for the City of Portland’s 90 Millions of Gallons per Day (MGD) backup wellfield along the Columbia River’s south shore. Management and protection of the wellfield from groundwater contamination is a primary concern of the Portland Water Bureau. Landau Associates was instrumental in evaluating the effects of pumping from the City of Portland`s Columbia South Shore Wellfield on a complex, regional multi-aquifer system, and played a leading role in developing the current conceptual hydrogeologic model and constructing a numerical (computer) model of groundwater flow in the aquifer system.

The numerical groundwater flow models included portions of Clark County in Washington and Multnomah County in Oregon. Numerical model calibration and simulations were conducted under steady state and transient conditions and included long-term (20 year) simulations of wellfield effects and groundwater flow. The regional numerical model represented an area approximately 17 by 20 miles; the local model represented an area approximately 2 by 3 miles. Models explicitly represented the Columbia River, Sandy River, Willamette River, and other surface water features, and accounted for regional land uses and recharge from precipitation.  

The Portland Water Bureau has used the conceptual and numerical models for wellfield management purposes, as tools to support aquifer restoration work, and in evaluations related to the City’s backup water supply system.