Although there was limited hydrogeologic information of the area, GSI’s knowledge of the aquifer in the area allowed us to help the District develop a flexible drilling program, well design and installation of drinking water wells. This helped to provide a reliable source of affordable drinking water for the District’s customers.

Background

Rockwood Water People’s Utility District provides water to a population of more than 50,000 residents, as well as commercial and industrial users, in a service area that encompasses portions of the cities of Gresham, Portland and Fairview, Oregon. Historically, the District has purchased wholesale water from the City of Portland, delivered through the conduits from the City’s Bull Run reservoirs. Faced with greatly increased wholesale water costs, the District decided to utilize its existing senior groundwater rights to develop a groundwater source to supply its customers. Groundwater also provides an alternative water source during peak demand periods and when turbidity levels in Portland’s reservoirs elevate after major rainfall events. However, very little information was available regarding the nature and productivity of the deep target aquifer within the District’s service area which would provide a basis for potential yields and well design.

GSI’s Solution

Using the limited information available from previously drilled boring, along with GSI’s extensive understanding of the regional aquifer framework, our team was able to develop a preliminary well design and drilling program for the District. The goal of the drilling program was to assess productivity of the aquifer to inform the location and design of the District’s future production wells.

Recognizing that adjustments to the well design at the completion of each well may be needed; GSI’s team built flexibility into the drilling program. The insights developed during drilling and construction of the first well, as well as an analysis of interference between the District’s wells and other regional pumping centers, helped the team further refine the design and drilling program for two additional, larger wells with pumping capacities of 4,500 and 5,400 gallons per minute. Additionally, methods used to drill the upper borehole and install the production casing were modified for the newer wells, which reduced drilling time and promoted more efficient seal installation, resulting in cost savings for the District.