Water Well Journal
Issue link: http://read.dmtmag.com/i/451364
T hroughout my career I've had the opportunity to design and engineer numerous and diverse types of water supply and other civil and environmental engineering related projects. Included in these projects were various types of irrigation systems, aquifer storage and recovery systems, water storage reservoirs, treatment plants, and several dewatering systems. For the most part, my engineering background has mostly involved production (water supply) type of water well and pumping facilities for the purpose of providing potable water to municipalities or other kinds of public or private water sys- tems. Occasionally, I am given the opportunity to design, and if I am lucky, supervise the construction of a unique type of groundwater-related water system. This helps keep my career interesting and challenging, not to mention the fact I get to learn and implement new techniques and technology. The geothermal project outlined in this two-part series is an example of a low-temperature geothermal water supply and recovery system I was involved with a few years ago. Part 1 introduces and details the background of geothermal sources, the project itself, and the investigation performed on the exist- ing water supply well. Part 2 will outline the specific design features of the system. Geothermal Background Geothermal energy, simply defined, is thermal energy generated and stored within the Earth. The energy (heat) associated with geothermal sources from the Earth's crust is comprised of either energy expelled from the original creation of the planet (20%) or from the natural radioactive decay of the materials within the Earth (80%). Geothermal systems are used for various purposes such as power generation, comfort heating, and for recreational uses. Generally, geothermal energy is found in one of two states: vapor (steam) or liquid. Energy in a liquid state can be further subdivided by high, moderate, and low temperatures that can each involve various types of water supply schemes and designs. In Oregon, owing to its proximity to a tectonic plate and past and present volcanic activity, geothermal energy is found in virtually all states possible. For example, the city of Kla- math Falls uses geothermal sources for the heating of schools and even melting of ice and snow on city sidewalks. Moderate to high temperature geothermal water sources from wells or springs are distributed throughout the Cascade mountain range and in eastern Oregon and are used for power genera- tion, heating, and recreational uses such as spas and hot tubs. Another use of geothermal energy, specifically in the mid- Willamette Valley, is vested in low-temperature water sources where typical groundwater temperatures average 50°-55°F, ideal for use in both comfort heating and air conditioning since the groundwater temperature is within the general midrange for efficiently accomplishing both purposes. Project Background As practices for the treatment of developmental disabilities changed in the late 1990s, the State of Oregon looked to sell the grounds formerly occupied by the Fairview Training Cen- ter, a large state-run facility located in Salem, which had by then been reduced to 275 acres and was surrounded by con- ventional suburban residential and industrial development. A group of forward-thinking Salem residents, developers, planners, and businesspeople had seen an opportunity to collaborate on a new model for sustainable development at Fairview. This group became known as Sustainable Fairview Associates (SFA). The site was offered for sale in 2002 and SFA successfully purchased all 275 acres. When logistical and economic chal- lenges slowed the ability to develop the whole site immedi- ately, SFA selected a Portland architectural firm to produce a 32-acre master plan for a smaller part of the site. Sustainable Development Inc., a separate company that included some of the original SFA members, purchased the 32 acres and began planning Pringle Creek Community as the first concrete expression of their vision for the overall Fairview site. The master plan envisioned a community with a diversity of housing types, land uses, and residents, structured in a way that respected and enhanced the natural features of the site. My firm, 4B Engineering and Consulting, was re- tained in early 2007 as a consultant to assist with implement- ing this goal. ED BUTTS, PE, CPI ENGINEERING YOUR BUSINESS GEOTHERMAL SUPPLY AND RECOVERY SYSTEM USING A GROUNDWATER SOURCE A low-temperature geothermal project review: Part 1 36 February 2015 WWJ waterwelljournal.com The unknown condition of the existing wells and extent of the aquifer reinforced the need for adequate testing and a careful source analysis.