Water Well Journal

February 2015

Water Well Journal

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Initial Design Objectives and Concept Master planning for Pringle Creek Community assumed the use of groundwater as the sole water supply for a parallel configuration of water-to-air heat pumps in each individual residence and any large facility (such as the planned green- house and community center) for heating and cooling pur- poses as well as retaining the use of groundwater for grounds irrigation and potential for potable water supply. One critical and still unknown factor during preparation of the preliminary design was the preferred method of disposal of the return water from the heat pumps. Obviously, disposal through grounds irrigation alone would be an irregular process, limited to an inconsistent flow rate and to only three to four months out of each year. Therefore, an alternate method for the disposal of the return water would ultimately need to be developed. The two most likely alternatives pointed toward direct well reinjection and city or private sewerage system disposal. One other important preliminary design factor, not believed to be of consequence, was the stability of the water tempera- ture since, as previously stated, the typical water temperature of the local groundwater was known to vary within a reason- ably tight range usually between 50°-55°F. The preliminary design concept included use of this resource for both heating and cooling as well as grounds irrigation. Initially, although the design team agreed with the plan to use the existing groundwater resource underlying the pro- posed development as an element of the new community, it was not clear what exact role or scope this resource would play. The unknown condition of the existing wells and extent of the aquifer on the site as well as the potential for local well interference, source contamination, overuse, or water quality issues reinforced the need for adequate testing and a careful source analysis. The developers were quite clear in wishing to implement their primary objective of using all the natural resources avail- able—including the groundwater supply—but without either overextending, exploiting, or abusing any of them. In accor- dance with these objectives, the design team recommended a cautious approach to using the existing water wells located on the property as well as the aquifer without executing a full series of well production and water quality testing as well as an analysis of the aquifer itself. Well Inspection The former Fairview Training Center had previously used three deep groundwater wells for water supply, industrial use (boiler feed), and for grounds irrigation. One of the wells was located at the site of the former phys- ical plant within the planned boundaries of Pringle Creek Community. This single well, deeded and sold to Sustainable Development Inc. as a portion of the 32 acres, was a former production water well drilled in 1922, but with an unknown current condition and yield. Upon initial inspection, it was observed the well was equipped with a 40 hp deep well vertical turbine pump that had been decommissioned and disconnected from piping and electrical power (Figure 1). Assuming this well was still usable, it was planned to be- come the water supply well for the geothermal system for Pringle Creek Community. In line with this objective signifi- cant testing, video inspection, and verification of the well was conducted. Following mobilization to the site and equipment setup, the existing pump was removed from the well and a color video inspection performed on the well using a down- hole view and a 90-degree view (or side view) of the well's interior. The video inspection began at the top of the well casing/ pump pedestal, which is about 4 feet above local ground sur- face, or roughly at elevation 280 feet MSL. As the camera was lowered in the pre-existing cased borehole, the static water level was found to be at 42 feet below the top of the casing (about 38 feet below ground). Further lowering of the camera unit revealed the bottom of the casing actually terminated 66 feet below the top of the well pedestal which, after com- pensating for the difference in the pedestal height from ground elevation, closely matched the originally recorded depth of 62 feet. The well casing was confirmed to be 12 inches in diameter with threaded and coupled joints, typical for a water well con- structed during the early 1920s before the use of welded well casing started to predominate. The well casing demonstrated some minor corrosion and scaling throughout its depth, but there were no apparent cracks exhibited in the casing or major degradation of the pipe material. The survey showed an open and uncased borehole existed below the casing with moderate to major fracturing occurring throughout the remaining depth of the well. ENGINEERING continues on page 38 WWJ February 2015 37 Twitter @WaterWellJournl Figure 1.

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