Background Information
The GGS Well Field was installed to lessen the impact at Gerald Gentleman Station of the ongoing drought. Basically, those impacts are two-fold: 1) High discharge water temperatures that exceed regulatory limits, and 2) Potentially low water levels in Sutherland Reservoir. In early 2005, the NPPD Board of Directors approved completion of 24 production wells to address those drought-induced impacts. The first wells were available June 26, and the final well was operational Aug. 1, 2005. Four wells were first utilized for temperature mitigation July 13, 2005.

GGS Well Field Operation
NPPD estimated that operating a relatively small number of the wells would enable GGS to comply with its discharge water temperature regulatory limits through the irrigation season. This estimate was based upon availability of water from Lake McConaughy (the source of most cooling water for GGS) and data from 2004. However, significantly warmer than expected water temperatures at Lake McConaughy and a heat wave that settled over the region with calmer than usual winds led to warmer than predicted water entering GGS and reduced effectiveness of the cooling canal and cooling pond. To maintain regulatory compliance, GGS has had to utilize various numbers of wells at different times and even all 24 of the well field wells. It should be noted that even with the operation of more wells than originally anticipated, GGS has been challenged to maintain the temperature of the discharge to Sutherland Reservoir within the regulatory compliance limit.

Operating separately from the well field’s temperature mitigation, water was being released from Lake McConaughy for irrigation downstream of GGS and Sutherland Reservoir. This water passes through Sutherland Reservoir, which made it necessary for the reservoir’s downstream gates to be opened. If the well field were being used to raise water levels in Sutherland Reservoir, those gates would be closed. Water being pumped into the Sutherland Reservoir, to date, has been solely for temperature mitigation at GGS; the wells have not been pumped for any downstream use, although the water may be leaving the reservoir.

Landowner Mitigation
From the beginning of the GGS Well Field project, NPPD has made it clear that it will be a good neighbor. With this in mind, the District, in conjunction with a landowner committee, formulated a mitigation plan to address potential impacts to irrigation wells, domestic wells and livestock wells. Agreements for mitigating the impacts to the wells were generated from this effort.

What’s Next?
NPPD and the Twin Platte Natural Resources District are closely monitoring the groundwater table near GGS. Since Dec. 14, 2004, NPPD has maintained 13 monitoring wells at eight sites. Twin Platte NRD began independently monitoring groundwater levels in the spring of 2004 on another 30 monitoring wells in the GGS vicinity. Data compiled through continued use of the GGS Well Field will assist NPPD in validating its groundwater models. NPPD has posted additional information regarding well field operation in 2005.

Summer 2006
While the summer of 2006 weather may have appeared to be similar to 2005, meteorological conditions in 2006 were more favorable. Wind speed increased when air temperatures increase which cause more cooling to occur and less operation of the wellfield to help with those cooling challenges.

For the first time, a model was available for use to help determine when wells needed to be operating. This decreased the well usage from approximately 4,450 acre-feet in 2005 to 3,450 acre-feet in 2006.