2007-02-05_REPORT - M1983194 - Laserfiche WebLink

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4.4 Geotechnica/ Progrom NSI monitors two (2) time-domain-reflectometry monitor wells, 4A-SM and3M-TDR These wells are located between cavities SH, 6H, and lA. There has been no indication of subsidence in 4A-SM since installation and that has continued throughout 2006: Subsidence we113M-TDR was drilled late in 2003. Two of the four TDR cables in 3M-TDR subsidence well appear to have water infiltrafion damage. In 2006, readings were again taken and data was gathered from cables two and three. In addition to the monthly NSI readings, the installafion contractor also collects data annually, (Figure 4.4); no significant subsidence was detected in 3M-TDR. The bi-annual surface survey was performed by an independent surveying company. The results did not detect subsidence at any of the surface monuments. A copy of the survey report maybe found in the Appendix. 5.0 Environmental Monitoring and Protection S.1 Hydrology Monitoring 5.1.1 Introduction NSI's hydrology monitoring program concentrates on ground water, as there are no perennial streams or springs located on the sodium leases. The USGS stream gauging station-monitoring program is conducted, with NSI support, to provide regional stream flow data. The hydrology monitoring plan is designed to detemune impacts of NSI's solution mining operations on underground sources of drinking water, as designated by the US EPA. Figure 5.1 illustrates the location of existing monitor wells. A thorough discussion of historical water monitoring data was presented in previous Annual Reports and will not be repeated in this report, Through 2006, dewatering did not affect the Perched aquifer or the nearby springs fed by this aquifer. The A and B-Groove aquifers were affected locally (WL by pumpage from water well). 5.1.2 Stream Gauging Stations NSI continues to contract with the USGS to monitor surface water for water quality and quantity. Monitoring was performed upstream and downstream of the mining operation on Yellow Creek and Piceance Creek at four existing stations with extensive historical data. Funding for the USGS stations was shazed with one of the other nahcolite projects (Solvay) in the azea. Data for the 2005 water year (October 2004-September 2005) was published the following year in 2006 by the USGS. The USGS water data is available to the public from the USGS web site at http://co.water.usgs.gov. Table 5.1 is a summary of key 2005 data for the NSI site. A review of USGS stream water quality data indicates no significant change in stream water quality through 2005. Therefore, no effect on stream water quality was noted from the NSI operafion. 2007 Annual Report 8 of 18