Laserfiche WebLink
Musco Family Olive Comp - 3 - 4 May 2012 <br /> Several water samples were collected from the suction lysimeters during 2011. Musco was able <br /> to collect liquid from lysimeter LY-6 (Pond A) in March and October and from LY-23 (Pond B) in <br /> March. Both lysimeters are set five feet below the secondary clay liner. The water samples from <br /> LY-6 had EC values between 1,000 and 1,400 pS/cm while the LY-23 sample was near 400 <br /> pS/cm. The Report suggested that water collected in these lysimeters was likely related to water <br /> previously injected into the lysimeters as part of the maintenance program. <br /> Musco also reported an EC field measurement from lysimeter LY-18, which is located 10 feet <br /> below the secondary clay liner and monitors the northwest end of Pond A. Approximately one <br /> ounce of water was recovered from the device in October and the EC measured at 7,842 <br /> pS/cm. The Report did not cite maintenance as a potential source of this water. This field <br /> measurement was approximately seven times the value reported in LY-6 and twice the EC <br /> value reported for the recovered injection water observed in the LCRS sumps. Monitoring wells <br /> MWA 2 and MW-22 is in the vicinity of LY-18 and groundwater samples from these wells have <br /> EC values near 3,000 pS/cm. <br /> The Report did not address the source of the higher salinity water found in LY-18. EC values for <br /> the lysimeters and other samples are summarized in the table below. <br /> COMPARATIVE LYSIMETER EC VALUES <br /> Lysimeter Number Depth of Lysimeter* Date Sample EC Value (pS/cm) <br /> or Sample Type Collected <br /> Pond A, LY—6 5-feet March 2011 1,320 <br /> Pond A, LY—6 5-feet October 2011 1,042 <br /> Pond A, LY— 18 10-feet Oct/November 2011 7,842 <br /> Pond B, LY—23 5-feet March 2011 428 <br /> Injection Water** NA Sept/Dec 2011 280 <br /> Recovered Water*** NA Sept/Dec 2011 3,800 <br /> Groundwater (MW22) NA November 2011 3,030 <br /> Groundwater (MW12) NA October 2009**** 3,600 <br /> *Depth of Lysimeters is feet below secondary clay liner. **Injection water used for LCRS test. <br /> ***Recovered water in sumps from Pond B LCRS test. ****Last sample reported for MW12. <br /> Board staff is concerned that the high EC water collected from LY-18 may indicate a wastewater <br /> release from Pond A. Data interpretation is complicated by the small sample size, which <br /> precluded a full chemical analysis of the sample. Interpretation is also complicated because no <br /> information for the unsaturated zone background samples has been provided. The concern still <br /> remains, however, given the failure of the LCRS in the impoundments, and that the lysimeters <br /> are constructed in fine grained materials with restricted hydraulic conductivities, that the LY-18 <br /> sample result could be evidence of a release from the unit. <br /> Other Concerns <br /> The lysimeter log sheet was not included in Appendix D, so staff was unable to review field <br /> observations made during lysimeter maintenance. Please provide these log sheets in the next <br /> semi-annual monitoring report, which is due 31 July 2012. <br />