2025-03-11-minutes-solid-waste-and-maintenance

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Ryegrass LPL and Ryegrass Balefill Landfill tfpgradient Groundwater Investigation Kipitas County Solid Waste additional wells 85 and B6 were added further south of the Balefill Landfill as part of the RI/FS. in 2004, B7 was added located west of the LPL following re -permitting of the CDL landfill into an LPL. There are several nearby springs of groundwater discharging to surface water where the Vantage Interbed and bottom Gingko Flow zone outcrop at land surface in the nearby shallow channels. These include Upper Clerf, Lower Clerf, Clerf #3, Clerf #4, and Poison Spring (Figure 3). Monitoring for the Balefill Landfill is completed at wells 82 (deep), B3, 134, 135, and B6 and Poison Spring on a semi-annual basis in accordance with the Post -Closure Monitoring Plan (HWA 2018), The Post -Closure Monitoring Plan called for quarterly monitoring but in 2018, post -closure monitoring of the Balefill Landfill was reduced to semi-annually (HWA 2018). Monitoring for the LPL is completed quarterly at monitoring wells 63 and B7 and the Clerf #4 spring in accordance with WAG 173-350- 400 and the SAP (HWA 2020). 3.2.1 Water Quality Evaluations The results of the 2023 groundwater monitoring program (Parametrix 2024) show exceedances of WAC 173-200 Groundwater Quality Standards (GWQSs) and Maximum Contaminant Limits (MCLs). No volatile organic compounds were identified in any of the samples. Due to the history of biosolids storage and land application at the Facility, several exceedances are potentially related to sources other than the Ryegrass LPL and Balefill Landfill. Exceedanees in 2023 (Parametrix 2024) included., a Specific Conductivity in well 84 for both the First and Third Quarters and in well B5 for the Third Quarter. im Nitrate in wells 84, B5, and 86, and Poison Spring for both the First and Third Quarters and in B7 for all four quarters. ■ TDS in wells B4 and 135 for both the First and Third Quarters a Total Iron in 67 dudng the Second, Third, and Fourth Quarters and dissolved Iron in 137 during the Fourth Quarter a Total Manganese in B7 during the Third and Fourth Quarters ■ Arsenic also exceeded GWQs and MCLs in wells B2, 133, 64, B5, and B6 and at Poison Spring; however, these results are below the background threshold values for the Yakima Basin, 3.3 Upgradlent Source Evaluation As discussed above in Section 2.1.3, there were six unlined septage lagoons that operated at the Facility. The four original lagoons are located on the northernmost portion of the Facility. Two replacement unlined lagoons operated near the current lagoon locations until the two current lined lagoons were constructed in 2006. All six historical unlined septage lagoons and two active lined septage lagoons are located upgradient of the Balefill Landfill and the LPL. A new monitoring well, B8, will be installed between the landfills and the historical and current septage lagoons to evaluate water quality. Figure 3 displays the proposed location of monitoring well B8. 3.4 Shallow Aquifer Details As discussed above, the Shallow Aquifer below the Facility is located within the bottom flow zone of the Wanapum Basalt, locally known as the Gingko Flow, The saturated zone of the Gingko Flow is comprised of pillow basalts, palagonite, and petrified wood. This is located approximately 70 to 185 April 2024 1 553-1763-a10 Revised May 2024