2016-12-09_REVISION - M1980244 - Laserfiche WebLink

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Table 2-1 Water Quality Monitoring Parameters 59) The Operator's response to this item proposed groundwater numeric protection levels (NPLs) for five parameters (Total Sulfate, pH, Dissolved Manganese, Dissolved Zinc and Weak Acid Dissociable Cyanide) for each of the drainages where compliance monitoring is required (Arequa Gulch, Grassy Valley, Vindicator Valley, Wilson Creek). However, the Operator did not provide NPLs for the groundwater compliance monitoring wells located in Squaw Gulch or Poverty Gulch (shown on revised Figure 2-1). Please propose NPLs for all groundwater compliance monitoring wells. RESPONSE: A revised Table 2-1 is provided below with numeric protection levels (NPLs)identified for Squaw Gulch and Poverty Gulch. These NPLs have been provided to DBMS along with submittal of quarterly groundwater monitoring data (See Groundwater Monitoring Data: I" Quarter 2016 report sent to DRMS on April 26, 2016). Note, the NPLs identified for these different drainages are based on historic values and background concentrations for these wells. The groundwater in the area should be classified as "Potentially Usable Quality" as defined by Regulation 41.4.4 as the groundwater in the defined area has IDS values less than 10,000 mg/I. Groundwater is not used for domestic or agricultural uses within the specified area, and background levels are generally not adequate to assure compliance with the human health and agricultural standards or the information is insufficient to make such a determination, and domestic or agricultural use of the groundwater can be reasonably expected in the future... "(S CCR 1002-41 Regulation 41.4.B.4). None of the wells in question are used for drinking water or for watering livestock and therefore, the NPLs identified in Table 1-3 in 5CCR 1002-41, Regulation 41.8 do not apply. In some instances, Sulfate is monitored and compared to historic values such as Squaw Gulch and Vindicator Valley. The NPLs for sulfate in these instances are set based on background concentrations as provided in the table below. Historically, there have not been NPLs listed for Squaw Gulch. Therefore CC&V proposes using NPLs in Squaw Gulch that are consistent with the NPLs used for Arequa Gulch and Poverty Gulch as shown in the following table. Table 2-1 Numeric Protection Levels for Groundwater Monitoring Points Sulfate, Manganese, Zinc, Weak Acid Drainage Total (mg/I pH Dissolved Dissolved Dissociable as SO4) (mg/I as Mn) (mg/I as Zn) Cyanide, mg/I Arequa Gulch 1070 6 through 9 8.1 2 0.2 Grassy Valley 250 6 through 9 1 2 0.2 Vindicator 800 6.5 through 8.5 4 2 0.2 WCMW 3 250 6 through 9 0.5 2 0.2 WCMW 6 250 6 through 9 0.5 2 0.2 Squaw Gulch 1070 6.5 through 8.5 8.1 2 0.2 Poverty Gulch 1070 6 through 8.5 8.1 2 0.2 Page 4 of 8