2021-08-18_REVISION - M2012032 - Laserfiche WebLink

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LUHAY 5B ER 111%U, Because DEHP detections were helow regulatory PQL-defined thresholds and because no sheen has been observed at SW-22, OSMI proposes to cease visually contingent monitoring at SW-22. Monthly visual inspection of Pond 3 in lieu of GW-4 replacement well. Pond 3 is a lined facility whose discharge is monitored at Outfall 002A, regulated bN the Colorado Department of Public Health and Environment WQCD. Pond 3 effluent is heavily sampled under Colorado Discharge Permit System Industrial Wastewater Discharge Permit No. CO0000003,therefore water qualit\ will be well known and should be high-quality as it is the final polishing step prior to discharge. OS v11 proposes that Pond 3 water quality is best monitored at Outfall 002A as required under Colorado Discharge Permit 000000003, in lieu of a groundwater ,Nell. Additionally, Pond 3 was excavated to bedrock. DUring Pond 3 commissioning and leak testing, leaks were identified through a visible surface expression on the down gradient(north) edge of Pond 3. Monthly Pond 3 inspections will be performed and submitted to DRMS. Where snow is present or rain fall has occurred, water ma} be present in pools or flowing. The presence of water during such times is not an indication of a pond leak, but continued presence of water during drier times would indicate a potential leak in the pond. OSMI withdraws the proposal for GW-4R because a well cannot be placed in the same vicinity as GW-4 without risking additional intersection ol'historic, ambient, organic rich groundwater. OSMI proposes to monitor Pond 3 via a combination of already required sampling at Outfall 002A under C00000003 included in quarterly and annual reporting)and visual leak inspections of the northern edge of Pond 3, also included in quarterl} reporting. Itemized Preliminary Adequacy Review Response 1) Throughout the revision materials submitted, Table 2 is referenced however Table 2 was not included in the TR package. Please provide Table 2 - Gii'--1 and Sii'-?2 Sample Results. Response: Table 2, missing in the original revision request, was provided in the first extension request. However, all data(including new data) related to organic sampling at GW-4 and SW-22 (see map, Attachment I) is presented in Attachments 2 through q. 2. Section 3 1 states that the (ail and Grease sample results have not vet been received hackftonl the lab. Please provide the Division with the results and a narrative once received. Response: All GA'-4 and SW-22 analytical results are presented in Attachments 2 through 4. As discussed in the revision request and adequacy review response extension request, organic material was noted in GW-4 during the development of the well. InitialIN this material was thought to be a small amount of drilling-related fluid from the drill rig. However repeated attempts to clean the well were not effective, leading OSMI to contact DRMS. DRMS requested analysis for DRO, GRO, MTBE, BTEX, and Oil and Grease. Oil and Grease results that had not been received are attached(Table 1 of Attachment 2) and generally reflect DRO results. DRO(C10-C28)was detected in GW-4 at 8.4 mg/L and SW-22 at 0.3 mg/L (an estimated value below the practical quantification limit). Oil and Grease was detected in GW-4 at 6.6 mo,1L and was not detected at SW-22. 3 �