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PERMIT#: M-1974-086 <br /> INSPECTOR'S INITIALS: ECS <br /> INSPECTION DATE: June 21,2018 <br /> CORRECTIVE ACTIONS:This possible violation will require a hearing before the Mined Land Reclamation Board.The <br /> schedule and other details for the MLRB hearing will be provided under a separate document to be sent via certified mail <br /> to the operator. <br /> OBSERVATIONS <br /> On June 12, 2018,T.C. Wait of the Division's Inactive Mines Program (IMP) was conducting field work in the area of <br /> Ralston Reservoir and Ralston Quarry with Denver Water staff. During this outing, Denver Water notified T.C.that the <br /> road along the east side of Ralston Reservoir was impassable due to a landslide that had recently occurred on the <br /> adjacent Ralston Quarry site. When T.C. returned to the DRMS office she provided this information regarding a possible <br /> unreported landslide with off-site impacts to Minerals Supervisor Michael Cunningham. DRMS staff Eric Scott and Tim <br /> Cazier were tasked to conduct an inspection to follow up on this report and gather additional information. <br /> The Ralston Quarry is a 271 acre 112c permit operated by Asphalt Paving Company (APC) in Jefferson County <br /> approximately 2.25 miles north of Golden and 0.6 miles east of Hwy 93. On June 21, 2018 Eric Scott and Tim Cazier <br /> travelled to the site and met with Mark Martin,the site health and safety officer. After a site safety briefing, DRMS <br /> followed Mr. Martin to the west side of the permit were they met with Stan Opperman,vice President of Operations for <br /> APC, and viewed the area affected by the landslide. <br /> Mr. Opperman stated that the slide occurred sometime between June 10 and the morning of June 11, and that <br /> response-remediation activity consisting of moving the slide material to a more stable location had commenced on June <br /> 13. The slide occurred on the west slope of the ridge that runs north/south through the permit area, and impacted the <br /> Denver Water access road where it crosses a drainage ravine between the west side of the permit and the east side of <br /> Ralston Reservoir(see attached map). <br /> The landslide material consisted of unconsolidated soils and overburden that have been pushed over the top of the <br /> ridge from the eastern mined area and left at the angle of repose on the western slope. Although the material is well <br /> vegetated, a review of available historical photos of the area on Google Earth indicate that slope stability in this area has <br /> been a recurring issue. The area will need to be evaluated to assess long term stability concerns and determine if <br /> corrective measures will need to be taken to ensure that these overburden slide events do not recur. <br /> DRMS informed Mr. Opperman that follow up reporting in accordance with Rule 8.2.3 would be required for all <br /> response-remediation activities, and that APC would be required to submit any follow up activity proposed for <br /> additional geotechnical slope stability analyses, site characterization and long-term stabilization to DRMS as a technical <br /> revision for approval prior to implementation. APC acknowledged and submitted the first follow up report to DRMS via <br /> e-mail on June 25, 2018. APC has submitted weekly reports to detail all response-remediation activity associated with <br /> this slide event, and committed to submit to DRMS for approval any plans for further remedial investigation and activity. <br /> DRSM conducted a follow up inspection on July 19, 2018 (after initial remedial activities had been completed) to <br /> document site conditions and final extent of disturbance. DRMS collected additional photos of the slide area and <br /> earthmoving activity. Representative photos have been attached to this inspection. <br /> DRMS confirmed that the access road owned by Denver Water had been reopened and was in good condition. DRMS <br /> also confirmed that a portion of the area that was being used as a haul route and to stockpile the slide material was also <br /> located outside of the permit boundary on property owned by APC. DRMS collected GPS data during the follow up <br /> inspection and documented the estimated area of off-site impact as approximately 5.25 acres, and noted that there <br /> appear to be ongoing stability concerns and settling within the original slide area. <br /> Page 2 of 5 <br />