2010-09-14_ENFORCEMENT - M1977300 (2)

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September 13, 2010 2 of 6 which was already enroute before the interceptor system was turned on, would eventually report to Ralston Creek and affect water quality over time. Due to this "lag time", the treatment system would not be expected to be fully effective immediately after it was turned on. (2) Pumping from Sump 1 alone is insufficient to fully capture all of the groundwater in the alluvial system. Although Sump 1 is well-placed to intercept groundwater before it enters Ralston Creek (because the sump is located near where the valley narrows and most of the groundwater flowing in the alluvium at that point will be intercepted), it does not intercept groundwater that reports to the creek upstream of capture zone around Sump 1. Cotter anticipated this condition and planned the system to be expandable to Sump 4 and MW9. (Sump 2 and Sump 3 were removed during reclamation activities and are no longer available.) Cotter informed DRMS during the June 15 2010 meeting at CDPHE offices that the piping system would be constructed to allow Sump 4 and MW9 to be added to the system. Susan Wyman's presentation before the MLRB on July 12 also stated that the piping system included tie-ins for Sump 4 and MW9, and those locations were shown in plan view and in construction details. The EPP states that water would be collected from Sump 1 and Sump 4 with the ability to tie in MW9. As stated, surface water monitoring results from the detailed/local monitoring stations would be used to determine the effectiveness of the treatment system and provide data to optimize groundwater capture and treatment. (3) Pumping at Sump 4 and MW9 did not begin until August 16 and 19, respectively. Pumping from Sump 4 and MW9 is intended to intercept groundwater that would reach Ralston Creek above Sump 1. Because pumping at Sump 4 and MW9 did not begin until August 16 and 19, no positive effect of this portion of the water treatment system would be evident in the water quality monitoring results in Ralston Creek samples collected at the compliance point, SW-BPL, before pumping began. Great effectiveness of the water treatment system is expected with improved hydraulic capture by pumping from Sump 4 and MW9. The effects of this pumping are also subject to a lag time, and it may take weeks to see the full effect of pumping at these locations. TRAVEL TIME, CAPTURE, AND TREATMENT OF WATER FROM THE 2-INCH PIPE Water was discovered flowing from the open end of a small pipe on July 20, 2010. The 2-inch plastic pipe sticks out of the ground along the eastern bank of the excavated former overflow retention pond. In a September 2009 photograph of the former overflow pond excavation, the pipe is visible in the foreground and is not flowing. The May 18 2010 inspection by Tony Waldron and David Bird of DRMS involved sampling the pond and conducting other activities in the direct vicinity of the pipe and did not make note any flow from the pipe. DRMS and Cotter collected