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Mining takes place in dry pits at the southem end of the property. Groundwater is collected in <br />perimeter ditches and flows by gravity to the dewatering pit at the southwest corner of the property. <br />There aze two 50-hp pumps in the dewater pit, and they each operate at 2,000 gallons per minute. <br />One of the pumps operates 24hours a day. The other is operated on a float switch, and typically runs <br />between IZ- and 24-hours a day depending on the season. The pumps are connected to piping that <br />allows dischazge to several outfalls. <br />The facility is planning to convert the dewatering pit to a settling pond. The dewatering pump <br />location will be moved to the southwest comer of the dry mining pit. This is not considered a major <br />process change. <br />The dewatering pumps dischazge clear water to a lateral of the Last Chance Ditch. The water mixes <br />with ditch water and flows for about 200 feet in a concrete channel. A portion of this water is then <br />diverted to the clean water pond for the gravel pit, and the rest remains in the lateral for agricultural <br />use. The dischazge to the ditch is not currently included on the dischazge permit. <br />Outfa11001 is a concrete-lined ditch at the southern edge of the property. Dewatering water is <br />occasionally dischazged to this point, although that has not occurred in the past 2 yeazs. <br />The clean water pond is used in the screening and crushing operation. The wastewater from this <br />activity flows to the wash pond, where the sediments aze settled out. Water then flows to the settling <br />pond, and the cleaz water is then dischazged through Outfall 004. <br />The dischazge flow is estimated based on the maximum flow rate from the dewatering pumps. <br />Sepazate flow measurement devices do not exist for Outfalls 001 and 004. With the reconfiguration <br />of the water handling system at this facility, the flow estimation method does not achieve the +/- 10% <br />accuracy required by the permit. <br />During our inspection, the following items were noted and need to be brought to your attention: <br />1. The facility has developed a new outfall, which must be added to the permit. The current <br />dewatering pump dischazge to the Last Chance Ditch lateral is a discharge point to State waters. <br />We understand that Varra Environmental Manager Brad Janes has contacted Chris Gates of the <br />Division's Permits Unit to address this issue. <br />2. Flow measurement is currently estimated using the maximum pump capacity. The pumps have <br />been calibrated by the manufacturer, but they are not equipped with run time meters. At 2,000 <br />gallons per minute each, the pumps are capable of producing up to 5.76 million gallons per day. <br />The permit currently shows a dischazge capacity of 0.72 MGD. A portion of the flow at the new <br />outfall is recycled onto the facility at the clean water pond, and the remainder stays in the Last <br />Chance Ditch lateral. <br />Under the current conditions, accurate flow measurement at the three outfalls is not possible. <br />Please contact Chris Gates of the Division's Permits Unit with a proposal for accurate flow <br />measurement. One potential solution is to install run time meters on all the calibrated dewatering <br />pumps, and a pazshall flume with ultrasonic level and data recorder at Outfa11004. Other flow <br />C:\d\AAPROJ\Denver\500346-1 Vaua Sand and Gravel Inspection in August 2002.doc <br />September 11, 2002 Page 2 of 3 Mike Havens <br />