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Blast Vibration Analysis: Proposed MMRR Quarry <br />Page 3 <br />BLACK HAWK/CENTRAL CITY SANITATION DISTRICT <br />WASTEWATER TREATMENT PLANT <br />OPERATIONS <br />The BHCCSD Wastewater Treatment Plant is astate-of--the-art wastewater treatment facility with a <br />treatment capacity of 2.0 million gallons per day (mgd) that commenced operations in August 2005. <br />It treats domestic sewage from the City of Black Hawk, Central City, the Gilpin County Justice <br />Center and Recreation Center, and immediate surrounding azeas. The plant consists of the following <br />wastewater treatment units: <br />1. Headworks -screening and grit removal <br />2. Biological treatment -activated sludge basins (two aerated and two anoxic) followed by two <br />final clarifiers <br />3. Multi-media filtration units (two) <br />4. Ultraviolet (UV) light disinfection <br />The plant also houses a biosolids processing facility consisting of three 25,650 cu.ft. reinforced <br />concrete holding tanks, a thickening/dewatering 2-meter belt filter press, and a 1.5 mgd biosolids <br />storage/handling/transportcapabtlity. Hazardous materials used in the wastewater treatment process <br />and stored at the plant include 50% sodium hydroxide, 12.5% sodium hypochlorite, 93% sulfuric <br />~ acid, 48% aluminum sulfate (alum), 50% magnesium hydroxide, and 66% acetic acid. <br />In addition to conventional wastewater treatment and pathogen disinfection, one additional feature of <br />the treatment plant is its nutrient (nitrogen and phosphorus) removal capability. This is important <br />because of the plant's receiving water course, North Clear Creek, which in turn dischazges to Cleaz <br />Creek, and then eventually into Standley Lake. This water body was the subject of an Inter- <br />governmental Agreement between numerous parties in the Cleaz Creek Watershed and the Standley <br />Lake Cities (the Cities of Westminster, Northglenn, and Thornton representing the municipal water <br />users from Standley Lake) that committed to significant nutrient removal goals by dischazgers <br />within the Clear Creek Watershed. <br />The treatment processes aze monitored by a myriad number of instruments that measure: 1) flow <br />rates, 2) liquid and sludge levels in tanks, 3) pH, 4) dissolved oxygen (DO) concentration, 5) <br />differential pressure, 6)oxidation-reduction potential {ORP), 7) hydrogen sulfide gas concentration, <br />8) combustible gas levels, and 9) turbidity. These instruments in turn provide data to a computer- <br />based supervisory control and data acquisition (SCADA) system that allows plant operators to <br />monitor and control the treatment processes in real-time. <br />~ Leonard Rice Engineers, Inc. November 10, 2005 -Job No. 1086BCS03D <br />