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