AWWA INF53958

The Alfred Merritt Smith Water Treatment Facility (AMSWTF) was originallyconstructed as part of the Southern Nevada Water System (SNWS) to deliver treatedwater from Lake Mead on the Colorado River to the communities within ClarkCounty, Nevada. The SNWS was created under the jurisdiction of the US Bureau ofReclamation (USBR) as part of a project to deliver Colorado River water to theState of Nevada. The SNWS is owned by the Colorado River Commission, an agency ofthe State of Nevada. The AMSWTF is located on Lake Mead west of Saddle Island.The AMSWTF was originally an in-line filtration facility without flocculation orsedimentation basins. Water is pumped from Lake Mead through a tunnel underSaddle Island and then into a 10-foot diameter cast-in-place conduit. Theoriginal plant had a 10-foot diameter Venturi meter as the primary flow measuringdevice. This Venturi meter was the means by which the State of Nevada's ColoradoRiver allocation is measured and reported to the US Bureau of Reclamation. It wasalso the means of controlling treatment processes within the AMSWTF. Over theyears, aeration and flocculation basins were added at the AMSWTF to improve watertreatment. During the last expansion, the capacity of the AMSWTF was increased to600 million gallons per day (mgd). In 1995, a decision was made to expand theSNWS by adding a new intake, a new tunnel under Saddle Island, a new raw waterpump station, a new tunnel through the River Mountains, and the new RiverMountain Water Treatment Plant (WTP). The Southern Nevada Water Authority (SNWA)was formed to implement this expansion to the SNWS. The ownership and operationsof SNWS were transferred from the Colorado River Commission to SNWA. The SNWA wasformed from the major water purveyors in Clark County, Nevada and includes theLas Vegas Valley Water District, the City of North Las Vegas, the City ofHenderson, and Boulder City. The SNWA retained Parsons as the overall ProgramManager for the expansion to the SNWS. A consortium of Montgomery-Watson (MW) andCH2M Hill was selected as the lead designers of the expansion. The joint ventureof Carollo Engineers and Black & Veatch (CBV), was retained to design elements ofthe expansion located at Lake Mead including improvements to the AMSWTF. Duringthis same time period, an epidemiological investigation concluded that the LasVegas area had experienced a cryptosporidiosis outbreak even though noCryptosporidium oocysts have been identified in either the finished water or theraw water from Lake Mead. Pilot plant studies were initiated by both CBV andMW-CH2M Hill, which resulted in the decision to add ozone treatment to the existingAMSWTF and the new River Mountain WTP. Adding ozone treatment tothe AMSWTF will make it the largest water treatment plant in the United Stateswith an ozonation unit process. This paper discusses the ozone additions toAMSWTF and the design, modeling and testing of the facilities for the ozoneadditions. Includes tables, figures.