Central Arkansas Water has two high-quality and well-protected raw water sources, Lake Winona and Lake Maumelle. Lake Winona, located in Saline County in the foothills of the Ouachita Mountains, is a scenic 1.9 square mile reservoir that supplies approximately 35 percent of daily system wide demand. Lake Maumelle, located in west Pulaski County, is a scenic 13.9 square mile reservoir, that provides approximately 65 percent of daily system wide demand.
On July 1, 2001, the Little Rock water utility and its largest wholesale customer, the North Little Rock Water Department, merged into Central Arkansas Water, a metropolitan water system serving a population of 388,000 in the Greater Little Rock-North Little Rock area.
Lake Winona History
Little Rock Municipal Water Works originally developed Lake Winona as its first municipally-owned raw water supply. In search of a more reliable and higher-quality water source for greater Little Rock-North Little Rock, the city of Little Rock (in 1935) applied for a loan and grant from the Works Progress Administration. This was one of the various governmental agencies established during the Great Depression to make possible the development of a water supply and eliminate the metropolitan area’s dependence on the Arkansas River.
In 1936, the City sold $6.59 million in 4 percent, 40-year, non-callable bonds. The bonds were purchased for $3.85 million from the Arkansaw Water Company-the existing plant and distribution system on the south side of the Arkansas River. Construction started on a dam, on the Alum Fork of the Saline River. Plans for the comprehensive supply project included the dam and lake (later named Lake Winona); a 39 inch diameter, 35 mile, raw water line; a new purification plant at Ozark Point, (the original site of the community water purification system); and an auxiliary reservoir three miles west of the plant. Burns & McDonnell Engineering Company of Kansas City, Missouri, was the consulting engineer on the project.
Little Rock Municipal Water Works began construction in July 1936, and completed the project in May 1938. The first water from the new supply flowed into the system on February 17, 1938.
The water utility delivers supply, by gravity, from Lake Winona to the Ozark Point Water Treatment Plant. It is then conveyed to the Jack H. Wilson Water Treatment Plant, thus to a significant part of the water utility’s service area. Set within the forested slopes of the Ouachita National Forest and supplied by rainfall, Lake Winona provides a high-quality, soft, and pure water.
Lake Maumelle History
Little Rock Municipal Water Works originally developed Lake Maumelle as a second raw water supply. Studies that began in 1947, preceded the water utility’s development of a second source lake to meet the area’s growing demand for water service. Construction of the first source, Lake Winona, located approximately 18 miles west of Lake Maumelle, in the foothills of the Ouachita Mountains, spanned from 1936 to 1938. The Lake Winona project got under way immediately after the city of Little Rock purchased the local water system, south of the Arkansas River, from private owners in 1936.
With the assistance of consulting engineers, the water utility thoroughly investigated several prospective sources prior to selecting a site for the second reservoir. Along with the decision to build the lake was a public vote on a new water rate schedule to finance the project.
The water utility initiated preliminary surveys and mapping of the Lake Maumelle site in February 1954, and completed the work in December 1954. Sub-surface investigations at the project site followed in March 1956. The studies proved favorable and the engineers proceeded with project design.
Water officials awarded the first major contract for construction of the dam and spillway in July 1956. In June 1958, water from the new Lake Maumelle source flowed into the system for the first time. The overall project included two, 30 million gallon per day (MGD), constant-speed pumps and cost approximately $9 million.
In 1975, a third pump increased the firm capacity of the Lake Maumelle Pumping Station to 90 MGD. The pump, driven by a 2,250 horsepower (hp) motor, also added variable speed drive capabilities to the facility. In 1984, the water utility replaced the 2,250 hp motor and variable speed drive with a constant speed, 2,500 hp motor. The third pump, motor, associated piping, and electrical equipment cost about $1 million.
In 1983, the water utility added a fourth, 30 MGD pump at a cost of $974,944. The last pump addition increased the station’s firm capacity to approximately 113 MGD.
In 1988, the installation of an emergency standby, power generating station, equipped the water utility with backup power in the event of a failure on the commercial electric system. The project included two, 3,000 hp diesel engines; two, 2,000 kilowatt generators; and variable frequency drive equipment. The generators have the capacity to power two of the 30 MGD pumps. This capability, coupled with the gravity supply from Lake Winona, can provide customers with up to 84 MGD (more than the current, average-daily demand) during a complete electrical power outage at Lake Maumelle.
With the standby generating facility, the water utility is also able to control additional electric power costs incurred during peak demand periods.
In 2004, CAW completed construction of a second intake structure at the Lake Maumelle pumping station. Phase I of the installation included two, 15 MGD pumps and space for an additional 30 MGD pump. In addition to supporting the increased treatment capacity of the Jack H. Wilson Treatment Plant, the new $7.7 million intake enhanced the overall reliability and integrity of the raw-water delivery system. The year 2010 brought about Phase II of the second intake project with the installation of the seventh pump at Lake Maumelle at a cost of $2.4 million. This 2,250 hp, 34 MGD pump project boosts the firm capacity of the pump station to approximately 133 MGD and completes the build-out of the intakes and pump station at the existing facilities.