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D.C. Municipal Regulations (Last Updated: September 13, 2017) |
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Title 10. PLANNING AND DEVELOPMENT |
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SubTilte 10-A. COMPREHENSIVE PLAN |
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Chapter 10-A13. INFRASTRUCTURE ELEMENT |
Section 10-A1302. POLICIES AND ACTIONS IN-1 DRINKING WATER
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1302.1The water system serving the District of Columbia consists of two primary components: the water supply and treatment system, and the water distribution system. 1302.1
1302.2Water Supply and Treatment
The supply and treatment system includes raw water sources, pipelines carrying this water to treatment plants, and the water treatment plants themselves. The Washington Aqueduct Division of the US Army Corps of Engineers (USACE) operates and maintains these facilities and supplies treated water to several distributors. These distributors (which include WASA) deliver water to over one million users in the District and Northern Virginia. 1302.2
1302.3The Washington Aqueduct was commissioned by Congress and built by the USACE in the 1850s to provide the nation’s capital with a plentiful water source. It has been in continuous operation ever since. 1302.3
1302.4The Aqueduct System is composed of the Great Falls and Little Falls intakes on the Potomac River, the Dalecarlia and McMillan Reservoirs, the Georgetown Conduit and Reservoir, the Washington City Tunnel, and the East Shaft Pump Station. Figure 13.1 shows the Washington Aqueduct System. 1302.4
1302.5 Figure 13.1: Washington Aqueduct System
1302.6Water from the Aqueduct is currently allocated based on a Low Flow Allocation Agreement (LFAA) that was signed by the United States, Maryland, Virginia, the District of Columbia, the Washington Suburban Sanitary Commission, and the Fairfax County Water Authority in 1978. The Agreement recognized the need to maintain a minimum flow in the Potomac River in order to sustain aquatic resources. It established a set of stages for river flow that would prompt action by the signatories to monitor and eventually restrict water withdrawal. It also established a formula for allocating Potomac River water during times of shortage. To date, the LFAA’s low-flow stages have never been triggered. 1302.6
1302.7In 1982, the major water utilities and the Interstate Commission on the Potomac River Basin (ICPRB) signed the Water Supply Coordination Agreement (WSCA). It required the major water suppliers to coordinate their operations during drought emergencies. The Agreement also required that a 20-year study of supply and demand be prepared and updated every five years. It also included cost-sharing agreements for new facilities and subsequently included the Jennings Randolph and Little Seneca Reservoirs that serve as back-up water supply during droughts. 1302.7
1302.8The ICPRB Year 2005 assessment concluded that even under a high regional growth scenario, the water supply system developed 25 years ago is adequate to meet 2025 demand under a repeat of the worst meteorological and stream flow conditions in the historical record. The Assessment found that the system would also be able to meet estimated future water supply demand in 2045 given a repeat of the same drought conditions. 1302.8
1302.9The historic maximum production from the Washington Aqueduct was 284 million gallons per day (mgd), which occurred in 1974. Since 1974, water demand has decreased due to declining population and water conservation measures. Water demand is now relatively stable. In 2005, the average daily production from the Washington Aqueduct Division was approximately 185 mgd with a maximum day use of approximately 245 mgd. 1302.9
1302.10The Corps of Engineers treats water from the Aqueduct at the Dalecarlia andMcMillan water treatment plants (WTPs). Both of these plants were designed for much larger populations and higher water use projections than have been realized. As a result, their treatment capacity exceeds present-day demands and peak requirements of the customers. The Dalecarlia facility has a design capacity of 164 million gallons per day (mgd) and maximum capacity of 264 mgd. The McMillan facility has a design capacity of 120 mgd and a maximum capacity of 180 mgd. WASA’s projected average water demand based on population in 2020 is 156.5 mgd. Both Dalecarlia and McMillan serve the needs of the District (Dalecarlia also serves Arlington and Falls Church), so projected demand is well within the respective design capacities. 1302.10
1302.11Projections for future water demand for the regional WASA Service Area are shown in Table 13.1. These projections are maintained by WASA and assume levels of growth consistent with this Comprehensive Plan and the plans of adjacent cities and counties in the service area. 1302.11
1302.12Table 13.1: Current and Projected Water Demands (mgd), WASA Service Area* 1302.12
1302.13Water Storage, Distribution, and Pumping
Water storage and pumping responsibilities are shared by WASA and the Washington Aqueduct. WASA operates four treated water pumping stations (Anacostia, Bryant Street, Fort Reno, and 16th and Alaska), and eight reservoirs and elevated tanks. The Washington Aqueduct operates the Dalecarlia Pump Station and three reservoirs: Foxhall, Van Ness, and Fort Reno. 1302.13
1302.14The DC Water and Sewer Authority is the primary agency responsible for the District’s treated water distribution system. This system consists of pipelines and hydrants that deliver water to customers and meet other municipal needs such as fire fighting. The system is divided into seven water distribution zones (also known as service areas) based on differences in ground elevation. These areas are shown on Figure 13.2. 1302.14
1302.15The distribution system includes almost 1,300 miles of pipes ranging in size from four to 78 inches in diameter. It also includes over 36,000 valves and approximately 9,000 hydrants. More than 50 percent of the water mains in the system are over 100 years old. These older cast iron water mains are vulnerable to breaks and also are subject to a problem called tuberculation, in which small mounds of corroded materials accumulate in the pipes. WASA continually assesses the reliability and integrity of the water and sewer system pipes. To the extent that maintenance, corrosion, and break reports reveal problems, specific upgrades are factored into the Capital Improvement Program 1302.15
1302.16Figure 13.2: WASA Water Service Distribution Zones
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