The District of Columbia Water and Sewer Authority (DCWASA) owns and operates a system that delivers water produced by the U.S. Army Corps of Engineers Washington Aqueduct (WA) to customers in Washington, D.C. During compliance monitoring for the Lead and Copper Rule (LCR) in July 2000 through June 2001, DCWASA exceeded the 15-ig/L action level (AL) for lead at the 90th percentile in home tap sampling. DCWASA repeatedly exceeded the AL during subsequent monitoring through the period ending in December 2004. A combination of factors not a single source or a single causative event contributed to the problematic release of lead in water at consumers taps in the DCWASA system. The primary source of lead release was attributed to the presence of lead service lines (LSLs) in the DCWASA service area. Since the mid-1990s, three notable occurrences in the DCWASA system likely contributed to elevated lead releases during 2000 through 2004.