TTHM (Total Trihalomethanes) violations in Maryland
63 active public water systems in Maryland had a TTHM (Total Trihalomethanes) violation in the past three years, 2 of them still unresolved. What TTHM (Total Trihalomethanes) is and why it matters.
Systems with a TTHM (Total Trihalomethanes) violation
Unresolved first, then largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
City of Baltimore Baltimore city County |
1,600,000 | 3 | 0 | |
|
Manor Shopping Center Baltimore County |
2,921 | 3 | 1 | |
|
Harford County D.p.w. Harford County |
104,567 | 1 | 0 | |
|
Lexington Park St. Mary's County |
43,030 | 3 | 0 | |
|
Patuxent Naval Air Station (navfac-Wash) St. Mary's County |
22,000 | 1 | 0 | |
|
Ocean Pines Worcester County |
11,890 | 1 | 0 | |
|
Town of North East Cecil County |
8,600 | 3 | 0 | |
|
Fort Detrick Frederick County |
7,900 | 1 | 0 | |
|
Town of Leonardtown St. Mary's County |
5,000 | 1 | 0 | |
|
Town of Perryville Cecil County |
4,413 | 4 | 0 | |
|
Country Lakes St. Mary's County |
3,016 | 1 | 0 | |
|
Town of North Beach Calvert County |
3,000 | 2 | 0 | |
|
Cedar Cove St. Mary's County |
2,728 | 1 | 0 | |
|
Town of Williamsport Distribution System Washington County |
2,400 | 1 | 0 | |
|
Lakeside Village Washington County |
1,575 | 1 | 0 | |
|
Glenelg High School Howard County |
1,532 | 1 | 0 | |
|
Springfield Hospital Distribution Carroll County |
1,500 | 2 | 0 | |
|
Wicomico Shores St. Mary's County |
1,262 | 1 | 0 | |
|
Webster Field Annex, ST Inigoes (navfac) St. Mary's County |
1,200 | 1 | 0 | |
|
Greenbrier St. Mary's County |
1,161 | 1 | 0 | |
|
Town of Willards Wicomico County |
1,021 | 3 | 0 | |
|
Breton Bay St. Mary's County |
1,012 | 2 | 0 | |
|
Hunting Quarters St. Mary's County |
715 | 1 | 0 | |
|
Town of Queenstown Queen Anne's County |
705 | 4 | 0 | |
|
Rolling Acres St. Mary's County |
699 | 1 | 0 | |
|
Piney Point St. Mary's County |
672 | 1 | 0 | |
|
Folly Quarter Middle School Howard County |
667 | 1 | 0 | |
|
St. Clements Shores St. Mary's County |
620 | 1 | 0 | |
|
Charlotte Hall St. Mary's County |
615 | 1 | 0 | |
|
Forrest Farm Subdivision St. Mary's County |
577 | 1 | 0 | |
|
Laurel Ridge St. Mary's County |
560 | 1 | 0 | |
|
North Bend Elementary School Harford County |
534 | 3 | 0 | |
|
Jarrettsville Elementary Harford County |
528 | 2 | 0 | |
|
Persimmon Hills St. Mary's County |
514 | 1 | 0 | |
|
Wilderness Run St. Mary's County |
511 | 2 | 0 | |
|
North Harford Elementary Harford County |
464 | 2 | 0 | |
|
Churchville Elementary School Harford County |
441 | 1 | 0 | |
|
Lutheran Village at Miller's Grant Howard County |
315 | 3 | 0 | |
|
Country Meadows of Frederick Frederick County |
295 | 1 | 0 | |
|
Pilot Travel Center & Arbys Restaurant Garrett County |
280 | 1 | 0 | |
|
Birch Manor St. Mary's County |
272 | 1 | 0 | |
|
Grandview Haven St. Mary's County |
269 | 1 | 0 | |
|
Piney Point Landings St. Mary's County |
239 | 1 | 0 | |
|
Villages at Leonardtown St. Mary's County |
239 | 1 | 0 | |
|
Fenwick Manor St. Mary's County |
234 | 1 | 0 | |
|
Norrisville Elementary School Harford County |
231 | 1 | 0 | |
|
Saint James School Washington County |
200 | 4 | 0 | |
|
Leonardtown Farm St. Mary's County |
193 | 1 | 0 | |
|
Southgate St. Mary's County |
188 | 1 | 0 | |
|
King & Kennedy St. Mary's County |
169 | 1 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved TTHM (Total Trihalomethanes), including monitoring and reporting lapses. Rules violated and status in the table are for the whole system, not TTHM (Total Trihalomethanes) alone.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The Maryland records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.