St. Mary's County, Maryland

St. Mary's is largely unsewered rural/suburban Chesapeake (after Calvert). MDE On-Site Wastewater Professionals / OSDS Registered Individuals list (Updated September 2, 2026) prints registration numbers with streets — those numbers are quoted. St. Mary's County also requires a county septic contractor license (SOP updated through Jan 30, 2025; annual renewal on the state fiscal year) and MDE registration; Health Department Perc Test FAQs and Bay Restoration Fund pages state the licensed-contractor list is available upon request (301-475-4321 / [email protected]) and do not publish a fetchable street roster online this pass — county scavenger/installer numbers are not invented. No official 2024–2026 county tank total was opened this pass; do not invent tank counts. PO Box-only, out-of-county Census matches (including Charlotte Hall Whisper Court → Charles County), Calvert firms already listed, and non-septic home-inspector/surveyor/portable-toilet rows are omitted.

15 listings · board: MDE / MD State Board of On-Site Wastewater Professionals (OSDS Registered Individuals); St. Mary's County Health Department (county septic contractor — no public street roster)

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