Mount Pleasant, SC Environmental Rules: Stormwater Management (2026)
Key Facts
- Simplified plan threshold
- Under 1 acre, residential (§153.040(D))
- Commercial simplified threshold
- Under 5,000 sq ft and under 10% impervious increase
- Full drainage plan
- Required at 1 acre or more disturbed
- Impaired waters threshold
- 25+ acres draining to a 303(d) water needs written assessment
- Enforcing officials
- Town Engineer and Stormwater Program Manager
- Civil penalty
- Up to $500 per day of violation (§153.070(B))
Summary
The Town of Mount Pleasant requires a stormwater land-disturbing permit for most construction under Chapter 153: less than an acre of residential disturbance needs only a simplified plan, but disturbing more than one acre triggers the full drainage-plan requirements enforced through the town's NPDES program.
(D) For residential land-disturbing activities involving less than one acre of actual land disturbance, which are not part of a larger common plan of development or sale, the property owner shall submit a simplified stormwater management control plan meeting the requirements listed in Chapter 155, Appendix B, § 13. ... (F) For land-disturbing activities disturbing more than one acre, all of the requirements of a drainage plan apply.
Full Breakdown
002(F). 040 scales the paperwork to the size of the project: residential land-disturbing activity under one acre, outside a larger common development, only needs a simplified stormwater management control plan under the Chapter 155, Appendix B checklist; a commercial project under one acre needs the same simplified plan if it stays under 5,000 square feet and does not add more than 10% impervious area, but must meet the full standard stormwater requirements if it exceeds either threshold. Disturbing more than one acre triggers every requirement of a full drainage plan, and disturbing 25 acres or more that drains to a water body on the state's 303(d) Impaired Waters list requires a written quantitative and qualitative pollutant assessment.
041 requires the drainage plan, including its stormwater pollution prevention plan, before preliminary plat approval or before any building permit issues, reviewed and approved by the Town Engineer, with the state NPDES notice of intent and fee submitted alongside it before a clearing and grading permit can be issued.
Violations & Fines
Violating any Chapter 153 requirement lets the Director of Public Services or Director of Engineering and Development Services issue written notice within 15 days describing the violation, the proposed penalty, and the time to fix it, per § 153.070(A). Each violation carries a civil penalty of up to $500, with each separate day of noncompliance counted as a new violation under § 153.070(B), and the town can also enter the property to correct the violation and bill the cost to the owner.
Frequently Asked Questions
Do I need a stormwater permit to build a single-family home in Mount Pleasant?
What counts as a small commercial project under the stormwater rules?
What happens if I violate the stormwater ordinance?
Sources & Official References
Other rules in Mount Pleasant
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Stormwater Management in Nearby Cities
How other cities in Charleston County handle stormwater management.