Lexington County, SC Stormwater Regulations

Lexington County operates under South Carolina's Small MS4 general permit and enforces stormwater rules through its Stormwater Management Ordinance (Ordinance 19-10) and Land Development Manual. Owners of private stormwater ponds must submit an inspection by a qualified inspector by July 1 each year. Lexington is an inland Midlands county, so coastal OCRM rules don't apply, but Lake Murray and stream buffers carry their own requirements.

Primary source: Lexington County Stormwater Management Ordinance 19-10

Permit Requirements

Two permits usually run together here. At the state level, SCDES requires coverage under the NPDES Construction General Permit (SCR100000) for any project disturbing one acre or more, or less if it is part of a larger common plan of development. At the county level, Ordinance 19-10 requires an approved Land Disturbance Permit before land disturbing work begins in unincorporated Lexington County.

The Land Development Manual (revised March 2026) sorts projects into permit types. A General Land Disturbance Permit covers clearing, grading, and storm drainage installation. A Small Commercial Land Disturbance Permit covers development that disturbs less than one acre with no clearing, grading, or storm drainage work. A single family home outside a larger development needs no land disturbance permit under one acre, though the building permit application must include the county's erosion protection and sediment control form. At one acre or more, that home needs a Single Family Residential Land Disturbance Permit and state permit coverage.

The county reviews plans first, then sends the approved package to SCDES. Work can't start until the site has state coverage, and the county issues its Land Disturbance Permit once it receives notice of that coverage. A permit stays valid for up to five years and expires if the project sits inactive for 24 consecutive months.

Exemptions are narrow. The ordinance exempts forestry done under SC Forestry Commission practices, agricultural disturbance under one acre, and larger agricultural disturbance that adds no new impervious surface. County review and inspection fees are set each year. The schedule effective July 1, 2026 lists commercial plan review at $2,520 plus $220 per acre and a Small Commercial Land Disturbance Permit at $440. The state permit fee is separate.

Inspection Obligations

If you own a privately maintained stormwater pond or other post-construction control structure, the county expects a report every year. Its 2026 compliance notice requires an annual inspection by a qualified inspector, documented on the county's forms with photos, and submitted by July 1 through the Lexington Countywide Stormwater Consortium site. Reports without the required photos get rejected.

A qualified inspector is someone currently certified through a Post-Construction BMP Inspector Certification Course, a professional engineer registered in South Carolina, or a person working under that engineer's direct supervision. The county mails a reminder each February to the owner address on file with the Register of Deeds. If a property changed hands, the letter may not reach you, and the deadline still applies.

One thing to know: the Land Development Manual also contains a sentence saying private BMPs are inspected once every five years, in the same section that calls a missing annual report a violation. The county's current notice and its inspection checklist both say annual, by July 1. Plan on yearly.

The county's pond maintenance requirements are specific. Woody vegetation comes off all fill embankments and out of the area within 30 feet of any structure or pipe. Sediment is removed down to the approved pond bottom elevations on the record drawings. The area within a 30-foot radius of the outlet structure stays clear of sediment and debris. Trash racks, outlet barrels, filter rings, headwalls, swales, and fences all have to be kept clear and in good repair.

Responsibility depends on the property. Commercial owners and lessees carry long-term maintenance of every stormwater component on their site. In residential developments, the county may accept maintenance of ponds built to its Unified Sizing Criteria after a two-year warranty period, while routine work such as mowing and trash removal can still be assigned to the HOA. During construction, the permittee's qualified inspector checks the site at least once every calendar week, and county staff inspect at least once a month.

Penalty Structure

Enforcement runs on two levels. At the state level, SCDES can assess civil penalties up to $1,000 per day under the Stormwater Management and Sediment Reduction Act (S.C. Code 48-14-140) and up to $10,000 per day under the South Carolina Pollution Control Act (S.C. Code 48-1-330).

At the county level, Ordinance 19-10 doesn't print a dollar figure. It makes violators subject to civil penalties and misdemeanor charges within the penalty jurisdiction of the magistrate's court, and it counts each day as a separate violation. Under S.C. Code 22-3-550, magistrates hear offenses carrying a fine up to $500, up to 30 days in jail, or both.

The county's 2026-27 fee schedule adds non-compliance fees on top: 25% of the original submittal fees for a stop work order on a permitted project, $945 plus double submittal fees for unauthorized land disturbance, $1,880 for installing infrastructure without notification, and $945 for missing the 48 hour notice.

The usual sequence is a verbal warning, a written corrective order, a notice of violation, then a stop work order, holds on building permits and certificates of occupancy, and civil citations. If a private pond or drainage system isn't maintained after written notice, the county can do the work or hire it out and bill the owner or lessee for its direct and related expenses. And if the county is fined over its own NPDES permit because of what someone did, the ordinance lets it pass that penalty through to the person who caused it.

Key BMPs

The Land Development Manual pre-approves a set of structural BMPs and sets county-specific sizing rules. Designs using anything outside the list take longer to permit. Common approved BMPs include:

• Stormwater ponds - Wet and dry detention ponds. Under the traditional design method, a pond with a permanent pool stores the first 1/2 inch of runoff and releases it over at least 24 hours. Detention volume must drain within 72 hours.
• Stormwater wetlands - Built treatment wetlands. Existing natural wetlands can't be used for stormwater quality or quantity management.
• Bioretention areas - Planted filter beds. The mulch, planting media, and vegetation all count as parts of the BMP and have to be maintained.
• Infiltration trenches, enhanced swales, and sand filters - Pre-approved for water quality treatment, with a pretreatment component such as a forebay required.
• Gravity separators and proprietary systems - Pre-approved, though the manual notes a hydrodynamic separator can work well on a commercial site where most runoff comes off pavement and less well in a residential subdivision. Near Lake Murray, commercial sites and parking lots over 2,000 square feet of impervious surface must capture hydrocarbons.
• Not allowed - Porous asphalt and media filter inserts are prohibited except in very limited circumstances, because of high failure rates and maintenance needs.

Local Ordinances

The Stormwater Management Ordinance of Lexington County (Ordinance 19-10) applies to all of unincorporated Lexington County. It treats the Land Development Manual as an extension of the ordinance with the same authority, so the manual's design and maintenance standards are enforceable. The county posts both, along with its current fee schedules, on its Fees, Ordinances and Manuals page.

Municipalities are a separate question. The ordinance says each municipality owns and operates its own stormwater system and may have stricter requirements. Plans for projects inside a town or city go to that municipality first, then on to the county. The state's list of regulated small MS4s names seven Lexington County municipalities alongside the county: Cayce, Irmo, Lexington, Pine Ridge, South Congaree, Springdale, and West Columbia.

Water quality buffers apply to permitted sites disturbing five acres or more. The manual requires at least 100 feet from the top of bank along perennial streams, 50 feet along intermittent streams, and 50 feet from pond and lake shorelines. On Lake Murray the shoreline buffer is measured from the 360-foot elevation contour. Buffers are no-disturb zones: no clearing, grading, filling, or fertilizer and pesticide use without county approval.

The manual also sets Special Protection Areas. In mapped flooding problem areas, post-development peak discharge is limited to half the pre-development rate for the 2, 10, and 25-year storms. Sites draining to an impaired stream or a stream with a TMDL must also reduce the pollutant of concern. Around Lake Murray, all BMPs have to sit above the 360-foot contour and outside the lake's Project Boundary Line.

Lexington County has no stormwater utility fee on file as of October 2026. The ordinance reserves the county's right to adopt one with County Council approval. A countywide fee was presented to Council in November 2020 and Council stopped work on it the following month.