Stormwater Design Standards Manual

About the Manual

The Stormwater Design Manual standardizes how stormwater elements of a project are designed, submitted, reviewed, approved, and inspected.

The 2020 Stormwater Design Standards Manual is available here as a PDF. 

Questions about the updated Stormwater Design Standards Manual? Check out the SWDSM Fact Sheet for a summary of the major changes.

The prior 2013 SWDSM manual is available here as a PDF.

History

In September 2007, the City of Charleston passed a more robust stormwater ordinance that incorporates requirements of the federally mandated NPDES Phase II stormwater program. As required, the new ordinance addresses elements of Minimum Control Measures (MCM) number four and five, construction-site stormwater control, and post-construction stormwater control, respectively.

The stormwater ordinance also authorized the development and implementation of a Stormwater Design Standards Manual (SWDSM) for use by the City of Charleston when reviewing, approving, and permitting construction, development, and re-development projects. The SWDSM standardizes engineering and construction practices within the City of Charleston’s jurisdiction. It will serve to:

  • Provide application submission requirements and the approval process
  • Provide technical design standards to address water quantity control
  • Provide technical design standards to eliminate the implementation of sub-optimal design and installation practices
  • Provide general information to improve water quality, prevent illicit discharges, and minimize stormwater runoff impacts
  • Provide other protection provisions related to stormwater discharges

The 2020 revisions to the SWDSM provide information that supports the implementation of an integrated, green infrastructure-based approach to natural resource protection, stormwater management, and site design that can be used to protect the City of Charleston’s and coastal South Carolina’s valuable natural resources from the negative impacts of land development and nonpoint source pollution.

Similarities to Other Standards

The SWDSM developed by the City of Charleston is very similar to the manual developed by Charleston County, and it shares many similarities to SCDOT standards. Where the SWDSM differs from other standards, in many cases the City of Charleston found that certain design or installation practices create water quality or maintenance problems and it is attempting to prevent those problems from reoccurring.

Adoption & Updates

The SWDSM was initially formally adopted by the City Council on January 12, 2010 and was subsequently updated in 2011 and 2013. In 2019, the Department of Stormwater Management convened a Stormwater Standards Task Force to provide input and feedback during the revisions and updates to the City’s SWDSM. The revisions were necessary to incorporate key requirements from new SCDHEC Construction General Permit (CGP), new SCDHEC Small MS4 Permit, and the City's Stormwater Management Program (SWMP).

After careful consideration and review, the revised SWDSM was approved by the City Council in February 25, 2020 with an effective date of July 1, 2020.

2020 SWDSM Workshops

The City of Charleston held four technical education workshops in 2020 regarding the manual updates. Below you can find recordings of these workshops and the materials provided. 

Workshop #1: Submittal, Permitting, and Closeout Process

Watch a recording of the workshop here

Workshop Presentation

SWDSM Technical Procedure Document #1 – Stormwater Permitting Process

SWDSM Technical Procedure Document #2 – Conceptual Planning

Workshop #2: Overview of Basin Analysis (‘the 10% Design Rule’) and Peaking Factor

Watch a recording of the workshop here

Workshop Presentation

SWDSM Technical Procedure Document #3 – Peaking Factor

SWDSM Technical Procedure Document #4 – 1 Percent AEP Storm Event Analysis

Workshop #3: Overview of the Special Protection Area (SPA) Requirements and City Watershed Modeling Data

Watch a recording of the workshop here

Workshop Presentation

SWDSM Technical Procedure Document #5 – City Watershed Modeling Data

Workshop #4: Overview of Wetland Modeling, Submerged Systems, and Using Low Impact Development (LID) Design Techniques

Watch a recording of the workshop here

Workshop Presentation

SWDSM Technical Procedure Document #6 – Wetland Systems Modeling

SWDSM Technical Procedure Document #7 – Equalization Pipes and Submerged Systems

SWDSM Technical Procedure Document #8 – LID and the Coastal SC LID Design Guide

Resources