Post-Construction Standards

When projects create and/or replace 2,500 ft2 or more of impervious surface, the MS4 Phase II General Permit requires the implementation of post-construction measures. Post-construction measures, also known as post- construction Best Management Practices (BMPs), are permanent onsite facilities that seek to better manage storm water onsite by implementing measures for site design, source control, runoff reduction, storm water treatment and baseline hydromodification management. These measures facilitate storm water soaking into the ground, where it can be treated with soils that have been amended with compost, vegetation, and other techniques; or use plants to transpire the storm water back to the atmosphere. The amount of impervious surface area created and/or replaced at a project site will determine what post-construction measures are applicable.

It is imperative that post-construction BMP selection, size, and placement be considered at the start of site design.

The City of Anderson has prepared a Post-Construction Standards Plan for use by project engineers a nd designers. This guidance document is to be used as a road map and for direction when preparing post-construction storm water treatment plans.

A brief description of the types of projects affected by the State’s post-construction requirements and the City's review process is provided below. Please refer to the City’s Post-Construction Standards Plan for a complete description of the requirements.

Small Projects

Small Projects are those that create and/or replace between 2,500 ft2 and 5,000 ft2 of impervious surface to a site.

Examples:

  • Single family homes that are not part of a larger development Replacement of a parking lot
  • Construction of a new parking lot Addition to a business
  • Demolition and reconstruction of a single family house that has the same or a greater impervious footprint.
  • New streets or roads
  • Widening of existing streets or roads with additional traffic lanes
  • New or contiguous impervious surface at a discrete location within a LUP project - such as a pump station or maintenance facility

Exclusions:

  • Projects that have less than 2,500 ft2 of impermeable surface
  • Linear underground/overhead projects (LUPs)-(such as utilities)

Three step process to Small Project Permits:

    1. Select Site Design Measures (SDMs)
    2. Quantifying the Runoff Reduction
    3. Preparing the Submittal

Site Design Requirements

One or more Site Design Measures (SDMs) must be implemented for all Small Projects. Site Design Measures (SDMs) include BMPs such as: stream buffers, porous pavement, tree planting and preservation, vegetated swales, rain barrels, disconnected downspouts, and green roofs. All SDMs proposed must be submitted to the City for review and approval.

Exclusions:

  • Routine maintenance or repair such as: exterior wall surface replacement; pavement resurfacing with the existing footprint
  • Interior remodels
  • Pavement grinding and resurfacing of existing roadways; routine replacement of damaged pavement, such as pothole repair or replacement of short non-contiguous sections of roadway
  • Roofing replacement or repairs
  • Bicycle lanes and sidewalks built as part of new streets or roads that direct storm water runoff to adjacent vegetated areas
  • Impervious trails built to direct storm water to adjacent vegetated areas or other non-erodible permeable areas
  • Construction of new sidewalks, pedestrian ramps, or bike lanes on existing roadways

Regulated Projects

Regulated Projects are those that create and/or replace 5,000 ft2 or more of impervious surface, including new and redevelopment projects on private or public land. Redevelopment is defined as any land-disturbing activity that results in creation, addition, or replacement of exterior impervious surface areas on a site where some past development has occurred.

Examples:

  • Single family homes that are not part of a larger development Replacement of a parking lot
  • Construction of a new parking lot Addition to a business
  • Demolition and reconstruction of a single family house that has the same or a greater impervious footprint.
  • New streets or roads
  • Widening of existing streets or roads with additional traffic lanes
  • New or contiguous impervious surface at a discrete location within a LUP project - such as a pump station or maintenance facility

Six Steps Process to a Regulatory Project Permit

  1. Identify Drainage Management Areas (DMA)s
  2. Identify Applicable Source Control
  3. Incorporate Low Impact Development (LID)s Designs
  4. Select and size site Design of Treatment Control Measures
  5. Select and size site Stormwater Treatment Control Measures
  6. Hydromodification Management Analysis

Site Design Requirements

The following apply to all Regulated Projects:

New Development

  • Please refer to the Post Construction Standards Plan for regulated projects "Section 5 Requirements For Regulated Projects".

Redevelopment

  • Please refer to the Post Construction Standards Plan regulated project "Section 5 Requirements For Regulated Projects" and Section 2.3 "The 50% Rule" for redevelopments.

Post Construction Standards Plan

Low-Impact Development Plan Worksheet

Post-Construction Standards Plan Preliminary Operation and Maintenance

Post-Construction Entitlement Process

Post-Construction BMP CASQA Factsheets

CASQA Municipal BMP Handbook

Other Resources

Low Impact Development Center