Stormwater Control Measures (SCM)

Stormwater Control Measures

What is an SCM?

Stormwater Control Measures (SCMs) are permanent structural devices that are designed, constructed, and maintained to remove pollutants from stormwater runoff before the water reaches our streams and drinking water supply reservoirs.  Additionally, SCMs provide stormwater storage to account for increased impervious surfaces that come along with development. Impervious surfaces are those that do not let what through and produce runoff including roads, sidewalks, driveways, and building rooftops. SCMs are designed to hold stormwater from a pre-determined amount of rain (called the design storm) and release it slowly over a few days. This allows engineers to meet the pre-development runoff attenuation requirement for the site. Some examples of more common SCMs include wet ponds, stormwater wetlands, bioretention cells, and permeable pavement.

Wet Pond

Wet ponds improve stormwater quality by holding stormwater over a 2-5 day period. A wet pond includes a forebay, a permanent pool of water, and a temporary pool of water. A forebay is the entry point to the wet pond where most of the suspended sediment falls out of the stormwater. A permanent pool of water stays in the pond between storms to slow stormwater down, allow pollutants to settle out, and creates a habitat for wildlife. A temporary pool is the additional depth of water that comes with a storm and is held and released slowly over the 2-5 day required timeframe.

Wet Pond

Stormwater Wetland

Stormwater wetlands are designed to mimic the exceptional pollutant removal capability of natural wetlands. Stormwater that is captured by the wetland area first enters a micropool (or forebay), which is a relatively deep pool that promotes the initial settling of larger pollutant particles (mainly sediment). The stormwater slowly flows through the shallow areas of the wetland where plants filter suspended pollutants and reduce nutrient pollution through root uptake.

Wetland

Bioretention Cell

A bioretention cell is an excavated area that is filled with an engineered soil media, plants, and topped with sod or mulch. It is designed to temporarily hold and filter stormwater. Bioretention cells are one of the most versatile SCMs since they can be installed in a variety of soil types and do not hold a permanent pool of water. They are also one of the most effective SCMs for removing pollutants, because they have many different mechanisms for doing so including infiltration, absorption, adsorption, evapotranspiration, microbial action, and plant nutrient uptake.

Bio Cell

Permeable Pavement

Permeable pavement is a hardened surface with openings that allow stormwater to soak through the pavement and be captured in a stone layer beneath the surface. From the stone layer, stormwater is either drained into the surrounding ground or is held and released over a period of 2-5 days. Permeable pavement is useful in existing urban development where the need to expand parking areas is hindered by lack of space to install more traditional SCMs (like those listed above) for stormwater management. Permeable pavement is also useful in new development with limited space due to the high cost of land.

Permeable Pavement

Why does the SCM in my neighborhood look like a muddy pit?

SCMs have been required for all new development projects disturbing more than 1 acre of land since 2000. If you live in a new neighborhood that is still under construction, the SCM is likely functioning as a sediment basin to trap and hold construction sediment. These temporary basins are converted to their final and planted form as an SCM once most of the construction is complete.

Construction Sequence

The Town has developed an SCM Construction Sequence (PDF) to provide specific information for developers on what is required for SCMs prior to Final Plat/CO.

Stormwater Design

Section 6.1 of the Apex Unified Development Ordinance (UDO) discusses Town stormwater regulations. The Town has adopted the NC Stormwater Design Manual as their stormwater design manual. Planting requirements for applicable SCMs can be found in the Town Design and Development Manual (PDF). All projects must submit use and submit the latest version of the NCDEQ SCM Supplement EZ forms with supporting calculations. Projects in the Neuse River Basin must use and submit the NCDEQ Stormwater Nitrogen & Phosphorous (SNAP) spreadsheet tool to meet the required nutrient reductions.

Operation & Maintenance (O&M)

SCMs require regular operation and maintenance in order to function properly in perpetuity.

  • SCMs do not work unless they are maintained properly according to the O&M agreement.
  • The type of maintenance needed is dependent on the type of SCM.
  • SCMs should be physically inspected on a quarterly basis at a minimum. It is also a recommended practice to inspect SCMs after larger storm events (exceeding 1-inch of rain over a 24-hour period).

Operation & Maintenance (O&M) Agreements

The Town of Apex requires eRecording for SCM O&M Agreements
The Town of Apex requires that O&M Agreements for SCMs be recorded prior to plats being recorded. In order to assist developers and surveyors, Apex is requiring eRecording for O&M Agreements. Effective 1/1/26, the fee for this service is $41.35 (Wake County Fee + Provider Fee).

 The following steps must be completed before Development Services staff will approve plat signing:

  1. E-mail draft O&M Agreement to Development Services for review at christine.masney@apexnc.org.
  2. Once draft is approved, deliver hard copy executed O&M Agreement along with $41.35 check to Development Services.
  3. Development Services will eRecord O&M Agreement and e-mail recorded agreement to developer.
  4. Development Services will write the book and page number of the recorded O&M Agreement on the plat to be recorded.

 View and download the applicable O&M Agreement listed here specific to each SCM:

As-Built Supplements

The Town requires that an SCM As-Built Supplement accompany each SCM As-Built drawing submittal. The purpose of the supplement is to ensure that as-built information for a SCM does not deviate significantly from design information. A supplement form is required for each SCM. A checklist for submitting as-built drawings can be found here.

Annual Inspection Reports

All SCM owners are responsible for maintaining written maintenance logs and having all SCMs on their property inspected annually by a qualified registered North Carolina professional engineer, land surveyor, or landscape architect performing services only in their area of competence. Each SCM owner will receive a courtesy 30-day notice in the mail from the Town the month before their annual inspection is due.

Apex Master SCM List

The Apex Master SCM List (PDF) is a listing of all SCMs and owners in Apex and their respective due date months. SCMs listed in red text have not yet been given final approval by the Town and are not yet due for annual inspection.

Annual Inspection Reporting Forms

View and download the Inspection Report for the applicable SCM(s) from the list below.  Please email the Report to Jimmy McClure as a single PDF document including a cover sheet, the appropriate Inspection Report form(s), photographs with captions, and proof of routine maintenance.  Incomplete reports will not be accepted.

Annual Inspection Report Guidelines
Please name the single PDF report file with the year, whether the inspection passed or failed, and the property name. E.g. 2026 SCM Certification - Apex Town Hall or 2026 SCM FAIL - Apex Town Hall. If a site fails inspection, the report is still due to the Town by the inspection deadline. A 60-day period is then granted for repairs. Note that annual inspection reports submitted are subject to follow-up inspection by Town staff.

SCM Inspectors & Repair Contractors
The Town does not endorse any specific stormwater SCM inspector or repair contractor, but those on the following lists have asked to be named on our website: