Stormwater Ordinance

Requirements or incentives for applying LID and BMP approaches to site design can be incorporated into existing land development codes, stormwater management regulations, or erosion and sediment control ordinances. They can also be implemented in local public works projects. Communities typically implement LID or BMPs by regulating development on a case-by-case basis through site development standards that require the peak flow and volume of runoff from a site to be no greater than before it was developed. This may include a range of options or requirements for developers such as the use of structural BMPs for temporary stormwater detention or nonstructural techniques such as LID to maximize a site’s ability to absorb site runoff. Communities must also specify certain criteria in the regulations such as the scale of development that is subject to the regulations and the performance standards (i.e., the design storm, which refers to a rainfall event of a specified frequency and magnitude) to be applied for facilities used to manage runoff from the site. The completion of hydrologic and hydraulic studies showing compliance with these standards is typically required of developers during site plan reviews.

Since 2007 the Southeast Metro Stormwater Authority (SEMSWA) has worked in close partnership with the City of Centennial, Arapahoe County, and Douglas County to provide stormwater management services for drainage and flood control facilities. Created by a local intergovernmental agreement for a “drainage authority” in Colorado, SEMSWA operates as a political subdivision and a public corporation of the State. Per its mission statement, SEMSWA provides services “essential to the protection, preservation, and enhancement of our neighborhoods, community and natural resources through flood control, water quality, construction, maintenance, and education.”

In addition to managing compliance with federal environmental regulations, SEMSWA reviews and approves various plans and reports for stormwater compliance through the planning and development process, including but not limited to land use cases, construction documents, drainage plans and reports, erosion and sediment control plans and reports, and floodplain development. They also plan and implement a variety of stormwater projects to ensure proper drainage, reduce flooding risks and property damage, and protect water quality. SEMSWA actively promotes the use of LID and stormwater BMPs for development projects throughout its service area, especially through minimizing impervious surface areas that are directly connected to the storm sewer system and maximizing pervious areas that receive stormwater runoff. Through its efforts SEMSWA has helped the City of Centennial, Arapahoe County, and Douglas County achieve among the highest credit scores in Colorado for stormwater management as assessed by FEMA’s Community Rating System (CRS).

Wheat Ridge promotes the use of LID and stormwater BMPs through specific requirements that must be followed by all proposed developments or re-developments. The City’s Site Drainage Requirements (2014) provide explicit information and guidance to development applicants that are based on the latest editions of the Drainage Criteria Manuals promulgated by the Urban Drainage and Flood Control District (UDFCD) and encouraged by the Colorado Association of Stormwater and Floodplain Managers (CASFM). This includes utilizing the UDFCD Four-Step Process that focuses on (1) reducing stormwater runoff volumes; (2) employing BMPs; (3) stabilizing drainageways; and (4) the implementation of long-term source controls. The requirements document includes clear descriptive language on the mandatory criteria and recommended practices for various development categories and activities, along with a series of flow charts to help applicants navigate the process with the City’s Public Works Department.

LID and BMP approaches to stormwater management provide communities and developers with flexible, cost-effective options for site design that maintain predevelopment volumes and rates of stormwater runoff. Other notable benefits include:

• Prevents future community development from increasing flood hazards to existing development.
• Helps maintain or improve surface water quality.
• Encourages small-scale designs for stormwater and water quality control that are tailored to specific site characteristics.
  Saves money:
  • The cost of LID is often less than the cost of conventional land development and stormwater management. Savings come from reduced costs for site preparation (clearing, grading, paving, stormwater infrastructure, etc.).
  • Reduces need for community infrastructure and utility maintenance costs (streets, curbs, gutters, sidewalks, storm sewers, etc.). In fact, many property owners and homeowner associations perceive LID/BMP systems as value-added amenities and actively provide for their maintenance.
• Decreases the need for large stormwater detention areas or treatment plants, possibly enabling more land to be developed or used for other community purposes.
• Improves regulatory expediencies. LID and BMP practices are currently promoted by the Environmental Protection Agency (EPA) as a method to help communities meet goals of the Clean Water Act.
• Increases the ecological health of riparian stream corridors due to lower amounts of sediment and pollutants and/or decreased erosion due to stormwater velocity entering the waterway.

Similar to other regulatory or capital project reviews for stormwater management, LID and BMPs often requires technical expertise to administer. For example, the review and enforcement of local regulations requires an engineer to review site plans, hydrologic and hydraulic studies, and other information demonstrating local compliance. Other challenges include:

• Requires that a community have stormwater management plans, regulations, and ordinances in place.
• Can be challenging to administer and enforce without trained staff.
• Adds an additional layer of requirements to the site plan or development review process.
• Requirements need to address the ongoing maintenance of LID or structures, which will become less effective over time without appropriate maintenance. Maintenance can be challenging for staff to monitor.
• Existing codes or regulations may prohibit or restrict the implementation of LID or BMP practices, requiring revisions or updates.