STORMWATER MANAGEMENT CODES ANALYSIS RICHLAND COUNTY, SC SITE PLANNING ROUNDTABLE Codes analyses for each subcommittee were completed to assist participants of the Richland County Site Planning Roundtable. Based on results from the Codes and Ordinances Worksheet (COW), excerpts from existing codes and ordinances, and interviews with engineers, developers and County staff, this analysis provides a summary of the regulatory barriers to utilizing innovative stormwater management in Richland County, SC. Information presented here is intended to serve as the foundation for subcommittee discussions and recommendations, but should not dictate or limit roundtable participants during the consensus process. The better site design principles are merely benchmarks; each subcommittee should adapt relevant principles and refine recommendations appropriate to local circumstance. The Stormwater Management codes analysis is organized by the following better site design principles: Better Site Design Principles 5: Vegetated Open Channels 10: Parking Lot Runoff 16: Rooftop Runoff 22: Stormwater Outfalls For each principle, a description of existing regulations, relevant ordinance excerpts, COW results, and potential targets for discussion is summarized. Space for comments is also provided to assist in organizing initial reactions, wordsmithing, and recommendation brainstorming. Overview Minimum stormwater management requirements in Richland County are established by the Richland County Code of Ordinances: Ch. 26, Land Development (Richland County, 2008). The primary source of design criteria for the construction of stormwater management practices, though, is the Storm Drainage Design Standards Manual (Richland County, 2001). The Best Management Practices Manual, developed by the County in 2001, provides further guidance on the design, placement, maintenance, etc. of stormwater facilities. While these documents address stormwater treatment at development sites, design criteria for several types of stormwater best management practices (BMPs), landscaping standards for parking lots, and other features that promote good stormwater management, might be changed to expand the use of the better site design principles in Richland County. Richland County Site Planning Roundtable 1
Principle #5 Vegetated Open Channels Principle Where density, topography, soils, and slope permit, vegetated open channels should be used in the street right-of-way to convey and treat stormwater runoff. Existing Codes Richland County s Storm Drainage Design Standards Manual, which was last revised in 2001, provides design criteria for grass swales, dry swales, and wet swales / wetland channels (Sec. 4.1). The County s BMP Manual also contains design criteria for grass swales and bioretention swales (Sec. 5.6 and 5.7). Thus, we can assume that open channel systems are available to local developers as an option for stormwater management in new development. Chapter 26 of the Richland County Code of Ordinances ( 26-181(b)(1)a) states that curb and gutters shall be installed on all paved roads unless the county engineer determines that another system is acceptable. 2/4 COW Score Richland County received 0 points for requiring curb and gutter on all paved roads where vegetated open channels could otherwise be used in certain residential settings and received 2 points for having established design criteria for open channel systems (e.g., grass swales and enhanced swales). The subcommittee needs to examine how the County can expand the use of vegetated open channels to convey and treat stormwater runoff. Discussion Points The County Code classifies all roads as one of the following 7 types (with varying ROW widths): Rural, Minor Residential, Local Residential, Local Commercial, Collector, Industrial, and Arterial. Should the Code directly expand the use of vegetated open channels for any of these road classifications in particular? If so, which types of roads? Which kinds of open channels should be used along these types of roads? Who is currently in charge of maintaining vegetated open channels in County roads ROW? Does this system of maintenance seem to successful? What pros and cons exist when using open channels versus curb and gutter systems? Comments: According to Richland County staff, it is very rare for plans to be approved (or requested) with an alternative to curb and gutter for new roads. Richland County Site Planning Roundtable 2
Principle #10 Parking Lot Runoff Principle Wherever possible, provide stormwater treatment for parking lot runoff using bioretention areas, filter strips, and/or other practices that can be integrated into required landscaping areas and traffic islands. Chapter 26 of the Richland County Code of Ordinances states that off-street parking areas must be planted with 1 large shade tree per 20 parking spaces ( 176(g)(3)b). Parking lots that are larger than 2 acres must have 4 planted medians (each 1,134 sq. feet) per 2 acres of parking lot. These medians must be a minimum of 7 feet wide ( 176(g)(3)e). Chapter 26 of the Richland County Code of Ordinances also states that street protective yards are required between road right-of-ways and adjacent properties. These yards can be no less than 7 feet wide and must be covered completely with ground cover, shrubs, mulch, and/or trees no bare ground is permitted ( 176(e)). Between land uses of different impacts (e.g., between single family lots and apartment buildings), buffer transition yards are required in order to provide separation and screening and must extend along the entire property line ( 176(f)). When no buffer yard is required and a parking lot is within 20 feet of an abutting property, a planting strip at least 5 feet wide is required planted with evergreens and deciduous shrubs ( 176(g)(2)a). The Code does not address the use of buffer yards for stormwater management purposes. Existing Codes Design criteria for a number of stormwater practices are provided in both the Storm Drainage Design Standards Manual and the County s BMP Manual, but there is no mention of using these practices within parking lot landscaping islands or setbacks. The manuals provide criteria for the following practices that could potentially be used in and around parking lots: Infiltration Trenches Bioretention Swales Grass Swales Bioretention Cells Innovative Technology BMPs (usually underground systems) The Drainage Design Standards Manual essentially disallows the use of porous asphalt and concrete as a stormwater BMP (although porous pavers are allowed) (Sec. 4.7.12). The latter point appears contradictory to Chapter 26, 173(d)(1)b of the County Code which states that Porous paving blocks and pervious paving materials are permitted and encouraged as material for parking lots. The use of grass as a parking lot surface is permitted for overflow parking. 2/4 COW Score Richland County received 2 points for requiring a minimum number of shade trees per number of parking spaces, and received 0 points for being silent on the issue of using landscape islands, other landscaped areas, and/or setbacks for stormwater treatment. The subcommittee needs to examine how the County can expand the use of landscaped areas and setback areas for stormwater practices. Discussion Points There is no direct mention in the Code about using landscaping islands and setback Richland County Site Planning Roundtable 3
Principle #10 Parking Lot Runoff areas for stormwater treatment. Should language be added to the Code to explain that these areas MAY be used for stormwater treatment? Or should we go one step further and REQUIRE that landscape islands, vegetated areas, and setbacks be used from stormwater treatment? Are there any other changes that need to be made to the County s parking lot landscaping requirements to better connect them with the County s overall stormwater management approach? What other incentives can the County provide to encourage the use of landscaped areas for stormwater treatment? What other types of stormwater BMPs could be used to treat parking lot runoff that are not addressed in the Storm Drainage Design Standards Manual? Comments: According to County staff, proposals for using bioretention or other on-site stormwater BMPs are very rare. There are very few such BMPs in the ground in the County. It is not clear if this has to do with something in the code that discourages the use of such BMPs or just that designers have not yet explored the use of stormwater BMPs in landscaped areas. Richland County Site Planning Roundtable 4
Principle #16 Rooftop Runoff Principle Direct rooftop runoff to pervious areas such as yards, open channels, or vegetated areas and avoid routing rooftop runoff to the roadway and the stormwater conveyance system. Chapter 26 of the Richland County Code of Ordinances states that surface runoff from single-family residential, duplex, or manufactured home developments must flow directly to a storm sewer, improved channel, sodded swale, or paved road without running more than 200 ft. Surface runoff from commercial, industrial, multi-family, and institutional development (and all their impervious surfaces) shall be drained into a stormwater management facility, with the exception that such drainage may flow directly into a road, curb and gutter system, or improved channel when of small area and approved by the county engineer ( 203(b)(3)g). Existing Codes Proposed Code Changes: The same code language is used in the stormwater ordinance amendments to Chapter 26, currently being proposed for adoption ( 202(c )(3)g). Looking at the above code language, there may exist some limited opportunities for disconnection of downspouts into vegetated swale systems, but for the most part it appears that the intention of the code is to direct drainage off-site to a conveyance system as quickly as possible. Yet, both the Storm Drainage Design Standards Manual (Sec. 4.7.8.) and the County s BMP Manual (Sec. 5.5) provide design criteria for infiltration trenches and dry wells. Both manuals mention using dry wells for rooftop runoff. Overall, there is nothing within the County Code or the Manuals that specifically allows for the temporary ponding of stormwater on front yards or rooftops. 2/4 COW Score Richland County received 2 points for allowing rooftop runoff to be discharged to yard areas as long as runoff reaches storm drain conveyance within 200 ft. The County received 0 points for not specifically allowing for the temporary ponding of stormwater on front yards or rooftops. The subcommittee should examine this principle to determine what improvements can be made to the code and/or manual to directly allow for the temporary ponding and treatment of stormwater on-site. Discussion Points Comments: Does it make sense for the County to encourage the disconnection of roof drains from the storm drain system? If so, what language should be added to the Code? Are there any technical issues associated with the use of downspout disconnection? How can these issues be addressed? According to County staff, there are zero to very few examples of the use of BMPs in yards to control rooftop runoff. According to County staff, most houses are far less than 200 ft. from a road anyhow, so the 200-ft. rule would not be a limitation in most cases. Richland County Site Planning Roundtable 5
Principle #22 Stormwater Outfalls Principle New stormwater outfalls should not discharge unmanaged stormwater into jurisdictional wetlands, sole-source aquifers, or other water bodies. Treatment of Stormwater The current version of Chapter 26 of the Richland County Code of Ordinances states that any construction or other development affecting the quantity and/or quality of stormwater runoff, or that is located in an area of special flood hazard, shall be in accordance with a stormwater management design plan approved by the Richland County Engineer ( 203(a)(1)). The following land uses, however, are exempt from this rule: Agriculture and silviculture Single-family home development, not part of a subdivision or common plan Industrial operations with a valid NPDES permit Mining with valid state permit Any agency with the power of eminent domain New developments with 20,000 sq. ft. or less of impervious area Redevelopment projects with 10,000 sq. ft. or less of impervious area Utility construction and maintenance activities The current Code reads that Storm Drainage Design Standards shall be established by the county engineer, and shall provide for the minimum quality control requirements for development ( 203(b)(4)). The Drainage Design Standards Manual, in turn, establishes that all temporary and permanent BMPs shall be designed and constructed to accommodate the expected sediment loading, from both construction activities and postconstruction land use with a removal efficiency of 80% of total suspended solids or 0.5 ml/l peak settleable solids concentration, whichever is less (Sec. 4.7.1.2) Existing Codes Proposed Code Changes: The proposed changes to Chapter 26 of the county s Code state more specifically that minimum water quality requirements are directed by the current Storm Drainage Design Standards and BMP Manual ( 202(c)(4)a.). The proposed Code changes also mandate that the surface of land in Richland County shall not be disturbed or changed for any purpose except in accordance with an approved Stormwater Pollution Prevention Plan (SWPPP). The SWPPP shall include a plan for erosion and sedimentation and provide for stormwater management ( 64). Both the current County Code of Ordinances and its proposed amendments require that stormwater be treated for quality prior to being discharged to natural water bodies. (It is assumed that this includes discharge to jurisdictional wetlands.) Design Criteria for BMPs As described above, Richland County s water quality treatment performance standard is based on a limit of Total Suspended Solids in stormwater runoff. The County s Drainage Design Standards Manual outlines the design criteria for a number of different types of stormwater facilities, mostly reflecting South Carolina s state standards. For retention ponds (Sec. 4.7.3), modified extended detention ponds (Sec. 4.7.4), extended detention ponds (Sec. 4.7.5), and constructed wetlands (Sec. 4.7.7) the Drainage Design Standards Manual requires that the water quality design volume be either 1 inch of runoff per acre or 1.5 inches of runoff per impervious acre, whichever is greater. Infiltration trenches and dry wells must be designed to accept a water quality design volume of 0.5 inches of runoff per acre or 1 inch per impervious acre, whichever is greater (Sec. 4.7.8). Richland County Site Planning Roundtable 6
Principle #22 Stormwater Outfalls Green Code: The Green Code portion of Chapter 26 of the Richland County Code of Ordinances ( 186), which is intended to encourage conservation of natural areas in new developments, also encourages the use of Low Impact Development stormwater mechanisms, such as grassy cul-de-sacs and neighborhood greens. It states that pervious material may be used for sidewalks and driveways and that the maximum impervious surface allowed for the entire developed area is 50%. Floodplain Management The Richland County Code of Ordinances does include a section ( 26-104) that outlines the rules applicable to the County s Floodplain Overlay District. It mostly consists of those restrictions mandated by the Federal Emergency Management Agency (FEMA). Nothing in this section indicates that development within the 100-year floodplain is prohibited or restricted. Green Code: Under the terms of the County s Green Code in Chapter 26 ( 186), a development s Conservation Area must provide for permanent protection of the 100-year floodplain, stream buffer zones, slopes greater than 40%, wetlands, endangered or threatened species, archaeological sites, cemeteries or burial grounds. This is a promising component of the County s Code, although adherence to the Green Code is voluntary in nature. 4/6 COW Score Richland County received 2 points for requiring stormwater runoff to be treated for water quality before it is discharged, 1 point for providing design criteria for stormwater best management practices, 1 point for not allowing untreated stormwater to be discharged to jurisdictional wetlands, and 0 points for not restricting development in the 100-year floodplain. Although Richland County does provide design criteria for a variety of stormwater BMPs, the standards for treating runoff could be set at a higher mark to provide for more effective water quality treatment. The County could also maintain greater protection of waterways and personal property if it sets restrictions on development in the 100-year floodplain. Discussion Points Comments: Does the stormwater management approach used in the County work to control the adverse impacts of development/stormwater runoff? If not, what approach or additional BMPs could be used? In what ways could the Code be amended to allow for or require more on-site treatment and infiltration of stormwater? What stormwater BMPs are typically used in the County? Are there any technical issues associated with their use? What needs to be done to address these issues? How often is the Green Code adhered to by developers? What can be done to incentivize the expanded use of the Green Code practices? According to County staff, most stormwater facilities in the watershed are retention or detention ponds. Although the Storm Drainage Design Manual and BMP Manual both have design criteria for other types of BMPs that are more effective at treating runoff (e.g., bioretention, infiltration), these are rarely used. Richland County Site Planning Roundtable 7
Resources and References Richland County. Development Code Chapter 26. 2008 Richland County. Proposed amendments to Chapter 26. 2008 Richland County. Storm Drainage Design Standards. May 30, 2001. Richland County. Storm Water Management Plan and 2007 Annual Report. September 2007. Richland County. Stormwater Best Management Practices and Stormwater Pollution Control Policies and Procedures Manual. 2001. Richland County Site Planning Roundtable 8