AGENDA # 6b
TO: Mayor and Town Council
FROM: W. Calvin Horton, Town Manager
SUBJECT: Report on Stormwater Management Issues
DATE: April 24, 2000
The following information responds to comments and questions raised by the Town Council subsequent to our January 10, 2000 report on soil erosion and sedimentation issues. This information includes discussion of Performance Zoning; Low Impact Development; Impaired Waters on the State 303D List; and Enhanced Sedimentation Protection related to State enabling legislation.
On January 10, 2000, the Town The council received a report on Soil Erosion and Sedimentation Control issues. Contained in the report was information regarding the City of Olympia, Washington, and its use of “Performance Zoning” to control impervious surface area. The Council asked that we examine the concept of Performance Zoning regarding its applicability to Chapel Hill. Additionally, the Council requested that we evaluate the concept of “Low-Impact Development” and consider how it could be applied to Chapel Hill and how it is related to Performance Zoning.
On March 6, 2000 we presented a report to the Council, in response to a petition from the Haw River Assembly, which discussed the State 303(d) list of impaired waters within Chapel Hill. The Council asked for additional information about the Town’s Stormwater Management Program, particularly as related to water quality issues. Excerpts from the March 6th report are attached for reference.
Finally, the Council requested further information on the Town’s efforts to enhance and increase sedimentation protection for concurrent developments within a watershed.
Performance
Zoning
Typically, city zoning ordinances are based on conventional zoning, which separates land into separate districts with each district dividing uses according to their compatibility.
Performance Zoning does not have a structure that separates uses, but rather sets specific standards for each use. Any use which meets the specific standards can be placed into any district. Lane Kendig, one of the early proponents of the performance based zoning concept, states that; “The performance approach to zoning regulates development mainly on the basis of four variables: open space ratio, impervious surface ratio, density, and floor area ratio.” The first two standards apply to all land uses, whereas density is applicable only to residential uses. For nonresidential uses, the floor area ratio is utilized in place of density.
OPEN SPACE RATIO relates the portion of a lot that is designated as open space to that portion of the lot which is developed. It is intended to benefit the neighborhood or community as a whole, and to provide for protection of natural areas.
IMPERVIOUS SURFACE RATIO relates the portion of a lot that is covered by impervious surfaces to that portion of the lot that is pervious. Impervious surfaces alter the natural environment, causing increased stormwater runoff (volume and rate), increased pollutant loading into creeks, lakes and wetlands, decreased natural habitat and increased radiant summer heat at the surface.
DENSITY refers to the number of dwelling units allowed per unit area, usually acres. As an example, the Town’s zoning designation R2 stipulates a density of four residential units per acre. The density variable is a direct measure of the impacts of a given development on road systems, community facilities, utilities, schools, and urban services. The floor area ratio is a nonresidential land use intensity measure analogous to density. It is a useful indicator of the impacts of land use and one that provides the flexibility appropriate to the considerable diversity of nonresidential uses.
The theory behind performance zoning is that any use should be allowed to be located anywhere, and regulation is related to intensity and impacts rather than to use. Chapel Hill currently uses a hybrid of conventional zoning and performance based zoning. We have zoning districts set up that establish permitted uses such as Office Institutional, Town Center, Neighborhood Commercial, etc. (A complete list can be found in Article 3 of the Development Ordinance.) We also integrate performance based zoning into our districts by incorporating the four variables mentioned above. Impervious surface ratios, however, are applied only to the portion of Chapel Hill (approximately ½) that is located within the Water Supply Watershed Overlay District.
The Council could decide to implement the use of an impervious surface ratio to control impervious surfaces on all new projects. This could be accomplished by applying the Water Supply Watershed Overlay District regulations Townwide.
On March 6, 2000, the Council received a report on Proposals to Reduce Impervious Surfaces. In the report, the following six options were proposed that could reduce impervious surface areas and/or ameliorate the effects of impervious surfaces:
· Adjust Permitted Uses in Resource Conservation Districts
· Set Maximum Parking Requirements
· Reduce Street Widths in Residential Areas Under Certain Conditions
· Require Planting between Sidewalks and Roadways
· Set Limits on Parking Lot Paving
· Encourage/Require Shared Parking Measures
The Council referred this item to the Community Design Commission; Parks and Recreation Board; Pedestrian and Bicycle Advisory Board; Planning Board; and Transportation Board for their comments before taking further action. It is likely that this item will return for the Council’s consideration in May. Excerpts from the March 6 report are attached for reference.
The Council is considering revisions of the Town’s Comprehensive Plan. The draft plan was presented to the Council on March 27, 2000. A recommendation of that proposed plan includes the utilization of the Conservation Development (Low-Impact) approach by suggesting that the Development Ordinance be revised to incorporate conservation development concepts into the Town’s regulations. Studies indicate that low-impact development may not only cost less to construct, but may also create more desirable land with higher property values than conventionally developed land. Low-impact development requires more attention to the existing natural resources in terms of preservation and overall impact reduction.
303(d)
List of Impaired Waters
Section 303(d) of the Federal Clean Water Act requires that States develop a comprehensive public accounting of all impaired waters. North Carolina Division of Water Quality submitted a draft list on April 1, 2000. The list includes waterbodies impaired by pollutants such as nitrogen, phosphorous, and fecal coliform bacteria, and by the effects of hydromodification and habitat degredation. The list describes the Total Maximum Daily Load (TMDL) for each stream. This load is the maximum amount of pollutant the water body can receive and still meet State standards.
The Town’s March 6, 2000 response to the Haw River Assembly petition includes reports and attachments describing the Town’s listed streams and the associated impairments. It discusses what the Town has done and continues to do to monitor and implement programs with the goal of improving surface water quality in Chapel Hill.
Also included is a report written by Mr. Allen E. Rimer, entitled “Stormwater Management in Chapel Hill”. The report is a generalized overview of the Total Maximum Daily Loads program and the related State and local efforts to capture, interpret and use the monitoring data. Over the past seven years Chapel Hill has monitored streams using methodology that meets State standards and is being used to estimate the “true pollution loading in the stream”. All of the key pollutants have been monitored, including metals. The NC Division of Water Quality will receive the data quarterly for their database.
The Town is a municipal stakeholder in the United States Environmental Protection Agency’s National Pollutant Discharge Elimination System; Phase 2 Rules and will be required to meet these new standards with a Notice of Intent by May, 2002. The initiatives listed below are being developed to meet those standards:
Current initiatives for Chapel Hill’s Stormwater Management Program include:
1. Include two additional stream monitoring sites on Booker Creek (State 303d listed as “high priority”).
2. Improve stream pollutant assessment procedures and strategy.
3. Improve digital storm sewer inventory collection processes.
4. Improve Global Positioning System database and coverage procedures.
5. Expand public education and participation programs. Include development of a new elementary education program, stenciling, signage and adopt-a-stream programs.
6. Develop and select water resources grant projects for flood mitigation, restoration, preservation and research.
Planned Stormwater
Management Initiatives:
1. Develop policy and programs to provide citizens with enhanced services in urban stormwater and floodplain management.
2. Develop recommendations for a Stormwater Utility.
3. Establish stream assessments to inventory and quantify stream conditions (water quality, habitat, bank erosion) and to develop restoration projects.
4. Establish watershed assessments to inventory existing and future land use characteristics, soil types and natural resources. Evaluate hydrologic impacts and develop sub-watershed Best Management Practices.
5. Create Town Best Management Practices standards.
6. Complete and maintain Global Positioning System stormsewer inventory.
7. Establish comprehensive stormwater education and participation program to include municipal operations, businesses and citizens.
8. Establish an illicit stormsewer discharge identification and elimination policy and program.
Enhanced
Sedimentation Protection
In 1999 the General Assembly passed local legislation that allows the Town of Chapel Hill to “require enhanced and increased sedimentation protection by reason of the concurrent construction of two or more projects in the same watershed.” The Town has been working in cooperation with Orange County, who has the regulatory authority, to provide the maximum protection possible from the effects of sediment from developments, whether one or one of many occurring within a given watershed.
Developers are required to provide plans that demonstrate how they propose to prevent erosion and provide protection from sedimentation. Project designers have a variety of methods applicable to any given situation. In the January 10, 2000 report on Soil Erosion and Sedimentation Issues, we discussed standard methods including stabilizing disturbed areas, diverting water away from disturbed areas, filtering and settling out soil particles, and armoring channels. These methods are commonly used throughout the State. Orange County and the Town are working to supplement routine sedimentation protection measures by employing the following methods and devices:
Skimmers – The skimmer is a device that floats on the water surface of a sediment
basin. As sediment settles to the
bottom of the basin the water near the surface is the cleanest. The skimmer takes the cleanest water in from
the top of the basin and discharges beyond the disturbed areas.
Flocculants – Flocculants are agents that attract individual sediment particles
creating clusters that more readily will settle out of the water
Filters – This technology involves moving water into a large bag or similar device
that captures all but the very finest clay particles.
In addition to those engineered measures intended to manage and control
sedimentation, the Town has certain legal remedies available including:
1. Injunctive Relief - Court orders or judgments can be initiated to stop a violation or threatened violation.
2. Penalties - Both criminal and civil penalties can be assessed for violations.
3. Damages – Awards can be made for damages caused by the failure to control sedimentation.
As a result of recent The council action, the Town is now requiring Sedimentation Bonds which can be used to restore areas that are affected when sedimentation control devices fail to function properly. These bonds provide incentive for developers to maintain sedimentation control devices and to monitor their operation.
We think that the Town is currently using practical resources for erosion and sedimentation control, which provide protection from the effects of land disturbing activities. We recognize that the adverse effects of sedimentation affect the health and use of our surface water resources. We continue to explore innovative measures to protect these resources from the effects of sedimentation, and we believe that changes resulting from the new Comprehensive Plan will assist the Town in those endeavors.
Chapel Hill development standards currently incorporate the four components of Performance Zoning: open space ratio, impervious surface ratio, density, and floor area ratio. These standards take into account the impacts that development will have on our community facilities, services, infrastructure, and natural resources.
Impervious surface area is currently regulated only in that portion of the community within the Watershed Supply Watershed Overlay District which includes about half of the Town. We believe that the impervious surfaces associated with development Townwide could be more tightly controlled. The proposals to reduce impervious surfaces which will be considered by the Council in May could help protect our waters from the negative impacts of imperviousness.
We believe that the quality of water in our streams and lakes is important to the entire community. We have established programs to identify impaired streams and the cause(s) of the impairment. We strive to inform and involve the public in protecting and cleaning up our streams. We continue to work on new initiatives to enhance effectiveness and to establish new procedures to protect all of our surface waters.
We think that the information provided in this report would be useful to the committee being formed to research the implementation of a Stormwater Utility in Chapel Hill. We will include this with other information to be provided to the committee.
1. Excerpts from March 6, 2000 Report on Stream Water Quality
2. Excerpts from March 6, 2000 Report on Impervious Surfaces