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Linking Land Use to Water Quality in South Carolina
    
by: Calvin B Sawyer, S.C. Sea Grant Extension Program

 

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Introduction
The Setting
The Need for NEMO
Project Description
The NEMO Strategy
Conlusion

The NEMO Strategy

Whether fortunate or unfortunate, pavement is an unavoidable fact of modern life. However, there are still many options available to local governments interested in reducing the water quality impacts of existing or future development. Strategies can be organized into a three-tiered approach, which can be summarized as: plan, minimize, and mitigate (Arnold and Gibbons, 1999). Communities involved in the South Carolina NEMO program are using one, or a combination of these three approaches.

Plan Development Based on Natural Resources –- Preventing pollution by planning in a comprehensive manner is by far the least expensive and most effective way to protect local waterways. To this end, a working knowledge of regional natural resources is critical to guide appropriate development. A natural resource inventory is an essential first step. Identifying important natural resources and setting protection priorities provides a framework within which the impacts of proposed or existing development can be evaluated. Formal inclusion of these priorities in comprehensive plans and procedures is also important (Arnold and Gibbons, 1999). Broad resource protection strategies applied at the local or watershed level, such as buffer zone and setback requirements, are increasingly coming into use. With regard to impervious surfaces, local officials could consider a "budget" approach that sets an overall limit for key areas, and above that limit require increases in pavement on one site to be compensated for with decreases on another site (or some other acceptable method of reparation). This technique might be appropriate, for instance, in a watershed where analyses show a threat to critical water resources from future growth.

Minimize Impacts through Creative Site Design – The site planning stage offers the best chance for local officials, designers and builders to work together to reduce polluted runoff from a site. Evaluate site plans with an eye to minimizing both impervious areas and disruption of natural drainage and vegetation. Studies have shown that impervious cover can be reduced by up to 50 percent through creative design (Arendt, 1994). Cluster development, which reduces the total area of paved surfaces and increases open space, is one method to be considered (Figure 3). Are the proposed sidewalks, roads and parking lot sizes absolutely necessary, or could they be reduced? Brick, crushed stone or other porous pavement options are often a viable alternative in low traffic areas. Are curbing and piping necessary, or could drainage be directed to vegetated swales? Designs which reduce grading and filling and retain natural features should be encouraged. In addition to protecting waterways, such designs can often be less expensive and more pleasing to the eye.

Figure 3 - Alternative Site Design (Arendt et al, 1994)

Alternate site design

Mitigate Unavoidable Impacts by Implementing Best Management Practices –- Best management practices (BMPs) include a whole range of methods designed to prevent, reduce or treat stormwater runoff. Choosing the correct BMP is often highly site-specific. Here are some basic BMP concepts that South Carolina NEMO conveys:

Slow down stormwater – This is the basic idea behind both detention ponds, which are meant to slow and hold stormwater before releasing it, and retention ponds, which are designed to hold the water permanently until it infiltrates into the ground. In both cases, pollutant removal takes place through settling of particles and through chemical and biological interactions in the standing water or in the soil. As with any device, these BMPs must be correctly designed in order to work properly. For instance, ponds must be large enough to treat runoff generated by the combination of local climate and site configuration.

Avoid direct connections – Break up the flow of polluted runoff by using grass swales, filter strips or other forms of vegetative BMPs wherever possible in place of curbing and piped drainage. In many cases, these methods are most effective when used in combination with structural BMPs like detention ponds.

Ensure regular maintenance –- Most structural BMPs require regular maintenance to retain peak pollutant-removal efficiency. Maintenance ranges from the frequent, but simple (sweeping parking lots, cleaning storm drains) to the infrequent, but complex (sediment removal from detention/retention ponds), but in all cases it must be budgeted and planned for at the front end of the project.

 

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