An Emerging Environmental Agenda for Sandy Springs: Healthy Streams
The City of Sandy Springs is in the process of fundamentally re-writing its Land Use Plan and Environment Sandy Springs is of the opinion that water quality
protections should be written into that plan. In this analysis we will outline some specific measures that the City incorporate into the final land use plan as well as some regulatory policies that would improve water quality.
We should note that the City’s current operations consultants have identified water quality enhancement as a major objective of the land use planning process.
In 1991 the State of Georgia compiled its initial list of impaired (polluted) streams and the major Sandy Springs streams (Nancy Creek, Ball Mill Creek, Long Island Creek and Marsh Creek) appeared on that list due to excessive concentrations of fecal coliform. Later, during the early parts of this century, Long Island Creek and Nancy Creek were additionally cited for impairments to the habitat of the fish community and later Marsh Creek was cited for the same impairment. Because some fish and aquatic life forms are sensitive to pollution in the streams the Index of Biological Integrity is often times used as a measure of overall stream health.
The common historical thread in both the pre and post 1991 periods is the growth of impervious surface in the watersheds. Not only do impervious surfaces wash chemicals and waste into streams but they also promote an increase in stream sedimentation that impairs aquatic habitats and ultimately the health of streams.
Measures to Promote Healthy Streams
Recent academic and professional research has established that streams in watersheds with more than 25% impervious surface are typically subject to severe degradation and are difficult to restore. The Sandy Springs watersheds have significantly more than 25% impervious surface (Marsh Creek has 74% impervious surface) so any approach to restore health to our streams must begin with an effort to reduce the amount of impervious surface. What follows are proposed actions that need to be taken to make our streams healthy again.
1) Initiate urban re-design efforts that will provide public amenities and reduce the amount of impervious surface in the watersheds. Recently Environment Sandy Springs successfully lobbied the City to develop an Environmental Modeling Tool (EMT) that prioritizes the location of storm water mitigation projects. The City and its consultants should incorporate the use of the use of the EMT into their effort to design the proposed Roswell Road “Boulevard”.
The lessons learned in the design of the boulevard should be a part of an ongoing program to improve the health of our streams by converting impervious surfaces of public properties into public amenities.
2) Develop Commercial re-development codes that reduce impervious surface. When the initial phase of commercial development occurred, circa 1960-1990, Fulton County not only required little or no environmental controls but also promoted a level of watershed developmentv(in terms of the amount of impervious surface) that was incompatible with healthy streams. The development of a unified development code offers the opportunity to incorporate up-to-date environmental controls into our ordinances, including the following:
- Requiring the use of silva cells or equivalent to support tree planting in the commercial district. Both Mill Creek and Ashton Woods have embraced this technology.
- Requiring the use of permeable pavers in redeveloped properties to reduce the amount of impervious surface.
- Whenever structurally possible, green roofs should be required, thereby reducing the amount of impervious surface.
- Mandatory green space(with minimum areas) should be required for all projects.
- City should consider height for green space
3) Write Residential re-development codes that reduce the rate of impervious surface growth in the watersheds or better manage existing stormwater. There needs to be a recognition on the part of the City that the watersheds already have substantial amounts of impervious surface and that residential and that these excessive amount of impervious surfaces has led to a degradation of our streams and creeks. Over time a sensible re-development code can promote an updated housing stock and promote the health of our creeks and streams by:
- Migrating away from the City’s current standard of “catch and release” facilities for large residential homes and toward “catch and recycle” which was implemented by Johnson Creek town homes. The catch and recycle approach reduces the amount of water flowing into creeks and stream and captures and recycles valuable rainfall when we are in drought conditions.
- Exploring the feasibility of requiring permeable driveways and sidewalks as part of residential re-development projects. With re-development housing stock being offered for sale in the $800,000+ price ranges the additional cost should not be an onerous burden.
- If the City is going to migrate to form-based residential codes, consider the feasibility of trading an increase in height requirements for a reduction in the residential footprint. Reductions in building footprints can promote greater ground absorption of storm water.
- Critically evaluate the environmental impact of assemblage re-development projects on water quality and canopy and make an assessment on conditions under which assemblages should be authorized. When developers assemble multiple properties for the purpose of re-development the combination of new roads, larger footprints and small lots often results in substantially more impervious surfaces which in turn causes down stream flooding and sometimes requires additional publicly funded projects to correct those situations.
4) Greater use of technology to improve stream health. The use of certain technologies can be specified in either City ordinances or City standards . For example:
- A technology such as a bio-filtration device, which can filter pollutants from storm water before they enter streams, could easily be incorporated into the City’s standards regarding new subdivision development or used as a replacement for existing outfalls.
- The data contained in the City’s Environmental Modeling Tool could be used as part of the City’s road way templates to require low impact features as an integral part of every project.