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As we discussed yesterday, identifying CSO control targets is an important step in the Long Term Control Plan (LTCP) process and once done, the next step is to look at the different control alternatives, whether traditional or green or both. According to the EPA, green infrastructure possibilities with any catchment are dependent upon three primary aspects:
1) Soil characteristics—many green infrastructure practices incorporate infiltration, which may not work well in clay soils, thus reducing the effectiveness of the practice. In such a case, amending the soil can enhance storage and infiltration as well as promote plant growth.
2) Topography—most green infrastructure practices should be located on land with a slope of less than 5 percent. Problems associated with steeper slopes pose design difficulties and projects may be less cost-effective. The EPA recommends using GIS software to identify and map slopes as well as areas with low infiltration potential.
3) Land use and ownership—Detailed parcel-level land-use data on everything from residential, commercial, and industrial use, to publicly owned and operated catchment lands, and street and drainage configurations are required to determine which green practices are best suited for what developed and undeveloped areas.
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The EPA also recommends minimum “robust” analysis of green infrastructure intended for inclusion in an LTCP, including:
- Community and political buy-in for green infrastructure to ensure long-term success, and
- Realistic potential for green infrastructure implementation as determined through investigation of local limiting factors such as the three aspects above as well as local regulations, codes, and ordinances, and social and political factors.
Another consideration is that of financial and institutional factors, including incentives to promote construction and maintenance of green infrastructure on private property, regulations requiring green infrastructure at existing sites or those under redevelopment, institutional barriers to requiring or incentivizing such practices, and budgetary considerations for public projects. Regarding redevelopment, some communities require new and redeveloped sites to meet on-site retention standards while others may consider incentives that encourage developers to incorporate green infrastructure in the design.
In late March, EPA Administrator Gina McCarthy and Assistant Secretary of the Army (Civil Works) Jo Ellen Darcy signed a proposed rule to “clarify” protections under the Clean Water Act for “streams and wetlands that form the foundation of the nation’s water resources.” Learn more.
Once assets and limitations are determined, the EPA recommends creating green infrastructure partnerships to promote both implementation and long-term maintenance. For example:
- Public-public partnerships between the sewer authority and local road commissions, park departments, and school districts can open the door to communitywide projects that can be integrated in capital improvement plans based on impact and cost-effectiveness. One such practical and cost-saving partnership is that of combining green infrastructure installation with road reconstruction projects, such as installing rain gardens in reconstructed right-of-ways between curbs and sidewalks.
- Public-private partnerships can help engage the private sector in construction financing while partnering with local business development districts can enable support of maintenance and operation needs associated with projects.
- Partnerships with local neighborhood groups and nonprofits also present the opportunity for educating the public and gaining support, input, and acceptance and may also result in volunteers to help manage oversight of projects that require upkeep.
Once analysis is complete, green infrastructure can realistically be determined and modeling can begin to simulate the effects of the chosen technology on actual system flows. For small communities, the EPA developed a tool called a Green LTCP-EZ Template, a planning tool that provides a framework for developing an LTCP and evaluating the use of both green infrastructure and pipe network CSO controls to meet CSO targets.The tool is available at http://water.epa.gov/infrastructure/greeninfrastructure/gi_modelingtools.cfm.