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The Post-Construction Storm Water Management in New Development and Redevelopment Program (Post-Construction SWM Program) of the Oahu SWMP institutes procedures to incorporate the installation of appropriate permanent BMPs for certain new development and significant redevelopment projects that HDOT Highways undertakes (e.g., contract projects), as well as certain types of encroachment projects. Permanent BMPs are designed to be installed and remain in place as part of a project to provide for long-term storm water quality or quantity control. New development and significant redevelopment projects include but are not necessarily limited to new roadways and roadway and intersection improvements or modifications, such as widening.
The Post-Construction SWM Program is complementary to the Construction Program in that permanent BMPs could sometimes be incorporated in a site-specific construction BMP plan, and therefore, be used to prevent the discharge of pollutants during construction and after the project is completed.
A Draft Storm Water Permanent Best Management Practices Manual (Permanent BMP Manual) has been developed. Permanent BMPs are designed to manage and treat storm water runoff prior to discharge from Oahu MS4 outfalls. The permanent BMP options include the following categories:
- Vegetated swales: dry swales and wet swales;
- Infiltration facilities: infiltration trenches; infiltration basins and bio-retentions;
- Storm water wetlands: shallow wetlands, extended detention wetlands and pocket/pond wetlands;
- Storm water ponds: wet ponds, extended detention ponds and multi-pond system;
- Filtering systems: sand filters, and organic filters; and
- Proprietary hydrodynamic type devices
Selection of the appropriate BMPs for a particular project should be site specific and applicable to site conditions. No single BMP would be able to achieve pollutant reduction for every given situation. Each BMP described in the manual has its advantages and disadvantages. Therefore, the designer or project/design manager should consider the benefits, costs, pollutant removal efficiency, aesthetical acceptability, and other pertinent factors when selecting BMPs for individual projects.
The Permanent BMP Manual is available for download. To download your copy of the Permanent BMP Manual, just click on the link in the Contractors Page.
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