Erosion and Sediment Control
Planning Ahead: Converting Your Sediment Basin to a Post-Construction Stormwater Control Measure
During active construction, temporary sediment basins are one of the most commonly used measures for containment and treatment of sediment laden water. After construction on a project is completed, erosion and sedimentation control measures are typically removed and their areas permanently stabilized. However, often these temporary sediment basins are converted and repurposed into permanent stormwater control measures for nutrient treatment or runoff control. Planning for this conversion and addressing it specifically in the design of erosion control plans can be essential to a successful conversion which will save time and money for the developer, while maintaining environmental protections for adjacent properties and waterways.
Conversion of these devices require several key steps, including:
• Planning for the locations and general dimensions for final stormwater control measures (SCMs) when designing a temporary sediment basin that can comply with erosion control requirements but be reasonably sized for the ultimate footprint of the SCM
• Timing of basin conversion with respect to the disturbance associated with the project and its stabilization
• Obtaining permission from the permitting authority to convert the basin
• Notifications to any additional permitting agencies regarding the anticipated bypass
• Dewatering of the basin and techniques to avoid erosion and sedimentation issues
• Preparation for conversion, including mucking out the basin and minor regrading or reshaping as needed
• Performing surveys of as-built dimensions for final stormwater control measure
• Installation and/or reconfiguring of required outlet devices
• Final stabilization of the device
Erosion and sediment control plans often do not address all of these steps, and many permitting agencies do not provide specific, detailed guidance or requirements for the conversion of these devices. However, EPA and/or your State permitting authority may require notification of this conversion as an anticipated bypass as a provision of your NPDES General Construction Permit. And your Certificate of Occupancy may be held by local regulators until the conversion is completed properly and any required as-built documentation accepted – all the more reason to plan ahead and do it right the first time!
Join us for this roundtable discussion with experienced regulatory reviewers and inspectors who have seen it all and will highlight the major issues related to planning and conversion of these temporary sediment basins to permanent stormwater control measures. Successes and failures will be shared, as well as lessons learned. Ideas taken from this open discussion will help you better address these conversions in the design of erosion control plans, know what to look for during review and approval of plans, and address issues that come up on site during the conversion process.