​Ohio EPA 2018 Construction General Permit Highlights

The US Environmental Protection Agency (USEPA) has designated Hamilton County and its unincorporated areas as urbanized areas subject to compliance with the National Pollutant Discharge Elimination System (NPDES) Phase II Municipal Separate Storm Sewer System (MS4) program requirements. This program addresses discharges to MS4 collection/conveyance systems and waterways under the 1972 Clean Water Act goal of improving water quality in local lakes, streams and rivers. The Ohio Environmental Protection Agency (Ohio EPA) is authorized to manage this program for MS4 communities located in the state of Ohio and does so under an NPDES Phase II Small MS4 General Permit. One of the requirements under the MS4 permit is compliance with the Ohio EPA Construction General Permit (CGP) which affects construction site erosion, sediment control, and post-construction storm water management. On April 23, 2018, the Ohio EPA issued the fifth generation of the CGP.
The following are a few of the changes to the CGP that have the potential to impact planning and implementation of new construction activities:

• Emphasis on preservation of existing soils, soil profiles, and vegetation.
• Strengthened protection of streams from construction activity impacts – particularly from erosive forces.
• Sediment settling ponds are now required for areas of collected storm water runoff as well as concentrated runoff.
• The term “sediment barrier” is introduced as a replacement to “silt fence” and provides for substitution of a 12-inch sediment barrier for a standard silt fence.
• Capture of the water quality volume (WQv) with an acceptable post-construction practice is now required for all sites disturbing over 1 acre.
• The precipitation depth for determining the WQv is increased from 0.75 inches to 0.9 inches and associated equations are revised.
• Pre-treatment is required for post-construction practices.
• A new method and treatment requirements for designing practices that use water quality flow.
• An increased and revised list of acceptable practices, drain times, and related technical notes.
• Introduces runoff reduction practices that may be applied to decrease the WQv.
• Incentives for use of impervious area reduction through soil restoration and use of green roofs at previously developed sites.
• Criteria for use of existing and regional storm water best management practices
• New performance and testing criteria for alternative post-construction practices.
• More detailed designs and calculations to be included in the storm water pollution prevention plan (SWP3)
• New required elements in site description, site map, and the long-term operation and maintenance plan to be included in the SWP3.

SWP3 approval by the local MS4 prior to submittal of the notice of intent to the Ohio EPA.
The Hamilton County Storm Water District is in the process of revising its earthworks and post-construction regulations to comply with the 2018 CGP requirements.