Introduction: Ohio EPA issued a draft general permit to control runoff during and after construction in the Big Darby Watershed. As in other OEPA stormwater permits, the essential requirement is for a Stormwater Pollution Prevention Plan which must be available on a construction site, but is not required to be submitted to OEPA. Stormwater runoff controls are required, including riparian setbacks, areas for runoff to recharge the groundwater, and sediment control practices. Permanent features to control runoff are required for sites larger than 5 acres. Setbacks along streams are welcome and should be large enough to protect water quality. Other stormwater controls could be greatly strengthened to ensure protection of the Big Darby area.


Draft General Permit for Storm Water Associated With Construction Activity in the Big Darby Watershed (Permit No. OHC100001)

Central Ohio Sierra Club
36 West Gay Street, Ste 314; Columbus OH 43215

Ohio Environmental Protection Agency
Division of Surface Water – Storm Water Section
122 South Front St, PO Box 1049
Columbus, OH 43216-1049


Thanks to Ohio EPA for creating a permit for the Big Darby Watershed. Many people and organizations have worked for protections in this biologically important area. For example, the External Advisory Group created recommendations for the Environmentally Sensitive Development Area. The Ohio EPA is finalizing the Big Darby Creek Watershed Total Maximum Daily Load Report and the 208 Areawide Waste Treatment Management Plan has just been released. In addition, watercourses have protections under Clean Water Act use designations and antidegradation requirements.


The most important general comment is that these other efforts/requirements/limits should be supported and strengthened by the proposed General Permit. For example, TMDL allocations are only briefly mentioned. Load limits should inform implementation of any general permit and storm water controls. Watercourse use designations under the Clean Water Act should be protected – and improved. Antidegradation requirements must be supported and, ultimately, restoration of the waters to Clean Water Act goals advanced. In its present form, the General Permit does not explicitly buttress other protections. Aquatic Life Use designations must be maintained and improved.


The second general comment is that the goal of maintaining pre-development groundwater recharge is better supported by mandating a baseline condition of meadow, brush, or forest. It is not acceptable to set a baseline drainage condition of tiled agricultural fields. Drained row crop fields are already extensively altered - the hydrologic equivalent of residential land use with significant impervious surfaces.


The Storm water Pollution Prevention Plan is the heart of what is required. Such a plan should be readily available onsite – for inspection by interested parties. It should be supplied upon written request. In fact, Notices of Intent and Storm water Plans should be accessible on the internet.


The General Permit gives great latitude to the applicant in choosing storm water controls. There should be a list of resources and suggestions. Non-structural practices which preserve existing vegetation are to be encouraged.


Setbacks should be expanded to include adjacent wetlands and steep slopes. Wetlands should have setbacks as well. Setbacks should not be smaller when use designations change. Large streams and rivers should have the same protections as smaller tributaries.


This General Permit should have stronger protections based on preservation of existing native vegetation. It should also call for native plants in planted areas, along with control of invasive weeds. Woody vegetation will provide shading to protect water temperatures and will prevent erosion.


This design does not reach use attainment goals in streams.  Natural Channel Design is preferred. 



Part III: Storm Water Pollution Prevention Plan (SWP3)

III.C.2 Plan Availability (page 9)

This section provides that a SWP3 plan be accessible on-site to OEPA personnel. Such a requirement for on-site availability should apply for other agencies and the public. The requirement for availability within 7 days by written request should also be extended and broadened to government agencies and the public. Further, NOIs and SWP3 documents should be available on the internet. The sentence in section c “However, the permittee may claim to Ohio EPA any portion of an SWP3 as confidential in accordance with Ohio law.” is unnecessary and may actually promote redaction and withholding information.

III.F. Total Maximum Daily Load (TMDL) allocations (p.11)

This appears to be the only mention of TMDL limits in the general permit. In fact, the whole permit should be in the context of the TMDL goals and allocations and there must be protections so that TMDL limits are not violated. As constructed, there are no guarantees or processes to ensure that TMDL limits will control. In any case, the language here should be altered to reflect that any SWP3 will reflect and enforce TMDL load allocations.

III.G SWP3 Requirements (p. 11)

Both the site description and the site map must identify environmentally critical areas: floodplain, wetlands, steep slopes, hydric soils, and woodlands. Environmentally critical areas should be preserved. The mild aspirational directive in III.G.2.a (p. 14) is not sufficient: “The SWP3 must make use of practices which preserve the existing natural condition as much as feasible.” In-stream activities and crossings are very damaging. (xiii, p. 13).

III.G.2 Controls (pp. 13-31)

The SWP3 list of “controls,” includes:

Non-structural preservation methods

Riparian setback requirements

Groundwater recharge requirements

Erosion control practices

Runoff control practices

Sediment control practices

Post-construction storm water management requirements

It would be useful to have a list of references or sources on storm water controls, although the Ohio Rainwater and Land Development manual is listed. The current edition is out of date and new revisions are not available. Within the range of possibilities, this General Permit should encourage those which will be most protective of biology and hydrology. Non-structural Best Management Practices are preferable to structural approaches.

III.G.2.b Riparian Setback Requirements (p. 14)

The SWP3 delineates riparian setbacks. Streams are defined; the definition should be included in Part VII. There should be an external check and confirmation of streams and wetlands since a developer/contractor/property owner has great incentives to not find them. Setbacks should be from the high water mark rather than the center line.

Setbacks should expand to include wetlands, steep slopes, and 100 yr. floodplain. We support the following approach: The setback distance from the stream high water mark shall be sized as the greater of the following:

1. The regulatory 100 year flood plain based on FEMA mapping;

2. A minimum of 100 feet on each side; or

3. Distance calculated: W = 133 DA.43

4. Setbacks will expand to include adjacent wetlands and steep slopes.

In addition, riparian setback requirements should specify native vegetation and control of invasive weeds. Structural storm water controls should not be in the riparian setback corridor.

III.G.2.b.iii Riparian Setback Mitigation (p. 16)

The goal should be protection or attainment of Exceptional Warm Water Habitat status. That goal is more effectively advanced by preventing encroachment than requiring mitigation. If mitigation is necessary, then it should be very “expensive” with even larger multiples required for mitigated land. Encroachments less than 25 feet from the stream edge should not be permitted. The mitigation method from Attachment B, over-wide channel design, should not be included or suggested, see comments under Attachment B.

III.G.2.c Groundwater Recharge (p. 17)

This section requires that post-development groundwater recharge not exceed pre-development volumes. The formula compares acre-feet pre- and post-development based on land use and soil group. Unfortunately, this approach leads to low groundwater recharge in agricultural land with drainage tiles. The reason is that pre-development row crops with drainage tiles has so little recharge that it has more runoff than suburban residential with 20% impervious surface. Studies have shown that streams are seriously degraded at 20% imperviousness. Since, hydrology and stream conditions degrade with more than 5% impervious surface, such an approach will not protect biology or hydrology. Pre-development conditions should be set at meadow, brush, or wood/forest as that is what existed pre-development. Tiled row crop fields have already been seriously altered, with runoff increased. This standard of groundwater recharge will not protect biology, listed species, hydrology, use designation, or antidegradation goals.

III.G.2.f Sediment Control Practices (p. 20-23)

The General Permit sets numeric limits for sediment settling pond effluent of 45 mg/l Total Suspended Solids. There is weak enforcement and monitoring, with the permittee responsible for sampling and record-keeping. Ideally, results would be submitted to the agency. Records should be available to interested parties who request them.

Silt fences are allowed on construction sites up to five acres. The encouragement “to keep runoff away from disturbed areas and steep slopes where practicable” is not strong enough. If there are more effective methods than silt fences, than they should be implemented.

III.G.2.g Post-Construction Storm Water Management Requirements (p. 24-27)

The General Permit requires structural BMPs on sites more than five acres, with capture of runoff from a ¾ inch rainfall event. There are sizing requirements, but no standards to be met for storm water release rates or volumes. Columbus in its new Storm water Drainage Manual has specified post-construction storm water release rates. Other jurisdictions have actually provided limits on post-construction storm water volumes, some going so far as to forbid increases in post-construction volume. The Sierra Club requests specific standards or limits for post-construction controls in the Big Darby watershed limiting storm water quantity and protecting water quality. The most protective approach, which we support, does not allow any increase in post-construction storm water runoff volume or rate.

Although the Permit requires ongoing maintenance by unspecified parties, including homeowners’ associations, there is no guidance on what should be in the maintenance plan or how it should be done.

Ideally, permanent storm water controls would include woody vegetation and protecting woodland. Trees anchor the soil and provide shading essential to protect cool temperatures. Shallow grass basins heat up runoff. Since the only reference is to the Rainwater and Land Development Book, which is being updated, there is little information on configuration of permanent storm water controls that this Permit requires.

III.G.2.h Surface Water Protection (p. 27-28)

Lakes, wetlands, and all surface water bodies should have setback requirements just like streams. Section 401 and 404 permits have not provided protection.

Attachment B Stream Assessment and Over-Wide Channel Design

Over-wide channel design, called two stage ditch design at the public meeting, satisfied no one. Natural channel design should be substituted to accomplish environmental restoration goals. Also, required should be installation of native woody vegetation. This would mean that mitigation projects have a greater chance of success, and that it would be less attractive to choose encroachments + mitigation. Provision for measuring, monitoring, and maintenance would support success of mitigation. The goal should be measured by restoration of Exceptional Warm Water Habitat aquatic use designation. That goal is more effectively advanced by preventing encroachments than by mitigation projects.