Last Updated 08/14/2026
Mahoning County Stormwater Manual
INTRODUCTION
1.1 Purpose and Manual Organization
The primary purpose of this manual is to provide detailed and supporting information with examples which will allow developers, designers, contractors, builders and planners the tools necessary to address the sub-division regulations and OEPA permit requirements for both construction site runoff (erosion and sediment control) and post-construction storm water management within Mahoning County.
4.0 POST-CONSTRUCTION STORM WATER MANAGEMENT REQUIREMENTS
4.1 OVERVIEW
Post-construction runoff controls are permanent controls which are intended and shall be designed to increase or maintain a receiving stream’s physical, chemical and biological characteristics. In addition, stream functions are maintained and post-construction storm water practices shall provide continued management of both quality and quantity facilities.
Detailed drawings and maintenance plans shall be provided for all post-construction Best Management Practices (BMP’s). Maintenance plans shall also be provided by the permittee to the post-construction operator of the site (including homeowner associations). For sites located within a community with a regulated municipal separate storm sewer system (MS4), the permittee, land owner or other entity with legal control over the property shall be required to develop and implement a maintenance plan to comply with local MS4 requirements. The use of innovative and/or emerging storm water management post-construction technologies shall be at the discretion of the Mahoning County Engineer and could require monitoring to ensure compliance with OEPA’s Construction General Permit (CGP) requirements part III, section G.2.e. The Post-Construction portion of the Storm Water Pollution Prevention Plan shall include the following required elements:
- Description of post-construction BMP’s to be installed during construction. Description shall include estimated installation schedule and sequencing plan.
- Rationale for selection shall incorporate anticipated impacts on the channel and floodplain, morphology, hydrology and water quality.
- Detailed Post-Construction BMP drawings shall be provided.
- BMP Maintenance plan- Maintenance plan shall be developed for all BMPs selected and presented to post-construction operator.
- Maintenance plan shall include a disposal statement for structural BMP’s. Ensure pollutants collected within structural BMP’s are disposed of in accordance with local, state and federal regulations.
- Linear Projects – No net increase in impervious areas, no need to comply with the conditions of Part III. G.2.e. of the CGP permit. Linear projects must minimize number of stream crossings and width of disturbance. Erosion and sedimentation controls are required for all projects with a minimum of 1-acre of land disturbance. Linear projects shall be required to document land disturbance area estimates and develop an erosion/sedimentation control plan.
4.4 Recommended Post-Construction Best Management Practices
The following post-construction best management practice controls are identified in OEPA’s CGP and shall be incorporated in project development and design. OEPA has identified six structural BMP’s to be considered and incorporated into storm water management for site development. The Mahoning County Engineer will also consider non-structural practices in combination with these structural practices in reviewing site plans. The Mahoning County Engineer requires supporting documentation of nonstructural BMP estimated pollutant removal information, map of BMP locations on-site, description of BMP type, and frequency with which the BMP will be performed or maintained. Examples of non-structural BMP’s include: site impervious area sweeping, natural buffers, creative mowing practice, etc. The six (6) post-construction structural BMP’s (as presented in the CGP) are addressed below::
- Vegetated Swales and Filter Strips – General principle is that treatment of storm water occurs via the interaction of vegetation with pollutants in the storm water runoff, specifically suspended solids. Suggested design considerations include quantity of flow, size of drainage area and slopes need to be reviewed prior to selection.
- Infiltration – General principle is that treatment occurs through storm water runoff interacting with a filtering substrate usually soil, sand or gravel. These could be trench or basin type structures. The captured treated storm water is discharged into the ground water rather than surface water. Suggested design considerations include quantity and velocity of runoff, slopes, site locations- these BMP’s potentially require high maintenance and could be expensive to operate.
- Extended Detention Basins (Dry) – General principle is the treatment occurs when storm water runoff is captured during rain events and is slowly released over a period of time. These could be above or below ground type structures. Suggested design considerations include size of drainage area will be in sizing of basin, which may impact site layout considerations. Sizing needs to account for both quantity and quality factors.
- Retention Basins (Wet) – General principle is that treatment occurs in the permanent pool portion of the basin and pollutants settle out during the hold times and runoff is released over a period of time to allow for settlement. Suggested design considerations include drainage area size, will influence basin size, which in turn could impact site layout. Health considerations include (i.e. West Nile virus), perimeter protection (fencing, maintenance access gates, ingress/egress, easements), maintenance issues.
- Constructed Wetlands – General principle is storm water runoff is treated through bio-retention. Suggested design considerations can include: 1.) Large surface areas, 2.) limit site layout, and 3.) Require additional permitting.
- Bio-retention – General principle is that storm water runoff is treated via evapotranspiration and filtration. These are generally depressed areas which collect runoff. Suggested design considerations include site locations, maintenance, drainage area size, site slopes.
The County Engineer will consider alternatives to these structural post-construction BMP’s after all have been considered during the project development process. Supporting rationale as to why they cannot be implemented, designed or incorporated into the site development must be provided. The County Engineer reserves the right to review and recommend alternatives or accept/reject alternatives based on level of maintenance requirements, public health or safety risks, limited water quality benefits and functionality.
11.6.1 Notice of Violation Procedure
Except as otherwise provided, the following notice procedure shall be used to enforce the provisions of this Ordinance. The notice of violation and assessment procedure for violations of the soil erosion and sedimentation control provisions in Section 7.4 of this Ordinance are set forth in Section 11.4.4.
- Notice Required Before Penalty
No penalty shall be assessed pursuant to this chapter unless and until the person alleged to be in violation has been notified of the violation in accordance with this section, with the exception of a violation of a stop work order, illegal placement of a temporary sign or violation of the soil erosion and sedimentation control provisions in Section 7.4. In the case of stop work orders, violations shall subject the violator to immediate imposition of a penalty. In the case of an illegal temporary sign, the Director shall be authorized to remove such sign immediately without notice. - Notice of Violation and Opportunity to Cure
Whenever the Director has reasonable cause to believe that a person is violating any of the provisions of this Ordinance or any plan, order, or condition which has been approved, issued, or imposed pursuant to this Ordinance, the Director shall notify that person of the violation. - Written Notice
Such notice of violation shall be in writing and shall be served by personal delivery or by certified or registered mail, return receipt requested. A copy of the notice may also be sent by regular mail. Service shall be deemed sufficient if the registered or certified mail is unclaimed or refused, and the regular mail is not returned by the post office within ten (10) days after the mailing. - Content of Written Notice
The notice of violation shall describe the violation, shall identify the provision or provisions of this Ordinance that are being violated, shall specify what actions must be taken to correct the violation (including an order to stop any and all work which violates this Ordinance), shall direct the person to correct the violation within a specified reasonable time period (beginning on the date such notice is received), and shall warn that more severe measures (such as a civil penalty or criminal prosecution) may be assessed or brought against the person if he or she fails to take appropriate action to cure or correct the violation. If the violator cannot be ascertained, then the notice of violation shall be sent to the record owner of the land on which the violation occurs. - Extension of Time to Cure
Upon receipt of a written request from the alleged violator or the property owner for an extension of time to cure or correct the violation, the Director may grant a single extension of time, not to exceed a period of thirty (30) days, in which the alleged violator may cure or correct the violation before the Director issues a citation pursuant to Section 11.6.2. Such extension of time shall not be granted unless the alleged violator or the property owner can demonstrate to the Director that the violation cannot be cured or corrected within the time period specified in the notice of violation because the labor or materials needed to take appropriate action are unavailable due to circumstances beyond the control of the alleged violator or the property owner. - Corrective Action Taken
If the violation is cured or corrected within the time period specified in the notice of violation, or extension of time granted in Section 11.6.1(E), then the Town shall take no further action against the person.
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Frequently Asked Questions
What stormwater regulations apply to properties in Mahoning County, Ohio?
Properties in Mahoning County are governed by the Mahoning County Storm Water Management Design Standards, enforced by the Mahoning County Engineer and the City of Youngstown.
Who enforces stormwater compliance in Mahoning County?
The Mahoning County Engineer, working alongside the City of Youngstown, enforces the county’s stormwater design standards, including reviewing site plans and approving best management practice designs.
Do I need a maintenance plan for stormwater BMPs in Mahoning County?
Yes. Permittees, landowners, or entities with legal control over a regulated property must develop and implement a maintenance plan for its stormwater BMPs, and that plan must be provided to the post-construction operator of the site.
What has to be included in a stormwater maintenance plan in Mahoning County?
A maintenance plan must include a disposal statement for structural BMPs addressing how pollutants will be managed under local, state, and federal regulations. Non-structural BMPs require supporting documentation showing their estimated pollutant removal.
What stormwater best management practices are approved in Mahoning County?
Six structural BMPs are approved: vegetated swales and filter strips, infiltration trenches or basins, extended dry detention basins, wet retention basins, constructed wetlands, and bioretention.
How can AQUALIS help with stormwater compliance in Mahoning County?
AQUALIS helps property owners and developers prepare the BMP descriptions, drawings, and maintenance plans required for permitting, develops the disposal statements and pollutant removal documentation maintenance plans call for, and performs the ongoing maintenance needed to keep approved BMPs functioning as designed.
The information on this page is provided for general informational purposes only and is not legal advice. Regulations change frequently — AQUALIS makes no warranty as to the accuracy or completeness of this content, and any reliance on it is at your own risk. Consult a qualified professional or your local regulatory authority to confirm requirements applicable to your specific property.
