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Stormwater Management Inspection and Maintenance


In April of 2018 the Maryland Department of the Environment (MDE) issued the County a letter designating St. Mary's County for coverage under the State's NPDES General Discharge Permit Number 13-IM-5500. This coverage became effective on October 31, 2018 when the County issued its Notice of Intent (NOI) to comply with the permit requirements for the extent of its 5-year term. Under this Small Municipal Separate Storm Sewer System (MS4) permit, owners and operators covered under this general permit must manage, implement, and enforce management programs for controlling all stormwater discharges in accordance with the CWA (Clean Water Act of 1972) Triennial Review and Field Inspection of stormwater management practices has been an ongoing activity in St. Mary's County since the program's inception in 1997 and is now addressed by the required Minimum Control Measure, "Post Construction Stormwater Management".

COMAR Requirements

In accordance with Code of Maryland Regulations Storm-water Management Maintenance Requirements the owner of a storm-water management facility shall perform or cause to be performed preventive maintenance to ensure proper functioning of the structure(s). The responsible agency of the County or municipality shall ensure preventive maintenance through inspection of all infiltration systems, retention or detention structures. The inspection shall occur during the first year of operation and then at least once every three (3) years thereafter. Inspection Reports will be maintained by the County and will include descriptions of needed maintenance. The County shall provide procedures to ensure that these deficiencies are rectified by notifying the owner of same, indicating a time frame for completion of the repairs, performing a follow-up inspection, and adopting effective enforcement procedures if repairs are not undertaken or are not done properly.

Inspection and Maintenance

The Maryland Environmental Service (MES) provides professional inspection program services for maintenance of the storm-water facility inventory, a management system /database and on-going maintenance inspections. Currently thee one and three year inspections are performed for more 1,000 stormwater practices throughout the County.

The Inspection Program itself is run out of the Department of Public Works & Transportation (DPW&T) office at located in the Arnold Building at 44825 St. Andrews Church Road (Rt 4). Additional Inspection activities are accomplished by DPW&T and will be discussed further, below.

Notice of Construction Completion

A Notice of Construction Completion (NOCC) Form is required for all stormwater practices addressing more than 5,000 square feet of drainage area. Once the practices are approved and the project is closed out, the data from these forms is compiled in accordance with The MDE Annual Reporting Requirements and the storm water practice is added to the Triannual Review Program to be included into the 1 year inspection plan.

Inspection Program specifics

The formatted inspection letter from MES includes a cover letter which generally describes the program and a checklist formatted Inspection report that identifies which area of the practice were inspected, which were judged deficient and at the end of the form set a summary of the deficiencies, a scoring, and usually a picture of the facility from the date of the inspection.

As the letter also identified, if the SCORING was 7 or less, (10 is brand new and working great) then a follow up inspection will be scheduled usually within the next 6 months, depending on workload.

Score Description
1 Catastrophic failure to the system. Significant safety risk possible. System not functioning.
2 Catastrophic Failure to the system. System not functioning.
3 Significant Failure to the system. Engineering/design work needed. System not functioning as designed.
4 Significant Failure to the system. Engineering/design work possibly needed. System not functioning as designed.
5 Major deficiencies observed, safety risks.
6 Multiple minor or major deficiencies observed. Possible safety risks.
7 Minor deficiencies observed.
8 System is working, some minor maintenance possibly needed.
9 System is working per design and is maintained.
10 System is in perfect working order.

Most inspections will fall into the 7 or 8 grades. As identified in the MES cover letter, a follow up inspection will be performed. That inspection will normally be accomplished by a St. Mary's County Inspector.

If the noted deficiencies remain, the County inspector will perform an up-to-date assessment and will document these finding in the follow up letter. This letter is the first step in what could become a Code enforcement issue. It will identify the relevant legal requirements as well as the site issues and require a 30 day response of the owner. We will discuss this further in a moment.

Don't get excited yet, the clock turns off as soon as contact is made with the inspector. The inspector will work with you throughout the process of making the necessary corrections, including discussion of any extended scheduling that may be necessary.

The purpose of the follow up letter is to set the stage for the State-mandated MS4 requirement to have enforcement actions programmatically addressing any outstanding non-compliance issues. The County is required to report on any Notices of Violation and/or Citations and the disposition of the related cases in the County's annual reports to MDE. The only purpose of this follow-up letter is to set that clock and make positive contact with the owner. Should contact not occur, an additional site visit will occur followed by the issuance of a separate letter that will be the Notice of Violation and the assignment of a Code Case Number.

What Normally Happens...

Once contact is made, the inspector will discuss the inspection finding with you and meet with both you and/or your contractor as necessary to ensure the proposed level of effort necessary to correct the deficiencies is identified.

Once the corrections are complete, you or your agent are requested to re-contact the Inspector to let them know that the practice has been corrected and stabilization of the area has occurred. If everything is acceptable, an inspection report will be issued identifying that all work has been completed satisfactorily and the complaint has been closed.

Regular Maintenance Guidance

In general, the maintenance requirements for any designed stormwater practice was included in the engineering design package that built it. For many owners, that information may no longer be available. For newer practices that information may still be available in the DPW&T office. For older ones this may be problematic. After you've looked over the following guidance, if you still have questions feel free to Contact the MS4 Office. If you email us, we can often email you back digital files related to your project. If you elect to call, and have to leave a message, please leave enough detail to allow us to locate the site you want to discuss. Addressing is great (Not necessarily yours). The one closest to the stormwater practice in question is helpful.


The following links provide guidance for pond maintenance

St. May's County Soil Conservation District I&M Plan Guidelines

Stormwater Management Practices

The County DPW&T has adopted a version of the State's Guidance on Maintenance Schedules.

The Chesapeake Stormwater Network, provides educational information on Stormwater Management including this download link on their web page to their Technical Bulletin No 10: "Bioretention Illustrated" which has useful information to assist in understanding these stormwater practices and their related maintenance requirements. This and many other useful information sources are available at their site. Membership is also encouraged.

Contact Information:

Senior Program Manager MS-4: or call (301) 475-4200 ext 3561
Inspector III, Stormwater, or call (240) 925-2693