# COMCOR — Chapter 19. Erosion, Sediment Control and Stormwater Management - Regulations ## COMCOR 19.00.01 Stormwater Management ### COMCOR 19.00.01 Stormwater Management #### 19.00.01.01Authority and Purpose A. In accordance with the authority conferred under Chapter 19, Section 19-3 1, of the Montgomery County Code, 1994, as amended (hereinafter referred to as the "Code"), the County Executive hereby promulgates this regulation for the purpose of implementing the County's stormwater management program as set forth in Chapter 19 of the Code. B. This regulation pertains to all applications for approval of preliminary plans, stormwater management plans and sediment control permits, the issuance of building permits for new construction, financial security requirements, easements, agreements and maintenance requirements for on-site stormwater management controls, best management practices design criteria, and waivers. #### 19.00.01.02 Definitions The definitions of terms used in this regulation are provided in Chapter 19, Section 19-21, of the Code. For purposes of this regulation, the following additional words and phrases will have the meanings respectively ascribed to them by this regulation: Hotspot: An area where land use or activities generate highly contaminated runoff with concentrations of pollutants in excess of those typically found in stormwater. Soil Survey: The Soil Survey of Montgomery County, Maryland, Natural Resources Conservation Service, U.S. Department of Agriculture, July 1995. Stormwater management concept plan: A statement or drawing, or both, describing the manner in which stormwater runoff from the proposed development will be controlled to minimize damage to neighboring properties and receiving streams and to also prevent the discharge of pollutants into surface waters. #### 19.00.01.03 General Administration; Stages of Plan Approval A. Stormwater management concept stage. 1. Plan required. Before the Montgomery County Planning Board approves a preliminary plan of subdivision, the Department of Permitting Services must review and approve a stormwater management concept plan submitted by the applicant. If a preliminary plan of subdivision or site plan is not required, then the Department must approve the stormwater management concept plan before the applicant may apply for a sediment control permit. 2. Contents. The concept plan must include the following information: a) A description of how stormwater runoff from the development will be controlled to preserve or improve water quality, prevent on-site and off-site stream channel erosion, and maintain groundwater levels; b) An analysis of existing water quality conditions, including locating streams, impoundments, and wetlands on the site; c) The results of geotechnical investigations, such as soil borings and perc tests when structural recharge is proposed; and d) An indication of the method of access to the facilities from public rights of way for the purpose of maintenance. 3. Notice to other property owners. The applicant must provide written notification of the pending preliminary plan application to the owners of any properties that adjoin the site of the proposed development or that are within 500 feet downstream of the proposed development within 10 days after having submitted the application. The notice must be sent by registered mail and must include a copy of the stormwater management concept plan, the preliminary plan reference number, and a statement informing the property owners that they must submit in writing any comments concerning the preliminary plan to the Department within 21 days after receiving the notice. The applicant must certify to the Department that the applicant has provided the required notice to property owners by submitting a copy of the notice and a list of the persons notified to the Department within 20 days after submitting the preliminary plan application. 4. Hydrology. This Section presumes that pre-development conditions are woodland or meadow in good hydrologic condition for the planning and placement of stormwater management structures. B. Sediment control permit stage. 1. Any person required under Chapter 19 of the Code to obtain a sediment control permit must include a stormwater management design plan as part of the application for that permit. The design plan must conform to the approved stormwater management concept plan. The application must include: a) construction drawings for all stormwater management facilities in accordance with criteria established in Chapter 19 of the Code; b) construction specifications; C) structural computations and certifications signed by an engineer registered in the state of Maryland; d) supporting hydrologic, hydraulic, and design computations; e) soil analysis; f) drainage area and watershed data; g) a landscape plan, prepared by a landscape architect registered in the state of Maryland, for all surface structures, that addresses aesthetic, habitat, and water quality needs, and is in conformance with Department standards; h) for ponds, if any, standard certifications and signature blocks must be on design drawings before submittal for signature to the Montgomery Soil Conservation District; and i) all other necessary information needed for review and approval by the Department. 2. If the proposed stormwater management facility is on land that is either owned by or proposed for dedication to the Maryland-National Capital Park and Planning Commission, the stormwater management design plan must be approved by the Board before the Department may approve the plan and issue a building permit for the proposed development. An applicant that proposes dedicating land to the Commission must enter into an agreement to dedicate land with the Board and provide a certified copy of that agreement to the Department along with the Board's written approval of the design plan. 3. If constructing a stormwater management facility on the proposed development site is likely to affect existing or proposed water and sewer lines, the Washington Suburban Sanitary Commission's approval of the stormwater management concept plan is required before the Department may approve the plan and issue a building permit for the proposed development. C. Qualifications for Both Concept and Design Plans 1. Stormwater management concept and design plans must be prepared by a professional engineer, professional land surveyor, or landscape architect licensed in Maryland. If a stormwater best management practice requires either a dam safety permit from the Maryland Department of the Environment or a small pond approval from the District, the design plan must be prepared by a professional engineer licensed in the State of Maryland. 2. Best management practices. The applicant must document adherence to minimum stormwater control requirements at the stormwater management concept plan approval stage and at the sediment control permit approval stage. Before an application for a sediment control permit is approved, the applicant must enter into an easement and maintenance agreement with the County, approved as to form and substance by the Director, to ensure continued compliance with structural and nonstructural best management practices; however, the Director may waive this requirement as it relates to nonstructural best management practices for single family lots or properties when the Director is satisfied and reasonably certain that the nonstructural best management practices will remain functional after construction of the development is complete. D. Installation Inspections 1. The applicant must notify the Department at least 48 hours before beginning any construction activity in conjunction with a stormwater management plan and hold a pre-construction conference with a designated representative of the Department. 2. The Department or a professional engineer licensed by the State of Maryland must perform installation inspections of any stormwater management facility under construction as needed to ensure that the facility complies with approved plans. The inspector must perform the inspections in accordance with Department-approved checklists for each type of stormwater management facility. The person performing the inspection must prepare a written inspection report for the Department to maintain that includes the following information: a) The date and location of the inspection; b) Whether construction was in compliance with the approved stormwater management plan; C) Any variations from the approved construction specifications; and d) Any existing violations of applicable County law. 3. The Department must notify the applicant in writing if the person conducting the inspection observes any violations of applicable County law during the inspection. The written notification must describe the nature of the violation and prescribe the corrective action needed. 4. No construction work on a stormwater management facility may proceed until the Department inspects and approves the work previously completed and furnishes the results of the inspection reports to the applicant after completing each required inspection. 5. If the applicant and the Department have entered into a financial security agreement that specifies the various stages of work to be completed on the facility, the applicant must contact the Department after completing each stage to request an inspection. After the Director certifies that the applicant has completed that stage of work in accordance with the approved plan, the Director may reduce the required financial security by a prorated amount or may direct the Director of Finance to refund to the applicant a prorated share of the amount of financial security that the applicant deposited with the County. 6. Once construction is complete, the applicant must submit an as-built plan and certification to the Department to ensure that the stormwater management facility has been constructed in conformance with approved plans and specifications. The plan and certification must be prepared by a professional engineer, professional land surveyor, or landscape architect that is licensed or registered in the State of Maryland or by any other person whose qualifications to prepare as-built plans and certifications are acceptable to the Department. A Maryland-licensed professional engineer must prepare the plans and certifications for ponds. #### 19.00.01.04 Stormwater Management Measures A. Structural Stormwater Management Measures 1. An applicant must design and construct the following structural best management practices in accordance with the Design Manual as well as local standards instituted by the Department to satisfy the applicable minimum control requirements established under County law: a) Stormwater management ponds; b) Stormwater management wetlands; C) Stormwater management infiltration; d) Stormwater management filtering systems; and e) Stormwater management open channel systems. 2. The applicant must consider performance criteria specified in the Design Manual in relation to general feasibility, conveyance, pretreatment, treatment and geometry, environment and landscaping, and maintenance when selecting structural management practices. 3. The applicant must select structural stormwater management practices to accommodate the unique hydrologic or geologic regions of the County. B. Nonstructural Stormwater Management Measures 1. An applicant must apply the following nonstructural best management practices in accordance with the Design Manual as well as local standards instituted by the Department to minimize increases in new development runoff. a) Natural area conservation; b) Disconnection of rooftop runoff; C) Disconnection of non-rooftop runoff; d) Sheet flow to buffers; e) Grass channels; and f) Environmentally sensitive development. 2. The Director may reduce the minimum control requirements specified under County law when nonstructural stormwater management practices are incorporated into site designs according to the Design Manual. C. Specific Design Considerations 1. Water quality. The design of best management practices must consider - the thermal effects of the development on receiving streams. The applicant must mitigate these effects if the Director determines that mitigation is necessary to preserve the water quality of the receiving streams. 2. Recharge. If the delineation is unclear in the Soil Survey or if a hydrologic soil group is not assigned to a specific soil, then the default hydrologic soil group for recharge design is "B."1 There are no recharge requirements for redevelopment project sites or for sites identified as hotspots. 3. Channel protection. All surface ponds in Use III, Use IV, and high quality Use I watersheds must be designed to provide 12-hour extended detention of the one-year, 24-hour storm event. All other surface ponds and all underground structures must be designed to provide 24-hour extended detention of the one-year, 24-hour storm event. 1Soil types are grouped hydrologically in the Soil Survey. 4. Flood protection. a) Overbank flood protection may only be required if the Director determines that the receiving floodplain, flow path, or storm drain system is insufficient to handle the flow from a 10-year storm. In such cases, the stormwater management concept plan must show how the peak discharge of the predeveloped 10-year, 24hour storm is maintained. b) Management of the 100-year storm is required only when the department determines that controls are necessary to protect existing buildings. 5. Nonstructural best management practices. The Director may accept nonstructural management practices to help satisfy the minimum stormwater control requirements when the Director is reasonably certain that the nonstructural management practices will remain functional after construction of the development is complete. #### 19.00.01.05 Contributions and Dedications A. An applicant making a contribution under Chapter 19 must provide the contribution to the County before the Director issues a building permit for the development. B. An applicant dedicating land under Chapter 19 must sign any agreement entered into with the Department or the Board before recording the plats for the land being dedicated. If no recorded plat is required, then the applicant must enter into the agreement with the Department or the Board before the Director may issue a building permit to the applicant. The applicant must provide to the Department a certified copy of any signed agreement entered into with the Board. #### 19.00.01.06 Inspections and Maintenance A. Notification required. A person must notify the Department of Environmental Protection at least 48 hours before initiating any maintenance work on a stormwater management facility. B. Qualifications of maintenance personnel. A person that performs repair or maintenance on a stormwater management facility must have demonstrated experience in stormwater management facility construction and inspection and hold a certificate of attendance awarded through a training program approved by the Department of Environmental Protection. A person that performs repair or maintenance on an underground facility must have the training and credentials required under applicable state and federal law. C. Final inspection. Upon completion of the repair or maintenance on a stormwater management facility, the Department must conduct a final inspection of the facility. If the Director determines that the facility is not in proper working condition, the Director must prepare a written report specifying the additional repair or maintenance needed to place the facility in proper working condition and provide a copy of the report to the owner of the facility. #### 19.00.01.07 Disposal Requirements A. Any person performing repair or maintenance on a stormwater management facility must ensure that the receptacle used to transport materials or debris resulting from the repair or maintenance has been cleaned of all septage residue if the receptacle was previously used to transport septage. B. Any person that transports waste materials resulting from repair or maintenance of a stormwater management facility must submit a report to the Department of Environmental Protection within 24 hours after disposing of the materials. The report must be on a form provided by the Department of Environmental Protection and must include the following information along with a copy of the receipt from the disposal facility where the materials are deposited: 1. Name, address, and phone number of the person transporting the materials; 2. Sequence number and location of the facility from which the materials were removed; 3. Types of structures from which the materials were removed and the number of structures at the site; 4. Amount and types of waste materials removed; 5. Date the material was removed; and 6. Location of the facility to which the materials were delivered for disposal. #### 19.00.01.08 Severability If a court holds that a portion of this regulation is invalid, the other portions remain in effect. #### 19.00.01.09 Effective Date This regulation takes effect upon approval by the County Council.