The State of Maryland operates under the National Pollutant Discharge Elimination System (NPDES) program under the authorization of the U.S. Environmental Protection Agency (EPA) through state regulation COMAR 26.17.02. The Department of The Environment manages the NPDES permit, authorizing municipalities for the permitting and compliance of stormwater discharge.
A. Unless the particular activity is exempted by this regulation, a person may not develop any land without an approved final stormwater management plan from the approving agency. A grading or building permit may not be issued for a property unless a final stormwater management plan has been approved.
B. The following activities are exempt from the provisions of this chapter:
(1) Additions or modifications to existing single family detached residential structures if they comply with §B(2) of this regulation;
(2) Any developments that do not disturb over 5,000 square feet of land area; and
(3) Land development activities which the Administration determines will be regulated under specific State laws which provide for managing stormwater runoff.
(1) County and municipal ordinances may contain waiver policies for individual developments if the ordinances are approved by the Administration. The Administration will approve county and municipal ordinances and waiver policies if:
(a) They reasonably ensure that a development will not adversely impact stream quality;
(b) Waiver decisions are made on a case-by-case basis; and
(c) The cumulative effects of the waiver policy are evaluated.
(2) Except as provided in §C(3) and (5) of this regulation, stormwater management quantitative control waivers shall be granted only to those projects within areas where watershed management plans have been developed consistent with §E of this regulation.
(3) Except as provided in §C(5) of this regulation, if watershed management plans consistent with §E of this regulation have not been developed, stormwater management quantitative control waivers may be granted to projects:
(a) That have direct discharges to tidally influenced receiving waters;
(b) That are in-fill development located in a Priority Funding Area where the economic feasibility of the project is tied to the planned density, and where implementation of the 2009 regulatory requirements would result in a loss of the planned development density provided that:
(i) Public water and sewer and stormwater conveyance exist;
(ii) The quantitative waiver is applied to the project for the impervious cover that previously existed on the site only;
(iii) ESD to the MEP is used to meet the full water quality treatment requirements for the entire development; and
(iv) ESD to the MEP is used to provide full quantity control for all new impervious surfaces; or
(c) When the approving agency determines that circumstances exist that prevent the reasonable implementation of quantity control practices.
(4) Except as provided in §C(5) of this regulation, stormwater management qualitative control waivers apply only to:
(a) In-fill development projects where stormwater management implementation is not feasible;
(b) Redevelopment projects if the requirements of §D of this regulation are satisfied; or
(c) Sites where the approving agency determines that circumstances exist that prevent the reasonable implementation of quality control practices.
(5) Stormwater management quantitative and qualitative control waivers may be granted for phased development projects if a system designed to meet the 2000 regulatory requirements and local ordinances for multiple phases has been constructed by May 4, 2010. If the 2009 regulatory requirements cannot be met for future phases constructed after May 4, 2010, all reasonable efforts to incorporate ESD in future phases must be demonstrated.
(1) An approving agency shall require that stormwater management be addressed for redevelopment. Unless otherwise specified by watershed management plans developed according to §E of this regulation, all redevelopment project designs shall do one of the following:
(a) Reduce existing impervious area within the limit of disturbance by at least 50 percent according to the Design Manual;
(b) Implement ESD to the MEP to provide water quality treatment for at least 50 percent of the existing impervious area within the limit of disturbance; or
(c) Use a combination of both §D(1)(a) and (b) of this regulation for at least 50 percent of the existing site impervious area.
(2) Alternative stormwater management measures may be used to meet the requirements in §D(1) of this regulation if the developer satisfactorily demonstrates to the approving agency that impervious area reduction and ESD have been implemented to the MEP. Alternative stormwater management measures include, but are not limited to:
(a) An on-site structural BMP;
(b) An off-site structural BMP to provide water quality treatment for an area equal to or greater than 50 percent of the existing impervious area; or
(c) A combination of impervious area reduction, ESD implementation, and an on-site or off-site structural BMP for an area equal to or greater than 50 percent of the existing site impervious area within the limit of disturbance.
(3) An approving agency may develop separate policies for providing water quality treatment for redevelopment projects if the requirements of §D(1) and (2) of this regulation cannot be met. Any separate redevelopment policy shall be reviewed and approved by the Administration and may include, but not be limited to:
(a) A combination of ESD and an on-site or off-site structural BMP;
(b) Retrofitting including existing BMP upgrades, filtering practices, and off-site ESD implementation;
(c) Participation in a stream restoration project;
(d) Pollution trading with another entity;
(e) Design criteria based on watershed management plans developed according to §E of this regulation;
(f) Payment of a fee-in-lieu; or
(g) A partial waiver of the treatment requirements if ESD is not practicable.
(4) The determination of what alternative stormwater management measures will be available may be made by the approving agency at the appropriate point in the development review process. Counties and municipalities shall consider the prioritization of alternative measures in §D(3) of this regulation after it has been determined that it is not practicable to meet the 2009 regulatory requirements using ESD. In deciding what alternative measures may be required, an approving agency may consider factors including, but not limited to:
(a) Whether the project is in an area targeted for development incentives such as a Priority Funding Area, a designated Transit Oriented Development area, or a designated Base Realignment and Closure Revitalization and Incentive Zone;
(b) Whether the project is necessary to accommodate growth consistent with comprehensive plans; or
(c) Whether bonding and financing have already been secured based on an approved development plan.
(5) Stormwater management shall be addressed according to the new development requirements in the Design Manual for any net increase in impervious area.
(6) The recharge, channel protection storage volume, and overbank flood protection volume requirements specified in the Design Manual do not apply to redevelopment projects unless specified by the approving agency.
(7) On-site or off-site channel protection storage volume requirements as specified in the Design Manual may be imposed if watershed management plans developed according to §E of this regulation indicate that downstream flooding or erosion need to be addressed.
(8) Variations of this redevelopment policy shall be approved by the Administration.
E. An approving agency may develop quantitative waiver and redevelopment provisions for stormwater management that differ from the requirements of this chapter. These provisions shall be developed only as part of an overall watershed management plan. Watershed management plans developed for the purposes of implementing different stormwater management policies for waivers and redevelopment shall:
(1) Include detailed hydrologic and hydraulic analyses to determine hydrograph timing;
(2) Evaluate both quantity and quality management;
(3) Include cumulative impact assessment of watershed development;
(4) Identify existing flooding and receiving stream channel conditions;
(5) Be conducted at a scale determined by the approving agency; and
(6) Specify where on-site or off-site quantitative and qualitative stormwater management practices are to be implemented.
A. The design of stormwater management plans shall be prepared by any individual whose qualifications are acceptable to the approving agency. The approving agency may require that the design be prepared by either a professional engineer, professional land surveyor, or landscape architect licensed in the State, as necessary to protect the public or the environment. If a stormwater BMP requires either a dam safety permit from the Department or small pond approval by the appropriate soil conservation district, the approving agency shall require that the design be prepared by a professional engineer licensed in the State.
B. Stormwater management and development plans shall be consistent with adopted and approved watershed management plans or flood management plans as approved by the Department in accordance with the Flood Hazard Management Act of 1976 (Environment Article, Title 5, Subtitle 8, Annotated Code of Maryland).
C. An operation and maintenance plan shall be required as a condition of stormwater management plan approval.
D. If a stormwater management plan involves direction of some or all runoff off of the site, it is the responsibility of the developer to obtain from adjacent property owners any easements or other necessary property interests concerning flowage of water. Approval of a stormwater management plan does not create or affect any right to direct runoff onto adjacent property without that property owner's permission.
E. Contents and Submission of Stormwater Management Plans.
(1) The owner/developer is responsible for submitting phased stormwater management plans for development projects according to the comprehensive review and approval process specified in Regulation .04 of this chapter, the Design Manual, and county and municipal stormwater management ordinances. Plans shall be submitted for the concept, site development, and final stormwater management construction phases of project design. Comments from the appropriate approval authority shall be addressed and approval received at each phase of project design before subsequent submissions.
(2) The owner/developer shall submit a concept plan that provides sufficient information for an initial assessment of the proposed project and whether stormwater management can be provided according to this chapter and the Design Manual. Plans submitted for concept approval shall include, but are not limited to:
(a) A map at a scale specified by the appropriate approval authority showing site location, existing natural features, water and other sensitive resources, topography, and natural drainage patterns;
(b) The anticipated location of all proposed impervious areas, buildings, roadways, parking, sidewalks, utilities, and other site improvements;
(c) The location of the proposed limit of disturbance, erodible soils, steep slopes, and areas to be protected during construction;
(d) Preliminary estimates of stormwater management requirements, the selection and location of ESD practices to be used, and the location of all points of discharge from the site;
(e) A narrative that supports the concept design and describes how ESD will be implemented to the MEP; and
(f) Any other information required by the approving Agency.
(3) Following concept plan approval by the appropriate authority, the owner or developer shall submit site development plans that reflect comments received during the previous review phase. Plans submitted for site development approval shall be of sufficient detail to allow site development to be reviewed and include but not be limited to:
(a) All information provided during the concept plan review phase;
(b) Final site layout, exact impervious area locations and acreages, proposed topography, delineated drainage areas at all points of discharge from the site, and stormwater volume computations for ESD practices and quantity control structures;
(c) A proposed erosion and sediment control plan that contains the construction sequence, any phasing necessary to limit earth disturbances and impacts to natural resources, and an overlay plan showing the types and locations of ESD and erosion and sediment control practices to be used;
(d) A narrative that supports the site development design, describes how ESD will be used to meet the minimum control requirements, and justifies any proposed structural stormwater management measure; and
(e) Any other information required by the approving Agency.
(4) Following site development approval by the appropriate authority, the owner/developer shall submit final erosion and sediment control and stormwater management plans that reflect the comments received during the previous review phase. Plans submitted for final approval shall be of sufficient detail to allow all approvals and permits to be issued according to the following:
(a) Final erosion and sediment control plans shall be submitted according to COMAR 26.17.01.05; and
(b) Final stormwater management plans shall be submitted for approval in the form of construction drawings and be accompanied by a report that includes sufficient information to evaluate the effectiveness of the proposed runoff control design.
(5) Reports submitted for final stormwater management plan approval shall include, but are not limited to:
(a) Geotechnical investigations including soil maps, borings, site-specific recommendations, and any additional information necessary for the final stormwater management design;
(b) Drainage area maps depicting predevelopment and post-development runoff flow path segmentation and land use;
(c) Hydrologic computations of the applicable ESD and unified sizing criteria according to the Design Manual for all points of discharge from the site;
(d) Hydraulic and structural computations for all ESD practices and structural stormwater management measures to be used;
(e) A narrative that supports the final stormwater management design; and
(f) Any other information required by the approving agency.
(6) Construction drawings submitted for final stormwater management plan approval shall include, but are not limited to:
(a) A vicinity map;
(b) Existing and proposed topography and proposed drainage areas, including areas necessary to determine downstream analysis for the proposed stormwater management facilities;
(c) Any proposed improvements including the location of buildings or other structures, impervious surfaces, storm drainage facilities, and all grading;
(d) The location of existing and proposed structures;
(e) Any easements and rights-of-way;
(f) The delineation, if applicable, of the 100-year floodplain and any on-site wetlands;
(g) Structural and construction details including representative cross sections for all components of the proposed drainage system or systems and stormwater management facilities;
(h) All necessary construction specifications;
(i) A sequence of construction;
(j) Data for total site area, disturbed area, new impervious area, and total impervious area;
(k) A table showing the ESD and unified sizing criteria volumes required in the Design Manual;
(l) A table of materials to be used for stormwater management facility planting;
(m) All soil boring logs and locations;
(n) An inspection and maintenance schedule;
(o) Certification by the owner/developer that all stormwater management construction will be done according to this plan;
(p) An as-built certification signature block to be executed after project completion; and
(q) Any other information required by the approving agency.
Maryland Stormwater Management Program Website
Maryland Stormwater Design Manual
Maryland’s Stormwater Management Act
Maryland NPDES MS4 Phase II General Permits
Maryland Water Permit Applications and Other Forms