THE CODE CHAPTER 21B STORMWATER MANAGEMENT CONTROL

Transcription

1 CHAPTER 21B STORMWATER MANAGEMENT CONTROL 21B.1. 21B.2. 21B.3. 21B.4. 21B.5. 21B.6. 21B.7. 21B.8. 21B.9. 21B B B B B B B B B B B B.21. Purpose and authority. Incorporation by reference. Grandfathering. Definitions. Applicability. Redevelopment. Variance. Stormwater management criteria. Stormwater management plans. Permits. Permit fee. Permit suspension and revocation. Performance and payment bond. Liability Insurance. Maintenance bond. Inspections. Maintenance. Approval and acceptance. Appeals. Penalties. Transition provisions. Section 21B-1. Purpose and Authority A. The purpose of this Chapter is to protect, maintain, and enhance the public health, safety, and general welfare by establishing minimum requirements and procedures that control the adverse impacts associated with increased stormwater runoff. The goal of this Chapter is to manage stormwater by using Environmental Site Design (ESD) to the maximum extent practicable (MEP) to maintain after development, as nearly as possible, the predevelopment runoff characteristics, and to reduce stream channel erosion, pollution, siltation and sedimentation, and local flooding, and use appropriate structural Best Management Practices (BMPs) only when necessary. B. It is the intent of this Chapter to restore, enhance, and maintain the chemical, physical, and biological integrity of streams, minimize damage to public and private property, and reduce the impacts of land development. C. The application of this Chapter and provisions expressed herein shall be the minimum stormwater management requirements and shall not be deemed a limitation or repeal of any other powers granted by state statute. The City of Bowie shall be responsible for the coordination and enforcement of the provisions of this Chapter. D. This Chapter applies to all new and redevelopment projects that have not received final approval for erosion and sediment control and stormwater management plans by May 3, Final approval shall mean document signature on the final technical stormwater management plans by the City Manager of the City of Bowie. Final stormwater management plans receiving approval on or before May 3, 2010, shall not be required to comply with this Supp. 33. Revision, Chapter 21B

2 Chapter unless the development pursuant to the plans has not been completed with the approval periods set forth in section 21b-3 of this Chapter. Section 21B-2. Incorporation by reference For the purpose of this Chapter, the following documents are incorporated by reference: A. The Design Manual. B. The Maryland 378 Pond Code. Section 21B-3. Grandfathering A. In this Section, the following terms have the meanings indicated: 1. Administrative Waiver means a decision by the City pursuant to this Chapter to allow the construction of a development to be governed by the Stormwater Management Ordinance in effect as of May 4, 2009, but does not include a waiver granted pursuant to subsection 5.c. of Section 21B-5 of this Chapter. 2. Approval means a determination, documented in writing, by the City that the materials submitted by or on behalf of the property owner in support of the property owner s request for approval of a development plan, including a stormwater management plan, comply with the requirements of a specified stage in the City s development review process, and a mere acknowledgement by the City that submitted material has been received for review does not constitute an approval. 3. Final project approval means approval of the final stormwater management plan and erosion and sediment control plan required to construct a project's stormwater management facilities. 4. Preliminary project approval means an approval as part of the City s preliminary development or planning review process. B. Preliminary project approval will not be granted until the property owner has submitted information to the City that includes, at a minimum: 1. The number of planned dwelling units or lots; 2. The proposed project density; 3. The proposed size and location of all land uses for the project; 4. An approved stormwater management concept plan pursuant to Subsection B.1. of Section 21B-9 of this Chapter; and 5. Any other information required by the city including, but not limited to: (a) The proposed alignment, location, and construction type and standard for all roads, access ways, and areas of vehicular traffic; 2

3 (b) A demonstration that the methods by which the development will be supplied with water and wastewater service are adequate; and (c) The size, type, and general location of all proposed wastewater and water system infrastructure. C. A project will not be deemed to have obtained a final project approval until the property owner has secured bonding and/or financing for final development plans if either is required by law or by agreement between the City and the property owner. D. The City may grant an administrative waiver to a development that received a preliminary project approval prior to May 4, E. Except as provided for in 21B-3.d of this Chapter, an administrative waiver shall expire on: 1 May 4, 2013, if the development does not receive final project approval prior to that date; or 2. May 4, 2017, if the development receives final project approval prior to May 4, F. All construction authorized pursuant to an administrative waiver must be completed by May 4, 2017 or, if the waiver is extended as provided in Subsection g. of this Section, by the expiration date of the waiver extension. G. An administrative waiver shall only be extended if, by May 4, 2010, the development: 1. Has received a preliminary project approval; and 2. Was subject to a development rights and responsibilities agreement, a tax increment financing approval, or an annexation agreement that provides a date for completion of development that is after the date on which the administrative waiver would otherwise expire. H. Administrative waivers extended pursuant to subsection g of this section shall expire upon the date set forth for completion of the development in the development rights and responsibilities agreement, the tax increment financing approval, or the annexation agreement. Section 21B-4. Definitions The following definitions are provided for the terms used in this Chapter: A. Administration means the Maryland Department of the Environment (MDE) Water Management Administration (WMA). 3

4 B. Adverse impact means any deleterious effect on waters or wetlands, including their quality, quantity, surface area, species composition, aesthetics or usefulness for human or natural uses which are or may potentially be harmful or injurious to 6 human health, welfare, safety or property, to biological productivity, diversity, or stability or which unreasonably interfere with the enjoyment of life or property, including outdoor recreation. C. Agricultural land management practices means those methods and procedures used in the cultivation of land in order to further crop and livestock production and conservation of related soil and water resources. D. Applicant means any person, firm, or governmental agency who executes the necessary forms to procure official approval of a project or a permit to carry out construction of a project. E. Approved plan means a set of representational drawings or other documents submitted by an applicant as a prerequisite to obtaining a stormwater management permit, which has been determined by the City of Bowie Department of Public Works (Department) to contain sufficient evidence and information to satisfy the requirements of this Chapter. F. Aquifer means a porous water-bearing geologic formation generally restricted to materials capable of yielding an appreciable supply of water. G. As-built plan means a set of approved plans and other documents submitted by the engineer-in-charge, which have been noted with actual construction information for approval by the Department and are sealed and signed by the engineer-in-charge. H. Beneficial user means a lot or parcel, the runoff from which was considered in designing a stormwater management facility to satisfy the requirements of this Chapter for developing land. I. Best management practice (BMP) means a structural device or nonstructural practice designed to temporarily store or treat stormwater runoff in order to mitigate flooding, reduce pollution, and provide other amenities. J. Bond means a cash bond, corporate bond, irrevocable letter of credit or other security approved by the city and required of the applicant by the Department before issuance of any stormwater management permit or grading permit. K. Building permit means an official document or certificate issued by the City authorizing construction of a structure as provided for in the Bowie City Code. L. Clearing means the removal of trees and brush from the land but shall not include the ordinary mowing of grass. M. COMAR means the Code of Maryland regulations. N. Concept plan means the first of three required plan approvals that includes the information necessary to allow an initial evaluation of a proposed project. 4

5 O. Department means the City of Bowie Department of Public Works represented by the Director. P. Design Manual means the 2000 Maryland Stormwater Design Manual, and all subsequent revisions, that serve as the official guide for stormwater management principles, methods, and practices. Q. Detention structure means a permanent structure for the temporary storage of runoff which is designed so as not to create a permanent pool of water R. Development means the construction of any residential, commercial, industrial, recreational, or institutional building, structure, roadway or paving; any mining or landfill; or any land-disturbing activities in preparation for the above. S. Direct discharge means the concentrated release of stormwater to tidal waters or vegetated tidal wetlands from new development or redevelopment projects in the critical area. T. Director means the Director of Public Works of the City. U. District means the Prince George's Soil Conservation District. V. Drainage area means that area contributing runoff to a single point measured in a horizontal plane, which is enclosed by a ridge line. W. Easement means a grant or reservation by the owner of land for the use of such land by others for a specific purpose or purposes, and which must be included in the conveyance of land affected by such easement. X. Engineer-in-charge means the professional engineer who is responsible for assuring that stormwater management facilities are built in accordance with the approved plans and in accordance with the assumptions made during the design and certified same to the Department. Y. Environmental site design (ESD) means using small-scale stormwater management practices, nonstructural techniques, and better site planning to mimic natural hydrologic runoff characteristics and minimize the impact of land development on water resources. Methods for designing ESD practices are specified in the Design Manual. Z. Erosion means the process by which the land surface is worn by the action of wind, water, ice or gravity. AA. Excavation means any act by which soil is cut, dug, quarried, uncovered, removed, displaced or relocated. BB. Exemption means those land development activities that are not subject to the requirements of the Stormwater Management Ordinance of the City Code. 5

6 CC. Filling means an act except agricultural tilling operations by which soil is deposited, dropped, placed, pushed, pulled or transported to a location different from its original position, and shall include the conditions resulting therefrom.. DD. Final grading means the grading of a site to the approved finished grade. EE. Final stormwater management plan means the last of three required plan approvals that includes the information necessary to allow all approvals and permits to be issued by the City. This definition applies only to those final stormwater management plans receiving technical approval after the end of business, May 3, FF. Finished grade means the final grade or elevation of the ground surface as shown on the approved plans. GG. Floodplain (100 year) means that land which is theoretically inundated by the stormwater runoff created by a 100-year frequency rainfall event (which is an event having a one percent chance of occurrence in any year) calculated using current standards approved by the administration and adopted by the department based on the maximum development of the watershed as currently zoned. HH. Forest harvest operation means the commercial logging or harvesting of timber by cutting trees at or above ground level including but not limited to the associated haul road, skid trails and staging areas. The removal of stumps or roots is not considered a forest harvest operation. II. Grading means any act by which soil is cleared, stripped, stockpiled, excavated, scarified, filled, or any combination thereof. JJ. Grading permit holder means any person to whom a grading permit is issued. KK. Impervious area means any surface that does not allow stormwater to infiltrate into the ground. Gravel surfaces, grass pavers or similar surfaces are not considered impervious surfaces. LL. Infiltration means the passage or movement of water into the soil surface. MM. Land-disturbing activity means any tilling, clearing, grubbing, or grading of the land, or any artificial movement of the soil, or the covering of land surfaces with an impermeable layer. Land-disturbing activity shall also include the disturbance or removal of existing pavement or other hard surface that results in the exposure of the aggregate or soil subbase or subgrade. Milling of pavement surface that does not expose the soil subbase or subgrade shall not be considered a land-disturbing activity. NN. Limit of disturbance or LOD means the outward limit of any land-disturbing activity. Such limit shall include all contiguous land-disturbing activities proposed for a particular project or phase of a project regardless of whether they are to occur at different times. OO. Maintenance bond means a cash bond, corporate bond, irrevocable letter of credit or other security approved by the City of Bowie and required of the applicant by the 6

7 department for the maintenance period. Each permit will require a separate individual and independent maintenance bond. PP. Maryland 378 Pond Code means the latest edition of the USDA Natural Resources Conservation Service Maryland Conservation Practice Standard Pond Code 378. QQ. Maximum extent practicable (MEP) means designing stormwater management systems so that all reasonable opportunities for using ESD planning techniques and treatment practices are exhausted and only where absolutely necessary, a structural bmp is implemented. RR. Nonpoint source pollution means pollution that is generated by diffuse land use activities rather than from an identifiable or discrete source and is conveyed to waterways through natural processes, such as rainfall, stormwater runoff or groundwater seepage rather than by direct discharge. SS. Off-site stormwater management means the design and construction of a facility necessary to control stormwater from more than one development. TT. On-site stormwater management means the design and construction of systems necessary to control stormwater within one development, and which systems are located within the boundaries of that development. UU. Permanent stabilization means a practice where vegetative cover and/or structural methods are applied to a site per requirements of the standards and specifications for soil erosion and sediment control, of the administration which will result in a permanent cover to prevent erosion or other adverse impacts from occurring. VV. Person means any governmental entity with jurisdiction over or a legal interest in a property to which the terms of this chapter are applied, or an individual receiver, trustee, guardian, executor, administrator, fiduciary, or representative of any kind, or any partnership, firm, association, public or private corporation, or any other entity. WW. Planning techniques means a combination of strategies employed early in project design to reduce the impact from development and to incorporate natural features into a stormwater management plan. XX. Point source pollution means pollution discharged through any discernable, confined, and discrete conveyance, including any pipe, ditch, channel, tunnel, conduit, well, or discrete fissure. YY. Professional engineer means an engineer duly licensed by in the State of Maryland to practice professional engineering in accordance with the provisions of the Annotated Code of Maryland, business occupations and professions Article, Title 14, as amended. ZZ. Professional landscape architect means a landscape architect duly licensed in the State of Maryland to practice professional landscape architecture in accordance with the provisions of the Annotated Code of Maryland, Business Occupations and Professions Article, Title 9, as amended. 7

8 AAA. Professional land surveyor means a land surveyor duly licensed in the State of Maryland to practice professional land surveying in accordance with the provisions of the Annotated Code of Maryland, Business Occupations and Professions Article, Title 15, as amended. BBB. Recharge volume (REV) means that portion of the water quality volume used to maintain groundwater recharge rates at development sites. Methods for calculating the recharge volume are specified in the design manual. CCC. Redevelopment means any construction, alteration, or improvement performed on sites where existing land use is commercial, industrial, institutional, or multifamily residential and existing site impervious area exceeds 40 percent. DDD. Retention structure means a permanent structure that provides for the storage of runoff by means of a permanent pool of water. EEE. Retrofitting means the implementation of ESD practices, the construction of a structural bmp, or the modification of an existing structural bmp in a previously developed area to improve water quality over current conditions. FFF. Sediment means soils or other surficial materials transported or deposited by the action of wind, water, ice, or gravity as a product of erosion. GGG. Sensitive areas means tidal and non-tidal wetland areas, natural resource districts, and the buffers associated with each. HHH. Site means any tract, lot, or parcel of land, or combination of tracts, lots, parcels of land that are in one ownership, or are contiguous and in diverse ownership, where development is to be performed as part of a unit, subdivision, or project. For redevelopment, any developed tract, lot or parcel or land or combination of contiguous tracts, lots or parcels of land which are in one ownership, or are contiguous and in diverse ownership where development is to be performed as part of a subdivision or project, the area of new construction shown on an approved site plan. (Final determination of the applicable site area shall be made by the Department.) III. Site development plan means the second of three required plan approvals that includes the information necessary to allow a detailed evaluation of a proposed project. JJJ. Slope means the deviation of the land surface from the horizontal expressed either as a ratio of horizontal distance to vertical distance or as a percentage (vertical distance divided by horizontal distance multiplied by one hundred). KKK. Soil means earth, sand, gravel, rock or other surficial material. LLL. Stabilization means the prevention of soil movement by any of various vegetative and/or structural means. MMM. Stop work order means an order issued by the Department, due to the existence of a violation of this Chapter on a site, to cease all work with the exception of work required to correct the violation until the violation is corrected to the satisfaction of the Department. 8

9 NNN. Stormwater means water that originates from a precipitation event. OOO. Stormwater management maintenance agreement means a signed agreement between the City and the property owner(s) recorded in the land records of the Prince George's County to ensure maintenance of privately owned stormwater management facilities. PPP. Stormwater management permit means the stormwater management permit issued by the city authorizing the installation of stormwater management measure(s). QQQ. Stormwater management system means natural areas, ESD practices, stormwater management measures, and any other structure through which stormwater flows, infiltrates, or discharges from a site. RRR. Stream means those perennial and intermittent watercourses identified through site inspection. The most recent Prince George's County photogrammetric maps may be used as a guide for the establishment of possible watercourses. SSS. Stream system means a watercourse together with the 100-hundred year floodplain and/or hydrologically connected nontidal wetlands. TTT. Stripping means any activity that removes the vegetative surface cover, including tree removal, clearing, grubbing, and storage or removal of topsoil. UUU. Temporary stabilization means a practice where vegetative cover and/or structural methods are applied per requirements of the standards and specifications for soil erosion and sediment control, of the Maryland Department of the Environment which results in a temporary cover to prevent erosion or other adverse impacts. VVV. Use and occupancy permit means an official document or certificate issued by Prince George's County authorizing the use of a structure for the purpose for which it was intended. WWW. Variance means the modification of the minimum stormwater management requirements for specific circumstances such that strict adherence to the requirements would result in unnecessary hardship and not fulfill the intent of this Chapter. XXX. Waiver means the partial or complete reduction from the requirements of this Chapter by the City Manager for a site when requested by the applicant. The review for a waiver for each article is independent of the remaining Chapter. YYY. Wastewater means liquid waste substances derived from industrial, commercial, municipal, residential, agricultural, recreational, or other operations or establishments; or other liquid substance containing liquid, gaseous, or solid matter and having characteristics which may cause pollution. ZZZ. Watercourse means any natural or artificial stream, river, creek, ditch, channel, canal, conduit, culvert, drain, waterway, gully, ravine or wash, in and including any adjacent area that is subject to inundation from overflow or flood water. 9

10 AAAA. Water quality volume (WQV) means the volume needed to capture and treat 90 percent of the average annual rainfall events at a development site. Methods for calculating the water quality volume are specified in the Design Manual. BBBB. Watershed means the total drainage area contributing runoff to a single point. CCCC. Waters of the state means both surface and underground watercourses within the boundaries of the State of Maryland subject to its jurisdiction, including that part of the Atlantic Ocean within the boundaries of the State, the Chesapeake Bay and its tributaries, and all ponds, lakes, watercourses, tidal and nontidal wetlands, and public drainage systems within this State, other than those designed and used to collect, convey, or disposed of sanitary sewage; and the floodplain of free-flowing waters determined by the State Department of the Environment on the basis of the 100-hundred year floodplain. Section 21B-5. Applicability A. Scope. No person shall develop any land for residential, commercial, industrial, or institutional uses without providing stormwater management measures that control or manage runoff from such developments, except as provided within this section. Stormwater management measures must be designed in a manner consistent with the design manual and constructed according to an approved plan for new development or for redevelopment in accordance with section 21B-6 of this Chapter. B. Exemptions. The following development activities are exempt from the provisions of this Chapter and the requirements relating to the provision of stormwater management facilities: 1. Agricultural land management practices; 2. Additions or modifications to existing single family detached residential structures if they comply with Subsection B.3 of this Section; and 3. Any development that does not disturb over 5,000 square feet of land area; 4. Land development activities that the administration determines will be regulated under specific state laws that provide for managing stormwater runoff. C. Waivers/watershed management plans. 1. Except as provided in Subsection C.2 and C.4 of this Section, the City shall grant stormwater management quantitative control waivers only to those projects that are within areas in which watershed management plans have been developed consistent with Subsection C.7 of this Section. Written requests for quantitative stormwater management 10

11 waivers shall contain sufficient descriptions, drawings, and any other information that is necessary to demonstrate that ESD has been implemented to the MEP. A separate written waiver request shall be submitted meeting the requirements of this Section if there are subsequent additions, extensions, or modifications to a development receiving a waiver. 2. Except as provided in Subsection C.4 of this Section, if watershed management plans consistent with Subsection C.7 of this Section have not been developed, stormwater management quantitative control waivers may be granted with respect to the following projects, provided that the property owner demonstrates that ESD has been implemented to the MEP: waters; or (a) Projects that have direct discharges to tidally influenced receiving (b) Projects 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: (1) Public water and sewer and stormwater conveyance exist; (2) The quantitative waiver is applied to the project for the impervious cover that previously existed on the site only; (3) ESD to the MEP is used to meet the full water quality treatment requirements for the entire development; and (4) ESD to the MEP is used to provide full quantity control for all new impervious surfaces; or (c) Projects as to which the City determines that circumstances exist that prevent the reasonable implementation of quantity control practices. 3. Except as provided in Subsection C.4 of this Section, stormwater management qualitative control waivers apply only to: (a) In-fill development projects where ESD has been implemented to the MEP, and it has been demonstrated that other BMPs are not feasible; or (b) Redevelopment projects, if the requirements of Section 21B-6 of this Chapter are satisfied; or (c) Sites as to which the City determines that circumstances exist that prevent the reasonable implementation of ESD to the MEP. 4. 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 the City ordinance for multiple phases has been constructed by May 4, If the 2009 regulatory requirements cannot be met for future phases 11

12 constructed after May 4, 2010, all reasonable efforts to incorporate ESD in future phases must be demonstrated. 5. Waivers shall only be granted when the property owner has demonstrated that ESD has been implemented to the MEP and a decision by the Department to grant a waiver must: and quality. (a) (b) Take into consideration the cumulative effects of the City s waiver policy; Reasonably ensure the development will not adversely impact stream 6. If the city has established an overall watershed management plan for a specific watershed, then the city may develop quantitative waiver and redevelopment provisions that differ from Subsection C.2 of this Section and Section 21B-6 of this Chapter. 7. A watershed management plan developed for the purpose of implementing different stormwater management policies for waivers and redevelopment shall: (a) hydrograph timing; Include detailed hydrologic and hydraulic analyses to determine (b) Evaluate both quantity and quality management and opportunities for ESD implementation; (c) Include a cumulative impact assessment of current and proposed watershed development; (d) (e) Identify existing flooding and receiving stream channel conditions; Be conducted at a reasonable scale; (f) Specify where on-site or off-site quantitative and qualitative stormwater management practices are to be implemented; (g) Be consistent with the general performance standards for stormwater management in Maryland found in the Design Manual; and (h) Be approved by the administration. 8. If the property owner satisfactorily demonstrates to the City that ESD has been implemented to the MEP on site and stormwater management requirements have not been addressed, practical alternatives to quantitative and qualitative stormwater management may be considered, including but not limited to: (a) Fees in lieu of compliance, in the amount of $1.00 per square foot of impervious area that are dedicated exclusively to provide stormwater management and/or stream restoration; 12

13 (b) Off-site ESD/BMP implementation for a drainage area comparable in size and percent of increased imperviousness to that of the project; (c) (d) Watershed or stream restoration and/or Other practices approved by the department and the administration. Section 21B-6. Redevelopment. A. Subject to the exemptions set forth in Subsection B.3. or B.4. of Section 21B-5 of this Chapter, stormwater management plans are required by the City for all redevelopment, unless otherwise specified by watershed management plans developed according to Subsection C.7. of Section 21B-5 of this Chapter. Stormwater management measures must be consistent with the Design Manual. B. All redevelopment designs shall: 1. Reduce impervious area within the limit of disturbance (LOD) by at least 50 percent according to the Design Manual; 2. Implement ESD to the MEP to provide water quality treatment for at least 50 percent of the existing impervious area within the LOD; or 3. Use a combination of the methods set forth in Subsections B.1 and B.2 of this Section for at least 50 percent of the existing impervious area within the LOD. C. Alternative stormwater management measures may be used to meet the requirements in Subsection B. of this Section, if the property owner satisfactorily demonstrates to the City that impervious area reduction has been maximized and ESD has been implemented to the MEP. Alternative stormwater management measures include, but are not limited to: 1. An on-site structural BMP; 2. 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 3. 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 LOD. D. Notwithstanding the requirements of Subsections a. and b. of this Section, the City may consider, at its sole discretion, separate policies for providing equivalent water quality treatment for redevelopment projects if the property owner satisfactorily demonstrates, with approval by the department, that the requirements of Subsections a. and b. of this Section cannot be met. Any separate redevelopment policy shall be reviewed and approved by the administration and may include, but not be limited to: 1. A combination of ESD and an on-site or off-site structural bmp; 13

14 2. Retrofitting including existing BMP upgrades, filtering practices, and off-site ESD implementation; 3. Participation in a stream restoration project; 4. Pollution trading with another entity; 5. Payment of a fee-in-lieu; or 6. A partial waiver of the treatment requirements if ESD is not practicable. E. The determination of the availability of alternative stormwater management measures may be made by the City at the appropriate point in the development review process. The City shall consider the prioritization of alternatives in Subsection d. of this Section after the City determines that it is not practicable to meet the regulatory requirements in effect at the time of the application using ESD. In deciding what alternatives may be permitted, the City may consider factors including, but not limited to: 1. Whether the project is in an area targeted for development incentives such as a priority funding area or a designated transit oriented development area; 2. Whether the project is necessary to accommodate growth consistent with comprehensive plans; or 3. Whether bonding and financing have already been secured based on an approved development plan. F. Stormwater management shall be addressed according to the new development requirements in the design manual for any net increase in impervious area. Section 21B-7. Variance. The City may grant a written variance from any requirement of Section 21B-8 stormwater management criteria, if there are exceptional circumstances applicable to the site such that strict adherence will result in unnecessary hardship and will not fulfill the intent of this Chapter. A written request for variance shall be provided to the City and shall state the specific variances sought and justification for granting such variances. Section 21B-8. Stormwater Management Criteria. A. Minimum control requirements 1. The minimum control requirements established in this Section and the Design Manual are as follows: (a) The planning techniques, nonstructural practices, and design methods specified in the Design Manual shall be used to implement ESD to the MEP. The use of ESD planning techniques and treatment practices shall be exhausted before any structural BMP is implemented. Stormwater management plans for development projects 14

15 subject to this Chapter shall be designed using ESD sizing criteria, recharge volume, water quality volume, and channel protection storage volume criteria according to the Design Manual. The MEP standard is met when channel stability is maintained, predevelopment groundwater recharge is replicated, nonpoint source pollution is minimized, and structural stormwater management practices are used only if determined to be absolutely necessary. (b) Control of the 10-year frequency storm event is required in accordance with the design manual and all subsequent revisions. (c) The city may require more than the minimum control requirements specified in this Chapter if hydrologic or topographic conditions warrant or if flooding, stream channel erosion, or water quality problems exist downstream from a proposed project. 2. Alternate minimum control requirements may be adopted subject to administration approval, upon a demonstration that alternative requirements will implement ESD to the MEP and control flood damages, accelerated stream erosion, water quality, and sedimentation. Comprehensive watershed studies may also be required. 3. Stormwater management and development plans, where applicable, shall be consistent with adopted and approved watershed management plans or flood management plans as approved by the Maryland Department of the Environment in accordance with the Flood Hazard Management Act of B. Stormwater management measures The ESD planning techniques and practices and structural stormwater management measures established in this Chapter and the Design Manual shall be used, either alone or in combination in a stormwater management plan. A developer shall demonstrate that ESD has been implemented to the MEP before the use of a structural BMP is considered in developing the stormwater management plan. 1. ESD planning techniques and practices. (a) The following planning techniques shall be applied according to the Design Manual to satisfy the applicable minimum control requirements established in Subsection a. of this Section: (1) Preserving and protecting natural resources; (2) Conserving natural drainage patterns; (3) Minimizing impervious area; (4) Reducing runoff volume; (5) Using ESD practices to maintain 100 percent of the annual predevelopment groundwater recharge volume; (6) Using green roofs, permeable pavement, reinforced turf, and other alternative surfaces; 15

16 (7) Limiting soil disturbance, mass grading, and compaction; (8) Clustering development; and/or (9) Any practices approved by the administration. (b) The following ESD treatment practices shall be designed according to the Design Manual to satisfy the applicable minimum control requirements established in Subsection a. of this Section: (1) Disconnection of rooftop runoff; (2) Disconnection of non-rooftop runoff; (3) Sheetflow to conservation areas; (4) Rainwater harvesting; (5) Submerged gravel wetlands; (6) Landscape infiltration; (7) Infiltration berms; (8) Dry wells; (9) Micro-bioretention; (10) Rain gardens; (11) Swales; (12) Enhanced filters; and (13) Any practices approved by the administration. (c) The use of ESD planning techniques and treatment practices specified in this section shall not conflict with existing state law or local ordinances, regulations, or policies 2. Structural stormwater management measures. (a) The following structural stormwater management practices shall be designed according to the Design Manual to satisfy the applicable minimum control requirements established in Subsection a. of this Section: (1) Stormwater management ponds; (2) Stormwater management wetlands; 16

17 (3) Stormwater management infiltration; (4) Stormwater management filtering systems; and (5) Stormwater management open channel systems. (b) The performance criteria specified in the Design Manual with regard to general feasibility, conveyance, pretreatment, treatment and geometry, environment and landscaping, and maintenance shall be considered when selecting structural stormwater management practices. (c) Structural stormwater management practices shall be selected to accommodate the unique hydrologic or geologic regions of the State. 3. ESD planning techniques and treatment practices and structural stormwater management measures used to satisfy the minimum requirements in Subsection a. of this Section must be recorded in the land records of Prince George s County and remain unaltered by subsequent property owners. Prior approval from the City shall be obtained before any stormwater management practice is altered. 4. Alternative ESD planning techniques and treatment practices and structural stormwater measures may be used for new development runoff control if they meet the performance criteria established in the Design Manual and all subsequent revisions, and are approved by the administration. Practices used for redevelopment projects shall be approved by the City. 5. For the purposes of modifying the minimum control requirements or design criteria, the property owner shall submit to the City an analysis of the impacts of stormwater flows downstream in the watershed. The analysis shall include hydrologic and hydraulic calculations necessary to determine the impact of hydrograph timing modifications of the proposed development upon a dam, highway, structure, or natural point of restricted streamflow. The point of investigation is to be established with the concurrence of the city downstream of the first downstream tributary the drainage area of which equals or exceeds the contributing area to the project or stormwater management facility. C. Basic design criteria The basic design criteria, methodologies, and construction specifications, subject to the approval of the City, shall be those of the Design Manual. Section 21B-9. Stormwater management plans A. Review and approval of stormwater management plans 1. For any proposed development, the owner/developer shall submit phased stormwater management plans to the City for review and approval. At a minimum, plans shall be submitted for the concept, site development, and final stormwater management construction phases of project design. Each plan submittal shall include the minimum 17

18 content specified in Subsection b. of this Section and meet the requirements of the Design Manual and Section 21B-8 of this Chapter. 2. The City shall perform a comprehensive review of the stormwater management plans for each phase of site design. Coordinated comments will be provided for each plan phase that reflect input from all appropriate agencies including, but not limited to the district and the Departments of Planning and Public Works of the City. All comments from the City and other appropriate agencies shall be addressed and approval received at each phase of project design before subsequent submissions. B. Contents and submission of stormwater management plans: 1. 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 Subsection B. of Section 21B-8 of this Chapter and the Design Manual. Plans submitted for concept approval shall include, but are not limited to: (a) A map at a maximum scale of 1 = 100 scale showing site location, existing natural features, water and other sensitive resources, topography, existing water quality BMPs, 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 City. 2. Following concept plan approval by the City, the owner/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 18

19 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 City. 3. Following site development approval by the City, 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 ; 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. 4. 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; and (e) (f) A narrative that supports the final stormwater management design; Any other information required by the City. 5. Construction drawings submitted for final stormwater management plan approval shall include, but are not limited to: (a) A vicinity map; 19

20 (b) Existing and proposed topography and proposed drainage areas, including areas necessary to determine downstream analysis for proposed stormwater management facilities; (c) Any proposed improvements including location of buildings or other structures, impervious surfaces, storm drainage facilities, and all grading; The delineation, if applicable, of the 100-year floodplain and any onsite wetlands; (d) (e) (f) The location of existing and proposed structures and utilities; Any easements and rights-of-way; (g) Structural and construction details including representative cross sections for all components of the proposed drainage system or systems, and stormwater management facilities; (h) (i) (j) total impervious area; All necessary construction specifications; A sequence of construction; Data for total site area, disturbed area, new impervious area, and (k) A table showing the ESD and unified sizing criteria volumes required in the design manual; planting; (l) (m) (n) A table of materials to be used for stormwater management facility All soil boring logs and locations; An inspection and maintenance schedule; (o) Certification by the owner/developer that all stormwater management construction will be done according to this plan; (p) completion; and (q) An as-built certification signature block to be executed after project Any other information required by the city. 6. 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. C. Preparation of stormwater management plans 20

21 1. The design of stormwater management plans shall be prepared by any individual whose qualifications are acceptable to the City. The City 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. 2. If a stormwater bmp requires either a dam safety permit from the administration or small pond approval from the district, the City shall require that the design be prepared by a professional engineer. 3. An agreement approved by the department allowing use of any off-site stormwater management facility shall be executed between the developer and the owner of the off-site facility shall be recorded in the land records of Prince George's County. 4. Final stormwater management plan approval shall be valid for a period of twenty-four (24) consecutive months. If no work has been initiated within twenty-four (24) months of final plan approval, the plan shall be subject to an update review and re-approval. If construction has been initiated within twenty-four (24) months of plan approval but has not been completed, the property owner may request in writing, within thirty (30) days prior to the end of the initial approval period an extension of the approval for one additional twelve (12) month period. An additional extension of plan approval may be granted when such an extension of time is required by a substantial modification of the stormwater management plan, for such time period as the department deems necessary to accomplish the modifications or where an administrative waiver has been granted pursuant to Section 12B-3 of this Chapter. A concept plan approval shall expire at the time of expiration of a final plan approval. 5. Stormwater management plans that specify the design and construction of retention or detention structures and that are required by state law to have district approval and/or approval from the administration, dam safety division, must receive district and/or dam safety approval prior to receiving approval from the City. D. Plan modification when: 1. Modifications of the approved plans may be approved by the Department (a) Inspection has revealed the inadequacy of the plan to accomplish the stormwater management objectives of the plan. The cost for modification shall be borne by the permittee. Further development of the site shall be prohibited until the modifications are made. (b) The property owner determines that the approved plan cannot be effectively executed and proposes revisions to the plan that are consistent with the requirements of this chapter and the design manual, and department and, where required, the district approve the proposed revisions. 21

22 2. The Department may, in emergency situations and at its discretion, order repairs or modifications in order to protect watercourses, other properties or the general public from damage, to remain in effect until such modifications or revisions to the plan shall have been approved and implemented. Further development of the site shall be prohibited until the modifications are made. 3. Requests for modification shall be submitted to the department and, when applicable, the district, and shall be processed in the same manner as the original stormwater management plan. Section 21B-10. Permits. A. Upon approval by the Department and, where required, the district, of a stormwater management plan meeting the requirements of this Chapter, and subject to the requirements of this Section, the City shall issue a stormwater management permit. The permit shall not be issued unless the property owner has submitted to the City: 1. An application for a stormwater management permit. 2. For commercial, institutional, and industrial sites, recorded easements for the stormwater management facility and easements to provide adequate access for inspection and maintenance from a public right-of-way, unless a special tax district has been established pursuant to Chapter 23 of the City Code. 3. For residential projects, dedication of lands to the City for all quantitative control measures, with an agreement to provide clear fee simple title upon satisfactory completion of the facilities and for all qualitative control measures, either dedication to the city with an agreement to provide clear fee simple title upon satisfactory completion or recorded easements sufficient to provide unimpeded access to the facility for inspection and maintenance purposes, as determined by the City. 4. Where a stormwater management facility is constructed off-site, an easement or dedication of land to the city sufficient to provide unimpeded access to the facility for inspection and maintenance purposes, as determined by the City. 5. Where a stormwater management system includes property located in the one hundred (100) year floodplain, an easement or dedication of land sufficient to prevent grading or other construction activities from occurring therein. 6. A stormwater management maintenance agreement that complies with the requirements of Subsection b. of Section 21B-17 of this Chapter, which agreement may be recorded by the City. 7. Performance and payment bonds as required by Section 21B-13 of this Chapter. 22