(A) SWM concept plan. The SWM concept plan shall be prepared prior to the submittal of a subdivision plan, zoning site plan, MXD Phase II plan, or PUD Phase II plan. The SWM concept plan may be submitted prior to or concurrently with a subdivision, zoning site plan, MXD Phase II plan, or PUD Phase II plan. The SWM concept plan shall contain sufficient information for an initial assessment of the proposed development and whether stormwater management can be provided in accordance with this chapter and the Design Manual. Plans submitted for SWM concept plan approval shall include:
(1) A map at a scale not smaller than 1" = 100 feet showing site location, existing natural features, water and other sensitive resources, topography, and natural drainage patterns;
(2) The anticipated location of all proposed impervious areas, buildings, roadways, parking, sidewalks, utilities, and other site improvements;
(3) The location of the proposed limit of disturbance, erodible soils, steep slopes, and areas to be protected during construction;
(4) 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;
(5) A narrative that supports the concept design and describes how ESD will be implemented to the MEP; and
(6) Any other information requested by the Division.
(B) SWM development plan. After the SWM concept plan has been approved, the developer shall submit a SWM development plan consistent with the approved SWM concept plan and all conditions of approval, and any written waiver or variance request. The SWM development plan may be submitted concurrently with or after the submission of a zoning site plan or preliminary subdivision plan application, or MXD Phase II plan or PUD Phase II plan. SWM development plans shall include:
(1) All details developed during the SWM concept plan review phase;
(2) Final site layout, impervious area locations and acreages, proposed topography, delineated drainage areas at all points of discharge from the site, proposed hydrologic analysis for runoff rates, storage volumes, and discharge velocities, individual ESD locations and sizing computations for ESD practices, locations and sizing computations for structural BMPs, and discharge calculations demonstrating safe conveyance off-site;
(3) Adequate information to determine the level of control required for the 10-year and 100-year frequency storm events;
(4) For waiver or variance requests under this chapter, the developer shall submit an analysis of the cumulative 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 Division, downstream of the first downstream tributary whose drainage area equals or exceeds the contributing area to the development or stormwater management facility.
(5) 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;
(6) A narrative that supports the SWM development design, describes how ESD will be used to meet the minimum control requirements, and justifies any proposed structural BMP; and
(7) Any other information required by the Division.
(C) Final SWM plans. After the SWM development plan has been approved, the developer shall submit final erosion and sediment control plans (in accordance with COMAR 26.17.01.05.) and final SWM plans that are consistent with the approved SWM development plan and all conditions of approval. Final SWM plans shall be submitted as a part of the improvement plans for the subdivision or development.
(1) Final SWM plans shall include:
(a) A vicinity map, at a scale not to exceed 1" = 2000';
(b) Existing and proposed topography (including source and date) and proposed drainage areas, including areas necessary to determine downstream analysis for safe conveyance and proposed stormwater management facilities;
(c) Any proposed improvements including location of buildings or other structures, impervious surfaces, storm drainage facilities, and all grading;
(d) The location of existing and proposed structures and utilities;
(e) All existing and proposed easements and rights-of-way, including recording references where applicable;
(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 construction;
(m) All soil boring logs and locations;
(n) An inspection and maintenance schedule;
(o) Certification by the developer that all stormwater management construction will be done according to this plan;
(p) An as-built certification signature block to be executed after development completion; and
(q) Any other information requested by the Division.
(2) The final SWM plan shall also include a report that includes:
(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 BMP measures to be used;
(e) A narrative that supports the final stormwater management design; and
(f) Any other information requested by the Division.
(D) If a stormwater management plan involves direction of some or all runoff off of the site, it is the responsibility of the developer, in accordance with state law, 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.
(Ord. 10-09-544, 5-20-2010; Ord. 14-23-678, 11-13-2014)