A. Stormwater management plan required for all developments. No application for development will be approved unless it includes a stormwater management plan detailing in concept how runoff and associated water quality impacts resulting from the development will be controlled or managed. A licensed professional engineer or a licensed landscape architect must prepare this plan. The plan must indicate whether stormwater will be managed on-site or off-site and, if on-site, the general location and type of management practices. The applicant must address any comments or issues raised by the city or state government in the final stormwater management plan. This final plan must be signed by a licensed professional engineer (PE), who will verify that the design of all stormwater management practices meet the requirements outlined in the stormwater design manual. No building, grading, or sediment control permits shall be issued until a satisfactory final stormwater management plan, or waivers thereof, have been approved by the Engineering Department.
B. Stormwater management concept plan requirements. A stormwater management concept plan shall be required with all permit applications and will include sufficient information (such as maps and/or hydrologic calculations) to evaluate the environmental characteristics of the project site. Other items that will be reviewed are the potential present and future impacts of the proposed development on the water resources affected by such development and the effectiveness of the proposed measures to manage the stormwater runoff from the project site. The intent of this conceptual planning process is to determine the type of stormwater management measures necessary for the proposed project, and ensure adequate planning for management of stormwater runoff from the proposed development. To accomplish this goal the following information shall be included in the concept plan:
1. A map (or maps) indicating the location of existing and proposed buildings, roads, parking areas, utilities, structural stormwater management and sediment control facilities. The map(s) will also clearly show proposed land use with tabulation of the percentage of surface area for various uses; drainage patterns; locations of utilities, roads and easements; the limits of clearing and grading.
2. Sufficient engineering analysis to show that the proposed stormwater management measures are capable of controlling runoff from the site in compliance with this chapter and the specifications of the stormwater design manual.
3. A written or graphic inventory of the waterways natural resources (i.e. rivers, streams, lakes) at the site and surrounding area as it exists prior to the commencement of the project, a description of the watershed and its relation to the project site. This description should include a discussion of soil conditions, forest cover, topography, wetlands, and other native vegetative areas on the site. Particular attention should be paid to environmentally sensitive features (i.e. fishery, wetlands) that provide particular opportunities or constraints for development.
4. A written description of the required maintenance for any proposed BMP.
For development or redevelopment occurring on a previously developed site, an applicant shall be required to include within the stormwater concept plan measures for controlling existing stormwater runoff discharges from the site in accordance with the standards of this chapter to the maximum extent practicable.
C. Final stormwater management plan requirements. After review of the stormwater management concept plan and modifications to that plan as deemed necessary by the engineering department, a final stormwater management plan must be submitted for approval. The final stormwater management plan, in addition to the information from the concept plan, shall include all of the information required in the stormwater design manual. This includes:
1. Contact information. The name, address, and telephone number of all persons having a legal interest in the property and the tax reference number and parcel number of the property or properties affected.
2. Topographic Base Map. A one inch = two hundred feet topographic base map of the site. The map must extend a minimum of two thousand, five hundred feet beyond the limits of the proposed development and indicate existing surface water drainage including streams, ponds, culverts, ditches, and wetlands; current land use including all existing structures; locations of utilities, roads, and easements; and significant natural and manmade features not otherwise shown.
3. Calculations. Hydrologic and hydraulic design calculations for the pre-development and post-development conditions for the design storms specified in this chapter. Calculations shall include:
a. Description of the design storm frequency, intensity and duration,
b. Time of concentration,
c. Soil Curve Numbers or runoff coefficients,
d. Peak runoff rates and total runoff volumes for each watershed area,
e. Infiltration rates, where applicable,
f. Culvert capacities,
g. Flow velocities,
h. Data on the increase in rate and volume of runoff for the design storms referenced in the Stormwater Design Manual, and
i. Documentation of sources for all computation methods and field test results.
4. Soils information. If the proposed control measure depends on the hydrologic properties of soils (for example, infiltration basins), then a soils report shall be submitted. The soils report shall be based on on-site boring logs or soil pit profiles. The number and location of the required soil borings or soil sits shall be determined based on the information needed to determine the suitability and distribution of the soil types present at the location of the control measure.
5. BMP O & M manual maintenance and repair plan. The design and planning of all stormwater management facilities shall include detailed maintenance and repair procedures to ensure their continued functionality as included in both the design engineers plans and/or the manufactures recommendations. These plans will identify the parts or components of a stormwater management facility that need to be maintained and the equipment and skills or training necessary. Provisions for the periodic review and evaluation of the effectiveness of the maintenance program and the need for revisions or additional maintenance procedures shall be included in the plan.
6. Landscaping plan. The applicant must present a detailed plan for management of vegetation at the site after construction is finished, including who will be responsible for the maintenance of vegetation at the site and what practices will be employed to ensure that adequate vegetative cover is adequately preserved. A registered landscape architect must prepare this plan.
7. Maintenance easements. The applicant must ensure access to all stormwater management practices at the site for the purpose of inspection and repair by securing all the maintenance easements needed on a permanent basis. These easements shall be recorded with the plan and shall be listed on the deed or plat to the property.
8. Maintenance agreement. The applicant must execute an easement and, an inspection and maintenance agreement binding on all subsequent owners of the land(s) served by an on-site stormwater management measure in accordance with the specifications of this chapter.
9. Erosion and sediment control plans for construction of stormwater management practices. The applicant must prepare an erosion and sediment control plan for all construction activities related to implementing any on-site stormwater management practices.
(Ord. 08-29, 2008)