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HomeMy Public PortalAboutResolution 07-97 Amending 6-97A Relating to Storm water Best ManagementRESOLUTION NO.7-97, AMENDING RESOLUTION NO. 6-97A Resolution No. 6-97A is amended to read as follows: A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF McCALL, IDAHO, RELATING TO THE APPROVAL OF THE USE BY THE CITY ENGINEER OF THE HANDBOOK OF VALLEY COUNTY STORMWATER BEST MANAGEMENT PRACTICES. WHEREAS: 1. The Council previously adopted Ordinance 712 as an amendment to Title 3 of the McCall City Code authorizing the City Engineer to consult concerning and to enforce best management practices with respect to storm and meltwater drainage; and 2. The joint consultative process among interested parties, including both Valley County and the City of McCall has resulted in the drafting of the Handbook of Valley County Stormwater Best Management Practices; and 3. It appears that Valley County and the State Division of Environmental Quality have approved the use of such Handbook; 4. It appears that in deference to the jurisdiction of Council the Commissioners did not adopt certain pages of such Handbook which relate to the planning jurisdiction of the City of McCall, BE IT RESOLVED by the Mayor and Council of the City of McCall that: Section 1. The Handbook of Valley County Stormwater Best Management Practices and the attached McCall Supplemental Stormwater Management Policy are approved for the use of the City Engineer in the administration of Titles 2 and 3 of the McCall City Code respecting drainage concerns arising in connection with those Titles. Section 2. Council requests Valley County to include this Supplemental Policy in the copies of the Handbook distributed by it, inserted in correct numerical position, and Council will advise Valley County of any changes made in accord with paragraph 3 below. Section 3. In the event that such Handbook or Supplemental Policy, or either of them, is ever revised in accord with its terms, such revision(s) shall be returned to Council for similar approval. Passed and approved August 14, 1997. William M. Killen, Mayor ATTEST: ames H. Henderson, City Clerk RESOLUTION NO. -97 A. A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF McCALL, IDAHO, RELATING TO THE APPROVAL OF THE USE BY THE CITY ENGINEER OF THE HANDBOOK OF VALLEY COUNTY STORMWATER BEST MANAGEMENT PRACTICES. WHEREAS: 1. The Council previously adopted Ordinance 712 as an amendment to Title 3 of the McCall City Code authorizing the City Engineer to consult concerning and to enforce best management practices with respect to storm and meltwater drainage; and 2. The joint consultative process among interested parties, including both Valley County and the City of McCa11 has resulted in the drafting of the Handbook of Valley County Stormwater Best Management Practices; and 3. It appears that Valley County and the State Division of Environmental Quality have approved the use of such Handbook; BE IT RESOLVED by the Mayor and Council of the City of McCall that: Section 1. The Handbook of Valley County Stormwater Best Management Practices. is approved for the use of the City Engineer in the administration of Titles 2 and 3 of the McCa11 City Code respecting drainage concerns arising in connection with those Titles. Section 2. In the event that such Handbook is ever revised in accord with its terms, such revision(s) shall be returned to Council for similar approval. Passed and approved June 26, 1997. William M. Killen, Mayor A1'1'J ST: ames H. Henderson, City Clerk 3.4 Policy as Adopted by the City of McCall Increased land development within the City of McCall and the City of McCall impact area has given rise to a concern for proper stormwater management. Development of rural lands often results in increased velocity and volume of stormwater runoff and erosion within the drainage basin. Land development generally increases the area of impervious surfaces (such as roads, sidewalks, parking lots and roof tops) within a drainage basin. Increased impervious surfaces within a basin cause reduced infiltration and decreased travel time which combine to significantly increase peak discharge and total runoff volumes. Both the quantity and quality of stormwater generated by urban development must be addressed. Without regulation, as urban areas develop, natural drainages often are constricted and sometimes eliminated. Stormwater management practices in McCall must accomplish two major goals: (1) Maintain or reduce present off -site discharge rates to the extent possible through control of runoff from an improved site. (2) Reduce pollutant loads associated with stormwater discharges to Payette Lake and the Payette River to the extent possible through use of Best Management Practices (see Chapter 4 and Chapter 5). This policy section has been prepared to provide consistent guidance to meet the goal of the minimizing developmental impacts on the surrounding environment and to control stormwater runoff. The City of McCall recognizes that special circumstances may arise which warrant the consideration of alternatives not specifically identified in this Handbook. The City of McCall reserves the right to impose, or entertain from an applicant, alternative means, measures or technologies that may be more appropriate for the accomplishment of the goal. The City of McCall's decision in such matters is final. Storm Drainage System McCall's storm drainage system consists mainly of unimproved borrow ditches with culverts at roadway crossings. There is a limited sub -surface storm drain system located in the downtown area (2nd Street area). Stormwater runoff from impervious areas typically enters the borrow ditches, where runoff either percolates into the ground, evaporates or flows down borrow ditches to discharge points at natural drainages. The natural drainages transport the water to either Payette Lake or the Payette River with the only means of treatment being the natural processes of biofiltration, percolation and evaporation occurring between the point of impact and point of discharge. Infiltration is limited to certain higher elevation areas and only during approximately four months out of the year. The lack of infiltration in the McCall area is due to high groundwater, frozen soils, and heavy snow. Compounding this problem even further, is the fact that the primary runoff events occur when rain falls on snow in the spring when the ground is still frozen. It is imperative that storm drainage conveyance and detention facilities be designed to address the circumstances described in the previous paragraph. The guidelines specified in this document are conservative in that they disregard infiltration in the calculations to estimate peak runoff. This is accomplished by applying conservatism to the factors that will effect infiltration in the determination of peak runoff estimates. Methods for estimating peak runoff are discussed in detail in Appendix D-2. On -site area topography must be evaluated by topography mapping (available either from the City of McCall Community Development Department, or a field generated topography map) with contour intervals of 2 feet or less. Stormwater Planning & BMP Requirements Any individual or group wishing to perform development on property within the City of McCall or the City of McCall impact area, which involves land disturbance are required to submit a Stormwater Application (page 3-9) and a Stormwater Management Plan which satisfies the requirements described in Section 3.1 entitled: Stormwater Management Plan Checklist. Table 3.4-1 list automatic exemptions to requirements in this policy section. The information required to be submitted varies depending on the size of the project site and/or the amount of land to be disturbed during the improvement(s) (Table 3.4-2). The following is a description of the BMP's required for various sizes of land development projects: • Projects with less than 2 acres of total site area or less than 5,000 square feet of proposed impervious surface will be required to submit to the City Engineer for review and comment, a Stormwater Management Plan which addresses: Section A - Basin Characteristics, Section B - Erosion and Sediment Control and Section F - Operation and Maintenance Plan, of the Stormwater Management Plan Checklist (Section 3.1). • Projects with 2 to 5 acres of total site area or from 5,000 to 15,000 square feet of impervious surface proposed will be required to submit, a Stormwater Management Plan prepared by a Professional Engineer licensed in the State of Idaho. Projects which fall under this category are required to address: Section A - Basin Characteristics; Section B - Erosion and Sediment Control; Section C - Conveyance System; Section D - First Flush Storm Treatment; and Section F - Operation and Maintenance Plan, of the Stormwater Management Plan Checklist (Section 3.1). • Projects with greater than 5 acres of total site area or greater than 15,000 square feet of proposed impervious surface will be required to submit, a Stormwater Management Report prepared by a Professional Engineer licensed in the State of Idaho. This Report will be required to address all sections of the Stormwater Management Plan Checklist (Section 3.1). Development which will cause discharge directly to a surface water body and containing greater than five acres of disturbed area or is from an industrial use (listed in Appendix A) may be covered under the National Pollution Discharge Elimination System (NPDES) permit. To receive more information on completing or applying for a NPDES permit contact the United States Environmental Protection Agency, Region Ten Stormwater Division. A copy of the permit, when required, shall be submitted to the City Engineer. A Storm Water Management Report, composed of the following information, must be submitted to the McCall City Engineer for review: 1. One copy of a signed Stormwater Application (page 3-9). 2. Three copies of the Stormwater Management Plan (based on section 3.1). 3. The engineer shall submit to the City Engineer, nomagraphs, tables, charts or calculations used to size pipes, inlets ditches or swales for runoff, Q, as determined from the Rational Method. It is strongly recommended that a preliminary submittal be made to the City Engineer for review of concepts and to determine general compliance with the City's requirements. Note: Land improvement activities which: involve the installation of new stormwater conveyance pipes or ditches; involve the alteration of existing stormwater conveyance systems; or will significantly alter existing drainage patterns will be required to address Section C - Conveyance System, of the Stormwater Management Plan Checklist in addition to the sections specified for the project based on site area or proposed impervious surface. feet STORMWATER APPLICATION City of McCALL Fill in all information. Submit one copy of signed application and three copies of Stormwater Management Plan to the City Engineer. 1. Project Name: Location: 2. Owner's Name: Street: City: State: Zip Code: Phone: 3. Project Description: a. Total property area, in acres. b. Proposed impervious surface (asphalt, rooftop, concrete sidewalk, etc.) in square c. Describe existing vegetation present on site. d. Start date of construction. e. Estimated length of time to complete improvements. 4. Three Stormwater Management Plans attached? Yes No 5. Circle the sections of the Stormwater Management Plan Checklist (section 3.1) which are applicable to project. A BCDEF 6. Party responsible for operation and maintenance of project, including maintenance of temporary and permanent Best Management Practices: Name Date Title Signature Address Daytime Phone After Hours Phone Do not write below this line. The submitted Stormwater Management Report (Stormwater Application and Stormwater Management Plan) is: Approved: Not Approved: Approved, with conditions: By The City of McCALL Representative Signature Title Date Table 3.4-1. Exemptions: The following activities are automatically exempt from the permit requirements of this Ordinance. (1) Activities that constitute normal and accepted farming activities. (2) Routine maintenance of existing public roads, private roads, driveways, trails where work is limited to the travelway and no cut or fill slopes are created and no drainage features are created or modified. (3) Road construction which proceeds in compliance with an is restricted by the Idaho Forest Practice Act, Chapter 13, Idaho Code. (4) Logging road construction and routine maintenance, and logging activity under a valid Forest Practice Act Notification. (5) Stream channel alterations which proceed under the terms of a permit issued by Idaho Department of Water Resources pursuant to Title 42, Chapter 38, Idaho Code, provided (6) Cemetery graves. (7) Drilling of wells under the terms of a permit issued by the Department of Water (8) In any 12-month period, an excavation of less than 50 cubic yards of loose material which: a) is less than two feet in depth; or b) which does not create a slope greater than (9) In any 12-month period, a fill less than one foot in depth placed on natural terrain with a slope flatter than five horizontal to one vertical (5:1), or a fill less than three feet in depth and not intended to support roadways, driveways, or structures, which does not exceed 50 cubic yards on any one lot and does not obstruct a stream, drainage course, or surface waters. In no case shall this exemption be combined with item 8 of this Section in a manner which would result in a cut and fill exceeding 50 cubic yards of (10) Installation, repair, replacement, or maintenance of septic system provided septic p permit requirements for BMPs are implemented. (11) Work related directly to vegetable and flower gardens, orchards, lawns, or similar (12) Land clearing and similar activities which occur as part of an emergency situation involving wild fire, danger to life or property, substantial fire hazards, or other public safety hazards as determined by the County, or during the period covered by an (13) Site projects that disturb an area that is less than 500 square feet. (14) Excavation of test holes for soil testing activities that are completed within a seven day time frame; provided that no access roads will be created for test hole excavation and that the total excavation is less than 50 cubic yards. Table 3.4-2. The following information further describes, in chart form, the requirements for submittals. Requirement Application Plan addressing Sections A, B and C of the Stormwater Management Plan Checklist Plan addressing Sections A, B, C, D and F of the Stormwater Management Plan Checklist Plan addressing Sections A, B, C, D, E, and F of the Stormwater Management Plan Checklist Temporary BMP's Permanent BMP's Detention of 1st flush storm(2 year design storm frequency) Detention of increased runoff caused by project Plan addressing Section C of the Stormwater Management Plan Checklist in addition to sections required for project based on size Total Area All All 2 to 5 acres greater than 5 acres All greater than 5 acres 2 acres and greater greater than 5 acres Proposed impervious surface All All 5,000 to 15,000 s.f. greater than 15,000 s.f. to infinity All greater than 15,000 s f 5,000 s.f. and greater 15,000 s.f. and greater Any land improvement project which involves the installation or modification of a storm water conveyance (pipe or ditch) METHODS USED FOR HYDROLOGICAL ANALYSIS Many hydrologic methods are available for the estimation of pre- and post -development runoff. These guidelines identify acceptable methods which provide a level of uniformity for storm drainage practices within McCall and assist the City Engineer in review of report submittals. The two methods available under these guidelines are the Rational Method and a simplified SCS Runoff Curve Number Method. Descriptions of both methods with examples of their use for a typical land development project are contained in Appendix D-2. Table 3.4-3 defmes the minimum required design storm frequency that must be used in the design of conveyance systems. Table 3.4-4 defmes the minimum required design storm frequency that must be used in the design of detention systems. TABLE 3.4-3. Minimum design storm frequency for conveyance systems. Stormwater conveyance systems shall be designed using the ten year design storm frequency, with the following exceptions: Land Use Zone Design Storm Frequency Any drainage crossing a roadway 25 Slopes in excess of 12% 25 Major structures, such as bridges 100 Where an existing, primary storm conveyance runs through a property (a primary storm conveyance is defined as a channel, ditch, or pipe with a drainage area 10 acres or larger). 100 Where an existing, secondary storm conveyance runs through a property (a secondary storm conveyance is defined as a channel, ditch or pipe with a drainage area from 3 to 10 acres) 25 Note: The minimum pipe size that will be accepted by the City of McCall for new conveyances will be 15" TABLE 3.4-4. Minimum design storm frequency for detention systems. All land improvement activities which contain from 2 to 5 acres of total site area or from 5,000 to 15,000 s.f. of proposed impervious surface must detain the 2 year design storm All land improvement activities which on -site, the increase contain greater than 5 acres of total is estimated will be site area or greater than 15,000 s.f. the proposed project of proposed impervious surface must detain, in runoff that caused by for the ten year storm Note: Emergency spillways must be designed for the 100 year design storm. For design information, specifications, and details refer to Chapter 5.