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40.380.060 Submittal Requirements for Stormwater, Erosion Control and Development Plans
A. General.
1. All applicants proposing development activities and redevelopment governed by this chapter shall submit the plans, studies, and information as provided herein.
2. Signatures. All plans, studies, and reports shall be stamped, signed and dated by the professional civil engineer(s), registered in the state of Washington, and registered soil scientist, if appropriate, responsible for their preparation, and by the project engineer responsible for preparation of the preliminary stormwater plan.
B. Abbreviated Preliminary Stormwater Plan Submittals. An abbreviated preliminary stormwater plan is allowed for certain projects specified in Section 40.380.030. All maps shall contain a scale and north arrow. Ensuring the accuracy of all the information is the applicant’s responsibility. Abbreviated preliminary stormwater plan submittals shall include:
1. Vicinity Maps. All vicinity maps shall clearly show the site of the development activity or drainage project.
2. Site Location Map. Minimum USGS (one to twenty-four thousand (1:24,000)) quadrangle topographic map showing natural and manmade drainage features adjacent to site including existing and proposed (if known) stormwater facilities.
3. Other Maps. The following additional vicinity maps shall be required in the situations noted below:
a. Floodplains. If a floodplain mapped by FEMA exists on or adjacent to the site;
b. Shoreline Management Area. If the site contains or is adjacent to a stream or lake regulated under the Washington Shorelines Management Act.
4. A preliminary development plan meeting the requirements of Section 40.380.060(F), additional site and vicinity information.
a. If wetlands exist on the site and will be impacted by the proposal, a wetland delineation report (Section 40.450.030(D)(4)) may be required.
b. If unstable or complex soil conditions exist which may significantly impact the design of the stormwater facilities, the responsible official may require a preliminary soils report to be completed that addresses stormwater design considerations arising from soil conditions.
c. The responsible official may require additional site or vicinity information if needed to determine the feasibility of the stormwater proposal.
5. Preliminary Stormwater Design Report. A written narrative shall be required to accompany the preliminary stormwater plan. The narrative shall describe the methods for meeting the requirements of this chapter and include the following information:
a. Listing of approximate volumes of runoff storage required;
b. Listing of tested percolation rates at sites to be used for infiltration, if required;
c. Listing of proposed BMPs which will meet the treatment requirements of this chapter and are appropriate for the site;
d. Description of the approximate size and location of stormwater facilities on the site;
e. Discussion of who will maintain the facility(ies) after completion and proposed method of funding if the facility(ies) will be privately maintained; and
f. Listing of additional permits (e.g., wetland, floodplain, and shoreline management permits) that may be required in connection with the stormwater facilities.
C. Preliminary Stormwater Plan Submittals.
1. Purpose. The purpose of this plan is to determine whether a proposal can meet the requirements set forth in Chapter 40.380. The preliminary stormwater plan shall identify how stormwater runoff originating on the site or flowing through the site is presently controlled and how this will change due to the proposed development activity, redevelopment, or drainage project. If the site is within the region covered by a basin plan pursuant to this chapter, then the information needed in the preliminary plan is reduced. All maps shall contain a scale and north arrow.
2. Types of Development Activity and Redevelopment. A preliminary stormwater plan is required for all development activities not exempted by Section 40.380.020 and Section 40.380.030 and the following activities:
a. Short plats;
b. Subdivisions;
c. Site plan reviews;
d. Planned unit developments;
e. Conditional uses meeting the applicability requirements of Section 40.380.020; and
f. Master plan developments;
g. Timing.
h. A preliminary stormwater plan shall be submitted with the land use application.
(1) A land use application shall be considered “fully complete” from the standpoint of stormwater information when a preliminary stormwater plan meeting the submittal requirements of this section is provided;
(2) To ensure adequate public review and avoid multiple reviews of preliminary plans by county staff, the preliminary stormwater plan shall not be significantly modified after public notice of the final SEPA determination without issuance of a new SEPA determination;
i. Contents. The preliminary stormwater plan submittal shall be prepared in the standardized format described below. The purpose of this standardized format is to promote a quick and efficient review of required information. The project engineer shall include a statement that all information required by this section is included in the preliminary stormwater plan and that the proposed stormwater facilities are feasible. All maps shall contain a scale and north arrow. Ensuring the accuracy of all the information is the applicant’s responsibility.
(1) Vicinity Maps. All vicinity maps shall clearly show the site of the development activity, redevelopment, or drainage project;
(2) Site Location Map. Minimum USGS (one to twenty-four thousand (1:24,000)) quadrangle topographic map showing (and labeling where appropriate):
(a) Contributing drainage areas and acreage both on-site and off-site, and
(b) Natural and manmade drainage features adjacent to the site including existing and proposed (if known) stormwater facilities.
(3) Soils Map.
(a) The soils map shall show soils within the contributing area draining to the site and the site itself. Copies of Clark County soil survey maps may be used; however, if the maps do not appear to accurately represent the soils for a site, the applicant is responsible for verifying the actual soil types existing on a site,
(b) Where unstable or complex soil conditions exist which may significantly impact the design of stormwater facilities, the responsible official may require a preliminary soils report to be completed that addresses stormwater design considerations arising from soil conditions. The preliminary soils report shall be prepared by a registered professional engineer proficient in geotechnical investigation and engineering, or a registered soil scientist. The preliminary soils report shall include a soils map, developed using the criteria set in the USDA, SCS National Soils Handbook and USDA, SCS Title 430 Soil Survey Manual at a minimum scale of one to five thousand (1:5,000) (12.7 in/mi.);
(4) Other Maps. The following additional vicinity maps shall be required in the situations noted below:
(a) Conveyance System. If a surface water discharge of stormwater is proposed from the site, a map showing the conveyance system downstream to a point where the stormwater enters a stream, wetland, or other natural water body shall be required,
(b) Wellhead Protection. If the site lies within the ten (10) year “zone of contribution” of a public water supply well, maps showing all the zones of contribution that overlap the site are required,
(c) Floodplains. If a floodplain mapped by FEMA exists on or adjacent to the site, a map showing the floodplain is required,
(d) Shoreline Management Area. If the site contains or is adjacent to a stream or lake regulated under the Washington Shorelines Management Act, a map showing the boundary of the shoreline management area in relation to the site is required;
(5) A preliminary development plan meeting the requirements of Section 40.380.060(F);
(6) Preliminary Stormwater Design Report. A written narrative shall be required to accompany the preliminary stormwater plan. The narrative shall describe the methods for meeting the requirements of this section and include the following information:
(a) Description of on-site hydrologic soil groups and their suitability for the proposed design and verification of soil conditions through field reconnaissance (to the maximum extent practicable),
(b) Identification of the approximate amount of new impervious surface contemplated for the proposal,
(c) Identification of where runoff characteristics will be altered, e.g., where runoff curve numbers will be revised by the proposed development,
(d) Discussion of how on-site conveyance system design will provide for ultimate build-out of the upstream area based on the maximum density achievable under the comprehensive plan, if applicable,
(e) Listing of approximate volumes of runoff storage required,
(f) Listing of tested percolation rates at sites to be used for infiltration, if required,
(g) Listing of proposed BMPs which will meet the treatment requirements of this chapter and are appropriate for the site,
(h) Description of the approximate size and location of stormwater facilities on the site,
(i) For agricultural sites with drain tiles, a discussion of the impact of construction on the drain tiles and site drainage and the impact of the drainage tiles on proposed stormwater facilities,
(j) Discussion of who will maintain the facility(ies) after completion and the proposed method of funding for maintenance, if the facility(ies) will be privately maintained, and
(k) Listing of additional permits (e.g., wetland, floodplain, and shoreline management permits) that may be required in connection with the stormwater facilities;
j. Modification of Content Requirements. The responsible official may waive in writing some or all of the content requirements in the preliminary stormwater plan if:
(1) The development activity or drainage project is included in an approved final stormwater plan which meets the requirements of this chapter; or
(2) A basin plan exists that makes some of the information irrelevant.
The waiver of some or all of the preliminary stormwater control plan does not relieve the applicant of a final stormwater control plan;
k. Review and Approval. For proposals connected with a land use application requiring a public hearing, the preliminary stormwater plan shall be heard and decided in accordance with the procedures applicable to the land use application. All other preliminary stormwater plans shall be acted on by the responsible official concurrent with the timeline for the preliminary land use decision;
l. Appeals. Preliminary stormwater plan decisions may be appealed in conjunction with the associated land use application.
(Amended: Ord. 2006-11-07)
D. Final Stormwater Plan Submittals.
1. Purpose. The final stormwater plan provides final engineering design and construction drawings for the stormwater aspects of a proposed development activity, redevelopment, or drainage project.
2. Timing. The final stormwater plan is required and must be approved by the responsible official prior to beginning construction related to a development activity, redevelopment, or drainage project.
3. Contents. The final stormwater plan shall include the following:
a. An engineer’s estimate of the cost for surveying and engineering to complete the record drawing(s) is required prior to site plan approval;
b. An escrow, letter of credit, cashier’s check, or other acceptable form of guarantee is required from the applicant or applicant’s representative for one hundred ten percent (110%) of the engineer’s estimate identified in Section 40.380.060(D)(1). Bonds are not acceptable instruments;
c. Any easements, covenants or agreements that are necessary to permit construction must be included;
d. The approved preliminary stormwater plan with an explanation of any differences between the design concepts included in the preliminary stormwater plan and the final engineering plans. A final stormwater plan which differs from the approved preliminary stormwater plan in a manner that, in the opinion of the responsible official, raises material water quality or quantity control issues, shall, if subject to SEPA, require another SEPA determination, and a post-decision review in accordance with Section 40.520.060;
e. Final engineering plans that provide sufficient detail to allow construction of the stormwater facilities. These plans shall be stamped, signed and dated by the engineer(s) registered in the state of Washington, responsible for hydrologic, hydraulic, geotechnical, structural and general civil engineering design and by the project engineer responsible for the preparation of the final stormwater plan. Additionally, the final engineering plan shall show all utilities to ensure conflicts between proposed utility lines do not exist;
f. The off-site analysis required under Section 40.380.040(B)(2);
g. A final development plan meeting the requirements of Section 40.380.060(F); and
h. A technical information report.
4. Technical Information Report (TIR). The TIR shall be a comprehensive report, supplemental to the final engineering plans, containing all technical information and analysis necessary to complete final water quality and quantity engineering plans based on sound engineering practices and appropriate geotechnical, hydrologic, hydraulic and water quality design. The TIR shall be stamped, signed and dated by the professional engineer(s), registered in the state of Washington, responsible for hydrologic, hydraulic, geotechnical, structural and general civil engineering design. The level of detail in the TIR is dependent on the complexity and size of the development activity. The TIR, which is part of the final stormwater plan, shall contain the following information:
a. Table of Contents.
(1) List section headings and their respective page numbers,
(2) List of tables with page numbers,
(3) List of figures with page numbers,
(4) List of attachments, numbered,
(5) List of references;
b. Site Location Map. The site location map (minimum USGS one to twenty-four thousand (1:24,000) quadrangle topographic map) shall be as required for the preliminary stormwater plan, updated to reflect additional data or revisions to concepts established in preliminary stormwater plan;
c. Soils Map. A soils map as required for the preliminary stormwater plan;
d. Section A – Project Overview.
(1) Identify and discuss existing stormwater system functions,
(2) Identify and discuss site parameters influencing stormwater system design,
(3) Describe drainage to and from adjacent properties, and
(4) Generally describe proposed site construction, size of improvements, and proposed methods of mitigating stormwater runoff quantity and quality impacts;
e. Section B – Approval Conditions Summary. List each preliminary approval condition related to stormwater control, wetlands, floodplains, and other water-related issues and explain how design addresses or conforms to each condition;
f. Section C – Quantity Control Analysis and Design.
(1) Hydrologic analysis, existing and developed conditions.
(a) Identify criteria used in completing analyses and their sources,
(b) Identify and discuss any assumptions made in completing analysis,
(c) Tabulate acreage; imperviousness; curve number; length and grade of overland, pipe and channel flow; and other hydrologic parameters used in completing analyses,
(d) Complete detailed hydrologic analysis for existing and developed site conditions in accordance with the requirements of Section 40.380.030(B). Compute existing and developed peak flows and volumes for the design storms for all sub-basins. Refer to labeled points shown on the site location map and development plan,
(e) Include and reference all hydrologic and hydraulic computations in the technical appendix, and
(f) Include all maps, exhibits, graphics and references used to determine existing and developed site hydrology,
(2) Quantity Control System Design.
(a) Reference conceptual design proposed in the preliminary stormwater plan,
(b) Identify revisions to conceptual design contained within the final engineering plans,
(c) Identify and discuss geotechnical or pedological study or information used in completing analysis and design,
(d) Identify criteria used in completing analyses and their sources,
(e) Identify initial conditions including stream base flows, beginning water surface elevations, hydraulic or energy grade lines, initial groundwater elevation, beginning storage volumes, and other data or assumptions used to determine initial conditions in order to complete analyses, referencing sources of information,
(f) Identify and discuss any assumptions used in completing analysis,
(g) Complete detailed hydrologic/hydraulic analysis of all on-site stormwater control facilities impacted by the proposal, in accordance with the requirements of Section 40.380.040(C). Compute inflow and outflow hydrographs and peakflows and storage volumes. Reference conveyance and stormwater control facilities to labeled points shown on the development plan,
(h) Tabulate existing and proposed peak flows and storage volumes,
(i) Include and reference all hydrologic and hydraulic computations, equations, rating curves, stage/storage/discharge tables, graphs and any other aids necessary to clearly show methodology and results in the technical appendix,
(j) Summarize results of quantity control system analyses and describe how the proposed design meets the requirements of this chapter, and
(k) Include all maps, exhibits, graphics and references used to complete quantity control system analysis and design;
(3) Quantity Control System Plan.
(a) Provide illustrative sketch of quantity control facility and its appurtenances,
(b) Show basic measurements necessary to confirm storage volumes,
(c) Show all orifice, weir and flow restrictor dimensions and elevations,
(d) Tabulate peak flow rates, storage volumes and ponding elevations for all design storms,
(e) Sketch shall correspond with final engineering plans. Alternatively, final site grading plan incorporating the above information may be included as an attachment to the final stormwater plan;
g. Section D – Conveyance Systems Analysis and Design.
(1) Reference conceptual drainage design proposed in the preliminary stormwater plan,
(2) Identify revisions to conceptual drainage design contained within the final stormwater plan,
(3) Identify criteria used in completing analyses and their sources,
(4) Identify and discuss initial conditions including stream base flows, beginning water surface elevations, hydraulic or energy grade lines, beginning storage elevations, and other data or assumptions used to determine initial conditions in order to complete analyses. Reference sources of information,
(5) Identify and discuss assumptions used in completing analyses,
(6) Complete detailed hydraulic analysis of all proposed collection and conveyance system elements and existing collection and conveyance elements influencing the design or impacted by the proposal, including outfall structures and outlet protection, in accordance with Section 40.380.040(C). Compute and tabulate design flows and velocities and conveyance element capacities for all conveyance elements within the development. Compute existing one hundred (100) year floodplain elevations and lateral limits for all channels, and verify no net loss of conveyance or storage capacity from development. Reference conveyance system elements to labeled points shown on the site location map or development plan,
(7) Verify capacity of each conveyance system element to convey design flow and discharge at non-erosive velocities. Verify capacity of on-site conveyance system to convey design flows resulting from ultimate build-out of upstream areas,
(8) Include and reference all hydraulic computations, equations, pipe flow tables, flow profile computations, charts, nomographs, detail drawings and other tabular or graphic aids used to design and confirm performance of conveyance systems in the technical appendix,
(9) Summarize results of system analyses and describe how the proposed design meets the requirements of this chapter;
h. Section E – Water Quality Design.
(1) Reference conceptual water quality design proposed in the preliminary stormwater plan,
(2) Identify revisions to conceptual water quality design contained within the final stormwater plan,
(3) Identify geotechnical or soils study or other information used in completing analysis and design,
(4) Identify best management practices used in design and their sources,
(5) Identify and discuss initial conditions including groundwater elevations, beginning storage elevations, and other data or assumptions used to determine initial conditions in order to complete analyses. Reference sources of information,
(6) Identify and discuss assumptions used in completing analysis,
(7) Complete detailed analysis and design of all proposed water quality system elements in accordance with Section 40.380.040(B). Reference water quality system elements to labeled points shown on the site location map or development plan,
(8) Include and reference all computations, equations, charts, nomographs, detail drawings and other tabular or graphic aids used to design water quality system elements in the technical appendix,
(9) Summarize results of water quality design and describe how the proposed design meets the requirements of this chapter;
i. Section F – Soils Evaluation.
(1) Identify on-site soil types and their erosive potential and discuss their suitability for implementation of proposed best management practices (BMPs) and quantity control facilities,
(2) Identify seasonal high water table elevations in cases where this will impact the stormwater facilities,
(3) Identify and discuss soil parameters and design methods for use in hydrologic and hydraulic design of proposed facilities,
(4) Report findings of testing and analysis used to determine the infiltration rate;
j. Section G – Special Reports and Studies. Where specific site characteristics, such as steep slopes, wetlands and sites located in wellhead protection areas pose difficult drainage and water quality design problems, the responsible official may require additional information or the preparation of special reports and studies which further address the specific site characteristics, the potential for impacts associated with the development, and the measures which would be implemented to mitigate impacts. Special reports shall be prepared by professional persons with expertise in the particular area of analysis, who shall date, sign, stamp and otherwise certify the report. Subjects of special reports may include, but not be limited to, the following:
(1) Geotechnical/pedological,
(2) Wetlands,
(3) Floodplains and floodways,
(4) Groundwater,
(5) Structural design,
(6) Fluvial geomorphology (erosion and deposition),
(7) All special reports and studies shall be included in the technical appendix, or as an attachment to the TIR;
k. Section H – Other Permits. Construction of roads and stormwater facilities may require additional water-related permits from other agencies. These additional permits may contain requirements that impact design of the stormwater system. This section shall list the titles of all other required permits, the agencies requiring the permits, and identify the permit requirements, if known, that affect the final stormwater plan. Approved permits that are critical to the feasibility of the stormwater facility design shall be included in this section. Examples of other permits are as follows:
(1) Clark County wetland permit,
(2) On-site sewage disposal: Clark County Public Health or Washington Department of Health,
(3) Developer/local agency agreement: Washington Department of Transportation,
(4) Short-term water quality modification approval: Washington Department of Ecology,
(5) Hydraulic project approval: Washington Departments of Fisheries and Wildlife,
(6) Dam safety permit: Washington Department of Ecology,
(7) Section 10, 404, and 103 Permits: U.S. Army Corps of Engineers,
(8) Surface mining reclamation permits: Washington Department of Natural Resources,
(9) Clark County floodplain permit,
(10) Clark County shoreline management permit,
(11) Clark County habitat permit;
l. Section I – Groundwater Monitoring Program. Where required under Section 40.380.040(H), a groundwater monitoring program shall be included in the final stormwater plan. The groundwater monitoring program shall be prepared by a person with expertise in groundwater contamination investigation, prevention and monitoring, and shall clearly describe a comprehensive groundwater testing and evaluation program designed to ensure compliance with federal and state of Washington laws and the requirements of this chapter. Proposed groundwater monitoring programs will be reviewed by the responsible official on a site-specific basis;
m. Section J – Maintenance and Operations Manual. For each stormwater control or treatment facility that is to be privately maintained and for those which constitute an experimental system under Section 40.380.040(H) to be maintained by the county, the project engineer shall prepare a maintenance and operations manual. The manual, which may be brief, shall be clearly written in an orderly and concise format that clearly describes the design and operation of the facility. The manual shall also provide an outline of required maintenance tasks with recommended frequencies at which each task should be performed. Use of the maintenance procedures outlined in the BMP Manual for various BMPs is encouraged;
n. Section K – Technical Appendix. All technical information reports (TIR) shall contain a technical appendix, including all computations completed in the preparation of the TIR together with copies of referenced data, charts, graphs, nomographs, hydrographs, maps, exhibits, and all other information required to clearly describe the stormwater runoff quantity and quality design for the proposed development activity. The format of the technical appendix shall follow as closely as possible the section format of the TIR, and shall be adequately cross-referenced to ensure that the design may be easily followed, checked and verified. The technical appendix shall also contain all special reports and studies, other than those included as attachments to the TIR.
5. Modification of Content Requirements. The responsible official may waive, in writing, some of the content requirements in the final stormwater plan if:
a. The development activity, redevelopment, or drainage project is included in an approved final stormwater plan which meets the requirements of this section and the applicant demonstrates to the satisfaction of the responsible official that the applicable provisions of the previously approved final stormwater plan will be met; or
b. The responsible official determines, upon receipt of a letter of request from the applicant, that less information is required to accomplish the purposes of this chapter; or
c. A basin plan exists that makes some of the information irrelevant.
6. Review and Approval.
a. Final stormwater plans shall be reviewed in accordance with the Type I review process in accordance with Section 40.510.010.
b. All final stormwater plans require approval by the responsible official. Approval is only for conformance with Clark County standards and does not relieve the engineer of record of responsibility for the design.
c. Approval of final stormwater plans does not relieve the applicant from the obligation to comply with this chapter and does not prevent the county from recovering for defective work or violation of this chapter.
(Amended: Ord. 2006-09-13)
E. Erosion Control Plans.
1. Small Parcel Developments.
a. Any person or entity undertaking a small parcel development shall agree to implement a small parcel development erosion control plan, provided by the county, which shall address the small parcel development requirements in Section 40.380.050(A).
b. Small parcel developments are not required to submit preliminary erosion control plans unless they are conducting land disturbing activities within an erosion hazard area.
c. Applicants may find “A Builder’s Guide to Erosion Prevention & Sediment Control,” published by Clark County Home Builders Association, a useful reference for implementation.
2. Large Parcel Developments. Any person or entity undertaking a large parcel development shall prepare and implement a large parcel development erosion control plan which shall address the large parcel development requirements in Section 40.380.050(B).
3. Erosion Control Plan.
a. An erosion control plan shall be submitted and approved prior to any person undertaking any land disturbing activity subject to this section. The erosion control plan shall be stamped by an engineer licensed in the state of Washington and shall be submitted with the final stormwater plan. Any revised plan shall be a refinement of the prior approved final erosion control plan clearly showing any changes or revisions.
b. Content. The erosion control plan shall include a description of the following:
(1) The BMPs that will be utilized to achieve compliance with the requirements of this chapter;
(2) The timing of installation of BMPs and installation techniques;
(3) The phasing of construction activities;
(4) Protection of project improvements from erosion and sedimentation;
(5) The construction of employee parking and equipment storage areas;
(6) The effect of weather on the project and temporary stoppages;
(7) An inspection log shall be provided to note any changes from the approved plan;
(8) The location, sizes, and other design features of the proposed BMPs to be applied to the site;
(9) A maintenance schedule for ensuring the BMPs continue to function until the site is revegetated and stable; and
(10) A contingency plan discussing additional BMPs to be applied if proposed BMPs fail or are insufficient to control erosion;
(11) Provisions for final stabilization prior to completion;
(12) Grading. Any grading to occur in conjunction with a development activity or development shall, in addition to requirements of this chapter, be designed in accordance with the requirements of Appendix J of the International Building Code.
4. Submittals. Erosion control plans shall be submitted, approved and implemented for all large parcel development activities and for small parcel development conducting land disturbing activities within an erosion hazard area.
(Amended: Ord. 2006-09-13)
F. Development Plans.
1. Preliminary development plan shall show the character of the existing site and proposed features, including but not limited to:
a. Existing and proposed property boundaries, easements and rights-of-way;
b. Existing and proposed contours with a two (2) foot maximum contour interval, unless the responsible official determines a lesser interval is sufficient to show drainage patterns. Grading shall conform to the requirements of Appendix J of the International Building Code;
c. Existing on-site water wells, known agricultural drain tiles, areas of potential slope instability, structures, utilities, and septic tanks and drainfields;
d. Location of the one hundred (100) year floodplain and floodways and shoreline management area limits on the site;
e. Proposed impervious surfaces outside of single-family residential lots;
f. Existing water resource features on and adjacent to the site including streams, wetlands, springs, sinks and stormwater facilities;
g. Existing and proposed drainage flow routes and existing discharge points to and from the site;
h. Approximate location and size of proposed stormwater facilities, including typical cross-sections of proposed facilities;
i. If wetlands exist on the site and will be impacted by the proposal, a wetland delineation report (Section 40.450.030(D)(4)) shall be required;
j. Water table elevations, flow directions (where available), and data on seasonal water table fluctuations with minimum and maximum water table elevations (where available) shall be required;
k. For sloping sites, a conceptual grading plan verifying the constructibility of a stormwater facility shall be required;
l. The responsible official may require additional site or vicinity information if needed to determine the feasibility of the stormwater proposal.
2. Final development plans shall be consistent with the preliminary stormwater plan. Final development plans may be combined with the final engineering plans. In addition to the information required of preliminary development plans, the following information is required:
a. Delineate sub-basins and show sub-basin acreage used in hydraulic/hydrologic calculations both on-site and off-site that contribute surface runoff;
b. Show directions and lengths of overland, pipe and channel flow;
c. Indicated outfall points and overflow routes for the one hundred (100) year storm;
d. Show storage volumes, pipe and weir invert elevations, and lengths of weir for stormwater control facilities;
e. The director may require additional site or vicinity information if needed to determine the feasibility of the stormwater proposal.
(Amended: Ord. 2006-09-13)