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For the purpose of this chapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
APPLICANT. An owner or developer of a site who executes the stormwater permit application pursuant to this chapter.
CONNECTION. Any ditch, pipe, or other device for the diversion or transmission of storm drainage, which will in any way affect the operation or maintenance of the drainage ways.
CONVEYANCE. Any feature of the landscape or earth, human-made or natural that carries water in a concentrated flow.
DETAIN. To store and slowly release stormwater runoff following precipitation by means of a surface depression or tank and an outlet structure.
DEVELOPMENT. Any land-disturbing activity which adds to or changes the amount of impervious or partially pervious cover on a land area or which otherwise decreases the infiltration of precipitation into the soil, other than a rebuilding activity that does not qualify as redevelopment.
DRAINAGE STRUCTURES. Shall include swales, channels, and storm sewers, curb inlets, yard inlets, culverts, and other structures designed or used to convey stormwater.
IMPERVIOUS SURFACE. Any surface that, in whole or in part, restricts, or prevents the natural absorption of water into the ground. Such surfaces may include, but are not limited to, gravel, concrete, asphalt, or other paving material, and all areas covered by the footprint of buildings or structures.
LAND-DISTURBING ACTIVITY. Any use of, or operations on, the land by any person in residential, industrial, educational, institutional, or commercial development, including road construction and maintenance, that results in a change in the natural cover or topography.
ONE-YEAR, 24-HOUR STORM. The surface runoff resulting from a 24-hour rainfall of intensity expected to be equaled or exceeded, on average, once in 12 months and with duration of 24-hours.
RETAIN. To capture and hold stormwater runoff following precipitation by means of surface depression allowing the water to infiltrate into the soil, thus reducing the hydrologic and pollution impacts downstream.
STORMWATER. Any surface flow, runoff, and drainage consisting entirely of water from rainfall events.
STREAM. A watercourse that collects surface runoff.
VELOCITY. The average velocity of flow through the cross section of the main channel at the peak flow of the storm of interest.
(2013 Code, § 20-4)
(A) The County Planning and Development will administer this chapter. The Director of Planning and Development will designate a Stormwater Administrator.
(B) In addition to the powers and duties that may be conferred, the Stormwater Administrator shall have the following powers and duties under this chapter:
(1) To review and approve or disapprove applications for approval of plans pursuant to this chapter;
(2) To make determinations and render interpretations of this chapter;
(3) To establish application requirements and schedules for submittal and review of applications and appeals, to review and approve applications;
(4) To enforce the provisions of this chapter in accordance with its enforcement provisions;
(5) To make records, maps, and official materials as relate to the adoption, amendment, enforcement, or administration of this chapter;
(6) To provide expertise and technical assistance to the county;
(7) To designate appropriate other person(s) who shall carry out the powers and duties of the Stormwater Administrator; and
(8) To take any action necessary to administer the provisions of this chapter.
(2013 Code, § 20-5)
(A) A stormwater permit is required for all development and redevelopment which equals or exceeds one acre of residential development, or on commercial lots that are one-half acre in size or more, unless exempt pursuant to this chapter.
(B) The County Board of Commissioners shall establish permit review fees as well as policies, and may amend and update the fees and policies when needed.
(C) For all activities which are subject to this chapter, no person shall initiate, proceed, or undertake any land-disturbing or development activity for which a permit is required without first being issued a written stormwater control permit. All other required applications must be received and permits must be obtained prior to the start of the work. These may include, but are not limited to, soil erosion and sedimentation control, flood damage prevention, subdivision, building permits and inspections, State Department of Transportation, State Division of Water Quality, U.S. Army Corps of Engineers, and State DENR-Dam Safety.
(D) Plan review fees shall be double the amount when land-disturbing activity begins before a stormwater permit is obtained from the county. Prior to presenting a stormwater plan to the County Planning and Development, a consultation meeting with the Stormwater Administrator or his or her designee is required to assess necessary stormwater management measures, constraints, opportunities, and potential approach.
(E) Two copies of the stormwater plan submittal shall be submitted to Planning and Development for review.
(F) The Department shall review the plan for completeness and for compliance with the requirements of this chapter. An incomplete or nonconforming stormwater plan will be returned to the applicant prior to review with an explanation of issues requiring resolution before plan review can be initiated.
(G) Within 30 days of receipt of application for stormwater plan approval, Planning and Development shall take action on the plan.
(1) Planning and Development shall forward a copy of the plan to the County Soil and Water Conservation District who, within 20 days of receipt of the plan, will review the plan and submit its comments and recommendations to the Stormwater Administrator at the County Planning and Development Department.
(2) Failure of the Soil and Water Conservation District to submit its comments and recommendations within 20 days shall not delay final action on the plan. Planning and Development is solely responsible for plan(s) review and will incorporate review comments and recommendations from the Soil and Water Conservation District into its examination of the plan application.
(H) (1) Approval, approval with modifications, or denial of the proposed stormwater plan shall be in writing, in the case of denial, the reasons for denial shall be clearly stated. The applicant may appeal the decision of the Stormwater Administrator at the County Planning and Development Department to a Plan Review Committee within 15 days after receipt of written notice of disapproval or approval with modifications. Only the applicant can appeal the decision of the Stormwater Administrator.
(2) A condition of plan approval will be the right to physical inspection of the drainage structures and stormwater management measures during and after construction.
(I) Hearings held pursuant to this section shall be conducted by a Plan Review Committee consisting of the Director of Planning and Development, the Director of the Soil and Water Conservation District, and the Director of General Services within 30 days after the date of the appeal or request for hearing.
(J) The Plan Review Committee shall decide appeals within 15 days after the date of the hearing on any stormwater plan. If the Review Committee upholds the disapproval or modification of a proposed plan following the hearing, the person submitting the plan shall then be entitled to appeal the local Plan Review Committee’s decision to the Board of Adjustment within 15 days.
(K) The Board of Adjustment will conduct a hearing in the nature of a quasi-judicial proceeding with all findings of fact supported by material evidence.
(L) Decisions appealing the final decision by the Board of Adjustment may be filed in County Superior Court, to be reviewed by proceedings in the nature of certiorari, within 30 days of the final decision of the Board of Adjustment.
(M) The Stormwater Administrator shall take action on revisions to a stormwater plan which has been previously denied, within 15 days of receipt of the revised plan application for approval.
(N) If a revised application is not re-submitted within 60 calendar days from the date the applicant was notified, the application shall be considered withdrawn, and a new submittal for the same or substantially the same project shall be required along with the appropriate fee and pursuant to the current standards.
(O) Application for an amendment to a stormwater plan in written and graphic form may be made at any time. Until such time that any amendment is approved by the Stormwater Administrator, it shall be unlawful to deviate from the approved plan.
(P) An approved plan shall become null and void if the applicant has failed to make progress on the site within six months after the date of approval. The Stormwater Administrator may grant a single, six-month extension of this time limit, for good cause shown, upon receiving a written request from the applicant before the expiration of the approved plan.
(2013 Code, § 20-6)
(A) (1) The stormwater permit application and plan shall refer to the drawings and technical documentation for planned site improvements necessary to fulfill the drainage and stormwater management requirements of this chapter.
(2) This shall include, but not be limited to:
(a) Location and topographic maps with the total drainage area delineated, including both on-site and off-site areas and sufficient information to define all ridges, existing streams, location of the 100-year floodplain and floodway, drainage ways, wetland areas, existing springs, and elevation of any proposed discharge point, and any additional information required to evaluate the existing and proposed drainage system, which may include a soil analysis;
(b) Architectural and engineering drawings showing plan, profile and details of piping, drainage structures, swales, and channels tying into a network of pre-existing human-made or natural channels;
(c) Written project specifications governing work performance and materials;
(d) Computations and assumptions sufficient to support the design of piping, drainage structures, retention/detention ponds, and permanent erosion control measures; and
(e) Whatever other narrative statements necessary to adequately describe the proposed site improvements and the measures planned to comply with the requirements of this chapter.
(B) The stormwater permit application and plan shall be prepared by and shall bear the seal and signature of a professional engineer or landscape architect licensed in the state, competent to perform all aspects of design.
(C) The stormwater permit application and plan shall be prepared to meet the basic objectives and design standards for drainage and stormwater management as described in this chapter.
(D) The stormwater permit application and plan shall show the existing site topography and proposed site drainage improvements in sufficient detail to facilitate plan review and construction. The plan drawings shall be presented at a scale no smaller than one inch equals 50 feet.
(2013 Code, § 20-8)
(A) The stormwater permit application and plan shall be accompanied by an operations and maintenance manual. The manual shall contain a narrative describing each installed measure and device and its design specifications. The manual shall indicate for each installed measure and device what operation and maintenance actions are needed and what specific quantitative criteria will be used to determine when these actions will be taken. The manual must indicate the steps that will be taken to restore a measure or device to the design specifications if a failure occurs.
(B) After the permit and plan is approved and installation is complete, if changes have been made to any installed measure or device, the manual shall be revised to reflect these changes, and such changes shall be subject to the review and approval of the Stormwater Administrator.
(2013 Code, § 20-9)
(A) The designer of the stormwater control plans shall provide as-built plans of all stormwater control and management plans showing the field location, size, depth, and planted vegetation of all measures and devices as installed. If the previously submitted plans remain unchanged, an as-built certification to the existing plans will be required. No certificate of compliance or occupancy shall be issued without said as-built plans.
(B) The designer shall certify, under seal, that the as-built stormwater measures and devices and their installation are in compliance with the county’s stormwater ordinance.
(C) The designer shall submit a final electronic file of the stormwater plan that is readable by GIS systems.
(2013 Code, § 20-10)
(A) In order to reduce drainage-related damage and hazards, adequate natural drainage systems or stormwater management installations are required to collect and transmit stormwater flows into either existing drainage facilities or a natural drainage system.
(B) All storm drainage facilities shall be designed, constructed, and maintained so that adjacent properties are not unreasonably burdened with surface waters as a result of such improvements, specifically:
(1) Off-site areas which drain to or across a site proposed for development must be accommodated in the stormwater plans for the development. The stormwater management system must be capable of conveying the existing off-site flows through or around the development such that the volume and rate of flow from the adjacent property is not altered. If brush flows are earned in the site system any detention system shall be sized to accommodate this flow. The flow must be released to the original drainage area; and
(2) Storm drainage facilities shall be designed to limit the discharge from the site to the rate that existed prior to development of the site. For projects that are redeveloping a developed site, the discharge will be limited to that which occurs before any new development. The type and location of the discharge will be as occurred before the current development unless the discharge is to a human-made conveyance system.
(C) All site improvements shall be provided with a drainage system that is adequate to prevent the undue retention of surface water on the development site.
(D) These goals for discharge can be accomplished by designing, constructing, and maintaining all stormwater management installations to the extent practicable:
(1) Avoid increases in surface runoff volume and velocity by including measures which promote the infiltration of stormwater;
(2) Maximize the time of concentration of stormwater runoff; and
(3) Promote the filtration and precipitation of pollutants from stormwater runoff in order to protect the water quality of the receiving watercourse.
(E) Whenever practicable, the drainage system of a development site shall coordinate with and connect to the drainage systems or drainage ways on surrounding properties or streets. Permission must be received from other applicable entities for connection.
(F) To the extent practicable, all site improvements shall conform to the natural contours of the land, and without disturbance, utilize the preexisting natural and pre-existing human-made drainage ways.
(G) To the extent practicable, lot boundaries within subdivisions shall be made to coincide with natural and preexisting human-made drainage ways to avoid creation of lots that can only be built upon by altering such drainage ways.
(H) Stormwater shall not be diverted from one natural drainage basin into another.
(I) Stormwater shall not be channeled or directed into sanitarily sewers.
(J) Stormwater controls shall not be located within the designated floodway.
(K) No built upon area shall be located within 30 feet landward from any perennial and intermittent surface waters. A surface water shall be deemed present if the feature is approximately shown on either the most recent version of the soil survey map prepared by the Natural Resources Conservation Service of the U.S. Department of Agriculture or the most recent version of the quadrangle topographic maps prepared by the USGS.
(L) Streams shall not be relocated unless it is demonstrated that the relocation of the stream will have a positive impact on water quality while reducing velocity. All other applicable permits must be received.
(2013 Code, § 20-11)
(A) Standards generally. Design standards are established for the purpose of promoting sound development practices which respect, preserve and enhance the county’s watercourses and are not intended to prohibit the use of innovative and alternative techniques which can be demonstrated to have the potential for successfully achieving the objectives stated in § 52.01.
(B) Design storm.
(1) The measures shall control and treat the difference in stormwater runoff volume leaving the project site between the pre- and post-development conditions for, at a minimum, the one-year, 24-hour storm. Runoff volume drawdown time shall be a minimum of 48 hours, but not more than 120 hours.
(2) All structural stormwater treatment systems used to meet the requirements of this chapter shall be designed to have a minimum of 85% average annual removal for total suspended solids (TSS).
(3) The hillside development standards of Ch. 70 of the county’s code of ordinances (§ 20-70-68) apply. This chapter limits the density of disturbed area and impervious surfaces on steep slopes.
(4) The design of drainage facilities in flood hazard areas shall be consistent with the requirements of the county’s flood damage prevention ordinance. No stormwater controls shall be allowed within the floodway. No built upon area shall be within 30 feet landward of any perennial and intermittent surface water.
(5) The computation of stormwater runoff shall follow established engineering practice. Acceptable methods of computation include the rational method, the peak discharge method as described in U.S.D.A. Technical Release Number 55 (TR-55), and U.S. Geological Survey regression equations, where applicable. If an alternate method is proposed, the method should be described and justification for using this method should be provided. The same method must be used for both the pre- and post-development conditions.
(6) Runoff coefficients shall be based on full development of the project and of the watershed to the extent of the current zoning or land use patterns, and shall include the complete development of the site through build-out, including roof tops and other impervious areas that may be proposed.
(7) (a) Stormwater detention shall be provided to ensure that the rate of discharge does not exceed the pre-development rate of discharge.
(b) In order to demonstrate this, pre- and post-development hydrographs will be submitted that demonstrate no increase in flow leaving the site during the one-year 24-hour storm. Inflow-outflow calculations shall also be submitted for any stormwater detention ponds.
(8) Stormwater controls that drain in whole or part to designated trout waters shall be designed
and shall implement the best stormwater practices that do not result in a sustained increase in the receiving water temperature, while still meeting the other requirements of this chapter.
(2013 Code, § 20-12)
The County Planning and Development Department may furnish additional guidance and standards for the proper implementation of the regulations of this chapter and may provide such information in the form of a Stormwater Design Manual. Stormwater management practices that are designed, constructed, or maintained in accord with the Stormwater Design Manual must be presumed to comply with these regulations; however, the Stormwater Administrator shall have the right to consult other engineers and duly qualified professionals, and to impose any conditions or require any modifications deemed necessary to meet the purpose, intent and requirements of this chapter.
(2013 Code, § 20-13)
(A) Stormwater management facilities shall be constructed in accordance with approved plans and maintained in proper working condition. The applicant/property owner is responsible for ensuring that the construction of drainage structures and stormwater management measures are completed in accordance with the approved plan and specifications. Inspections which may be performed by the county during construction will not relieve the developer of the responsibility to install stormwater management and drainage facilities in accordance with the approved plan.
(B) In response to a complaint, or as a compliance check with the requirements of the ordinance, the Stormwater Administrator or the designee shall perform a physical inspection of the construction of drainage structures and stormwater management measures, or monitor long-term maintenance procedures.
(C) The property owner will be notified in writing of any substandard and/or non-conforming work identified by the Stormwater Administrator. The notification shall state the specific work that is out of compliance, the specific reasons for noncompliance, and the corrective measures necessary to bring the work into compliance.
(D) Failure of the property owner or developer to correct substandard and/or nonconforming work identified by the Stormwater Administrator shall be sufficient reason to refuse or revoke building permits, and/or deny occupancy permits for buildings serviced by said work. Appeals on determination of nonconforming or substandard work and/or the adequacy of the corrective measures executed shall be made in accordance with § 52.06. Pending the ruling on the appeal, the determination of the Stormwater Administrator remains in effect.
(E) Revisions which affect the intent of the design or the capacity of the system shall require prior written approval by the Stormwater Administrator.
(2013 Code, § 20-14)
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