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§ 52.08 MAINTENANCE MANUAL.
   (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)
§ 52.09 AS-BUILT PLANS AND SPECIFICATIONS.
   (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)
§ 52.10 STORMWATER MANAGEMENT OBJECTIVES.
   (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)
§ 52.11 STORMWATER MANAGEMENT DESIGN STANDARDS.
   (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)
§ 52.12 STORMWATER DESIGN MANUAL.
   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)
§ 52.13 CONSTRUCTION AND MAINTENANCE.
   (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)
§ 52.14 PERFORMANCE SECURITY AND MAINTENANCE.
   (A)   The county will require the submittal of a surety performance bond made by a surety bonding company licensed and authorized to do business in the state, a bond of the owner/developer with an assignment to the county of a certificate of deposit as security for the bond, a bond of the owner/developer by an official bank check drawn in favor of the county and deposited with the county, or cash or an irrevocable letter of credit deposited with the county prior to issue of a permit in order to ensure that the stormwater system is installed by the developer and functions as required by the approved stormwater plan.
   (B)   The amount of an installation performance security shall be the total estimated construction cost of the system and devices approved under the permit, plus 25%.
   (C)   The performance security shall contain forfeiture provisions for failure, after proper notice, to complete work within the time specified, or to initiate or maintain any actions which may be required of the applicant in accordance with this chapter.
   (D)   Upon default of the applicant to construct, maintain, repair, and if necessary reconstruct any stormwater device in accordance with the applicable permit, the Stormwater Administrator shall obtain and use all or any portion of the security to make necessary improvements based on an engineering estimate. Such expenditure of funds shall only be made after requesting the applicant to comply with the permit. In the event of a default triggering the use of installation of performance security, the county shall not return any of the unused deposited cash funds or other security, which shall be retained for maintenance.
   (E)   If the county takes action upon such failure by the applicant, the county may collect the difference should the amount of the reasonable cost of such action exceed the amount of the security held. This difference will be collected from the applicant.
   (F)   Within 60 days of the final approval, the installation performance security shall be refunded to the applicant or terminated.
(2013 Code, § 20-15)
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