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§ 160.12 DEFINITIONS.
   For the purpose of this chapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
   BANKFUL ELEVATION. It is the water level, or stage at which the stream, river or lake is at the top of its banks and any further rise would result in water moving into the floodplain.
   BEST MANAGEMENT PRACTICES (BMP). They are a schedule of activities prohibitions of practices, maintenance procedures and other management practices, which are proved to be effective in preventing or reducing runoff, erosion and sedimentation.
   DETENTION FACILITY. Any structure which is designed to collect and store surface water for subsequent gradual discharge.
   DRAINAGE FACILITY. Any component of the drainage system.
   EXCESS STORMWATER RUNOFF. That portion of stormwater which exceeds the safe storm drainage capacity of storm sewers or natural drainage channels serving a specific watershed.
   IMPERVIOUS AREAS. The horizontal-projected plain area of roof and paved areas of all permanently constructed roofs of houses, garages, mobile homes, businesses, industries, paved driveways, patios and parking lots, but does not include non-permanent structures such as temporary buildings and tents. Also excluded are impervious areas of stored materials and equipment, swimming pools, ponds and lakes; and stormwater retention and detention basins. Gravel or rock roads and gravel or rock parking areas are not considered as impervious areas.
   PROTECTED CHANNEL. A channel which receives stormwater discharge and which is paved, rip-rapped, or otherwise improved by addition of man-made materials so as to reduce the potential for erosion.
   SAFE STORM DRAINAGE CAPACITY. The quantity of stormwater runoff that can be transported by a channel or conduit without giving the water surface rise above the top of the channel and conduit.
   STORMWATER CHANNEL. A natural or man-made open watercourse with definite bed and banks which periodically or continuously contains moving water, or which forms a connecting link between two bodies of water.
   STORMWATER RUNOFF. Water that results from precipitation, which is not absorbed by the soil or vegetation or evaporated, and which flows over the ground surface or is collected in channels or conduits.
   STORMWATER RUNOFF RELEASE RATE. The rate at which stormwater runoff is released from dominant to servient land.
   TWENTY-FIVE-YEAR, 24-HOUR FREQUENCY RAINFALL. A precipitation event of 24-hours duration, having a 4% chance of occurring in any one year.
   COMPLIANCE WITH OTHER REQUIREMENTS. Before starting any activities regulated by this chapter, an applicant shall comply with the requirements set forth in other applicable ordinances with respect to the submission and approval of preliminary and final subdivision plats, improvement plans, building and zoning permits, inspections, appeals and similar matters, along with those set forth in this chapter and as may be required by state statutes and the regulations of any department of the Commonwealth of Kentucky.
   STORMWATER MANAGEMENT PLAN.
      (1)   A stormwater management plan shall be required for any new single-family residential development having a gross aggregate area, including roads, utility rights-of-way, and any other dedicated land of five or more acres, and having a density of greater than one dwelling unit per acre or for any new commercial, multi-family residential, industrial, institutional or utility development having a gross aggregate area of 0.5 acres or more. A plan shall also be required for any new development or redevelopment of fully developed areas as designated on the watershed drainage map. The official watershed drainage map shall be kept in the office of the Stormwater Manager. No final subdivision plat shall be approved and no building permits shall be issued until and unless the stormwater management plan has be reviewed and approved by the Stormwater Manager. Owners of residential property within subdivisions for which final subdivision plats have approved prior to the date of the approval of this chapter shall not be required to comply with this chapter. The Stormwater Manager may also require stormwater management plans for any drainage area if adverse impacts are anticipated. A stormwater management plan may also be required prior to any grading or excavation which would fill, obstruct or otherwise alter any creek, stormwater channel or drainage facility.
      (2)   The required Stormwater Management Plan shall identify means for controlling the stormwater runoff release rate from the development and providing storage potential for the excess stormwater runoff (where required). All computations, plans and specifications related to the implementation of this chapter must be prepared and sealed by a professional engineer registered in the state.
(Ord. 2809, passed 12-10-2012)
REQUIREMENTS AND STANDARDS
§ 160.20 REQUIREMENT FOR CONTROLS OF RUNOFF FROM PROJECTS UNDER CONSTRUCTION/NEW CONSTRUCTION.
   (A)   The following Best Management Practices which address the problem of urban runoff shall apply to all projects undergoing construction in the city. The Best Management Practices list set forth below is required by the city. The requirements set forth below shall apply at the time of demolition of an existing structure or commencement of construction and until receipt of a certificate of occupancy:
      (1)   Runoff sediment and construction waste from construction sites and parking areas shall not leave the site;
      (2)   Any sediments or other materials which are tracked off the site shall be removed the same day as they are tracked off the site. Where determined by the Stormwater Manager or his or her designated representative, a temporary sediment barrier shall be installed;
      (3)   On an emergency basis only, plastic covering may be utilized to prevent erosion of an otherwise unprotected area, along with runoff devices to intercept and safely convey the runoff;
      (4)   Excavated soil shall be located on the site in a manner that eliminates the possibility of sediments running into the street or adjoining properties. Soil piles shall be covered until the soil is either used or removed. A plastic or micro-mesh fabric should be used;
      (5)   No washing of construction or other industrial vehicles shall be allowed adjacent to a construction site. No runoff from wash vehicles on a construction site is allowed to leave the site;
      (6)   Drainage controls shall be utilized as needed, depending on the extent of proposed grading and topography of the site, including but not limited to the following:
         (a)   Detention ponds, sediment ponds or infiltration pits;
         (b)   Dikes, filter berms, silt fences or ditches;
         (c)   Down drains, chutes or flumes.
   (B)   Observe basic principles such as:
      (1)   Preserve existing vegetation as much as possible;
      (2)   Mulch or seed bare soil immediately for the best and cheapest erosion protection;
      (3)   Use silt fences, brush barriers, or other approaches to pond and filter sediment from runoff;
      (4)   Install silt check dams made of rock, brush or other products to prevent ditch erosion and remove sediment;
      (5)   Protect inlets and outlets; and
      (6)   Settle out soil particles in sediment traps and basins.
   (C)   The Stormwater Management Plan shall contain, but not be limited to, the following information unless specifically excluded by the Stormwater Manager.
      (1)   A topographic map of the project site and adjacent areas, of suitable scale and contour interval, which shall define the location of streams, the extent of flood plains and calculated high water elevations, the shoreline of lakes, ponds, swamps and detention basins including their inflow and outflow structures, if any.
      (2)   The location and flow line elevation of all existing sanitary, storm or combined sewers.
      (3)   Detailed determination of runoff anticipated for the entire project site following development indicating design volumes and rates of proposed runoff for each portion of the watershed tributary to the storm drainage system, the calculations used to determine said runoff volumes and rates and restatement of the criteria which have been used by the project engineer throughout calculations.
      (4)   A layout of the proposed stormwater management system including the location and size of all drainage structures, storm sewers, channels and channel sections, detention basins, and analyses regarding the effect said improvements will have upon the receiving channel and its high water elevation.
      (5)   The slope, type, and size of all existing and proposed storm sewers and other waterways impacting or impacted by the proposed development on the site.
      (6)   For all detention basins, a plot of tabulation of storage volumes with corresponding water surface elevations and of the basin outflow rates for those water surface elevations
      (7)   For all detention basins, design hydrographs of inflow and outflow for the 25 year, 24-hour events for the site under existing and developed conditions.
      (8)   A profile and one or more cross sections of all existing and proposed channels or other open drainage facilities, showing existing conditions and the proposed changes thereto, conditions called for by these regulations and the relationship of structures, streets and other utilities to such channels.
(Ord. 2803, passed 12-10-2012) Penalty, see § 160.99
§ 160.21 DESIGN CRITERIA.
   The following rules shall govern the design of improvements with respect to managing stormwater runoff:
   (A)   Methods of determining stormwater runoff rate and volume. The volume of required stormwater storage and runoff shall be calculated on the basis of the runoff from a 25-year frequency storm with 24-hour duration. The calculations can be made in accordance with the instantaneous runoff factor method, the rational method or other methods that may be deemed appropriate by the Stormwater Manager.
   (B)   Release rate.
      (1)   All developments undertaken as outlined in that chapter shall be done in such a way as to insure that stormwater falling on a given site shall be absorbed or detained on site to the extent that the controlled release rate of stormwater runoff from all developments shall not exceed the pre-development stormwater runoff rate. The rate at which stormwater runoff is delivered to a designated stormwater storage area shall be unrestricted.
      (2)   In the event that the Stormwater Manager determines that the natural downstream channel or storm sewer system is inadequate to accommodate the release rate provided above, then the allowable release rate shall be reduced to that rate permitted by the capacity of the downstream channel or storm sewer system.
   (C)   Development design.
      (1)   Where it can be demonstrated by the developer that a higher storm water release rate will not be contrary to the purpose and intent of this chapter and where such proposed release rate will not adversely affect properties in the downstream portion of the watershed, the Stormwater Manager may permit such release to be used as deemed appropriate.
      (2)   Streets, blocks, lots, parks and other public grounds shall be located and laid out in such a manner as to minimize the velocity of overland flow and allow maximum opportunity for infiltration of stormwater into the ground and to preserve and utilize existing and planned streams, channels and detention basins and include whenever possible, streams and floodplain within parks and other public grounds.
   (D)   Excess stormwater passage.
      (1)   An excess stormwater passage shall be provided for all stormwater areas. Such passage shall have the capacity to convey through the proposed development the excess stormwater. The capacity for a passage shall be such that it will be able to transport the peak rate of run-off from a 100-year, 24-hour return frequency storm.
      (2)   There shall be no buildings or structures constructed within excess storm water passage, however, parking lots, playgrounds and park areas, which shall not impair or endanger the water holding capability of a development, shall be considered compatible uses.
      (3)   Appropriate land planning shall be undertaken to preserve the existing natural drainage of a proposed development as part of the excess stormwater passage.
      (4)   Open channels shall be protected from erosion by appropriate vegetative covers, lining or other treatment and earthen channel side slopes shall be no steeper than two to one. Open channels with lining shall have a maximum gradient on side slopes of 67% and channel side slopes steeper than 67% shall be designed as structural retaining walls.
   (E)   Stormwater storage/detention areas. The increased stormwater runoff resulting from the proposed development may be accommodated by the provision of appropriate detention facilities including wet or dry bottom reservoirs, flat roofs, parking lots or streets. Storage areas shall be designed, if possible to provide secondary purposes for recreation, open spaces, parking lot or other types of use that will not be adversely affected by intermittent flooding. The following shall govern the design of detention facilities:
      (1)   Storage volume.
         (a)   All stormwater storage areas must be designed to contain and safely pass stormwater runoff. The combined capacity of these storage areas shall be sufficient to contain the storm from the development. The detention facility must be designed for periodic maintenance and energy dissipaters shall be provided at points necessary.
         (b)   The ponding of stormwater runoff shall not exceed a depth of one foot on a pedestrian mall area or 1-1/2 feet maximum in parking lots. Where these areas are used for ponding the maximum depth should occur in the most remote and least used areas.
         (c)   The drainage and grading design shall be prepared to insure that in a 100-year storm the depth of water run-off in any street, alley, or pedestrian mall will not exceed the level of the first floor of any building.
         (d)   For wet pond storage areas when calculating the storage capacity, only the volume available to store excess stormwater shall be considered. Permanent water storage does not constitute control of excess storm runoff.
      (2)   Release rate. At no time during the design storm shall the stormwater runoff release rate exceed the allowable release rate as set forth in division (B) of this section.
      (3)   Release velocity. Detention facilities shall release stormwater at a non-erosive velocity. The protected channel receiving the detention discharge shall incorporate features to reduce velocity to non-erosive levels at the point where such discharge enters the unprotected channel. If release is into a subsurface conduit the energy gradient in the receiving facility shall not be increased beyond the slope of the conduit.
      (4)   Spillway.
         (a)   Overflow for each stormwater storage area shall be provided in the event of a storm in excess of the design capacity occurs. Such overflows shall be constructed to function without specific attention and shall become part of the excess stormwater passage.
         (b)   Emergency spillways shall be provided to permit the safe passage of runoff generated from a 100-year, 24-hour storm, or greater if required by state law.
         (c)   Where rooftop storage or excess stormwater is provided, the building shall be provided with adequate structural design to insure that roof failure does not occur. Overflow areas shall be provided so that the weight of stored stormwater will not exceed the structural capacity of the roof.
      (5)   Freeboard. Detention facilities shall have adequate capacity to contain storage volume of tributary stormwater runoff with at least one foot of freeboard above the water surface of flow in the emergency spillway in a 100-year, 24-hour storm or as required by state law.
   (F)   Sinkholes and subterranean water channels.
      (1)   The use of sinkholes or subterranean water channels for direct drainage of excess stormwater shall not be permitted although they may be used to drain a stormwater storage area. The introductions of any foreign matter or the filling, clogging or interfering with the natural drainage capabilities of the sinkholes shall not be permitted.
      (2)   Sinkholes shall not be altered in any way which would negatively affect the drainage capabilities of the sinkhole. Development within the 100-year floodplain of a sinkhole shall not be permitted.
(Ord. 2809, passed 12-10-2012) Penalty, see § 160.99
§ 160.22 PERFORMANCE STANDARDS.
   (A)   Stormwater channel location. Generally acceptable locations of stormwater channels in the design of a subdivision may include but are not limited to the following:
      (1)   Adjacent to roadways.
      (2)   In a depressed median of a divided roadway, provided the median is wide enough to permit slopes of one foot drop in six feet horizontal or flatter.
      (3)   Centered on lot lines or entirely within the rear yards of a single row of lots or parcels.
   (B)   In each of the foregoing cases drainage easement with sufficient width to facilitate maintenance and design flow shall be provided and shown on the plat.
   (C)   Storm sewer outfall. The storm sewer outfall shall be designed to provide adequate protection against downstream erosion and scouring.
   (D)   Lot lines. Whenever the plans call for the passage and/or storage of stormwater runoff along lot lines, the grading of all such lots shall be prescribed and established for the passage and/or storage of waters, and no structure or vegetation which would obstruct the flow of stormwater shall be allowed nor shall any change be made to the prescribed grades and contours of the specified stormwater channels.
   (E)   Manholes. All utility sewer manholes constructed in an area designed for the storage or passage of stormwater, shall be provided with either a watertight manhole cover or be constructed with a rim elevation of a minimum of one foot above the high water elevation of the design storm.
   (F)   Easements. Permanent easements for the detention and conveyance of stormwater, including easements of access to structures and facilities, shall be dedicated to the city.
   (G)   Obstruction of drainage. The keeping or disposal of grass clippings, trash, debris, obstruction or unwanted materials into the storm sewers or within or along stormwater channels or in adjacent floodplain areas which may wash into sewers and channels is prohibited.
   (H)   Maintenance. Required maintenance for detention basins or other structures shall be permanently provided by the developer with responsibility becoming that of the private landowner after complete development, subject to inspection of the Stormwater Manager. Every entity shall be specified. Refer to § 160.31 for maintenance requirements.
   (I)   Encroachment permit (city right-of-way).
      (1)   All new construction projects (residential, commercial or industrial) which require a permanent or temporary entrance onto an existing city street or a newly developed street which is to be dedicated to the city at a later time and which can impact proper street drainage shall apply for an encroachment permit at the Office of Public Works. The encroachment permit form will be supplied by the city. The encroachment permit should be complete in sufficient detail to show the location of said entrance with respect to property lines. The encroachment permit shall detail the pipe size, material and slope/grade.
      (2)   This encroachment permit shall be obtained prior to issuance of a building permit by the Planning and Zoning Office.
      (3)   The fee required for the encroachment permit shall be as listed in § 97.17 Application Fee; Bond. This encroachment permit fee is fully refundable provided the entrance is constructed as detailed and approved on said encroachment permit.
(Ord. 2809, passed 12-10-2012) Penalty, see § 160.99
§ 160.23 POST-CONSTRUCTION STORMWATER MANAGEMENT PLAN.
   (A)   Purpose.
      (1)   Land development projects and associated increases in impervious cover alter the hydrologic response of local watersheds and increase stormwater runoff rates and volumes, flooding, stream channel erosion and sediment transport and deposition; this stormwater runoff contributes to increased quantities of water-borne pollutants and; stormwater runoff, soil erosion and nonpoint source pollution can be controlled and minimized through the regulation of stormwater runoff from development sites.
      (2)   The purpose of this chapter is to establish minimum post stormwater management requirements and controls to protect and safeguard the general health, safety and welfare of the public residing in watersheds within this jurisdiction. The goal is to maintain or improve the quality of all streams within the MS4 boundaries to meet their designated use. This chapter seeks to meet that purpose through the following objectives:
         (a)   Minimize increases in stormwater runoff from any development in order to reduce flooding, siltation and stream bank erosion and maintain the integrity of stream channels;
         (b)   Minimize increases in nonpoint source pollution cause by stormwater runoff from development which would otherwise degrade local water quality;
         (c)   Minimize the total annual volume of surface water runoff which flows from any specific site during and following development to not exceed the pre-development hydrologic regime to the maximum extent practicable.
         (d)   Reduces stormwater runoff rates and volumes, soil erosion and nonpoint source pollution where possible, through stormwater management controls and to ensure that these management controls are property maintained and pose no threat to public safety.
   (B)   The Post-Construction Stormwater Management Plan shall be submitted for all subdivisions that discharge to MS4 high quality waters. This includes residential, commercial, and industrial developments. The PC-SWMP is required for all sites one acre and larger in size, and all sites part of a greater common development.
   (C)   The city reserves the right to develop or adopt other guidance documents to serve as design and implementation standards. Other guidance documents distributed by the city should be reviewed and considered when preparing the Post Construction SWMP. These documents may be applied as standards by which designs are to be prepared and controls implemented.
   (D)   The city shall have the authority to implement this chapter by appropriate regulations, guidance or other related materials. In this regard, technical administrative or procedural matters may be modified as needed to meet the objective herein.
(Ord. 2809, passed 12-10-2012)
§ 160.24 POST-CONSTRUCTION PERFORMANCE STANDARDS.
   (A)   The city reserves the right to develop or adopt guidance documents to serve as design and implementation standards. Other guidance documents distributed by the city should be reviewed and considered when preparing the Post-Construction SWMP. Technical, administrative or procedural matters may be modified as needed to meet the objectives defined in this chapter as long as they are not contrary or beyond the intent of the objectives listed above. Such documents given authority by this chapter include Best Management Practice (BMP) manuals, design regulations and requirements, checklists that address submittals, plan review and inspections certification, stormwater manuals, and operation and maintenance manuals. Said documents may be updated periodically to reflect the most current and effective design and construction practices and be made available to the public. Failure to update the manual does not relieve the applicant from complying with this chapter.
   (B)   Post-construction stormwater BMPs shall be designed in accordance with the most current manual or requirements to achieve the following performance standards:
      (1)   The development shall be designed with management measures that are built and maintained to treat, filter, flocculate, infiltrate, screen, evapo-transpire, harvest and reuse stormwater runoff, or otherwise manage the stormwater quality produced from the 80th percentile rain event (0.6 inches of rainfall).
      (2)   BMP’s shall be designed to remove pollutants and reduce runoff volume. The designated use and any existing in-stream use of the stream being discharged to shall be protected. Some land uses produce higher concentrations of certain pollutants such as hydrocarbons or heavy metals, than those normally found in urban areas. These areas will be reviewed for effective removal of the particular pollutant which they discharge. Effective removal will be that which existed prior to development. Examples of land uses that produce higher levels of pollutants are:
         (a)   Gas/fueling stations.
         (b)   Restaurant dumpster areas.
         (c)   Vehicle repair facilities.
         (d)   Vehicle washing/steam cleaning facilities.
         (e)   Auto recycling facilities.
         (f)   Outdoor material storage areas.
         (g)   Loading and transfer areas.
         (h)   Landfills.
         (i)   Industrial sites.
      (3)   BMPs shall reduce or buffer increases in stormwater runoff temperature caused by contact with impervious surfaces as well as minimize increases in stormwater runoff volume and flow rate caused by increases in impervious surfaces.
      (4)   The PC-SWMP shall include provisions for buffers. A buffer shall be defined as:
         (a)   Area contained within a boundary established by the FEMA floodplain boundary or city master planning; or
         (b)   Where a floodplain is not defined or calculated, the buffer will be 25 feet on each side from the top of waterway bank as defined by geomorphic shape (not by current water surface elevation).
            1.   Buffers shall be provided to all blue-line streams as shown on the USGS map.
            2.   Buffer areas and floodplain may be used for stormwater quality devices provided erosion prevention, sediment control, cut-fill practices area addressed appropriately as determined by the city to meet this chapter.
            3.   Exemptions can be granted to buffers so long as erosion and sediment control, water quality are addressed. Exemptions for building in the buffer area shall be granted for:
               a.   Roads and utilities crossing waterways.
               b.   Pedestrian trails and walkways adjacent to waterways.
               c.   Other exemptions may be made at the discretion of the city representative.
      (5)   Redevelopment not previously addressing water quantity or quality control shall reduce the discharge from their site according to the formula below:
         Q(redeveloped) = Q(existing) + q(undeveloped)
                     2
         Q(redeveloped) = maximum discharge rate for the re-development
         Q(existing) = current discharge rate of the developed parcel
         Q(undeveloped) = discharge rate of the parcel prior to any development
         The reduction of allowable flow rate for redeveloped areas shall not exceed more than 30% of the existing developed flow rate. These flow rates are based on redevelopment sites that disturb one acre or more.
      (6)   The City of Glasgow reserves the right to require superseding or additional treatment criteria or objectives for specific pollutants(s) as necessary to meet overall stormwater quality management program objectives or directives under a watershed improvement or Total Maximum Daily Load (TMDL) program as administered by the USEPA or Commonwealth of Kentucky.
      (7)   The Stormwater Manager, in accordance with good engineering practice, may exercise the following options:
         (a)   Off-site mitigation option: Entails infiltration/evapotranspiration/reuse measures that may be implemented at another location within the same watershed as the original project, approved by the city. The city shall identify priority areas within the watershed in which mitigation projects can be completed.
         (b)   Payment-in-lieu option: Allows the owner of a project that falls within the quality criteria, to make a payment to the city in lieu of implementing post-construction BMPs. The city will apply the in-lieu funds to a public stormwater project. The fee shall be used for acquisition, design, construction or maintenance of one or more such facilities in the same watershed in which the development is located.
      (8)   Permanent easement for all stormwater drainage ways, quality and quantity facilities shall be dedicated to the City of Glasgow. There shall also be dedicated easement for access to all stormwater management facilities.
(Ord. 2809, passed 12-10-2012)
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