Loading...
HomeMy WebLinkAboutAgenda - 08-27-2001-c2V~i 1 ORANGE COUNTY BOARD OF COUNTY COMMISSIONERS PUBLIC HEARING ITEM ABSTRACT Meeting Date: August 27, 2001 Action Agenda Item No. c2 (2 ) SUBJECT: Orange County Soil Erosion and Sedimentation Ordinance DEPARTMENT: Planning and Inspections PUBLIC HEARING: (Y/N) ATTACHMENT(S): INFORMATION CONTACT; Sail Erosion and Sedimentation Control Ordinance Ren Ivins ext 2586 Amendments Craig Benedict ext 2592 TELEPHONE NUMBERS: Hillsborough 732-81$1 Chapel Hill 96$-4501 Durham 688-7331 Mebane (336)227-2031 PURPOSE: To provide consistency among the water quality critical areas, and to match existing regulations within the University Lake Watershed. To provide greater water quality protection within Orange County. BACKGROUND: The attached Soil Erosion and Sedimentation Control Ordinance amendments conform to the amended Model Ordinance of the North Carolina Sedimentation Control Commission. These changes will exceed the minimum requirements of NCDENR- Division of Land Resources, and will provide areas in Orange County that are deemed water quality critical areas for our drinking water supply with greater protections. At the time the Soil Erosion and Sedimentation Control Ordinance was adopted, only the University Lake watershed contained a water quality critical area. These amendments are to update the Ordinance to incorporate the critical areas in the Cane Creek and Upper Eno Watersheds. Location Lands within Orange County jurisdiction which are classified as water quality critical areas by NCDENR- Division of Water Quality. g:\erosion\amendments\sept00abstract.dac Q~~ Existing and Proposed Conditions Existing: Erosion and Sedimentation Control, and Water Supply Watershed Requirements currently in place. • Ordinance contains a ,higher disturbed acreage threshold far the Cane Creek and Upper Eno Watersheds than for the University Lake Watershed before a permit and approved plan is required. Proposed: • To lower the disturbed acreage that requires an approved Erosion Control Plan and aLand- Disturbing Permit from 20,000 square feet to 10,000 square feet for the Cane Creek and Upper Eno Watersheds. Develo meat Process Schedule and Action • Upon approval by the Board of County Commissioner's, amendments will be incorporated into the Soil Erosion and Sedimentation Control Ordinance, and brought before the Board on September 18t" for final approval. FINANCIAL IMPACT: Existing Erosion Control staff will implement the attached amendments. RECOMMENDATION(S): Administration recommends approval of the attached amendments, or as the Board decides. a:\erosion\amendments\seot00abstract.doc Q~ Sediment and Erosion Control Ordinance Stormwater Program Existing: Nitrogen Control Pending: Neuse Buffers Sections 3&4 Enforcement NPDES Phase II Spring 2003 ~~ Amendments to the Orange County Soil Erosion and Sedimentation Control Ordinance June 2001 NOTE: The bold, underlined text will be added to the Ordinance and the struck- through text will be deleted. Section 2.1 Findings of Fact Relating to Sedimentation and Erosion in Universi Lake Cane Creek and U er Eno Protected Watershed Areas The County Commissioners find that, without strict sedimentation and erosion controls, the development of land within the University Lake, Cane Creek and U er Eno Protected Watershed Areas will have a significant adverse impact upon the health, safety, and welfare of all persons served by the University Lake Cane Creek and U er Eno Protected Watershed Areas. More specifically: A. Stormwater runoff carries pollutants into Universi Lake Cane Creek and U er Eno Protected Watershed Areas, degrading water quality. These pollutants include, but are not limited to, organic and inorganic chemicals. B. The increase in nutrients such as phosphorus and nitrogen will accelerate eutrophication of University Lake, Cane Creek, and Upper Eno Protected Watershed Areas, adversely affecting flora and fauna. C. The improper channelization of watercourses and drainage areas in the Universi Lake Cane Creek and U er Eno Protected Watershed Areas will increase the velocity of runoff, thereby increasing erosion and sedimentation. D. The alteration of the natural topography and removal of vegetation will increase erosion by increasing velocity of runoff. E. The siltation of water bodies resulting from increased erosion will decrease the capacity of the water bodies to hold and transport water, and harm flora and fauna. F. Sedimentation further reduces water quality because it transports pollutants into the water, then releases them in the water as it settles. G. Impervious surfaces will increase the volume and rate of stormwater runoff. This allows less water to percolate into the soil, thereby decreasing G:\EROSION\AmendmentsWMENDS2001.doc 04G groundwater recharge. Increased velocity of runoff also reduces the filtering effect of the sail. H. Improperly managed stormwater runoff will increase the incidence of flooding and the level of floods which occur. Section 2.2 Objectives of Reguiations Applicable to Uniiversity Lake, Cane Creek and U er Eno Protected Watershed Areas The regulations set forth in this Ordinance applicable to the University Lake. Cane Creek, and Upper Eno Protected Watershed Areas, are designed: 1. To protect and maintain the chemical, physical and biological quality and integrity of University Lake. Cane Creek, and Upper Eno Protected Watershed Areas and other critical watershed areas. 2. To prevent harm to the residents of the community by prohibiting .activities which adversely affect University Lake, Cane Creek, and Upper Eno, Protected Watershed Areas as a public water supply. 3. To encourage the protection of natural systems and the utilization of these systems in a manner which does not impair their beneficial functioning. 4. To discourage the construction of drainage systems which do not functionally approximate the natural drainage pattern. 5. ~ To minimize sedimentation and erosion, within the watershed, and as a result, minimize the transport. of sediment and pollutants to University Lake, Cane Creek, and Upper Eno Protected Watershed Areas. 6. To protect and maintain the existing habitat of fish and wildlife. 7. To prevent damage from flooding while recognizing that natural fluctuations in water levels are beneficial. 8. To protect the absorptive, purifying and retentive functions of the natural systems existing in the Universi Lake Cane Creek and U er Eno Protected Watershed Areas. 9. To ensure the attainment of these objectives by requiring the approval and implementation of sedimentation and erosion control .plans for all activities which may adversely affect the Universi Lake Cane Creek and U er Eno Protected Watershed Areas. 10. To provide and enforce design and performance standards for control of post-development erosion and sedimentation in order to preserve the G:\EROSION\Amendments\AMENDS2001.doc fl4' characteristics that existed in the Universi Lake Cane Creek and U er Eno Protected Watershed Areas prior to development. Section 3 Definitions As used in this Ordinance, unless the context clearly indicates otherwise, the following definitions apply: Cane Creek Protected Watershed Area- com rises all the land area con#ributin water to Cane Creek U er Eno Protected Watershed Area- com rises all the land area contributin water to the U er Eno University Lake Protected Watershed Area -comprises all the land area contributing water to University Lake Section 4 Jurisdiction and Effect Jurisdiction This ordinance shall apply within Orange County, including the municipalities of Carrboro, Hillsborough, and the portion of Mebane within Orange County, but excluding the municipal boundaries and planning extraterritorial limits of Chapel Hill. Effect It shall be unlawful, within the jurisdiction of this Ordinance, to engage in land- disturbing activity, except as provided herein, without first obtaining a permit as required by this Ordinance and without complying with the conditions of the issuance of said permit. Conflicts and duplications among portions of this Ordinance shall be resolved in favor of the more stringent regulation. Whenever conflicts exist between federal, state or local laws, ordinances, or rules, the more restrictive provision shall apply. G:\EROSION\Amendments\AMENDS2001.doc ors Section 5 Scope and Exclusions (Countywide) This Ordinance shall apply to land-disturbing activities undertaken by any person, with the following exclusions: A. Agriculture Activities, including the breeding and grazing of livestock, undertaken on agricultural land for the production of plants and animals useful to man, including, but not limited to: 1. forages and sod crops, grains and feed crops, tobacco, cotton and peanuts; 2. dairy animals and dairy products; 3. poultry and poultry products; 4. livestock, including beef cattle, sheep, swine, horses, ponies; mules or goats, including the breeding and grazing of any or all such animals; 5. bees and apiary products; 6. fur animals. B. Forestland Activities undertaken on forestland for .the production and harvesting of timber and timber products and conducted in accordance with best management practices set out in Forest Practice Guidelines Related to Water Quality as adopted by the Department. If land-disturbing activity undertaken on forestland for the production and harvesting of timber and timber products is not conducted in accordance with Forest Practice Guidelines Related to Water Quality, the provisions of this ordinance shall apply to such activity and any related land- disturbing activity on the tract. C. Mining Activities far which a permit is required under the Mining Act of 1971, Article 7 of Chapter 74 of the General Statues. D. State Jurisdiction Those land-disturbing activities over which the State by statute (G.S. 113A-56(a)) has exclusive regulatory jurisdiction, which are activities: (1) Conducted by the State, (2) Conducted by the United States, (3) Conducted by persons having the power of eminent domain, G:\EROSION~Amendments~AMENDS2001.doc ~' (4) Conducted by local governments, (5) Funded in whole or in part by the State or the United States. S@CtlOn 6 General Requirements for Areas Other Than University Lake. Cane Creek, and Upper Eno Protected Watershed Areas A. Protection of Property Person(s) conducting land-disturbing activities shall take all reasonable measures to protect all public and private property from damage by such activities. This requirement shall apply to any areas to be disturbed, regardless of the size of the area to be uncovered. B. Erosion Control Plan Requirement Priar to the commencement of any land-disturbing activity that will result in the uncovering of more than 20,000 square feet of land, the person(s) conducting the land-disturbing activity must prepare and submit an Erosion Control Plan for the proposed site. The Plan must be approved and a Grading Permit obtained prior to the start of the disturbance. Section 6.1 General Requirements for University Lake, Cane Creek, and Upper Eno Protected Watershed Areas A. Plan Requirement ` Except as otherwise provided in subsection B., an erosion and sedimentation control plan shall be prepared and filed with and approved by the Erosion Control Division prior to the commencement of any land- disturbing activity within the Universi Lake Cane Creek and U er Eno Protected Watershed Areas. B. Plan Waiver The person(s) conducting the land-disturbing activity need not submit an erosion control plan if such person obtains an Erosion Control Plan Waiver Form from the Erasion Control Division. An application for this form shall be submitted and shall contain the name, address, and phone number of the developer and owner, a description and drawing of the proposed development or activity, the location of the development, and any other information requested by the Orange County Erosion Control OfFicer that G:\EROSION\Amendments\AMENDS2001.doc ono is reasonably necessary to evaluate the proposed development. The Erosion Control OfFicer shall issue the Plan Waiver Form if he finds that: The land-disturbing activity will not result in the uncovering of more than 10,000 square feet; and 2. The land-disturbing activity is not to be conducted in connection with any of the following types of developments: a. shopping, centers b. industrial and commercial facilities c. major subdivisions d. roads e. any activity involving the temporary or permanent storage (above or below ground) of any noxious, toxic,, or hazardous substance, including fuel storage facilities. 3. The proposed land-disturbing activity will not: a. significantly increase or decrease the rate or volume of surface water runoff; b. significantly contribute to the degradation of water runoff; c. have a significant adverse impact on a wetland, watercourse, or University Lake, Cane Creek, and Upper Eno Protected Watershed Areas; d. occur within a buffer area circumscribing Universitv Lakes Cane_Creek, and_ Upper Eno Pro#ected Watershed Areas. C. Protection of Property . Persons conducting. land-disturbing activity shall take all reasonable measures to protect all public and private property from damage by such activities. This requirement shall apply to any area to be disturbed. Section 7 Basic Control Objectives An Erosion and Sedimentation Control Plan may be disapproved pursuant to Section 1 S of this ordinance if the plan fails to address the following control objectives: A. Identify Critical Areas On-site areas which are subject to severe erosion, and off site areas which are especially vulnerable to damage from erosion and/or sedimentation, are to be identified and receive special attention, and appropriate, mitigative measures are to betaken to protect those areas. G:\EROSION\Amendments\AMENDS2001.doc 05: B. Plan for Erosion Control Design the development and prepare the site plan so that the necessary sediment-trapping devices and erosion control measures can be accommodated and are accessible for maintenance and removal. Observe the requirements and standards in Orange County's Soil Erosion and Sediment Control Manual. C. Limit Exposed Areas All land-disturbing activities are to be planned and conducted to minimize the size of the area to be exposed at any one time. D. Limit Time of Exposure All land-disturbing activities are to be planned and conducted to limit exposure to the shortest feasible time. E. .Control Surface Water Surface water runoff originating upgrade of exposed areas should be controlled to reduce erosion and sediment loss during the period of exposure. F. Control Sedimentation All land-disturbing activities are to be planned and conducted so as to prevent off-site sedimentation damage. G. Manage Stormwater Runoff When the increase in the peak rates and velocity of storm water runoff resulting from gland-disturbing activity is sufficient to cause accelerated erasion of the receiving watercourse, plans are to include measures to control the velocity and the rate of release at the point of discharge so as to minimize accelerated erasion of the site and increased sedimentation of the stream. Section 8 Mandatory Design and Performance Standards for Land~Disturbing Activity No land-disturbing activity subject to the control of this Ordinance shall be undertaken except in accordance with the following mandatory standards: A. Buffer Zone 1. No land-disturbing activity during periods of construction or improvement to land shall be permitted in proximity to a lake or natural watercourse unless a buffer zone is provided along the margin of the watercourse of sufficient width to confine visible siltation within the twenty- five percent (25%) of the buffer zone nearest the land-disturbing activity. Waters that G:\EROSION\Amendments\AMENDS2001.doc ~~~ have been classified as trout waters by the Environmental Management Commission shall have an undisturbed buffer zone 25 feet wide or of sufficient width to confine visible siltation within the twenty-five percent (25%) of the buffer zone nearest the land-disturbing activity, whichever is greater. Provided, however, that the County may approve plans which include land-disturbing activity along trout waters when the duration of said disturbance would be temporary anal the extent of said disturbance would be minimal. This subdivision shall not apply to aland-disturbing activity in connection with the construction of facilities to be located on, over, ar under a lake or natural watercourse. Unless otherwise provided, the width of a buffer zone is measured from the edge of the water to the nearest edge of the disturbed area, with the 25 percent of the strip nearer the land- disturbing activity containing the natural or artificial means of confining visible siltation. 2. The 25 foot minimum width for an undisturbed buffer zone adjacent to designated trout waters shall be measured horizontally from the tap of the bank. 3. Where a temporary and minimal disturbance is permitted as an exception by Section 8 (A) (1) of this ordinance, land-disturbing activities in the buffer zone adjacent to designated trout waters shall be limited to a maximum of 10% of the total length of the buffer zone within the tract to be distributed such that there is not more than 100 linear feet of disturbance in each 1000 linear feet of buffer zone. Larger areas may be disturbed with the written approval of the Director of the Division of Land Resources of the Department of Environment, Health, and Natural Resources. 4. No land-disturbing activity shall be undertaken within a buffer zone adjacent to designated trout waters that will cause adverse temperature fluctuations, as set forth in 15 NCAC 26.0211 Fresh Surface Water Classification and Standards, in these waters. B. Graded Slopes and Fills The angle for graded slopes and fills shall be no greater than the angle which can be retained by vegetative saver ar other adequate erosion control devices or structures. In any event, slopes left exposed will, within 30 working days of completion of any phase of grading, be planted or otherwise provided with ground saver, devices, or structures sufficient to restrain erosion. C. Ground Cover Whenever land-disturbing activity is undertaken on a tract comprising mare than 20,000 square feet, if more than 20,000 square feet are uncovered, the person cohducting the land-disturbing activity shall install G:\EROSIONWmendments\AMENDS2001.dac such sedimentation and erosion control devices and practices as are sufficient to retain the sediment generated by the land-disturbing activity within the boundaries of the tract during construction upon and development of said tract, and shall plant or otherwise provide a permanent ground cover sufficient to restrain erosion after completion of construction or development. Except as provided in Section 8 (D) (2) (e) of this ordinance, provisions for a ground cover sufficient to restrain erosion must be accomplished within 30 working days or 120 calendar days, whichever period is shorter, fallowing completion of construction or development. D. Design and Performance of Control Measures 1. Design Storm Except as provided in Section 8(D)(2)(b) of this Ordinance and in the standard for sediment ponds in the Soil Erosion and Sediment Control Manual erosion and sedimentation control measures, structures, and devices shall be so planned, designed, and constructed as to provide protection from accelerated erosion and sedimentation from the calculated maximum peak rates of runoff from the ten-year frequency storm. Runoff rates shall be calculated using the procedures in the USDA Soil Conservation Service's "National Engineering Field Manual for Conservation Practices," or other calculation procedures acceptable to the Erosion Control Officer. 2. Standards for High Quality Waters In High Quality Water (HQW) zones the following design standards shall apply: a. Uncovered areas in HQW zones shall be limited at any time to a maximum total area of 20 acres within the boundaries of the tract. Only the portion of the land-disturbing activity within a HQW zone shall be governed by this section. Larger areas may be uncovered within the boundaries of the tract with the written approval of the Director of the Division of Land Resources of the Department of Environment, Health, and Natural Resources. b. Erosion and sedimentation control measures, structures, and devices within HQW zones shall be so planned, designed, and constructed to provide protection from the runoff of the 25-year storm which produces the maximum peak rate of runoff. The peak rate of runoff shall be calculated according to procedures in the United States Department of Agriculture Soil Conservation Service's National Engineering Field Manual for Conservation Practices or according to procedures adopted by any other agency of this state or the United States or any generally recognized organization or association. G:\EROSION\Amendments\AMENDS2001.doc 0~4 c. Sediment ponds (also called "sediment basins") within HQW zones shall be designed and constructed such that the pond will have a settling efficiency of at least 70% for the 40 micron (0.04 mm) size soil particle transported into the basin by the runoff of that 2-year storm which produces the maximum peak rate of runoff. The peak rate of runoff shall be calculated according to procedures in the United States Department of Agriculture Soil Conservation Service's National Engineering Field Manual for Conservation Practices or according to procedures adopted by any other agency of this state or the United States or any generally recognized organization or association. d. Newly constructed open channels in HQW zones shall be designed and constructed with side slopes no steeper than 2 horizontal to 1 vertical if a vegetative cover is used for stabilization unless soil conditions permit a steeper slope or where the slopes are stabilized by using mechanical devices, structural devices or other acceptable devices. In any event, the angle for side slopes shall be sufficient to restrain accelerated erosion. e. Ground cover sufficient to restrain erosion must be provided for any portion of a land- disturbing activity in a HQW zone within 15 working days, or 60 calendar days, whichever period is shorter, following completion of construction or development. E. Prior Plan Approval No person shall initiate any land-disturbing activity on a tract if more than 20,000 square feet are to be uncovered unless, thirty or more days prior to initiating the activity, an erosion and. sedimentation control plan for such activity is filed with, approved by, and a Grading Permit obtained from the County. Section 8.1 Additional Standards for Land-Disturbing Activity in Universi Lake Cane Creek and lJ er Eno Protected Watershed Areas The provisions of Section 8 shall apply to land-disturbing activity within the University Lake. Cane Creek, and Upper Eno Protected Watershed Areas. In addition, the design, construction, and maintenance of drainage systems in developments within the University Lake. Cane Creek, and Upper Eno Protected Watershed Areas shall also be consistent with the following standards; and these standards shall control to the extent that they are more restrictive than those set forth in Section 8. G:\EROSION\,gmendments\AMENDS2001.doc ~~~ A. Channeling Runoff -channeling runoff directly into water bodies shall be prohibited. Runoff shall be routed through swales and other systems designed to increase time of concentration, decrease velocity, increase infiltration, allow suspended solids to settle, and remove pollutants. B. Alteration of Watercourses -natural watercourses shall not be dredged, cleared of vegetation, deepened, widened, straightened, stabilized or otherwise altered except in accordance with an approved erasion contra) plan. Water shall be retained or detained before it enters any natural watercourse in order to preserve the natural hydro-dynamics of the watercourse and to prevent sedimentation. C. Limit Land-Disturbing Activity -the area of disturbance by development shall be as small as practical. D. Land Alterations - no grading, cutting or filling shall be commenced until erosion and sedimentation control devices have been installed between the disturbed area and water bodies, watercourses, wetlands, or adjoining properties. E. Wetland Protection -wetlands and other water bodies shall not be used as sediment traps during development. F. Maintenance Requirements and Responsibility -erosion and sedimentation facilities shall receive regular maintenance to ensure that they continue to function properly. Temporary basins shall be cleaned out when they are filled to fifty (50) percent of their design capacity. G. Artificial Watercourses -any artificial watercourse (where the need is demonstrated) shall be designed considering soil type so that the velocity of flow is low enough to prevent accelerated erosion. H. BufFer Area Requirements -soil and pollutants carried overland, primarily from roads, trails, and/or land-disturbing activities, can be effectively trapped by leaving a relatively undisturbed strip of vegetation parallel and adjacent to the watercourse. Properly managed overland water flow can be directed into this buffer area in a manner that will reduce velocity and cause dispersion of the water. Sediments carried by the water will settle out as a result of this slowing and dispersion process. The width of these buffer areas shall depend on the type of stream or drainage area. The width of the buffer strips shall be as follows: 1. Creeks and tributaries - (i.e., permanent streams flowing directly into Universi Lake Cane Creek and U er Eno Protected Watershed Areas and permanent streams flawing into such streams). Measure along a line running perpendicular to the G:\EROSION\Amendments\AMENDS2001.doc D56 edge of the floodplain (or if no floodplain has been demarcated, the center of the stream) fifty feet from the edge of the floodplain (or if no flood plain has been demarcated from the edge of the water) plus an additional distance equal to: 4 x slope x 100 where "slope" is expressed as a percentage derived by dividing by 100 the rise in elevation between the floodplain boundary line (or if no floodplain has been demarcated, the centerline of the watercourse) and a point one hundred feet from that point along the above described perpendicular line. 2. Intermittent streams flowing into creeks and tributaries. Measure along a line running perpendicular to the centerline of the intermittent stream fifty feet from such stream centerline. 3. Intermittent streams flowing directly into Universi Lake Cane Creek, and lJPper_Eno Protected Watershed Areas. Measure along a line running perpendicular to the centerline of the intermittent stream one hundred feet from such stream centerline. 4. Intermittent streams flowing into streams which flow directly into University Lake, Cane Creek, and Upper Eno Protected Watershed Areas. Measure along a line running perpendicular to the centerline of the intermittent stream fifty feet from such stream centerlines. 5. University Lake, Cane Creek, and„Upper Eno Protected Watershed Areas. Measure along a line running perpendicular to the high water mark or floodplain boundary (whichever is farther from the Lake) one hundred feet from such high water mark or floodplain boundary (whichever is farther from the Lake) plus an additional distance equal to: 4 x slope~x 100 where "slope" is expressed as a percentage derived by dividing by 100 the rise in elevation between the high water line of the Lake and a point one hundred feet from that point along the above described perpendicular line. The existing natural vegetation in the designated buffer areas shalt not be disturbed in any way that would reduce the area's effectiveness in achieving the objectives set forth in this subsection. In addition, buffer areas from which the vegetative G:\EROSION\AmendmentslAMENDS2001.doc cover has been removed shall be planted or otherwise provided with ground cover devices or structures sufficient to allow the buffer area to accomplish the objectives set forth in this subsection. Buffers shall not be used as temporary erosion control devices during construction. I. Sediment Storage -sediment shall be retained on the site of the development. J. Detention or Retention Areas - retentian and detention ponds may be used to retain and detain the increased and accelerated runoff which the development generates. Water shall be released from detention ponds into watercourses or. wetlands at a rate and in a manner approximating the natural flow which would have occurred before development. Retention and detention ponds shall be designed so that they maintain their structural integrity when subject to a 100-year storm. Detention and retention areas shall be designed so that shorelines are sinuous rather than straight and so that the length of the shoreline is maximized, thus offering more space far the growth of littoral vegetation. The banks of detention and retention areas shall slope at a gentle grade into the water as a safeguard against drowning, personal injury or other accidents, to encourage the growth of vegetation and to allow the alternate flooding and exposure of the areas along the shoreline as water levels periodically rise and fall. K. Open Space -the use of drainage facilities and vegetated buffer zones as open space, recreation, and conservation areas shall be encouraged. Recreational activities undertaken in these open space areas shall be limited to passive or leisure activities. L.. Grassed Swales -drainage within the development shall be accommodated by the natural drainage systems whenever possible. The use of grassed drainageways to channel water shall be encouraged. The velocity of travel in this grassed swale shall range between 2-4 feet/second. M. Retention of Runoff from Industrial Sites - On sites developed for industrial purposes (i.e., uses involving the manufacturing, processing, creating, repairing, renovating, painting, cleaning, or assembly of goods, merchandise, or equipment), retention or detention areas meeting the standards set forth in subsection j. shall be used to insure that runoff is retained on the site before being released. The purpose of this requirement is to insure that, not only will the standard set forth in G:\EROSION\Amendments\AMENDS2001.doc ~ .~! subsection 9A, be met, but also a mechanism will be provided to safeguard the watershed against the spillage of toxic or dangerous substances. SGCtIOn 9 Stormwater Qutlet Protection A. Control of Discharge in University Lake, Cane„Creek, and Uuper Eno Protected Watershed Areas Provisions shall be made for the control of stormwater discharges for the types of development as specified below. After development of the site, the peak discharge of stormwater runoff resulting from aten-year storm shall be no greater than that which would result from aten-year storm on the same site prior to development. This requirement shall apply to: 1. Commercial, industrial, offce, and institutional developments 2. Multi-family residential developments of more than 10 units 3. Single-family detached residential developments where more than three lots are to be created. B. Control of Velocity Persons shall plan and conduct land-disturbing activity so that the post- construction velocity of the 10-year storm runoff in the receiving watercourse to the discharge point does not exceed the greater of: 1. the velocity established by the table in paragraph 3 of the subsection; or 2. the velocity of the 10-year storm runofF in the receiving watercourse prior to development. If conditions (1) or (2) of this paragraph cannot be met, then the receiving watercourse to and including the discharge point shall be designed and constructed to withstand the expected velocity anywhere the velocity exceeds the "prior to development" velocity by 10%. Standards 1. Acceptable Management Measures Measures applied alone or in combination to satisfy the intent of this subchapter are acceptable. if there are no objectionable secondary consequences. Innovative techniques and ideas will be considered and may be used when shown to have the potential to produce successful results. Some alternatives are to: G:\EROSION\Amendments\AMENDS2001:doc 05 a. avoid increases in surface runoff volume and velocity by including measures to promote Infiltration to compensate for increased runoff from areas rendered impervious; b. avoid increases in stormwater discharge velocities by using vegetated or roughened swales and waterways in lieu of closed drains and high velocity paved sections; c. provide energy dissipators at outlets of storm drainage facilities to reduce flow velocities to the point of discharge; these may range from simple rip-rapped sections to complex structures; d. protect watercourses subject to accelerated erosion by improving cross sections and/or providing erosion-resistant lining. 2. Exceptions This rule shall not apply in areas other than the University Lake, Cane Creek, and Upper Eno Protected Watershed Areas where it can be demonstrated that storm water discharge velocities will not create an erosion problem in the receiving watercourse. 3. Permissible Velocities The following is a table of permissible velocity for stormwater discharges: MATERIAL Maximum Permissible Velocities FPS MPS Fine Sand (noncolloidal) 2.5 0.8 Sandy Loam (noncolloidal) 2.5 0.8 Silt Loam (noncolloidal) 3.0 0.9 Ordinary Firm Loam 3.5 1.1 Fine Gravel 5.0 1.5 Stiff Clay (very colloidal) 5.0 1.5 Graded, Loam to Cobbles (noncolloidal) 5.0 1.5 Graded, Silt to Cobbles (colloidal) 5.5 1.7 Alluvial Silts (noncolloidal) 3.5 1.1 Alluvial Silts (colloidal) 5.0 1.5 Coarse Gravel (noncolloidal) 6.0 1.8 Cobbles and Shingles 5.5 1.7 Shale and Hard Pans 6.0 1.8 Source: Adapted from recommendations by Special Committee an Irrigation Research, American Society of Civil Engineers, 1926, far channels with straight alignment. For sinuous channels, multiply allowable velocity by 0.95 for slightly sinuous, by 0.9 for moderately sinuous channels, and by 0.8 for highly sinuous channels. G:\EROSION\Amendments\AMENDS2001.doc ~. Q60 Section 1 Q Borrow and Waste Areas When the person conducting the land-disturbing activity is also the person conducting the borrow and waste disposal activity, areas from which borrow is obtained and which are not regulated by the provisions of the Mining Act of 1971, and waste areas for surplus materials other than landfills regulated by the Department's Division of Solid Waste Management shall be considered as part of the land-disturbing activity where the borrow material is being used or from which the waste material originated: When the person conducting the land-disturbing activity is not the person obtaining the borrow. snd/or disposing of the waste, these areas shall be considered a separate land-disturbing activity. Section 11 Access and Haul Roads Temporary access and haul roads, other than public roads, constructed yr used in connection with any land-disturbing activity shall be considered a part of such activity. With respect to development in the Universi Lake Cane Creek and U er Eno Protected Watershed Areas, these access and haul roads shall have gravel pads placed at the entrance of the site of aland-disturbing activity. G'\ERC7S1(7N\Amc~nrimr?nts\AMFNI~S~(]~1.dnr.