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HomeMy WebLinkAboutAgenda - 08-23-1993 - C 2 and C 3 attch 111 C- 2andC-3 Zoning Atlas Zoning Ordinance Text Amendments 112 PROPOSED AMENDMENTS TO ORANGE COUNTY ZONING 113 ORDINANCE (Public Hearing - August 23, 1993) 4.2..27 WATERSHED PROTECTION OVERLAY DISTRICTS a) Intent The purpose of the Protected Watershed Overlay Districts is to prevent significant future water quality deterioration in existing or potential future drinking water reservoirs into which receive stormwater runoff from land within Orange County. Protection of all water supplies within the State in accordance with minimum standards was mandated by the Watersupply Watershed Protection Act passed by the General Assembly in 1989. The quality of water in drinking water reservoirs can be affected by activities of man including farming,construction of highways and roads, subdivision development, industrial development, and other land-disturbing activities. Types of water pollutants resulting from these activities include sediment, bacterial contamination, heavy metals, synthetic organic compounds and low-level radioactivity. The intent of the Protected Watershed Overlay Districts is to apply a set of regulations involving land use and in some cases, structural best management practices which protect the watersheds by reducing the pollution from future development which enters drinking water supplies. Land use management practices involve minimum lot size and impervious surface restrictions, since impervious surfaces such as roads, roof tops and driveways are a major source of pollution. Structural best management practices allow for more intensive land use by providing for temporary detention of stormwater runoff so that pollutants may settle. b) Application Criteria The Protected Watershed Overlay Districts as established in Article 4.27.2.1 overlay other zoning districts established in this Ordinance. The new use of any land or new structure within any Protected Watershed Overlay District shall comply with the use regulations applicable to the underlying zoning district as well as the requirements of the applicable Watershed Protection Overlay District. A Watershed Protection Overlay District will be applied to the Orange County portion of watershed which have been classified as WS-II, WS-III or WS-IV watersheds by the North Carolina Environmental Management Commission in its implementation of the Watersupply Watershed Protection Act of 1989. In accordance with the State Mandate, ten (10) Watershed Protection District Overlays, as listed in the following table, are hereby established. 114 115 DISTRICT GENERAL LOCATION UNIV-CA University Lake Critical One-half mile from the normal pool of Area Overlay District University Lake, or to the ridgeline of the watershed, whichever is less. UNIV-PW University Lake Protected The portion of the drainage basin of Watershed Overlay District University Lake not covered by UNIV-CA. CANE-CA Cane Creek Critical Area One-half mile from the normal pool of Cane Overlay District Creek Reservoir, or to the ridgeline of the watershed, whichever is less. CANE-PW Cane Creek Protected The portion of the drainage basin of Cane Watershed Overlay District Creek Reservoir not covered by CANE-CA. U-ENO-CA Upper Eno Critical Area One-half mile from the normal pool of Lake Overlay District Orange, Corporation Lake, and potential reservoir sites on the West Fork of the Upper Eno and Seven Mile Creek, or to the ridgeline of the watershed, whichever is less. U-ENO-PW Upper Eno Protected The portion of the existing or potential Watershed Overlay drainage basins of Lake Orange, Corporation Lake, West Fork of the Upper Eno and Seven-Mile Creek not covered by U-ENO- CA. L-ENO-PW Lower Eno Protected The Orange County portion of the Eno River Watershed Overlay District Watershed within ten miles of the City of Durham Emergency Water Intake east of US 501 (Roxboro Road). LITTLE- Little River Protected The portion of drainage basin of the Little PW Watershed Overlay District River Reservoir which is located in Orange County. BACK-PW Back Creek Protected The portion of the drainage basin of Back Watershed Overlay District Creek which is located in Orange County. HYCO-PW South Hyco Creek The portion of the drainage basin of South Protected Watershed Hyco Creek which is located in Orange Overlay District County. FLAT-PW Flat River Protected The portion of the drainage basin of the Flat Watershed Overlay District River which is located in Orange County. HAW-PW Haw River Protected The portion of the drainage basin for the Watershed Overlay District Haw River which is located in Orange County. 116 DISTRICT GENERAL LOCATION JORDAN- Jordan Lake Protected The Orange County portion of the Jordan PW Watershed Overlay District Lake Watershed which extends five miles from the normal pool elevation of the impoundment. • • 117 6.23 EXTRA REQUIREMENTS FOR WATERSHED PROTECTION OVERLAY DISTRICTS Ten (10) Watershed Protection Overlay Districts, as described in Article 4.2.27.2 of this Ordinance, have been established for lands within the watersheds of existing or potential drinking water rivers and reservoirs. These districts overlay other zoning districts established in this Ordinance and delineated on the Orange County Zoning Atlas. Wherever standards of the underlying zoning district differ from the watershed overlay standards, the more restrictive provisions shall apply. 6.23.1 LAND USE RESTRICTIONS All uses and activities allowed in the underlying zoning district are permitted with the following exceptions: DISTRICT LAND USE RESTRICTIONS UNIV-CA No new landfills are permitted. UNIV-PW No sludge application is permitted. CANE-CA No commercial or industrial uses are permitted. U-ENO-CA CANE-PW U-ENO-PW No discharging landfills are permitted. HYCO-PW Industrial use is limited to non-hazardous light industrial uses characterized by LITTLE-PW low water use (less than 10,000 gpd, excluding domestic water (25 gpd per BACK-PW employee) and water used for heating and air conditioning). FLAT-PW HAW-PW L-ENO-PW No additional use restrictions. JORDAN-PW 11s 6.23.4 SETBACKS Setbacks shall be as required by the underlying zoning district, with the following exceptions: DISTRICT SETBACK RESTRICTIONS UNIV-CA CANE-CA U-ENO-CA No structures (with exception of water-dependent structures as defined in Article 22 of this Ordinance) may be constructed within 150 feet of (Applies only to lots the high water mark of a water supply impoundment; and created by Preliminary Plans for major New septic tanks and their nitrification fields shall be located at least subdivision and Final 300 feet from the edge of a water supply impoundment, or perennial or Plats for minor intermittent stream as shown on the USGS Quadrangle maps. subdivisions approved or recorded after December 31, 1993. All Other Watershed New septic tanks and their nitrification fields shall be located at least Overlay Districts, and 100 feet from a perennial or intermittent stream as shown on the USGS lots approved in U- Quadrangle maps. ENO-PW after December 31, 1993. (See also Article 6.23.11.) 6.23.5 RESIDENTIAL DENSITY Maximum residential density shall be as indicated in the Table below, or as required by the underlying zoning district, whichever is less. DISTRICT MAXIMUM DENSITY UNIV-CA Up to 5 lots at least 2 acres in size can be created from a lot of record as of UNIV-PW October 2, 1989. Thereafter, each lot shall contain at least 5 acres, and the - density shall not exceed 1 dwelling unit (du)/5 acres. CANE-CA U-ENO-CA 1 du/ 2 acres LITTLE-PW FLAT-PW CANE-PW 1 du/ 40,000 square feet (.92 acre) BACK-PW HYCO-PW 2 119 DISTRICT MAXIMUM DENSITY U-ENO-PW Maximum density is as permitted in the underlying zoning district. L-ENO-PW HAW-PW BMPs are required in some cases where density exceeds 1 dwelling unit per JORDAN-PW acre. Refer to Article 6.23.6c1. 6.23.6 STORMWATER INFILTRATION AND DETENTION As a watershed becomes more developed, the amount of impervious surface increases, causing a decrease in the rate at which stormwater runoff which can be absorbed into the soil. This results in more stormwater flowing directly into streams and other water bodies. Because this direct runoff has not been filtered through the soil, pollutants from the air and land surface enter streams and increase the potential for pollution of drinking water supplies. The effects of stormwater pollution on drinking water supplies can be minimized by one of two general approaches. First, the amount of stormwater runoff which reaches drinking water supplies can be controlled by assuring that there is adequate ground area into which water can be absorbed. This type of non-structural control is achieved through limitations on impervious surface. A second approach is to collect stormwater run-off in engineered ponds so that pollutants may settle. The water is then slowly released and contains fewer impurities when it reaches the water supply reservoir. The watershed protection standards adopted by Orange County utilize a combination of these two approaches. a) Non-Structural Stormwater Control The first inch of stormwater run-off shall be controlled to the extent possible through on- site infiltration and through the use of methods which rely on natural soil properties for absorption and treatment. In order to promote infiltration of stormwater runoff into the soil and minimize direct and immediate runoff into streams and water supply impoundments, the maximum percentage of the total lot area which may be covered with an impervious surface shall be specified. This limit is referred to as the "impervious surface ratio". Impervious surface calculations for an individual development shall be cumulative for original construction and any subsequent additions. One-half of the width of any of any existing or proposed road adjacent to an individual lot shall be included as impervious surface for that lot, except in the case where an existing road was contained within a dedicated public right-of-way on January 1, 1994. Infiltration techniques not only remove both suspended and dissolved pollutants, but they require less maintenance, reduce flooding,promote groundwater recharge and help maintain stream flow during dry periods. Where on-site infiltration methods are utilized, areas for such purposes shall be designated on the plat and shall remain undisturbed both during and after construction. 3 12 0 Undisturbed areas for infiltration of run-off shall also be located downslope from impervious surfaces and shall not include areas characterized by floodplains, highly erodible or impervious soils, steep slopes or previously disturbed areas. Areas designated as suitable for septic tank nitrification fields may not be used for stormwater infiltration purposes. Run-off from roads, parking lots, and/or sidewalks shall be directed to undisturbed areas through use of berms, grassed diversion ditches or swales, or other acceptable means to reduce run-off velocity and filter out pollutants. b) Structural Measures Non-structural methods may not adequately control the first inch of stormwater runoff due to the amount of impervious surface proposed to be developed, and other factors such as soil type, slope, presence of floodplains and erodible soils, and/or lack of vegetative cover. In such cases, structural detention ponds, which capture stormwater for slow release through an outlet, are required. Where required, detention ponds shall be constructed in accordance with Appendix c) Impervious Surface and Detention Pond Requirements For all protected watersheds, there is a absolute limit on the percentage of lot area which can be covered with impervious surfaces. In some cases, detention ponds are required when the proposed impervious surface ratio exceeds a specified percentage, which is below the absolute limit. 4 121 1. Residential Development DISTRICT IMPERVIOUS SURFACE/DETENTION POND REQUIREMENTS (RESIDENTIAL) UNIV-CA Lots created prior to Lot Size Impervious Lot Size Impervious UNIV-PW April 2, 1990 (Acres) Surface (Acres) Surface 6.0 + 4.0% 2.0 12.0% 5.0 6.0% 1.0 14.0% 4.0 8.0% 0.8 14.4% 3.0 10.0% 0.5 15.0% The impervious surface ratios (ISR)for fractional acreage values between 5 acres and 0.5 acres which are not included in the table above shall be interpolated. For each 1/10 (.10) acre increase in lot size, the ISR shall decrease by 2/10 (.20)percent. Detention ponds (BMPs) are not required. Lots created after 6% impervious surface limit, with no BMPs required. April 2, 1990 CANE-CA 6% impervious surface limit OR 2 acre minimum lot U-ENO-CA size. BMPs are not required. LITTLE-PW FLAT-PW CANE-PW 12% impervious surface limit OR 1 acre minimum lot HYCO-PW size. BMPs are not required. U-ENO-PW 30% impervious surface limit, with BMPs required if impervious surface exceeds 12%. L-ENO-PW . _ 50% impervious surface limit, with BMPs required when: a) curb and gutter is not used, and density exceeds 3 du/acre AND impervious surface exceeds 36%; OR b) curb and gutter is used, and density exceeds 2 du/acre AND impervious surface exceeds 24%. 5 1 2 DISTRICT IMPERVIOUS SURFACE/DETENTION POND REQUIREMENTS (RESIDENTIAL) HAW-PW 24% impervious surface limit, BMPs not required. JORDAN-PW For new subdivisions, the total amount of allowable imperious surface shall be calculated as the applicable percentage of the entire tract. This impervious surface allotment shall be distributed equitably among the lots of the subdivision. The allotment for each lot shall be indicated on a separate document recorded together with the final subdivision plat 2. Non-Residential Development DISTRICT IMPERVIOUS SURFACE/DETENTION POND REQUIREMENTS (NON-RESIDENTIAL) UNIV-CA Same as Residential (See previous Table) UNIV-PW CANE-CA Up to 6% impervious surface without BMPs, U-ENO-CA 6% - 24% with BMPs. CANE-PW Up to 70% impervious surface without BMPs'. LITTLE-PW HYCO-PW BACK-PW FLAT-PW U-ENO-PW Up to 70% impervious surface, with BMPs required when impervious surface exceeds 12%.' L-ENO-PW Up to 50% impervious surface, with BMPs required HAW-PW when impervious surface exceeds 24% (if curb and JORDAN-PW gutter is used) or 36% (no curb and gutter). After new non-residential development with impervious surface greater than 12% occurs on 5% of the watershed, impervious surface for subsequent development may not exceed 30%, and BMPs will be required when impervious surface exceeds 12%. 6 123 6.23.7 OPERATION AND MAINTENANCE OF DETENTION PONDS a) Posting of Financial Security All stormwater control structures shall be conditioned on the posting of adequate financial assurance for the purpose of maintenance, repairs or reconstruction necessary for adequate performance. Financial assurance shall be in the form of one of the following: 1. Security Performance Bond or Other Security The permit applicant shall obtain either a performance bond from a surety bonding company authorized to do business in North Carolina, an irrevocable letter of credit or other instrument readily convertible into cash at face value payable to Orange County or placed in escrow with a financial institution designated as an official depository of Orange County. The bond or other instrument shall be in an amount equal to 1.25 times the total cost of the stormwater control structure, as estimated by the applicant and approved by the County Engineer. The total cost of the stormwater control structure shall include the value of all materials such as piping and other structures; seeding and soil stabilization; design and engineering; and, grading, excavation, fill, etc. The costs shall not be prorated as part of a larger project, but rather under the assumption of an independent mobilization. Upon default of the permit applicant to complete and/or maintain the stormwater control.structure as spelled out in the performance bond or other security, the County may obtain and use all or any portion of the funds necessary to complete the improvements based on an engineering estimate. The Board shall return any funds not spent in completing the improvements to the owning entity. 2. Cash or Equivalent Security Deposited After Release of the Performance Bond Consistent with Section IA, the permit applicant shall deposit with Orange County either cash or other instrument approved by the County Attorney that is readily convertible into cash at face value. The cash or security shall be in an amount equal to fifteen (15) percent of the total cost of the stormwater control structure or the estimated cost of maintaining the stormwater control structure over a ten (10) year period, whichever is greater. The estimated cost of maintaining the stormwater structure shall be consistent with the approved operation and maintenance plan or manual provided by the developer under Section IIA. The amount shall be computed by estimating the maintenance cost for twenty-five (25) years and multiplying this amount by two-fifths or 0.4. Upon default of the owning entity to maintain, repair and, if necessary, reconstruct the stormwater control structure in accordance with the Operation and Maintenance Agreement, the County shall obtain and use all or any portion of the cash security to make necessary improvements based on an engineering estimate. Such expenditures of funds shall only be made after exhausting all other reasonable remedies seeking the owning entity to comply with the terms 7 124 and conditions of the Operations and Maintenance Agreement. The County shall not return any of the deposited cash funds. b) Maintenance and Upkeep 1. Operation and Maintenance Agreement Required The permit applicant shall enter into a binding Operation and Maintenance Agreement between Orange County and all interests in the development. Said Agreement shall require the owning entity to maintain, repair and, if necessary, reconstruct the stormwater control structure in accordance with the operation and management plan or manual prepared by the developer. The Operations and Maintenance Agreement shall be filed with the Orange County Register of Deeds. 2. Operation and Maintenance Plan Required An operation and maintenance plan or manual shall be provided by the developer for each stormwater control structure, indicating what operation and maintenance actions are needed, what specific quantitative criteria will be used for determining when those actions are to be taken and, consistent with the Operations and Maintenance Agreement, who is responsible for those actions. The Plan shall clearly indicate the steps that will be taken for restoring a stormwater control structure to its design specifications if a failure occurs. 5 Landscaping and Grounds Maintenance Landscaping and grounds maintenance shall be the responsibility of the owning entity. However, vegetation shall not be established or allowed to mature to the extent that the integrity of the control structure is diminished or threatened, or to the extent of interfering with any easement or access to the stormwater structure. 4. Repair or Reconstruction Except for general landscaping and grounds maintenance, the owning entity shall notify the County prior to any repair or reconstruction of the stormwater structure. All improvements shall be made consistent with the approved plans and specifications of the stormwater control structure and the operations and maintenance plan or manual. After notification by the owning entity, the County Engineer and/or Erosion Control Supervisor shall inform the owning entity of any required additions, changes or modifications and of the time period to complete said improvements. 5. Minor Amendments to Plans and Specifications Amendments to the plans and specifications of the stormwater control structure and/or the operation and maintenance plan or manual may be approved by the County Engineer, provided that the changes do not involve a change in the size 8 12 5 or location of the structure. Proposed changes shall be prepared by a North Carolina registered professional engineer or landscape architect(to the extent that the General Statutes, Chapter 89A, allow) and submitted to and reviewed by the Erosion Control Supervisor prior to consideration by the County Engineer. a. If the County Engineer approves the proposed changes, the owning entity of the stormwater control structure shall filed sealed copies of the revisions with the Erosion Control Supervisor. b. If the County Engineer disapproves the changes, the proposal may be revised and resubmitted to the Erosion Control Officer as a new proposal. If the proposal has not been revised and is essentially the same as that already reviewed, it shall be returned to the applicant. c. The County Engineer shall report any such revisions to the Board of County Commissioners at the next available regular meeting. 6 Major Amendments to Plans and Specifications Amendments to the plans and specifications of the stormwater control structure and/or the operation and maintenance plan or manual which involve a change in the size or location may be approved by the Board of Commissioners after receiving a recommendation from the County Engineer. Proposed changes shall be prepared by a North Carolina registered professional engineer or landscape architect (to the extent that the General Statutes, Chapter 89A, allow) and submitted to and reviewed by the Erosion Control Supervisor prior to review by the County Engineer. 7 Revision of Plan Required if Found to be Inadequate If the County finds that the operations and maintenance plan or manual is inadequate for any reason, the owning entity shall be notified of any required changes and shall prepare and file copies of the revised agreement with the Orange County Register of Deeds, the Erosion Control Supervisor, and the owning entity. c) Inspection and Release of the Performance Bond 1. Inspection by Erosion Control Supervisor The stormwater control structure shall be inspected by the Erosion Control Supervisor, after the owning entity notifies the Erosion Control Supervisor that all work has been completed. At this inspection, the owning entity shall provide: a. The signed deed, related easements and survey plat for the stormwater control structure ready for filing with the Orange County Register of Deeds; and 9 126 b. A certification sealed by an engineer or landscape architect(to the extent that the General Statute, Chapter 89A, allow) stating that the detention pond is complete and consistent with the plans and specifications. Submittal of Inspection Report to County Engineer The Erosion Control Supervisor shall present materials submitted by the developer and the inspection report and recommendations to the County Engineer. a. If the County Engineer approves the inspections report and accepts the certification, deed and easements, he/she shall file the deed and easements with the Orange County Register of Deeds, released up to seventy-five (75) percent of the value of the performance bond or other security and issue a Watershed Protection Compliance Permit for the stormwater control structure. b. If deficiencies are found, the County Engineer shall direct that the improvements and inspections be made and/or documents corrected and resubmitted to the County Engineer. 3. Watershed Protection Compliance Permit Required Prior to Occupancy No Building Permit or Certificate of Occupancy may be issued in the absence of a valid Watershed Protection Compliance Permit. 4 Release of Remaining Security No sooner than one (1) year after the filing date of the deed, easements and maintenance agreement, the developer amy petition the Board of Commissioners to release the remaining value of he performance bond or other security. Upon receipt of said petition, the County Engineer shall inspect the stormwater control structure to determine whether the controls are performing as designed and intended. The County Engineer shall present the petition, inspection report and recommendations to the Board of Commissioners. a. If the Board of Commissioners approves the report and accepts the _ petition, the developer shall deposit with Orange County a cash amount equal to that described in Section I, after which, the Board shall release the performance bond or other security. b. If the Board of Commissioners does not accept the report and rejects the petition, it shall provide the developer with instructions to correct any deficiencies and all steps necessary for the release of the performance bond or other security. 5 Annual Inspection Required 10 7 w a. All stormwater structures shall be inspected at least on an annual basis to determine whether the controls are performing as designed and intended. Records of inspections shall be maintained on forms approved or supplied by the North Carolina Division of Environmental Management. Annual inspections shall begin within one (1) year of the filing date of the deed for the stormwater control structure. b. In the event the County Engineer discovers the need for corrective action of improvements, he/she shall notify the owning entity of the needed improvements and the date by which the corrective action is to be completed. All improvements shall be made consistent with the plans and specification of the stormwater control structure and the operation and maintenance plan or manual. After notification by the owning entity, the County Engineer shall inspect and approve the completed improvements. d) Appeals Any requirement, decision or determination of the County Engineer may be appealed to the Board of Commissioners for consideration at its next available regular meeting. 6.23.8 PLACEMENT OF STREETS, DRIVEWAYS AND BUILDINGS Streets, driveways, and buildings or other structures shall be located, to the extent reasonable possible, so as to take full advantage of the absorptive capacity of the soils on which they are to be situated and to avoid the following environmentally sensitive areas: 1) Stream buffer zones as required by Article 6.23.10; 2) Wetlands as defined by the U.S. Army Corps of Engineers; 3) Land with slopes greater than fifteen percent (15%); and 4) Natural areas as identified in the Inventory of Natural Areas and Wildlife Habitats of Orange County, NC. To avoid creating lots that will be difficult to build upon in compliance with the standards of this Article, the subdivision plats shall show proposed building envelopes and approximate driveway locations for all lots within such subdivisions. Thereafter, no zoning compliance permit may be issued for the construction of buildings or driveways outside the areas so designated on the preliminary plat unless the Zoning Officer makes a written finding that the proposed location complies with the provisions of this Article. 6.23.9 UNDISTURBED AREA Because soils which are seriously disturbed, even if re-vegetated, can generate nearly as much run-off as paved areas, a portion of property being developed within watershed critical areas must remain undisturbed during construction. 11 128 DISTRICT UNDISTURBED AREA UNIV-CA A minimum of the area necessary to meet impervious surface CANE-CA requirements shall remain undisturbed during the construction process. U-ENO-CA The area to remain undisturbed shall include portions of the lot utilized for stormwater infiltration. All clearing limits shall be clearly marked and observed. All Other Watershed As may be required pursuant to an approved grading permit or erosion Overlay Districts control plan. 6.23.10 STREAM BUFFERS a) Definition A stream buffer is an area of land adjacent to perennial and intermittent streams which, except as stated below, must remain undisturbed in its natural state. Perennial streams are those streams shown as solid blue lines and intermittent streams as broken blue lines on the USGS Quadrangle maps for Orange County. b) Permitted Uses Within Stream Buffers The following uses are allowed as a matter of right in stream buffers. All other uses are prohibited. 1) Above-ground and buried utility lines for local distribution of electricity, telephone and cable television service, accessory and appurtenant apparatus such as poles, guy wires, transformers and switching boxes. 2) Bona fide farms, except any use of farm property for non-farm purposes. 3) Public and private streets, bridges and railroad rights-of-way, provided that they enter and exit the buffer area as nearly perpendicular as possible. • c) Land Disturbance and Planting of Vegetation 1) Area within a stream buffer which is subject to serious erosion may be disturbed for the purpose of planting and maintaining erosion-resistant vegetative cover. 2) Existing forested areas or any other healthy vegetation cannot be removed from a stream buffer, except where replaced with vegetation resulting in comparable stormwater runoff velocity and quantity one year after planting. 12 129 3) New vegetation shall be planted to capture non-source pollutants before they reach the perennial stream, as per applicable Orange County Standards. d) Calculating Width of Stream Buffer 1) How to Calculate Slope a. Draw a line perpendicular to the stream. b. Determine the elevation at the stream itself (1), and at the point 250' from the stream along the perpendicular line (2). c. Subtract (1) from (2). d. Divide c. by 250. e. Multiple d. by 100 Hereinafter, the number derived in e. will be referred to as "slope value". 2) Method A - Stream Buffer Based on Slope The width of the buffer shall be fifty (50) feet from each edge of the floodplain, plus the slope value multiplied by four. 3) Method B - Stream Buffer Based on Slope and Groundcover STREAM BUFFER WIDTH (IN FEET) BASED ON SLOPE AND GROUNDCOVER Slope Value Type of Groundcover Grass Woods • 2 to 4.9 100 50 5to9.9 150 100 10 to 14.9 200 100 15 or greater 250 150 In addition to the buffer zone resulting from the calculations below, a stream buffer shall include any portion of a floodplain as defined in the Orange County Flood Damage Prevention Ordinance, by special survey by a registered engineer or surveyor, or by alluvial soils as designated in the Orange County Soils Survey. 'The required stream buffer zone shall not be limited to one calculation, but shall be based on calculations made at points where topographical and ground cover conditions change based on an analysis of the site. 13 130 e) Minimum Buffer Width Required DISTRICT MINIMUM STREAM BUFFER WIDTH' UNIV-CA The buffer width shall be calculated for both Method A and Method B, and at UNIV-PW any given point along the stream, the width of the buffer shall be the larger of the two. CANE-CA The buffer width shall be the width calculated using Method A. U-ENO-CA U-ENO-PW The buffer width shall be as calculated using Method A, or 150', whichever is L-ENO-PW less, except where density exceeds 1 du/ac and impervious surface exceeds 12%. Where density exceeds 1 du/ac and impervious surface exceeds 12%, the buffer width shall be calculated as above, but shall not be less than 100'. CANE-PW LITTLE-PW BACK-PW The buffer width shall be the width calculated using Method A, or 150', HYCO-PW whichever is less. FLAT-PW HAW-PW JORDAN-PW 6.23.11 WATER SUPPLY/SEWAGE DISPOSAL FACILITIES DISTRICT WATER SUPPLY/SEWAGE DISPOSAL UNIV-CA Water supply and sewage treatment systems shall be limited to individual wells UNIV-PW and on-site septic tanks systems or individual on-site alternative disposal systems. No new treatment system will be permitted where effluent disposal occurs on a separate lot from the source of wastewater generation. Repair systems are permitted on a lot other than the lot which is the source of wastewater generation provided that the Orange County Health Department certifies that: 1. The residence or use has a failing system, AND there is not a suitable location for a repair system on the same lot as the residence or use, or 2. In the case of an unimproved lot created by recorded deed, valid probated will or recorded plat prior to June 15, 1991, there is not a suitable location for a repair system on the same lot as the residence or use. 14 131 DISTRICT [ WATER SUPPLY/SEWAGE DISPOSAL All Other Repair systems are permitted on a lot other than the lot which is the source of Watershed wastewater generation provided that the Orange County Health Department Overlay certifies that: Districts 1. The residence or use has a failing system, AND there is not a suitable location for a repair system on the same lot as the residence or use; or 2. In the case of an unimproved lot created by recorded deed, valid probated will or recorded plat prior to January 1, 1994, there is not a suitable location for a repair system on the same lot as the residence or use. 6.23.12 CLUSTERING DISTRICT CLUSTERING REQUIREMENTS UNIV-CA Clustering of residential lots is permitted in accordance with Section IV-B-10 of UNIV-PW the Orange County Subdivision Regulations, with the additional provision that each lot contains a minimum of one acre. All Other Clustering of residential lots is permitted in accordance with Section IV-B-10 of Overlay the Orange County Subdivision Regulations. Districts 6.23..13 APPLICABILITY a) Existing Development Existing development is not subject to the requirements of this Article. Existing developments include projects that are built, or at a minimum have established a vested right under North Carolina zoning law as of January 1, 1994 based on at least one of the following criteria: 1. substantial expenditures of resources (time, labor, money) based on a good faith reliance upon having received a valid local government approval to proceed with the project; or 2. having an outstanding valid building permit; or 3. having expended substantial resources and having an approved site specific or phased development plan. 15 13 2 b) Redevelopment Non-residential redevelopment is allowed if the rebuilding activity does not have a net increase in built-upon area or provides equal or greater stormwater control than the previous development. There are no restrictions on single-family redevelopment. c) Expansion of Existing or New Developments Expansions to structures classified as existing development must meet the requirements of this Article, however, the impervious surface and lot area involved in the existing development is not required to be included in the calculation of the impervious surface ratio. Expansions to structures other than existing development must meet the density requirements for the entire project. 6.23.13 ADMINISTRATION a) Appeals Decisions of the Zoning Officer in the implementation of this Article may be appealed to the Orange, County Board of Adjustment in accordance with Article 2.3.7 of this Ordinance. b) Exemptions Development activities may be granted minor exemptions by the Board of Adjustment in accordance with Article 2.3.6 of this Ordinance. An exemption which results in one or more of the following shall be considered a major exemption, requiring approval by the Environmental Management Commission. 1. the complete waiver of a management requirement; '2.-- the relaxation by more than ten percent of any management requirement that takes the form of a numerical standard; and 3. the relaxation of any management requirement that applies to a development project requiring construction of a detention pond. A description of each project receiving an exemption and the reason for granting the exemption shall be submitted to the Commission on an annual basis. All other local governments having jurisdiction within the watershed area and the entity using the water supply for consumption shall be notified of the proposed exemption. 16 133 ARTICLE 22 - DEFINITIONS Best Management Practices (BMPs) A structural or non-structural management-based practice used singularly or in combination to reduce non-point source pollution to receiving waters in order to achieve water quality protection goals. (See also, Detention Pond and Engineered Stormwater Controls) Critical Area The land area within one-half mile of the normal pool of an existing or proposed watersupply impoundment, or the branch of the first major tributary, whichever is farther. Detention Pond A engineered stormwater control consisting of a pond constructed and maintained in accordance with Appendix of this Ordinance, which allows for pollutants to settle and provides for the gradual release of the impounded water. The detention pond is the Best Management Practice which must be used within protected watersheds when engineered stormwater controls are required. (See also, Best Management Practices and Engineered Stormwater Controls) Engineered (or Structural) Stormwater Controls A structural Best Management Practice (BMP) used to reduce non-point source pollution to receiving waters in order to achieve water quality protection goals. (See also Best Management Practices and Detention Pond) High-Density Option One of two approaches available for for development in some watershed overlay districts. Generally, the high-density option relies on density limits and engineered stormwater controls to minimize the risk of water pollution. Impervious Surface A surface composed of any material which impedes or prevents the natural infiltration of water into the soil. Such surfaces include all concrete, asphalt and gravel surfaces. These include, but are not be limited to, streets and parking areas, sidewalks, patios, and structures which cover the land. Infiltration The absorption of stormwater run-off into the ground. Infiltration allows for pollutants to be filtered from the water prior to its reaching the groundwater table, preventing the deposit of the pollutants directly into drinking water supplies. Landfill, Discharging A landfill facility with liners, monitoring equipment and other measures to detect and/or prevent leachate from entering the environment and in which the leachate is treated on site and discharged to a receiving stream. Landfill, Non-discharging A landfill facility which does not discharge leacheate into a receiving stream. Low-Density Option One of two approaches available for development in watershed overlay districts. Generally, the low-density option relies on density and impervious surface limits to minimize the risk of water pollution. Non-Point Source Pollution Pollution which enters waters mainly as a result of precipitation 134 and subsequent run-off from lands which have been disturbed by man's activities and includes all sources of water pollution which are not required to have a state or local or state permit for discharge into a stream. Non-Residential Development Development of any land use which is not residential in nature, including uses (such as churches) which are allowed in residential zoning districts. State Mandate The minimum Rules adopted by the Environmental Management Commission for application to North Carolina's watersupply watersheds, as required by the Water Supply Watershed Protection Act. The purpose of the Act, as stated in its opening paragraph, is "... to protect and enhance the quality of the State's surface water supplies by establishing a cooperative program of watersupply protection to be administered by local governments consistent with statewide management requirements established by the Environmental Management Commission (EMC)." Stream Buffer A stream buffer is an area of land adjacent to perennial and intermittent streams which, except as permitted in Article of this Ordinance, must remain undisturbed in its natural state. Perennial streams are shown as solid blue lines and intermittent streams as broken blue lines on the USGS Quadrangle maps. Water-Dependent Structure Any structure for which the use requires access to or proximity to or citing within surface waters to fulfill its basic purpose, such as boat ramps, boat houses, docks and bulkheads. Ancillary facilities such as restaurants, outlets for boat supplies, parking lots and commercial boat storage areas are not water-dependent structures. Watersupply Watershed (or Protected Watershed) Land that drains to existing reservoirs which are public water supplies or potential reservoir sites or stream intakes which have been designated for protection. All such lands have been classified by the Environmental Management Commission as WS-II, WS-III or WS-IV watersheds and require protection in accordance with the State Mandate. 131 Appendix Extended Wet Detention Pond Standards Scope These standards are intended to meet the State's requirements for wet detention ponds in protected watersheds where a High Density Development Permit has been approved. These guidelines and standards are for designing and building ponds on a small scale, less than 100 acres drainage area, serving individual developments. Other appropriate standards should be used for regional basins serving larger, developed watersheds. Details of runoff calculations, pond design guidelines, etc. are not included since proven references are readily available from other sources. Refer to the references at the end of this standard. General Description Extended wet detention ponds are intended to capture and treat polluted runoff from developed areas during both infrequent small storms and infrequent larger events. Why Ponds Are Favored Because of the low infiltration capacity of soils in Orange County detention ponds are the preferred Best Management.Practice (BMP) and extended wet detention pond are preferred over other types of ponds. Detention ponds that are dry between rainfall events lack the most desirable conditions for capturing pollutants. In addition, dry ponds cannot maintain the favored biological conditions between events that are necessary to breakdown pollutants. A Typical Pond In Orange County the topography and soil conditions are such that most ponds are created by constructing an earthen dam between two hills and impounding runoff in the valley above the dam. Pipes through the dam and an emergency spillway around one end of the dam control the waterievel and release overflow. Figures 1 and 2 illustrate a typical wet detention pond. The site plan must locate the pond so that it intercepts runoff and pollutants from the developed area. Diversions and storm drains can be used to intercept and channel runoff to the pond. Other Possible Locations It may be possible, where suitable soil conditions exist, to construct a basin on a slope where there is no valley. This approach involves excavating and constructing a dam on three sides and building diversions to intercept runoff and channel rcep an el it to the Po nd. Such sites must be evaluated carefully so that the pond is positioned where diversions will work and the watershed is sufficient to establish a viable pond. Excavated Ponds Simply digging a hole to create a pond is usually impractical in Orange County because of the shallow soil in most locations. There may be exceptions where soil borings show that the depth DRAFT 1 June 1993 136 to bedrock is sufficient and that the soil type and other criteria are met. Where such sites exist the function of the pond can be enhanced by infiltration into the soil. High water level Normal water level Emergency spillway A — B — C 7,,� Dam------........._ ill . - . Baffle Sediment forebay Riser Entrance channel Pier to allow fishing Barrel recreation, and other uses. Figure 1 : Illustration of a Typical Wet Detention Pond Showing the Various Components. Inlet channel High water level N A .._....)__\,_.\/._______,-------" ""1"---Normal water level Sediment forebay B � High water level Shallow water Normal water level High water level — Normal water level C Deep water for fish, recreation, etc. DRAFT 2 June 1993 137 Figure 2: Cross Sections of a Wet Detention Pond. A Proven BMP Studies have shown that wet detention ponds can be very effective in removing and treating pollutants washed off impervious surfaces. Research has found that most pollutants are removed by the first half inch to one inch of runoff, the so called "first flush of runoff The degree of pollutant removal is a function of the size and shape of the permanent pool, the characteristics of individual urban pollutants, and the intensity of development (area covered by impervious surfaces and the type of land use) in the watershed. When properly sized and designed wet ponds have a high removal rate of sediment, nutrients, and trace metals. Biological processes in the pond remove soluble nutrients that cause eutrophication of streams below the pond even though this may result in periodic water quality problems in the pond itself. Multiple Use Ponds Properly designed detention ponds can serve several purposes: removal of pollutants; mitigating flooding by controlling the rate of stormwater runoff from the project; prevent downstream channel erosion; provide wildlife habitat, landscaping, and recreation; and serve as a component of open space. In some situations it can be used as a temporary sediment pond during construction and then be converted (sediment and debris removed, outlet structure converted) into a permanent detention pond. This can make pond construction more economical. Designing the pond for multiple uses can make it an attractive, integrated part of a development instead of just an eyesore and maintenance problem in a remote corner. Minimum Drainage Area As a general rule, 10 acres of drainage area per acre of surface area in a pond is the recommended minimum to provide sufficient runoff and provide a reliable source of water so that the permanent pool is maintained, desirable biological activity is sustained, and fish habitat created. This is a conservative recommendation; the necessary watershed will vary depending upon the runoff coefficients of the watershed: wooded land will produce very little (but very clean) runoff because the soil, leaf litter, and other debris act like a sponge and absorbs water; most of the rainfall on pavement will run off (but is not of very desirable quality) because the soil is effectively sealed. Leaks, evaporation, and infiltration losses can result in pond drawdowns where there is insufficient inflow to replace these losses. These losses vary depending on location. Springs can help maintain volume, but few locations have adequate flow to actually fill a pond that has significant volume. Runoff from rainfall is needed to fill the pond after construction and replenish it after a drawdown. However, drawdown is more of a nuisance and aesthetic problem that may adversely affect fish population but does not necessarily affect its ability to remove pollutants. A partially filled or dry pond may increase holding time, allowing more sedimentation, and removing more pollutants. The Purpose of a Wet Pond The goal is to establish a permanent impoundment of water above which stormwater runoff is stored and released at a much lower rate than which it enters the pond. The purpose of the permanent pool is to create a viable pond environment between rainfall events and to create a mechanism to capture pollutants and either retain them or treat them. A possible additional benefit is to more closely approximate the runoff conditions that existed below the pond prior DRAFT 3 June 1993 1',_ '3 to development. However, above the pond development will almost certainly increase the volume and rate of runoff. How a Wet Detention Pond Works The basic mechanism of pollutant removal is that suspended pollutant particles in runoff are captured by gravity settling as runoff enters the relatively still water in the pond (the same process that creates a delta). In the stream channel the energy of flowing water suspends the particles, but this churning action is lost as runoff enters the pond. This causes the particles to settle toward the bottom, the larger, heavier ones settling out first while very small ones may take days or weeks. Over time pollutants are trapped in the sediment that accumulates on the bottom. There may be some infiltration into the soil, but this is probably minimal in Orange County because of the tight soils and low infiltration rates. Particles, especially larger ones, are relatively easy to trap, but soluble nutrients have minimal settling velocities, so biological uptake is necessary. Soluble nutrients are removed by the biological activity of plants, alae, and other organisms that reside in the permanent pool. Plants convert soluble nutrients into biomass which can settle to the bottom where they can be consumed by bacteria. The ability of resident organisms to treat soluble nutrients is why wet detention ponds are preferred over dry ponds. Creation of the Desirable Environment A certain pond depth and volume must be established for these pollutant trapping and treatment processes to function properly. Consideration must be given to the particular pollutants to be captured, the size of the developed area the pond is built for, and the total drainage area to the pond, even if the offsite drainage area does not contribute significant pollution. The depth, volume, surface area, and shape of the pond must be such that inflow and wave action do not resuspend accumulated sediment and pollutants. Otherwise, pollutants will be washed through the pond and its purpose adversely affected. This is especially important at the shallow upper end where most pollutants accumulate as runoff enters the still water in the pond. Specifics from studies done on the efficiency of wet ponds can be found in the references listed in the bibliography. Designing the Pond To take advantage of the potential for pollutant removal, the pond must be designed to create conditions favorable for capturing and retaining pollutants and for sustaining the desired biological activity necessary to treat them. Such considerations as sufficient drainage area, adequate soils, runoff calculations, engineering, inspection during construction, and periodic inspection, maintenance, and repair must be considered. Who Designs, Inspects, and Certifies the Pond? A qualified registered professional engineer or landscape architect must design the pond, certify construction in writing, and provide as-built plans. DRAFT 4 June 1993 11a!/ Design and Construction Standards Determining the Minimum Volume of the Pond. For accuracy the design must be based on a field topographic survey of the pond site. USGS topographic maps or other sources can be used to determine total drainage area, ground cover, existing land use, etc. Permanent Pool The permanent standing volume must be at least four (4) times the volume of runoff (not the "peak rate of runoff') resulting from a one (1) inch rainfall over the entire watershed. Methods for calculating this volume can be found the in references and other text. This design volume should result in a pond capable of removing 85-90% of suspended solids and 65% of the phosphorus. Purpose of this Volume This volume is designed to achieve an average of two weeks of retention so that sedimentation processes occur for even small particles and to maximize biological uptake of pollutants. The theory behind the design is that "new" polluted runoff into the pond will displace "old" treated water in the pond from previous events. The "new" water will be held and treated until the runoff from the next rainfall event (if the storm is heavy enough to produce any) displaces it. As far as volume is concerned,bigger is better, but a threshold is reached where increasing it has little additional benefit and may disturb more area. Evaluation of the Volume Calculation This calculation is the minimum volume of the permanent pool for water quality purposes. It does not necessarily mean this should be the minimum volume of the pond. The watershed and development being considered may be such that only a small volume is required. However, other factors, such as the ratio of surface area to watershed, fish habitat, stormwater detention, recreation, etc. must also be considered in the design. Therefore,,a larger pond may be needed or desired. Offsite Drainage Area In calculating this volume, if there is offsite drainage area the projected future development of it must be taken into account in calculating the volume and and designing the outlet structures. Reasonable estimates can be taken from the County's land use plan. This is necessary so that the pond's function of capturing pollution and structural integrity is not threatened by future upstream development. Storage Volume Above the Permanent Pool and Control of the Peak Rate of Runoff An additional storage volume between the permanent pool and the top of the riser must be provided to store the runoff resulting from a one (1) inch rainfall over the drainage age. (This DRAFT 5 June 1993 is the same volume of runoff used to determine the minimum volume of the permanent pool.) The purpose is to capture and store the volume of runoff that contains most of the pollutants. 1 U To capture this runoff the overflow device that controls the water level must be configured with a small orifice that establishes the permanent water level but is small enough to impound this volume and store it. The orifice must be designed so that the runoff from a one inch rainfall is stored for not less than 2 days and not more than 5 days. There are various methods and outlet configurations capable of meeting this requirement. It is beyond the scope of this standard to cover the means and calculations since more than adequate references are readily available. Refer to the references. Sizing the Pond Using the topographic information on the proposed site and the calculations of the required volumes the height of the dam and the extent of the pond can be determined. A trial and error process can be used. However, computer programs that can easily and quickly perform these calculations are recommended that allow minipulation of the variables to discover the best fit for the particular location. The Dam Suggested design procedures for the dam are those from the US Department of Agriculture Soil Conservation Service. A minimum of one foot of freeboard is required between the calculated maximum depth of flow for the design storm through the spillway (where one is used) or the maximum water level (when only a riser is used) and the top of the dam. A maximum 3:1 slope (preferably flatter) of both sides of dam is required to facilitate mowing and maintenance and discourage the growth of undesirable vegetation and to discourage borrowing animals. A qualified person must examine the soil and determine if it is suitable for holding water and constructing the dam. During construction of the dam, supervision must be provided to ensure that good soil is used and properly compacted. The soil used in the dam must be free of rocks larger than 6, inches, stumps, roots, and other debris that could compromise the structure's integrity. If the dam height is 15 feet or more (measured from the highest point in the dam to the toe of the dry slope in the bottom of the downstream channel) and the pond impounds 10 acre/feet or more (measured to the crest of the dam) then the necessary permits under the Dam Safety Act of 1967 must be obtained from the State and copies submitted. The Basin An average depth of 3 to 6 feet is optimal for pollutant removal and treatment. Depths over 8 feet should be avoided to prevent thermal stratification, which tend to become anoxic. However, topography and required volume will also have to be considered. Thermal stratification and thermal impacts can be mitigated by placing the riser in the deepest point and designing a coldwater bottom release in the riser. DRAFT 6 June 1993 The upper ends of the basin must be configured so that inflow minimizes turbulence to promote sedimentation and prevent resuspension of accumulated sediment and pollutants. 14 1 Cutoff Trench Care must be taken when excavating the cut off trench not to expose underlying rock fractures that may cause leaks and effect the pond's ability to maintain the desired water level as well as its appearance if multiples uses are planned. Soils While infiltration into the soil is desirable for pollutant removal, it should not be to the extent that it threatens to drain the pond or lower the water level below the designed permanent volume. (Some drawdown during the summer and draughts is almost inevitable in ponds with small watersheds such as is expected with detention ponds.) Soil at the site should be suitable for dam construction. A soils investigation by a qualified professional is necessary as part of the plans. Other Permits Wetlands If the pond site involves a wetland, the necessary permits must be obtained. This should be determined as part of the site investigation. Floodplains If the pond will be constructed in a designated floodplain the approvals and permits necessary to place fill will be required. This will usually not be the case since ponds designed and built under this standard will not be located on streams large enough to have a designated floodplain. However, maps should be checked to make sure that a floodplain from a larger stream does not extend up a tributary where the dam is proposed. Erosion Control If more than 20,000 square feet will be disturbed, erosion control plan approval and grading permit will be required. If streets and other improvements are to be made the pond can be included in the erosion control plan for all the work. Others Depending upon the location, size of project, area disturbed, and other factors additional permits may be necessary, such as an environmental assessment or evaluation, natural areas study, etc. Shape of the Basin A long, narrow basin maximizes the length of flow between points of inflow and the outlet structure. Baffles can be used to increase the flow length where a long basin is not possible. A baffle near the inlet(s) is necessary to concentrate sediment so that it can be removed periodically. The shape and dimensions should be such that, for reasons of economy, the pond above the baffle can be reached by a rubber-tired backhoe to remove and load sediment into a dump truck for removal to an onsite disposal area. Depth of Basin To maximize pollutant capture and treatment at least 25% of the pond should be less than two DRAFT 7 June 1993 feet deep. A shallow forebay and an "aquatic bench" 10 to 20 feet wide around the perimeter is suggested. (To avoid access problems that shallow edges create for recreational use, 14 ,constructing a pier before the pond is filled can provide access for swimming, boating, and ffishing.) The Pond Environment Many of the characteristics of a pond that enhance pollutant capture and treatment (shallow water, plant and algae growth) have a negative impact on its aesthetic qualities (mosquitos, odor, turbidity, algae). These must be balanced if the pond is to serve multiple uses, such as recreation, by providing shallow areas to encourage vegetation and deeper areas for access and recreation. WARNING ! Designers, developers, and potential residents must be informed that the pond will not necessarily be an ideal water environment because its purpose of capturing and treating pollution almost certainly precludes this. The intent is to protect water quality downstream, not in the pond itself. To improve the quality of the water in the pond the volume should be increased above the minimum required while not exceeding the size that the watershed can keep the pond full. Peak Discharge Control for Streambank Protection An additional function of the pond must be to control the increase in the peak rate of runoff from the site. The post-development discharge below the outlets for the two-year and ten-year storms must not exceed the predevelopment rates. The purpose is to protect the receiving channel from erosion resulting from the increased rate and volume of runoff. Installing a dewatering device to store the one inch runoff volume above the permanent pool may meet or exceed this requirement, but this needs to be confirmed and calculations provided. The optimal level of flood control and streambank protection is when multiple design storms are controlled, both the 2-year and 10-year design storm is sufficient. Because development of the site will surely increase the rate and volume of runoff above the pond, provisions must be made for protecting the channels upstream of the pond so that they do not erode and cause unacceptable levels of sediment to be carried into the pond. Pipes The use of reinforced concrete pipe is encouraged because of its long life even though it may be more difficult and expensive to install initially. Plain corrugated metal pipe (CMP) is not acceptable. It must be coated (preferably aluminized) because of the short life expectancy of plain pipe and the trouble and expense of replacement, in addition to the risk of failure of the structure. Pipe Inlet Protection A trash rack or hood is required to trap debris in the pond and prevent the outlet from clogging. Wire screen or bars across the inlet is not acceptable because trash and debris can accumulate over the inlet and such devices reduces the efficiency of the inlet. DRAFT 8 June 1993 Provisions for Draining the Pond A means of completely draining the pond must be provided (except in the instance of an excavated pond). This can be accomplished by extending a pipe from the riser into the basin with a valve or gate on the end (one designed expressly for the purpose of use in a pond) or a 1�` separate pipe through the dam with a valve on the downstream end (buried in the embankment to prevent freezing and vandalism) to drain the pond. The device should be sized to drain the pond within two to five days. Aesthetics Care should be taken in the design and construction so that the pond fits in with the surrounding development and environment. Debris should be burned (where possible) or otherwise properly disposed of instead of left in a pile. On industrial, institutional, commercial or multifamily projects other configurations of impoundments may be more desirable to fit in with the surroundings. Stabilization and landscaping of the finished pond should be planned with consideration given to the appropriateness of other uses. Sediment Storage, Removal, and Disposal It is highly recommended to.provide a sediment storage area in the forebay of the pond. The goal is to concentrate the majority of the sediment in a confined area so that it can be eventually removed. The intent is to make sediment removal more economical by confining most of the sediment in an area that is within reach of a rubber-tired backhoe sitting on the shore. This will hopefully eliminate the necessity and expense of having to drain the pond for excavation or bring in a larger tracked backhoe or dragline to remove sediment. A sediment storage area can be provided by constructing a baffle across the basin to enhance sedimentation. The recommended method is to use a rip-rap gabion (wire baskets filled with stone) to build the baffle. This is a long lasting method durable enough to withstand the impact of a backhoe excavating the accumulated sediment behind it. Sediment Disposal Area A disposal area must be provided within the project upstream of the pond for convenience and economy. This area must be designated on the site plan. Accumulated sediment must be removed when half the depth is taken up in the sediment forebay. Access Access for maintenance and periodic sediment removal must be provided. Access connected to a public right-of-way must be designated on the subdivision or site plan . The access must be cleared at least 30 feet wide during construction of the pond. A stone travelway at least 12 feet wide and 4 inches thick must be provided down the center of the access. DRAFT 9 June 1993 Creating Optimum Conditions for Pollutant Removal and Treatment 14 4 renting a marsh at the inlet enhances the growth of vegetation and the trapping of sediment and other pollutants. Aquatic benches along the sides also encourage vegetation. The plants enhance pollutant removal by drawing nutrients from sediments. Algae attaches to these plants and can draw nutrients directly from the water. A created wetland is desirable, but consideration should be given to restricting vegetation to a confined area where it can be managed so the entire pond does not become a jungle of vegetation, cold blooded wildlife, and insects. The greatest initial settling occurs in the upper end of the pond where the larger, heavier particles fall out as the flowing runoff looses velocity as it enters the still water in the pond. For this reason it is necessary to provide a baffle or other structure near the inlet to concentrate sediment accumulation where it can be reached for periodic removal as part of maintenance. Consideration for Multiple Uses Careful evaluation and planning is needed since vegetation may make the pond unattractive for use as recreation and landscaping. If the pond is to be multipurpose, marshes and benches should be isolated from other areas to be used for fishing, boating, swimming, etc. Vegetation on or close to the dam should be discouraged and prevented through routine maintenance. Roots can weaken the dam, and vegetation attracts burrowing animals that can weaken it further. Thick vegetation makes maintenance more difficult, which may delay work and allow growth to spread further until major clearing is required. Refer to the sources listed in the references for more information and for suggested plants to establish in a pond. Safety A fence is required around the pond to control access. Gates sized for either pedestrian or vehicular access (for maintenance) should be installed at appropriate locations. At the designated access to a public right-of-way the gate must be wide enough to accommodate equipment needed to mow and otherwise maintain the pond and to excavate accumulated sediment when the time comes. The owner should consult with an attorney concerning liability for accidents, legal requirements for fencing and access, insurance, etc. Review of Pond Design A pond can have both positive and negative impacts on the natural environment and the development and review of the design will consider these impacts. However, develop of the site will have impact downstream with or without the pond, so the pond is necessary to mitigate the impact and contain pollutants before they are washed downstream. DRAFT 10 June 1993 Ponds can severely disturb the sensitive ecology of headwater streams. Water can heat up rapidly in the summer and increase downstream water temperature. This can be mitigated somewhat by including a bottom water release, over-sizing the pond, and providing shading near the 1 4 perimeter. Inspections and Maintenance of the Completed Structure Inspections The pond must be inspected at least once a year by the owner or their agent. If the owner or homeowner's association is not capable or qualified, a qualified professional, preferably the designer, should be retained to perform the inspections. Responsibility is the owner's even though County personnel will perform periodic inspections to ensure continued compliance and performance. Inspection should look for: embankment subsidence; erosion of slopes or spillway; cracking of the embankment; growth of undesirable vegetation; condition of riser, barrel, and other pipes, seepage below or through dam (often indicated by wet soil below the dam); sediment accumulation, clogging of inlets to pipes; and condition of upstream and downstream channel protection. Those inspecting the pond show use as built plans. Where problems are discovered corrective action should be initiated by the owner and not put off for County staff to discover. Maintenance Routine maintenance should include: mowing grass; fertilizing_grass and reseeding areas where vegetation may have failed, particularly on the dam and the emergency spillway; removal of undesirable vegetation; removal of trash and other debris that could clog the outlet structure; removal of floating debris from the trash guard around the pipe inlet; Dedication of land and Responsibility for Maintenance Dedication Responsibility of owner or owners. may be homeowners association but this can always be dissolved so plat and agreement (deeds) must state that it belongs to the owners. DRAFT 11 June 1993 Plan Submission 14 6 Predevelopment Consultation Consultation with those reviewing the site plan and pond design are encouraged before submission of the application for development approval. The purpose is to review the proposal and discuss how these standards apply to the specific site. It is also an opportunity to answer questions and attempt to work out any conflicts before submitting a formal application. Plan Content At a minimum the plan must include the following: A topographic map of the pond location and surrounding area (not the entire watershed) based on a field survey by a registered engineer or surveyor. Calculations to support the requirements of this standard, assumptions, the design, etc. including runoff, storage volumes, surface area, pipe and spillway sizing, velocity in spillway for lining, outlet protection, flood routing, etc. Plans of the design with pertinent information required to evaluate design and for it to be built according to the design. Soils investigation report performed by a qualified individual. Profile of dam with outlet structure elevations. Illustrative cross sections of the basin with finished elevations showing areas to be left shallow to encourage the growth of vegetation or, if part of the design, to be deeper to discourage growth and provide recreation or other.uses. Erosion control plan, if applicable, along with application, fees, etc. (Erosion control should at least be considered in the design, but the actual submission of the plan for approval will depend on the proposed date for the start of construction.) Landscaping, stabilization, other pertinent information, such as establishing marsh vegetation, providing recreation facilities, etc. DRAFT 12 June 1993 - REFERENCES BMPs (Best Management Practices) BMP Handbook for the Occoquan Watershed, Northern Virginia Planning District Commission, Annandale, Virginia; August, 1987. Northern Virginia BMP Handbook. Northern Virginia Planning District Commission. November 6, 1992. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban BMPs. Metropolitan Washington Council of Governments; July, 1987. Pond Design U.S. Department of Agriculture Soil Conservation Service guidelines and standards for pond design and construction. Stormwater Control and Detention BMP Handbook for the Occoquan Watershed. Northern Virginia Planning District Commission, Annandale, Virginia; August, 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban BMPs. Metropolitan Washington Council of Governments; July, 1987. DRAFT 13 June 1993 X48 o\ Orange Water and Sewer Authority 400 Jones Ferry Road OWASA P.O. Box 366 Carrboro, NC 27610 (919) 968-4421 STATEMENT TO THE ORANGE COUNTY BOARD OF COMMISSIONERS PUBLIC HEARING ON PROPOSED AMENDMENTS TO THE COUNTY'S ZONING ORDINANCE AND SUBDIVISION REGULATIONS REGARDING THE PROTECTION OF WATER SUPPLY WATERSHEDS Superior Courtroom, Orange County Courthouse Hillsborough, North Carolina August 23, 1993 Orange Water and Sewer Authority's position on the proposed watershed protection requirements is summarized as follows: • Strong support and appreciation for strict measures to be left in place for the University Lake watershed. • Support for amendments pertaining to the Jordan Lake Protected Area. • Disagreement with and substantial concern regarding proposals to weaken existing regulations in the Cane Creek watershed. The Authority respectfully requests the Board of Commissioners to apply the following interim regulations to the Cane Creek watershed, pending completion of the comprehensive watershed study to be conducted for OWASA and subsequent actions taken pursuant to its recommendations. 1. Continue to prohibit all commercial or industrial land uses throughout the Cane Creek watershed. 2. Apply the same minimum lot and impervious surface limits to the entire Cane Creek Reservoir watershed as proposed for the University Lake watershed, basically 5-acre minimum lots plus other strong protective measures. 3. Allow the provision of water and wastewater service only through individual onsite wells and disposal systems; no municipal or community level wastewater disposal. There is ample justification for assigning more protective rules to Cane Creek than to other WS-II watersheds in Orange County. The Cane Creek watershed merits special protection for a number of very important reasons including: • Field observations and unreduced monitoring data suggest that water in the Cane Creek Reservoir may be of substantially lower quality than originally predicted. An Equal Opportunity Employer 3 el:eafryet � - Fr RESOLUTION AUTHORIZING COMMENTS TO ORANGE COUNTY BOARD OF COMMISSIONERS REGARDING PROPOSED WATERSHED PROTECTION REQUIREMENTS FOR JORDAN LAKE, UNIVERSITY LAKE, AND CANE CREEK RESERVOIR WHEREAS, the Orange County Board of Commissioners will conduct a public hearing on August 23, 1993 to receive comments on proposed changes to its watershed protection requirements. NOW, THEREFORE, BE IT RESOLVED: 1. That the Board of Directors of Orange Water and Sewer Authority endorses the principles embodied in the draft comments prepared by Authority staff as presented in the Board's August 12, 1993 agenda, Item 7, pertaining to Jordan Lake, University Lake, and Cane Creek Reservoir; and 2. That the Acting Chair or his designate is authorized to present a statement at the public hearing scheduled for August 23, 1993 which reflects the concerns of Orange Water and Sewer Authority that land use regulations for the Cane Creek Reservoir watershed be sufficiently stringent, particularly until a site specific study is completed, to adequately protect the water quality of the Cane Creek Reservoir. Adopted this 12th day of August 1993. 1'446.'.b. L 1. amen T. Mergner, Actin:, hair ATTEST: G ` "71,,,46 , iel A. Textoris Secretary-Treasurer Orange Water and Sewer Authority Statement to Orange County Commissioners August 23, 1993 Page 2 • The Cane Creek Reservoir represents a $20 million dollar investment by nearly 60,000 Orange County customers served by OWASA. Except for University Lake, no other water supply in the County is so essential to as large a number of residents. • We acknowledge that Cane Creek still lacks a comprehensive watershed analysis such as the one conducted for University Lake, and this strongly suggests stronger interim regulations. OWASA's current timetable is to have a completed Cane Creek study by the end of calendar 1994. Especially worrisome are proposed amendments that would allow commercial activities in a watershed where no such uses are now permitted. The allowance of up to 70 percent impervious coverage for non-residential development without stormwater controls on up to 900 acres of Cane Creek watershed land does not appear to be justifiable, even though consistent with the EMC's statewide minimum. The Authority strongly urges that, at a minimum, these non-residential allowances be eliminated from further consideration. The Authority has demonstrated a commitment to maintaining its $20 million dollar investment at Cane Creek Reservoir through a number of strong actions including: • Investing hundreds of thousands of dollars in purchasing critical acreage around the lake, • Supplementing the North Carolina Agricultural Cost-Share Program to help private farmers pay for conservation management practices, and • Spending thousands of dollars on special technical studies and monitoring projects. is • Prohibiting the use of gasoline powered motorboats. Along with this demonstrated commitment to protecting Cane Creek Reservoir comes the expectation that Orange County's Zoning Ordinance and Subdivision Regulations will provide a level of protection commensurate with the reservoir's value to the community, and commensurate with the financial investment underwritten by its users. We believe that the higher level of interim protection, as outlined above, is justified both on the basis of the preliminary water quality data and the community value that Cane Creek represents to a majority of Orange County's residents. The Board of Directors of Orange Water and Sewer Authority respectfully offers these recommendations for your consideration.