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HomeMy WebLinkAbout20090576 Ver 1_More Info Received_200906220q-oSIca DR. J.H. CARTER III & ASSOCIATES, INC. Environmental Consultants P.O. Box 891 • Southern Pines, N.C. 28388 (910) 695-1043 9 Fax (910) 695-3317 Letter of Transmittal To Attn: Ian McMillian Division of Water Quality 401 Wetlands Unit 2321 Crabtree blvd Raleigh NC, 27604 WE ARE SENDING YOU Attached Copy of letter Prints Date:6-19-09 Job #0759 Attn:Ian McMillian Re: Johnston Community college permit info DWQ# 09-0576 Reports Maps Plans Data Photos COPIES DATE # Pgs I DESCRIPTION 5 6-17-09 5 Stormwater and Erosion/Sediment Control information additional mapping D THESE ARE TRANSMITTED For approval X For your use X As requested X For review and comment - "o nnu O l uKMWRTER BRANCH Approved as noted Approved as submitted Returned for corrections For your information If enclosures are not noted, please contact us immediately Endangered Species Surveys 9 Environmental Assessments 9 Land Management 9 Wetlands Mapping and Permitting Here is the additional information you requested for the Johnston County College w NCDENR Stormwater BMP Manual 8. Level Spreaders Revised 09-28-07 Level spreaders do not remove pollutants by themselves, but they are so crucial in assuring the effectiveness of certain BMPs and in protecting the function of riparian buffers that an entire chapter is devoted to them in this manual. Potential locations for a level spreader include, but are not limited to, the following: - The inlet of a bioretention cell or an infiltration basin, where a level spreader can reduce inlet velocities and diffuse flow for proper stormwater treatment. - Prior to a restored riparian buffer or a filter strip, where a level spreader can diffuse the flow to allow the vegetation to effectively remove pollutants. - Prior to a stormwater discharge to a riparian buffer or a wetland, where a level spreader can diffuse the flow into the vegetated area to prevent erosion and allow for pollutant removal. 8.1. General Characteristics A level spreader consists of a concrete linear structure constructed at virtually zero percent grade. Depending on the use of the level spreader, other elements may include a high flow bypass system, a forebay and a filter strip. If the level spreader is not outleting to a bioretention cell or another infiltration system, it will outlet to a filter strip. The filter strip is defined as the land between the outlet of the level spreader continuing downslope to the top of the stream bank or other surface water. Often, the filter strip consists of the 50-foot wide area beside a stream or other surface water that is protected by one of the Riparian Area Protection Rules. Outside of areas covered by Riparian Area Protection Rules, the filter strip must be a minimum of 30 feet in width. A filter strip is not required if the purpose of the level spreader is to outlet to wetlands. One of the main purposes of a level spreader is to disperse concentrated stormwater flows over a wide enough area to prevent erosion of the BMP or filter strip where it outlets. Erosion can undermine a BMP, and an eroded filter strip can be a significant source of sediment pollution to the streams and other natural water bodies. The other main purpose of a level spreader is to increase the interaction between the stormwater and the vegetation and soils in the BMP or filter strip. The vegetation and soils bring about pollutant removal via filtration, infiltration, absorption, adsorption, and volatilization. A level spreader may be used as a stand-alone device or as part of a larger BMP system. For example, a level spreader may also be used to diffuse the outflow of a BMP through a filter strip. If the flow from a drainage area exceeds the capacity of a level spreader, another BMP such as a dry extended detention basin or a wet detention pond may be used before the level spreader to attenuate the flow to an appropriate rate. Level Spreader 8-1 July 2007 NCDENR Stormwater BMP Manual Revised 09-28-07 Figure 8-1: Plan View of a Level Spreader (adapted from Hathaway 2006) Filter Strip: Could be a riparian buffer, vegetated Flow Bypass filter strip or restored riparian buffer. Structure % From Watershed Forebay Reinforced Channel Receiving Stream Reinforced Swale (necessary if level spreader is designed for the 1 in/hr storm) Level Spreader Lip / #57 Stone on Fabric Length =13' to 130' (parallel to contour lines) Figure 8-2: Profile View of a Level Spreader (adapted from, Hathaway 2006) Level Spreader Lip , 3' Layer of Flow Path: 1Y #57 5tone Riparian BLdTer n / or Filter Strip Channel 3 ft Wide Une4rcirain - 5aed 5tnp of for 5rte Sod filter Fabrc Condltlon5 - Drain Appropnately 5aed Into Bypass Swalc Concrete Footer Level Spreader 8-2 July 2007 NCDENR Stormwater BMP Manual Chapter Revised 09-28-07 8.2 Siting for Level Spreaders Used With Filter Strips A filter strip, as stated previously, is simply the land between the level spreader and the receiving stream. This land could consist of a protected riparian area, a vegetated buffer required by another stormwater program, a restored riparian buffer, or a filter strip used as a BMP (see Chapter 13 for appropriate design). Regardless of the reason for constructing or protecting the filter strip, it is important to determine whether the site is appropriate for a level spreader. In order to do this, the designer will need to gather the following information: - The peak flows during the one inch per hour intensity storm and the ten-year storm, - The topography of the proposed filter strip (obtained during a field visit), and - A characterization of the vegetation in the proposed filter strip (obtained and photographed during a field visit). After the field visit, the filter strip vegetation should be characterized as one of the following: - Grass: an area that is densely covered with grass. - Thick ground cover: a natural or naturalized area containing that is densely covered with a mixture of grasses, shrubs and herbs. Some trees may be present, but they are not the predominant species. The vegetation must be allowed to grow and not be cut back. - Forest: an area that is densely wooded with a ground cover of mulch or leaves. One required characteristic of all three types of filter strip vegetation is that it be dense, with no areas of bare soil. If existing vegetation is not dense, then the filter strip should be enhanced with additional plants so that it will not erode as stormwater flow is diffused across it. Once the above information is obtained, the designer has enough information to determine whether the site is appropriate for a level spreader. The following criteria must be met depending on the vegetation in the filter strip: - Filter strips with grass or thick ground cover: Slopes must be less than or equal to 8% for filter strips and the flow resulting from the 1 inch per hour intensity storm may not exceed 10 cfs. - Filter strips with forest vegetation: Slopes must be less than or equal to 6% and the flow resulting from the 1 inch per hour intensity storm may not exceed 2 cfs. - Filter strips with a combination of either grass or thick ground cover AND forest vegetation: Slopes must be less than or equal to 6% and flow requirements are met (see Design and Construction section for computing flow limits for a combined vegetation filter strip). In addition, for all vegetation types, uniform, diffuse flow must be possible (i.e., no draws may be present in the filter strip). Level Spreader 8-3 July 2007 NCDENR Stormwater BMP Manual Revised 09-28-07 Level spreaders are not appropriate when one or more of the following conditions exist: - There is a draw located within the filter strip downslope of the proposed level spreader. - The stormwater flows exceed the above guidelines unless another BMP is installed to attenuate the flow before it is discharged to the level spreader. - The slope in the filter strip exceeds the above guidelines unless DWQ approves level spreaders to be placed in series (explained in the paragraph below). Level spreaders must be placed outside of protected riparian areas unless the designer obtains a variance from the Environmental Management Commission. In addition, they may only be installed where the existing filter strip topography is appropriate and the stormwater flow will not exceed the capacity of the level spreader. If diffuse flow is not achievable based on site topography and stormwater flow rate, level spreaders may not be used. Other BMP choices for areas where level spreaders are not appropriate will be discussed in the Design and Construction section. If a filter strip exceeds the allowable slopes given above and up to a 15% maximum slope, installing level spreaders in series is a possibility if it can be shown that no other solution is practicable. Level spreaders in series may be approved by DWQ on a case-by- case basis following a site visit. Placing level spreaders in series will require siting a level spreader within a protected riparian area; therefore, a variance will be required from the Environmental Management Commission. See the Design and Construction section for appropriate placement of level spreaders in series. It is important to site the level spreader in a location where safe and legal access is available for construction and maintenance. 8.3 Design and Construction A level spreader system the drainage area consists of up to separate four parts (see Figures 8-1 and 8-2 above): 1. Flow Bypass System: A diverter box (or other type of flow splitter) that passes all flow above the one inch per hour intensity to a swale capable of safely passing the ten-year storm without eroding. A flow bypass system is not needed if the level spreader lip is constructed to be long enough to handle the flow from the ten-year storm. Also, if the level spreader is receiving flow from another BMP such as a wet detention basin, then a forebay is not needed. 2. Forebay: A bowl-shaped feature that slows the stormwater runoff and settles out some sediment and debris. If the level spreader is receiving flow from another BMP such as a wet detention basin, then a forebay is not needed. 3. Level Spreader Lip: The main body of the level spreader that receives water from the forebay (or directly from a BMP). The concrete lip is constructed so that it is level along its entire length. A swale is constructed immediately upslope of the level spreader lip, which allows stormwater to rise and fall evenly over the lip. Level Spreader 8-4 July 2007 NCDENR Stormwater BMP Manual ter Revised 09-28-07 4. Filter Strip: The densely vegetated area that receives flow from the level spreader. 8.3.1 High Flow Bypass System The flow bypass system must be constructed so that all flows above the one-inch per hour intensity are diverted to a bypass channel. If the level spreader is receiving flow from another BMP such as a wet detention pond, then a flow bypass system is not necessary. Additionally, a flow bypass system is not necessary if the level spreader is designed to handle the peak flow from the ten-year storm event. For a stand-alone level spreader, high flows will be bypassed through the use of a diverter box or other flow splitting device. Please see Section 5.3 for more information on flow splitters. This bypass channel must be designed to safely pass the ten-year design storm without erosion. If there is enough sunlight in the filter strip to support it, it is preferable to use turf reinforcement in place of riprap. This will reduce the cost of constructing the bypass channel while increasing pollutant removal and flow capacity of the bypass channel. The outlet of the bypass channel must be designed to reduce the impacts to the receiving stream. The bypass channel should be designed to enter the stream at an angle rather than a directly perpendicular manner, which may create erosion on the opposite stream bank. The bypass channel should discharge into a pool (deep section) of the stream. At the point of entry, stream banks may need to be protected with riprap or other engineered solution. Another option is to direct the bypass channel to a velocity dissipater or to use a bypass pipe that discharges to a culvert. Bypass channels are considered an "allowable" use within a protected riparian buffer. Tree removal and disturbance must be minimized and a buffer authorization must be obtained from the DWQ 401 Oversight/ Express Permitting Unit or the local delegated buffer permitting authority. 8.3.2 Forebay After passing through the flow bypass system, stormwater should be directed to a forebay (unless the level spreader is receiving flow from another BMP, in which case a forebay is not necessary). The forebay is an excavated, bowl-shaped feature that slows the stormwater and allows sediment and debris to settle out. Horizontal angle of entry pipe is 30° [recommended]; armor may be needed to prevent scour. Figure 8-3 shows a schematic of a forebay specifically designed for use with a level spreader. It is recommended that the forebay be designed so that its surface area is 0.2% of the contributing area's impervious surface. The recommended depth is one foot at the back end, sloping to three feet on the front side (portion closest to the inlet). A forebay is required unless no practical alternative is demonstrated and the level spreader is Level Spreader 8-5 July 2007 NCDENR Stormwater BMP Manual Chapter Revised 09-28-07 maintained by a municipal stormwater utility or NCDOT. The forebay can be lined with Class B riprap to dissipate energy. Design guidelines for the forebay provided are recommendations based on field research. Best professional judgment should be used with regard to forebay surface area and depth. Figure 8-3: Schematic of a Forebav for Use With a Level Spreader (Hathawav and Hunt 2006 Pipe: F-oni X lrt L C CC f T-. 1 a 8.3.3 Level Spreader Lip The level spreader lip consists of a grassed swale to distribute the water along the length of a level concrete weir. Water rises and falls evenly over the lip of the level spreader, which therefore distributes the flow evenly over its length. The lip of the level spreader should constructed out of concrete and should be 3 to 6 inches higher than the existing ground (downslope side) and anchored into the soil with an appropriately-sized concrete footer. The lip shall be installed at a 0-0.05% grade (level). An under drain is recommended to reduce ponding in the swale. One of the most important design criteria for the level spreader lip is that it must be constructed parallel to contour lines. Often, this will result in a level spreader that is curved, which is perfectly acceptable. The level spreader must be a minimum of 13 feet and a maximum of 130 feet in length (see Table 8-1 for determining required length). The appropriate length for the level spreader is determined based on two criteria: The type of vegetation in the filter strip and the design flow. Significantly longer level spreaders are needed when the filter strip is composed of forest vegetation. This is due to the fact that the forest flow is much more susceptible to erosion than an area with grass or thick ground cover. If the level spreader is outleting to a bioretention area or another filtration BMP, then the lengths appropriate for a forested filter strip should be used to prevent erosion within the BMP. Level Spreader 8-6 July 2007 NCDENR Stormwater BMP Manual Chanter Revised 09-28-07 The design flow will be based upon one of the following: - The peak flow resulting from the one inch per hour intensity flow (in which case a high flow bypass system and a forebay will be required). - The peak flow resulting from the ten-year storm (in which case a forebay will be required). - The drawdown rate from the upslope BMP if one is present (in which case neither a high flow bypass system or a forebay will be required). Table 8-1: Level spreader lengths Grass or thick ground cover filter strip Forest filter strip 13 feet of level spreader lip per 1 cfs of flow for slopes from 0 to 8 percent 65 feet of level spreader lip per 1 cfs of flow for slopes from 0 to 6 percent If the filter strip is composed of a mixture of grass or thick ground cover and forest vegetation, then the level spreader length should be determined by calculating the weighted average of the lengths required for each vegetation type. For example, if a level spreader is constructed adjacent to a 50-foot Neuse Riparian Buffer where Zone 2 (the outer 20 feet) will be maintained as grass and Zone 1 (the inner 30 feet) has existing forested vegetation, the appropriate level,,Spreader length will be: (20/50) x (13 ft/1cfs) + (30/50) x (65 ft/1 cfs) = 44.2 or 44 feet per cfs of flow The downstream side of the level spreader should be designed to further encourage diffuse flow of water and minimize erosion. The first 3 feet from the level spreader lip should use geotextile fabric with a 3-4 inch deep layer of #57 stone placed on top, or permanent erosion control matting. If geotextile fabric is used, it should be selected based on the soil type (sand, silt or clay). The fabric should be extended 3 feet from the level spreader lip to the downslope area in order to reduce erosion and located outside of Zone 2 of riparian buffer. 8.3.4 Filter Strip If the filter strip does not contain dense vegetation, it should be enhanced with additional plantings to reduce the chance of erosion. The first 10 feet of the filter strip downslope of the level spreader is not recommended to exceed 4 percent slope. 8.3.5 Level Spreaders in Series b.' If a filter strip slope exceeds 6 percent for filter strips that contain forest vegetation or 8 percent for filter strips with grass or thick ground cover up to a maximum of 15 percent slope, installing level spreaders is a possibility if it can be shown that no other solution is practicable. Level spreaders in series may be approved by DWQ on a case-by-case basis following a site visit. Level Spreader 8-7 July 2007 NCDENR Stormwater BMP Manual Revised 09-28-07 At the higher slopes of 6 or 8 to 15 percent, level spreaders will need to be placed every 25 feet in order to maintain diffuse flow. In an area covered by a Riparian Area Protection Rule, this will necessitate placing one level spreader just outside the buffer (50 feet from the stream bank) and a second level spreader in Zone 1 of the buffer (25 feet from the stream bank). Constructing a level spreader in Zone 1 will require a major variance from the Environmental Management Commission. 8.3.6 Options where Level Spreaders are not Appropriate Level spreaders may not be installed on sites where flows are too high to be conveyed by a 130-foot level spreader or the topography of the filter strip (if applicable) is too steep. The option that is selected in these cases will depend if the problem results from high flows from the drainage area or steep slopes in the filter strip. If the flows are too high, but slopes within the filter strip are within the allowable range, then a BMP that captures the stormwater runoff and releases it to the level spreader at a slower rate may be installed upslope. BMPs that attenuate flow include: - Dry extended detention basin: This BMP will eliminate the need for a high flow bypass system and a forebay. - Wet detention basin: This BMP will also eliminate the need for a high flow bypass system and a forebay. One option is to use 2-1/2" floating [Faircloth] skimmer in the pond to achieve a stable flow to the level spreader. If the topography of the filter strip is too steep for a level spreader, a different type of BMP will be needed. If the intended filter strip is an area protected by the Riparian Buffer Rules, then the stormwater will have to be treated by a BMP that removes 30 or more percent of the nutrients rather than using a level spreader. The outfall of this BMP can then be routed directly through the buffer with written approval from the DWQ. 8.3.7 Preformed Scour Holes Preformed scour holes are preshaped, riprap-lined basins located directly downgrade of an outfall. The purpose of a preformed scour hole is to dissipate energy and diffuse flow. They may be used to provide diffuse flow only when all of the following requirements are met: - The outfall area must be flat (less than 2 percent slope). - The scour hole must be located outside of protected riparian areas. The maximum allowable discharge to a scour hole from a 15-inch pipe is 6 cfs based on the ten-year storm discharge. The maximum allowable discharge to a scour hole from an 18-inch pipe is 10 cfs based on the ten-year storm discharge. Pipes larger than 18 inches may not be discharged to a scour hole. Once flow has filled the shallow basin, it overtops the preformed scour hole and is redistributed as diffuse flow to the surrounding area. A typical example of a preformed scour hole layout and its components is shown in Figure 8-4. Figure 8-5 is a cross section of a typical preformed scour hole. Level Spreader 8-8 July 2007 NCDENR Stormwater BMP Manual Chapter Revised 09-28-07 Figure 8-4 Typical preformed scour hole layout and components (NCDOT 2006) PIPF A (d.715" OR I'c NJ (STANDARD ROLL WICT?1; SOUP.RF PRFFORPAE SCOUR MOLE (PFS10 (RIPRAP IN BASIN NOT SHOWN FOR CLARITY) PFRLIANFr1T SOIL 1# RFiN70RCFf,.1EN- MATTING ;PSRL:1). PSRM SHALL BF SEEDED WITH VEGETATION AT INSTAL I.ATION Figure 8-5 Preformed scour hole cross section (NCDOT 2006) PIPE. PSRM c1-15 OR 15) INSTALL LEVEL AND ???1 61FLUSI I 'i`11 Ti i W JRAL ?DEPTH OF SCOUR F1O1_E GROUND r (1' MIN. - Y P,1AX.) Y NATURAL 71" rt??1 GROOND LINER: CLASS G RIPRAP j WIT}I TYPE 2 FILTER FABRIC r,11N. 1' TUCK. DEPTH OF RIPRAP (1'} BASF dVIDTH Once these site constraints are met, the size of the preformed scour hole is calculated based on the class of riprap used to line the hole and the diameter of the discharge pipe. For optimum energy dissipation, the ratio of the scour hole depth should be between 16 and 32 inches deep. The basin should be stabilized with filter fabric and riprap to absorb the impact of the discharge and to prevent additional erosion. Class B riprap (d50 = 8 inches) should be used on top of the filter fabric to line the preformed scour Level Spreader 8-9 July 2007 NCDENR Stormwater BMP Manual Chapter Revised 09-28-07 hole. The minimum and maximum stone sizes for Class B riprap are 5 inches and 12 inches, respectively. To prevent erosion immediately downgrade, an apron of permanent soil reinforcement matting (PSRM) is required downgrade of the preformed scour hole. Design requirements for scour holes: - The base of the scour hole is square. The width is calculated as follows: Base width = 3 x Discharge pipe size. - Riprap must be Class B (d50 = 8 inches). - Minimum width of the PSRM apron is the standard PSRM roll width. - PSRM must be tucked a minimum of 1 foot underneath the filter fabric and natural ground around the perimeter of the scour hole. - Side slope for all four sides of the scour hole is 2H:1V. - Riprap thickness is equal to 1.5 times the midrange riprap stone size (d50), or 1 foot for Class B riprap. - Minimum depth of the scour hole is 1 foot. - Maximum depth of the scour hole is 3 feet. Construction requirements for scour holes: - To avoid shifting of the scour hole after installation, the BMP should be installed in undisturbed soil instead of in fill material. - Install preformed scour holes after site stabilization. - Ensure that the apron is flush with natural ground. The elevation of the top of the preformed scour hole should be the same as the elevation of the PSRM. - Ensure that riprap consists of a well-graded mixture of stone. Smaller-size riprap stones should be used to fill voids between larger stones. - Where practical, route off-site runoff away from the BMP. - Immediately after construction, stabilize the exit areas with vegetation. - Clear the area of all construction debris and check the exit areas for any potential obstructions that could promote channelized flow. Note: This entire Scour Hole section was condensed from the 2006 NC Department of Transportation BMP Manual. DWQ appreciates their willingness to share their expertise on scour hole design. Level Spreader 8-10 July 2007 NCDENR Stormwater BMP Manual Chapter Revised 09-28-07 8.4. Construction Immediately before the level spreader is constructed, verify that ground contours are parallel to the level spreader location called for in the plans, slopes are less than 6 to 8 percent, and that no draws are located in the filter strip adjacent to the level spreader. If this is the case, the level spreader may need to be relocated to a more appropriate area. Also verify in the field that the level spreader is fully 50 feet away from the stream if it is being installed in an area covered by a Riparian Area Protection Rule. Before construction, reassess the vegetation in the filter strip. The filter strip should be densely vegetated prior to the construction of the level spreader. If not, additional plantings will need to be added prior to the construction of the level spreader. If grass cover needs to be re-established in the filter strip (only allowed within Zone 2 of a protected riparian buffer), construction may be limited to the growing season. The most important construction task is to insure that the level spreader is actually level. A correctly installed level spreader will have no greater than 0.05% grade on the spreader lip to ensure a uniform distribution of flow; otherwise water will channelize below the structure and become a source of erosion. Level spreaders should be constructed on undisturbed soil whenever possible. If the use of fill is unavoidable, it shall be constructed on material compacted to 95% of standard proctor test levels prior to seeding for that area not considered the seedbed. The level spreader and filter strip must be protected from harm (e.g., sediment and stormwater flows) during construction. A temporary stormwater diversion will likely be necessary until the level spreader has fully stabilized. If the disturbed areas are minor, they often can be stabilized with vegetative measures. 8.5. Maintenance 8.5.1. Common Maintenance Issues During the first one or two years after construction, filter strips and level spreaders should be inspected for proper distribution of flows and signs of erosion during and after major storm events. After the first one or two years, the strip may be inspected annually or biannually. If evidence of erosion exists, the eroded areas should be filled in and reseeded. The cause of the erosion should then be determined and, if possible, eliminated. Filter strips that are not maintained properly may quickly become nonfunctional (Schueler et al., 1992). Maintenance involves routine activities such as mowing, trimming, and replanting when necessary. Strips that receive excessive sediment may require periodic regrading and reseeding of their upslope edge because deposited sediment can kill grass and change the elevation of the edge such that the stormwater no longer flows through the strip in thin sheets. Maintenance requirements are as follows: Level Spreader 8-11 July 2007 NCDENR Stormwater BMP Manual 8.5.2. Sample Inspection and Maintenance Provisions Revised 09-28-07 Important maintenance procedures: - Immediately after the filter strip is established, any newly planted vegetation will be watered twice weekly if needed until the plants become established (commonly six weeks). - Once a year, the filter strip will be reseeded to maintain a dense growth of vegetation - Stable groundcover will be maintained in the drainage area to reduce the sediment load to the vegetation. - Two to three times a year, grass filter strips will be mowed and the clippings harvested to promote the growth of thick vegetation with optimum pollutant removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and may be allowed to grow as tall as 12 inches depending on aesthetic requirements (NIPC,1993). Forested filter strips do not require this type of maintenance. - Once a year, the soil will be aerated if necessary. - Once a year, soil pH will be tested and lime will be added if necessary. After the filter strip is established, it will be inspected quarterly and within 24 hours after every storm event greater than 1.0 inch (or 1.5 inches if in a Coastal County). Records of inspection and maintenance will be kept in a known set location and will be available upon request. Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately. Table 8-2 Sample Inspection and Maintenance Provisions for Level Spreaders, Filter Strips and Restored Riparian Buffers BMP element: Potential problem: How to remediate the problem: The entire filter strip Trash/debris is present. Remove the trash/debris. system The flow splitter device The flow splitter device is Unclog the conveyance and dispose (if applicable) clogged. of an sediment off-site. The flow splitter device is Make any necessary repairs or damaged. replace if damage is too large for repair. The Swale and the level The swale is clogged with Remove the sediment and dispose lip sediment. of it off-site. The level lip is cracked, Repair or replace lip. settled, undercut, eroded or otherwise damaged. There is erosion around the Regrade the soil to create a berm end of the level spreader that that is higher than the level lip, and shows stormwater has then plant a ground cover and bypassed it. water until it is established. Provide lime and a one-time fertilizer Level Spreader 8-12 July 2007 NCDENR Stormwater BMP Manual Revised 09-28-07 application. Trees or shrubs have begun Remove them. to grow on the swale or just downslo e of the level lip. The bypass channel Areas of bare soil and/or Regrade the soil if necessary to erosive gullies have formed. remove the gully, and then reestablish proper erosion control. Turf reinforcement is Study the site to see if a larger damaged or riprap is rolling bypass channel is needed (enlarge if downhill. necessary). After this, reestablish the erosion control material. The filter strip Grass is too short or too long Maintain grass at a height of if applicable). approximately three to six inches. Areas of bare soil and/or Regrade.the soil if necessary to erosive gullies have formed. remove the gully, and then plant a ground cover and water until it is established. Provide lime and a one-time fertilizer application. Sediment is building up on Remove the sediment and the filter strip. restabilize the soil with vegetation if necessary. Provide lime and a one- time fertilizer application. Plants are desiccated. Provide additional irrigation and fertilizer as needed. Plants are dead, diseased or Determine the source of the dying. problem: soils, hydrology, disease, etc. Remedy the problem and replace plants. Provide a one-time fertilizer application. Nuisance vegetation is Remove vegetation by hand if choking out desirable species. possible. If pesticide is used, do not allow it to get into the receiving water. The receiving water Erosion or other signs of Contact the NC Division of Water damage have occurred at the Quality local Regional Office, or the outlet. 401 Oversight Unit at 919-733-1786. 1 NOTE: Contact NC Division of Water Quality, 401/ Wetlands Unit at 919-733-1786 BEFORE any work in Protected Riparian Buffers. Level Spreader 8-13 July 2007 NCDENR Stormwater BMP Manual Chapter Revised 09-28-07 September 28, 2007 Changes: 1. 8.0: Removed the reference to "sand infiltration basin" and replaced it with "infiltration basin." 2. 8.3.6: Clarified the requirements for areas where the terrain is too steep for level spreader use. 3. 8.5: Updated the maintenance section. 4. Figure 8-1: Altered for clarification. 5. Figure 8-2: Corrected to indicate that level spreaders can drain to either riparian buffers or filter strips, not just buffers. 6. Table 8-1: Deleted, "If the forest vegetation is 100-150 feet wide, then the length can be reduced to 50 feet of level spreader per 1 cfs of flow. If the forest vegetation is more than 150 feet wide, then the length can be reduced to 40 feet of level spreader per I cfs of flow." Level Spreader 8-14 July 2007 A RMA NCDENR North Carolina Department of Environment and Natural Resources Division of Water Quality Beverly Eaves Perdue Coleen H. Sullins Dee Freeman Governor Director Secretary May 21, 2009 CERTIFIED MAIL: RETURN RECEIPT REQUESTED Mr. Herman Kight Johnston Community College 245 College Road Smithfield, NC 27577 DWQ Project # 09-0576 Johnston County Subject Property: Johnston Community College Library Ut to Neuse River [030402, 27-(41.3), WSIV, NSW, CA] REQUEST FOR MORE INFORMATION Dear Mr. Kight: On May 19, 2009, the Division of Water Quality (DWQ) received your application dated May 18, 2009, to fill or otherwise impact 1.4 acres of Isolated Wetlands to construct the proposed Johnston Community College library at the site. The DWQ has determined that your application was incomplete and/or provided inaccurate information as discussed below. The DWQ will require additional information in order to process your application to impact protected wetlands and/or streams on the subject property. Therefore, unless we receive five copies of the additional information requested below, we will place this project on hold as incomplete until we receive this additional information. If we do not receive the requested information, your project will be formally returned as incomplete. Please provide the following information so that we may continue to review your project. Additional Information Requested: 1. Please re-submit your site plans on full plan sheets at a scale of no smaller than 1 "=50' with topographic contours shown. 2. Please indicate all wetland impacts including fill slopes on the site plan. 3. Per the requirements of the Neuse River Basin Riparian Buffer Rule, you must show that this site meets diffuse flow requirements with a level spreader or other BMP per Chapter 8 of the BMP Manual (see http://h2o.enr.state.nc.us/su/bmp forms.htm). 4. Please provide all site plans as required in the PCN checklist (link: http://h2o.enr.state.nc.us/ncwetlands/documents/PCNChecklist_v 1 _4.doc) Please submit this information within 30 calendar days of the date of this letter. If we do not receive this requested information within 30 calendar days of the date of this letter, your project will be withdrawn and you will need to reapply with a new application and a new fee. 401 Oversight/Express Review Permitting Unit 1650 Mail Service Center, Raleigh, North Carolina 27699-1650 Location: 2321 Crabtree Blvd., Raleigh, North Carolina 27604 Phone: 919-733-17861 FAX: 919-733-6893 Internet: http://h2o.enr.state.nc.us/ncwetlands/ NorthCarolina ?aturalCr? An Equal Opportunity 1 Affirmative Action Employer Johnston Community College Page 2 of 2 May 21, 2009 This letter only addresses the application review and does not authorize any impacts to wetlands, waters or protected buffers. Please be aware that any impacts requested within your application are not authorized (at this time) by the DWQ. Please call Ms. Cyndi Karoly or Mr. Ian McMillan at 919-733-1786 if you have any questions regarding or would like to set up a meeting to discuss this matter. Sincerely, , // j -01 Oversight/Express Review Permitting Unit CBK/ijm cc: Lauren Witherspoon, DWQ Raleigh Regional Office USACE Raleigh Regulatory Field Office File Copy William Mullin, J.H. Carter III & Associates, Inc., 515F Midland Road, Southern Pines, NC 28387 Filename: 090576JohnstonCCU brary(Johnston)On_Hold Version 1.4 January 9, 2009 401 Oversight/Express Permitting PCN Submittal Checklist ? The application fee (Checks may be made out to "N.C. Division of Water Quality" - $240.00 for 401 Water Quality Certification with minor impacts - $570.00 for 401 Water Quality Certification with major impacts - Express Review Fee (Amount requested on Acceptance Letter) ? Five (5) complete and collated copies of the PCN Application and supporting documentation (instead of providing 5 copies of the full size plans you may provide two copies of full size plans along with three copies of 11 X 17 plans) ? Stormwater Management Plan (if applicable - see PCN Form Help File Section E) 1) Please provide three (3) copies of the stormwater management plans along with all supporting information pertaining to this project including the following: a. Entire site development/layout plans delineating all drainage areas; b. Design calculation sheets for all proposed BMPs) sized for both on-site and off-site drainage; c. BMP supplements for each proposed BMP and Required Items Check List (http://h2o.enr.state.nc.us/su/bmp forms.htm) along with all required items; d. A Notarized Operation & Maintenance Agreement for each stormwater management facility; e. Detailed construction drawing sheets shall include (i) Erosion and sediment control plans; (ii) Installation and planting schedules for the proposed BMPs; (iii) Appropriately scaled plan views and cross sectional details of all BMPs and associated components - inlet and outlet structures, forebay, respective zones and pertinent elevations. ? If your project is located within a State implemented Riparian Buffer Rule Area, submit the following along with site plans and PCN form: 1) Three (3) copies of the details for on-site diffuse flow provisions, (refer to http://h2o.enr.state.nc.us/su/bmp_forms.htm). ? DWQ Stream Determination Forms for streams on property and DWQ determination letter for wetlands or streams (if applicable). The following is the most critical of all the information that you must provide. The quality and detail of the information will often determine the expeditiousness of the review. The following is a checklist of the types of pertinent information required at a minimum: Maps and Plans: ? The most recent version of the 1:24,000 USGS Topographic Map - Please cleanly draw or delineate the site boundaries on the topographic map. _??.. ? The most recent version of the bound and published County NRCS Soil Survey Map - (required for projects within the Neuse River Basin, Tar-Pamlico River Basin, Randleman Lake Watershed and the Catawba River Basin, also recommended for all projects) - Please clearly delineate the site boundaries, etc. on the map. If the delineation obscures any of the features, it is recommended that a clean copy be provided. Copies of the Version 1.4 January 9, 2009 current soil survey and/or soil survey map sheets can be obtained from the local NRCS County Office (http://www.nc.nres.usda.gov/). GIS soil layers are not acceptable. ? Vicinity map - Please clearly mark the location and approximate boundaries of the property and project on the map. Please indicate north arrow and scale. Please include applicable road names or State Road numbers. ? The Site Plan - The most critical map to be provided is the site plan. You must provide full sized plans. The following is the minimum list of plans that are typically needed. ? Pre-construction/Pre-existing conditions - This sheet (or sheets) must include: • All jurisdictional and non-jurisdictional wetland, stream, water features, State regulated buffers (delineated into Zones 1 and 2) • Topographic contours with elevations • Any existing structures and impervious areas • Existing utility lines and easements • Existing roads, culverts, and other pertinent features • North arrow and the scale (1":50' scale is recommended). ? Proposed conditions - This sheet (or sheets) must include: • All jurisdictional and non-jurisdictional wetland, stream, water features, State regulated buffers (delineated into Zones 1 and 2) • Lot layout (if a subdivision or commercial development is proposed) - lots must be developable without further impacts to jurisdictional and non-jurisdictional wetlands streams, water features, and State regulated buffers. Building envelopes must be provided when streams, wetlands, riparian buffers, or water features exist on a lot • All built-out structures and impervious cover • Final grading contours with elevations • All utilities and easements (including septic fields on all lots within 100 feet of stream, wetland, or water features - if applicable) • Impacted areas - these should correspond with the Impact numbers listed on your PCN form. ? Drainage Plans - Final drainage plans must include the following: • Locations and pertinent elevations and sizes of the stormwater collection system and drainage ways • All inlets and outlets must also be shown with pertinent elevations (All outlets to wetlands must be at a non-erosive velocity, generally less than 2 ft/sec during the peak flow from the 10-yr storm) • Scaled stormwater BMPs must also be indicated as required by DWQ rules and policies • In certain cases (see Section E of PCN form), final stormwater management plans must also be provided (see Stormwater Management Plan Checklist) ? Proposed Impacts - All impacts to jurisdictional and non-jurisdictional wetland, stream, water features, and State regulated buffers must be shown and labeled on the site plans at a scale no smaller than 1" = 50'. All excavation, fill, flooding, stabilization, and other impacts that will be conducted in or near jurisdictional and non-jurisdictional wetland, stream, water features, and State regulated buffers must be indicated. Please provide cross sectional details showing the provisions for aquatic life passage (burial of culvert 20% for culverts <_ 48 inches, and 1-foot for culverts > 48 inches). Version 1.4 January 9, 2009 Wetland Impacts: ? Precise grading and final elevation contours must be provided. Existing vegetation and any clearing must be specified. ? All subsurface utility lines must indicate the location of anti-seep collars. Construction detail for anti-seep collars must be provided. ? Roadway or other crossings of riparian wetlands may require floodway culverts to maintain existing hydrological conditions. ? Plans should show that the hydrology of remaining wetlands on the site will be maintained. Stream Impacts: ? Stream impacts must be clearly shown on the plans. The centerline as well as the banks of the stream must be surveyed or located by GPS for the portion of the stream to be impacted. ? The inlet and the outlet of all culverts should be aligned with the stream as much as possible. Inlet and outlet elevations and streambed elevations should be indicated. Any inlet or outlet protection must be shown and enumerated on the impact map(s). ? For bottomless culverts or other spans, a vertical cross section should be provided that shows the minimum distance from each span to each stream bank, the stream cross section, the height of the span above the stream and the minimum distance from the edge of each footer to each stream bank. Additionally, please provide a signed and sealed geotechnical report of subsurface soils at the proposed bottomless culvert location. The report must comply with the Division of Highways - Guidelines for Drainage Studies and Hydraulic Design, prepared by A. L. Hankins, Jr., State Hydraulics Engineer - 1999. ? Multiple culverts or sectioned box culverts typically require the use of sills, off- setting or other means to match the cross section of the existing stream (in order to maintain stream stability and provide aquatic life passage). A vertical cross section of the culverts should be shown overlain with the up and downstream stream cross section including the stream flood-prone area. ? Impacts associated with dam construction must indicate and enumerate all fill associated with the dam footprint, spillway and any bank stream bank stabilization. The length of stream impounded must also be indicated and enumerated. L - n57zo IktnOry o 1 ALo\ rya` r l' •. .r Creek ??i Y ., w• WT 'y <t COJrasoJSl? ?PO THFIEL Tra?Y-um Sch I..: aasF Ory ?{ / i a a? y 4 - ?I iA r tR crtoa • 1 ?T.+ r Ii +?. T f • ,+ 14R 1 h fi t, - _ s-??,?.;. ?` ? - ?• ? ???; ? ca, :a a? 1 f .4? Cem, trbr 4 7: ice; Wrd ng S:r.p , Sandpit .. 0 0.1 0.2 0.4 0.6 0.8 approximante site Miles locaiton Johnston County Community College Proposed Library Site i [ 190000 FEFT P o MaB MCB, PAD FaB a Ma61-.. • PaE Am PaE Ce8 D AaAy w< PaE C ;h PaD i PaD PaD ~ Mc8 ' , ? Pad ? Ch PaD a PaE I- \ PaE B J \ PaD PaD \ ? G e McB 1 a _ ?Ww NuA ?. 3 - NoA M 8 1 ! f Nob *,' c NOB IN N4 w - NnE PbA ? t• Noe FaB Wh GoA >y RbA Ww No8 N StA " e GoA u? Ma6 ``- r _ Ra B L NoA Y v Ro Wt t w StA - GeB r R NuA o I .{M „ StA , Su ' ' 3R AaA *A 4•tC6 wt c i wt Ch Ch ch AzA BLb' No COB Nob mao mi P UCB 1003 D Cob s Uc8 ? m •?_ 4 0 •' + PaD Coe t ., ?, Ge6 ' ? W ? , _ S2 NoA r bl(? ! ^rry COB , , Ud r ` = °. ? .? 'No8 Was '. ,. NOB U. c'l AuA 2 Ns NuA „' '? Fi o t` Q LY AM %A Ro SSA La NO P A 301 - B rs' '' '?. A O >K N r 4c n a . u ( RbA M NuA C . c .. ; GOA wan Le \ &°a : _A ? N(iA O f ? L JJ k _ NoA ff A 5 b t ? ` . +? ? RbA f + Ly a w LY N " Y•` 7 .. - ? l . Re UOO k COB U9 a1;A wo. N A NoA u Na Na .r- GoA } - n s COB t .' 96 NoA 1 *' ; WuA GDA Qp Na 9b `, dy ?? No RbA ? GoA GOA C-R Project area and location of the proposed Johnston Community College Library Building, Smithfield, Johnston County, North Carolina 0 0.2 0.4 0.8 Miles ^' EROSION AND SEDIMENT CONTROL PLAN JOHNSTON COMMUNITY COLLEGE LIBRARY BUILDING 245 COLLEGE ROAD SMITHFIELD, NC 27577 JOHNSTON COUNTY MAY 2009 PROJECT DESCRIPTION: A new Library Building and associated site work is proposed on the south side of College Road between Martin Luther King Drive and Highway 70 Business north of Hwy I-95 in Johnston County of the City of Smithfield, North Carolina. The project is located within the Neuse River watershed. Site work for this project consists of clearing and grading for the construction of a new Library Building. The access to the construction area will be from College Road. The clearing limits are shown on sheet C 2.0, C 3.0, C 4.0 & C 6.0. Approximately 8 acres of the land will be disturbed during construction. The project will impact existing wetlands. The community college has previously reached an agreement regarding this planned impact, and mitigation has already been completed. NCDENR Division of Water Quality (DWQ) is currently reviewing the application for this impact. Written proof of DWQ's approval will be forwarded to the Division of Land Quality as soon as it has been received. Stormwater from the new Library project will drain to an existing stormwater pond located north of College Drive. This pond is owned and maintained by the Town of Smithfield. PLANNED EROSION AND SEDIMENT CONTROL PRACTICES: Silt Fence: Silt fence will be utilized to filter sediment-laden runoff in locations where the drainage area is less than 'A acre per 100-ft of fence. 2. Inlet Protection: Block and gravel inlet protection devices will be installed at new inlets as they are constructed to filter sediment-laden runoff prior to the runoff entering the storm drainage system. 3. Construction Entrance: Temporary gravel construction entrances will be utilized to minimize soil being tracked off the site by construction traffic. Outlet Protection: Riprap outlet protection aprons will be installed at outlets as they are constructed to slow storm-water velocities and dissipate energy to protect downstream channels from erosion. 5. Sediment Skimmer Basins: Sediment skimmer basins will be installed to filter concentrated sediment laden runoff prior to discharge from the site. Tree Protection Fencing: Tree protection fencing will be installed to protect existing trees that are intended to remain. In some locations, silt fence will serve as tree protection fence. Refer to drawings C4.0 for Construction Sequence and Maintenance Plan & C 7.1-C 7.4 for details.