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HomeMy WebLinkAbout20010185 Ver 1_Major Variance_20001129 ¦ Variance Request Plantation Point 0 01 489 US-1 at I-540 Raleigh, North Carolina Prepared for: Bobby Murray Chevrolet, Inc. C Kimley-Hom and Associates, Inc. 2000 ?=? Kimley-Horn m and Associates, Inc. I I I Nil, ?r ~k I JP PPP- Kimley-Horn hhh, and Associates, Inc. November 20, 2000 Mr. David Moreau Chairman North Carolina Environmental Management Commission 1621 Mail Service Center Raleigh, North Carolina 27699-1621 Re: Neuse River Buffer Variance Request Plantation Point US-1 at I-540 Raleigh, North Carolina Dear Mr. Moreau: Enclosed are copies of a variance request for the subject proposed project located in north Raleigh. Because the project will involve considerable traffic and roadway negotiations with the City of Raleigh and the NC Department of Transportation, the request is being made at the preliminary stage. To develop final plans for the project without a variance determination would be extremely expensive and clearly not necessary for the Commission to have adequate information upon which a decision could be rendered. The owner will stipulate to working with the Division of Water Quality to achieve the necessary plan development and approvals prior to any impacts to the buffer in question and to provide the mitigation requirements as determined by the Commission. This request is submitted for inclusion on the EMC Water Quality Committee's December 2000 agenda and copies are being provided to the staff for both the Commission's and staff review purposes. Please advise if there are any questions or a need for additional information. Very truly yours, EY-HORN AND ASSOCIATES, INC. Harlan K. Britt, P.E. Associate ¦ TEL 919 677 2000 FAX 919 677 2050 ¦ P.O. Box 33068 Raleigh, North Carolina 27636.3068 ?J w L7 7L I I Kimley-Horn and Associates, Inc. November 20, 2000 Mr. David Moreau Chairman North Carolina Environmental Management Commission 1621 Mail Service Center Raleigh, North Carolina 27699-1621 Re: Neuse River Buffer Variance Request Plantation Point US-1 at I-540 Raleigh, North Carolina Dear Mr. Moreau: Enclosed are copies of a variance request for the subject proposed project located in north Raleigh. Because the project will involve considerable traffic and roadway negotiations with the City of Raleigh and the NC Department of Transportation, the request is being made at the preliminary stage. To develop final plans for the project without a variance determination would be extremely expensive and clearly not necessary for the Commission to have adequate information upon which a decision could be rendered. The owner will stipulate to working with the Division of Water Quality to achieve the necessary plan development and approvals prior to any impacts to the buffer in question and to provide the mitigation requirements as determined by the Commission. This request is submitted for inclusion on the EMC Water Quality Committee's December 2000 agenda and copies are being provided to the staff for both the Commission's and staff review purposes. Please advise if there are any questions or a need for additional information. Very truly yours, EY-HORN AND ASSOCIATES, INC. Harlan K. Britt, P.E. Associate ¦ TEL 919 677 2000 FAX 919 677 2050 ¦ P.O. Box 33068 Raleigh, North Carolina 27636-3068 t OFFICE USE ONLY: Date Received ............ Request # ._ State of North Carolina Department of Environment and Natural Resources Division of Water Quality Variance Request Form Neuse River Basin: Nutrient Sensitive Waters Management Strategy Protection and Maintenance ofr Riparian Areas Rule (15A NCAC .0233) NOTE. This form may be photocopied for use as an original. Part 1: General Information 1. Applicant's name (the corporation, individual, etc. who owns the project): . Mr. Bobby L. Murray. Bobby Murray Chevrolet 2. Print Owner/Signing Official (person legally responsible for the facility and its compliance) Name: Mr. Bobby L. Murray. Title: Owner Street address: 1820 Capitol Blvd. City, State, Zip: Raleigh. North Carolina 27604 Telephone: (919) 834-6441 Fax: (919) 834-1399 3. Project Name (Subdivision, facility, or establishment name - consistent with project name on plans, specifications, letters, operation and maintenance agreements, etc.): Plantation Point. Raleigh NC 4. Location of Facility Street address: 6401 Capitol Blvd. City, State, Zip: Raleigh NC 27616 County: Wake.-- -- ------- - --- - --- Latitude/longitude: N 35 52 25.6 W 78 34 53.5 5. Directions to facility from nearest major. intersection (Also attach a map): Site is located approximately 300' North of intersection of Capital Boulevard and Old Wake Forest Road in Raleigh, North Carolina See Figure 1. 6. Contact person who can answer questions about the facility: Name: Mr. Brent King - Telephone: ( 919) 834-2353_.....__.........._............ ......... ..... ......... ....... _... _ . ................. ..................... ............................... ........ ............. _..... ........................... Fax: ( 919 ) 834-1399 Email: bking C bobbymurray.com 7. Requested Environmental Management Commission Hearing Date: -.__December. 2000 Version 1: September 1998 Part 2: Demonstration of Need for a Variance . ... .. . _....... . NOTE: The variance provision of the Neuse Riparian Area Rule allows the Environmental Management Commission to grant a variance to an affected party when the following conditions apply on a given project: (a) practical difficulties or hardships would result from strict application of the rule: (b) such difficulties or hardships result from condition which are peculiar to the property involved, and (c) the general purpose and intent of the Rule would be preserved, water quality would be protected and substantial justice would be done if the variance were granted. This part of the application is to explain how the project meets criteria (a) and (b). _ _..._._ Attach a detailed description (2-3 pages) explaining the following: • The practical difficulties or hardships that would result from strict application of the Rule. • How these difficulties or hardships result from conditions that are unique to the property involved. Why reconfiguring and/or reducing the built-upon area to preserve a greater portion of the riparian area is not feasible on this project. If economic hardship is the major consideration, then include a specific explanation of the economic hardship and the proportion of the hardship to the entire value of the project. Part 3: Water Quality Protection t NOTE: This part of the application is to explain how the project meets criterion (c): the general purpose and intent of the Rule would be preserved, water quality would be protected and substantial justice would be done if the variance were granted. ....... ..._ ....... ......... ._...... ........... .................... _......... ............ ....... ..... ......... ............ ......................... _................. .............__..._._........... ... _....................... ....._...... __..__..._........._...__._ ... 1. Briefly summarize how water quality will be protected on this project. Also attach a detailed narrative (1-2 pages) describing the nonstructural and structural measures that will.be used for protecting water quality and reducing nitrogen inputs to surface water. As discussed in Part 2. the watershed will drain to a BMP structure on-site. The BMP structure an extended detention stormwater wetland will be explicitly designed to mitigate the impacts of stormwater quality and guantity. In the stormwater wetland extra runoff storage is created above a shallow marsh by temporary detention of stormwater'runoff. Designed and constructed to guidelines set by the Stormwater BMP. NCDENR manual. April 1999, the BMP structure Will achieve the 85% TSS removal standard, while"reducing Nitrogen loading rates to below'10ib/ac/vr per the Neuse River Stormwater Rule (15A NCAC 2B 0235)The additional total nitrogen reduction from 101b/ac/yr to the regaired 3 6lb/ac/yr will be through the one-time offset payment of $330/lb. 2. What is the total project area in acres? 48.5 3. Which of the following permits/approvals will be required for this project? CAMA Major X_ Sediment/Erosion Control X 401 Certification/404 Permit Variance Request Form, page 2 Version 1: September 1998 1 1 1 1 1 r t Part 3: Water Quality Protection, continued 4. Complete the following information for each drainage basin. If there are more than two drainage basins in the project, attach an additional sheet with the information for each basin provided in the same format as below. Project Information Drainage Basin 1 Drainage Basin 2 Receiving stream name Unnamed Tributary to Gresham Lake/Perry Creek Receiving stream class' Intermittent/Class NSW Drainage basin area (total2) 48.5 acres Existing impervious area3 (total2) 9.07 acres Proposed impervious area3 (total2) 75% %.Impervious area3 (on-site) 75% % impervious area3 (total2) 75%- 'Percent Impervious based on property at maximum Dunaow. Imnarvinus arpa3 I Drainaae basin 1 I Drainage basin 2 1 On-site buildings On-site streets On-site parking On-site sidewalks Other-on-site Total on-site Off-site Total •_c_?_a: r-u-../M n.... 's..{.. .. w/nfrrra.l.. e.n/ L.i.../ m. Hfm/ 2 nrrcurc: anc rvre urwsrnrvnnasr......,...y. ..............................,..-.........._.»__.».?..».._.......... Irrc lu off-site area that drains through the project. Total means on-sit pl'u's' 3 Impervious area is defined as the built-upon area including, but not limited to, buildings, parking areas, sidewalks, gravel areas, etc. 5. How was the off-site impervious area listed above derived? No off-site drainage area 6. What will be the annual nitrogen load contributed by this site after development in.pounds per acre per year without structural BMPs (stormwater pond, wetland, infiltration basin, etc)? Attach a detailed plan for all proposed structural stormwater BMPs. Drainage basin Size of drainage basin ac Post-development nitrogen loading rate. without BMPs4 Ibs/ac r BMP nitrogen removal efficiencl % Final nitrogen loading rate (Ibs/ac/yr) Final nitrogen loading from drainage basin Ibs r 1 48.5 16.25 40 9.75. 472.92 2 3 4 Totals 48.5 _16.25 ; 40 9.75 472.42 " Attach calculations and references. s Attach calculations and references. Variance Request Form, page 3 Version 1: September 1998 Part 3: Water Quality Protection, continued ?. 7. The applicable supplemental form(s) listed below must be attached for each BMP specified: N/A, No form available for Extended Detention Stormwater Wetland Form SWU-102 Wet Detention Basin Supplement Form SWU-103 Infiltration Basin Supplement Form SWU-105 Curb Outlet System Supplement Form SW U-106 Off-Site System Supplement Form SWU-107 Underground Infiltration Trench Supplement Form SWU-109 Innovative BMPs Supplement Part 4: -Submittal Checklist . A complete appplication submittal consists of the following components. Incomplete submittals will'be returned to the applicant. The. complete variance request submittal must be received 90 days prior to the EMC meeting at which you mish the request to be heard.. Initial below to indicate that the necessary information has been provided. fit4ft. bETA1L5 'FOR EAC" i3M? 'WI.1. tie Sk1 AIrMD To T}de DWR r-CA APORovAL P2109, Applicant's To ANIV IMPACr$ To T kE SU43)EGT . PfLO.)ECT BU pFiE R. Initials Item NLT NAT MIT rJt,7 NLS Nit r t1a • Original and two copies of the Variance Request Form and the attachments listed below. • A vicinity map of the project (see Part 1, Item 5) • Narrative demonstration of the need for a variance (see Part 2) • A detailed narrative description of stormwater treatment/management.(see Part 3, Item 1) • Calculations supporting nitrogen loading estimates (see Part 3, Item 6) • Calculations and references supporting nitrogen removal from proposed BMPs (see Part 3, Item 6) • Location and details for all proposed structural stormwater BMPs (see Part 3, Item 6) • Three copies of the applicable Supplement Form(s) for each BMP and/or narrative for each innovative BMP (see Part 3, Item 7) • Three copies of plans and specifications, including: 0 Development/Project name 0 Engineer and firm 0 Legend and north arrow 0 Scale (1" =100' or 1" = 50' is preferred) 0. Revision number & date 0 Mean high water line (if applicable) 0 Dimensioned property/project boundary 0 Location map with named streets or NC State Road numbers 0 Original contours, proposed contours, spot elevations, finished floor elevations 0 Details of roads, parking, cul-de-sacs, sidewalks, and curb and gutter 0 Footprint of any proposed buildings or other structures 0 Wetlands delineated, or a note on plans that none exist 0 Existing drainage (including off-site), drainage easements, pipe sizes, runoff calculations 0 Drainage basins delineated 0 Perennial and intermittent streams, ponds, lakes, rivers and estuaries 0 - Location of forest vegetation along the streams, ponds, lakes, rivers and estuaries Variance Request Form, page 4 Version 1: September 1998 Part 5: Deed Restrictions By your signature in Part 7 of this application, you certify that all structural-stormwater best management practices required by this variance shall be located in recorded stormwater easements, that the easements will run with the land, that the easements cannot be changed or deleted without concurrence from the State, and that the easements will be recorded prior to the sale of any lot. Part 6: Agent Authorization If you wish to designate submittal authority to another individual or firm so that they may provide information on your behalf, please complete this section: Designated agent (individual or firm): Kimlev-Horn and Associates, Inc. (Attn: Harlan Britt) Mailing address: 3001 Weston Parkway City, State, Zip: Cary North Carolina 27513 Telephone: (919) 677-2000 Fax: (919) 677-2050 Email: hbritt@kimley-horn.com Part 7: Applicant's Certification I, Bobbv L Murray (print or type name of person listed in Part I, Item 2), certify that the information included on.this permit application form is correct, that the project will be constructed in. conformance with the approved plans and that the deed restrictions in accordance with Part 5 of this form will be recorded with all required permit conditions. Signature: Date: Title: Variance Request Form, page 5 Version 1: September 1998 t 1 1 1 1 1 z W H az a O W a W H W Z ~ a z 4 cc Q0. C? O U E E N 1 O. O (L C ?. \ 'T 00 N N rn > m N O O d N 4)O C o CL le co x H CD 3 O Z IL L c co coa a°) II I LO to U p O O 04 T z J e 12 01 to i. 0 0 0 0 o d Z £ N W m C co d 3 N E E IL 0. 0 O m i' d co N i > ? 0 Ch co I- o c . x c d >az i ` to (O N N Ul) a Z a N U) N ( o z T F l0 y ' N U) to d _ L Q v r ? o tl ? s J ? V U N = ca L 3 0 U (`o O ll > O M d d Y CO N U n E c a = Q d ? N 3 d '- U 41 N m to ( 0 O E C O ' £ CO d v d > Q w d y V) 6 d O C > L O ?• ` 2 7 CL C. N N 9 A N w d o N l0 A 3 t 4) a C m 4) CL > • C N C N ? 'C U d c E d N C d d a a o n a O d a O w c c c c c i I 0 (D Ul) 'gr q1t 400 n C ce) s 0 k (3. L U w c C O >a) M 7 U) a d O' U * U N tp a U S O c d (D a II a: CD (D N O d E -c >, a) w d E (C (C O N CL N E O OC m O a. ca [0 N O w ? Kimley-Horn i and Associates, Inc. DWQ Stormwater Wetland Required Minimum Design Parameters Requirement per NCDENR's Stormwater BMP Manual Project Information Project Name: Plantation Point KHA Project #: 11166001 Designed by: nit Date: 11/21/00 Checked by: wrw Date: 11/21/00 Proposed Site Information Sub Area Location: Entire Site Drainage Area (DA): 48.5 Acres Impervious Area (IA): 36.4 Acres Percent Impervious (1): 75 % Required Surface Area at Permanent Pool Depth Range: (0-1.50') Proposed Depth= 1.50 feet Average depth= 0.75 feet TSS Removal= 85 % SA / DA= 3.12 % (from Table 1.1 in BMP Manual) Surface Area (SA)= 65,861 Sq Feet = 1.5 Ac Required Volume: (Simple Method - prefered) Design Storm = 1 inches Determine Rv Value= 0.05 +.009 (1) = 0.73 in/in Volume Required= 127,649 CF Req. Depth of Temp. Pool = 1.94 Feet above Permanent Pool Elev. 3.44 Feet from bottom Avg Volume = 49,395.47 CF Using a depth of. 75' Avg Forebay Volume = 9,879.09 CF 2.5' Minimum Depth of forebay 11111i`-?17 Kimley-Hom !? ? / 1 ana Associates. Inc. . DWQ Stormwater Wetland Peak Discharge for Point of Interest Project Information Project Name: Plantation Point KHA Project #: 11166001 Designed by: nit Date: 11/21/00 Checked by: wrw Date: 11/21/00 Using The Rational Method Proposed Site Information Defined Parameters • Drainage-Area (DA): 48.5 Acres Assumed Parameters Impervious Area (IA): 36.4 Acres Percent Impervious (1): 75 Time of Concentration (to): 10 Minutes Runoff Coefficient (C) for Qp: 0.8 Runoff Coefficient (C) for Qo: 0.5 Runoff Coefficient for Maximum Build-out R in( I) h tensity Duration = 10 minutes. Storm Event Intensity (in/hr) 2-year 4.76 5-year 5.54 10-year 6.13 25-year 7.01 50-year 7.71 100-year 8.40 Read from Intensity-Duration-Frequency Chart, Raleigh-Durham, NC Calculations D charge (Qp) Q CIA-C Intensity*Are_a Rainfall Intensity (in/hr) Qp (cfs) Storm Event (yr) 4.76 184.69 2 5.54 214.95 5 6.13 237.84 10 7.01 271.99 25 7.71 299.15 50 8.40 325.92- 100 Peak Discharge (Qo): Discharge (Qo) Q -CIA=C Intensity"Arga Rainfall Intensity (in/hr) Qo (cfs) Storm Event (yr) 4.76 115.43 2 5.54 134.35 5 6.13 148.65 10 7.01 169.99 25 7.71 '186.97 50 8.40 203.70 100 Plantation Point Variance. Request Part 2: Demonstration of Need for a Variance NOTE: The variance provision of the Neuse Riparian Area Rule allows the Environmental Management Commission to grant a variance to an affected party when the following conditions apply on a given project. (a) practical difficulties or hardships would result from strict application of the rule: (b) such difficulties or hardships result from conditions which are peculiar to the property involved, and (c) the general purpose and intent of the Rule would be preserved, water quality would be protected and substantial justice would be done if the variance were granted. This part of the application is to explain how the project meets criteria (a) and Attach a detailed description (2-3 pages) explaining the following: • The practical difficulties or hardships that would result from strict application of the Rule. • How these difficulties or hardships result from conditions that are unique to the property involved. • Why reconfiguring and/or reducing the built-upon area to preserve a greater portion of the riparian area is not feasible on this project. If economic hardship is the major consideration, then include a specific explanation of the economic hardship and the proportion of the hardship to the entire value of the project. Practical Difficulties/Economic Hardship The property on which the conflict exist is bounded on the north by Interstate 540, presently under construction, which is a controlled access highway, on the east by US-1, a limited access highway and on the south by Old Wake Forest Road. The subject property was acquired in the 1988 and since that time the property has undergone a number of development concept evaluations. However, the property has retained its present use and I-2 zoning since it was acquired. The proposed project will encompass approximately a total of 48.5 acres at final development. This includes the property on which the stream exists and several surrounding properties to the south and west. The proposed land use may require re- zoning however, the general land use will remain commercial and retail. To understand the difficulties associated with developing this property it is important to understand the history and future of the property and the surrounding roadway system. Over the previous thirty plus years the property had access to US-1 via a service road that connected to the north to a signalized intersection near Greshams Lake and south to a connection with Old Wake Forest Road. This service road gave the property full access to US-1. However constructing of I-540 around the City of Raleigh has removed the service road and the access to and from areas north of the property. Access from US-1 may be granted, however, it is believed that is will only be a limited right-turn only driveway. The location of the proposed driveway will be dictated by the NC DOT and it is believed that it will be located. as shown on the attached concept plan. The proposed location is necessary to reduce traffic conflicts between the signalized intersection of US-1 and Old Wake Forest Road and the proposed new drive. The intersection of US-1 and Old Wake Forest Road and the remaining service road can not accommodate the traffic generated by the subject proposed project. Therefore a new intersection is proposed as a part of the project. Given the highway access limitations it is imperative that a new access road be constructed. A proposed road located on the south side of the project will be constructed to provide the necessary and required access to the property. The new road and the limited access drive to US-1 dictate that the proposed buildings be located to face US-1 and the new road. It is the ' opinion of the traffic engineering and land planning consultants that the proposed building location will satisfy traffic concerns and be acceptable from a land planning position. ' Because a stream is located on the northern portion of the property, the preferred location for buildings, there is a significantly conflict with the development potential of the property. The stream, projecting 200 feet into the building area seriously limits the ability of the owner to ' develop the property given the restrictions for access and the need for having a marketable product. Unique Property Issues The Wake County Soil Survey map indicates a stream exists on the property extending from the southern boundary to the northern boundary with a small pond at the northern property line. Before the I-540 construction project began the stream apparently extended from the upper reaches of the watershed continuously down to Greshams Lake. With the construction of I-540, and it's interchange with US-1, the stream has been piped from the pond area on the subject property downstream for approximately 1000 feet. Additionally, ramp construction for the interchange has required the placement of earth fill into the pond area. This filling of a portion ' of the pond and the stream piping has been completed. As stated previously, the soil survey map suggests that a stream existed from the upper areas of the watershed through the pond down to Greshams Lake. Field investigations determined that the stream above the pond as shown on the soil survey map was in fact not a stream but rather a drainageway that carried only stormwater during and immediately following a storm events. Therefore, the drainageway above the pond was determined not to be subject to the buffer rules. Determination of the whether the pond was subject to the Neuse River rules was not as easy to establish as the drainageway above the pond. . t Inspection of the dam found that it was covered with large trees, some of which had been damaged by past storms. The owner had concerns that the dam may fail if one or more of these large trees on the back of the dam were to fall. Therefore, breaching of the dam and subsequent draining of the pond had been under consideration for some time. The dam had no bottom drain by which the dam could be drained. In October 2000, the dam was breached and a pipe placed through the dam to prevent future impoundment of water. Draining of the water exposed the bottom of the pond and provided a method of determining if the pond should be subject to the Neuse River rules. Following the draining representatives of the owner and the DWQ Raleigh Regional Office inspected the pond and observed a small seep flowing approximately 200 feet south of the 1-540 right-of-way. This seep of groundwater became the basis for the DWQ staff determining that a stream exists in the pond bottom and therefore the stream created by the seep is subject to the Neuse River buffer rules. C r1 The seep is an area where apparently ground water is breaking out of the ground and forms a small channel, approximately six inches wide, flows to the north. (Photographs of the pond area and the seep are provided as an attachment.) The seep and stream extends approximately 225 feet through the pond and onto the I-540 right-of-way where it enters the pipe under Interstate 540 and subsequently discharges into Greshams Lake. It is important to recognize the importance of this stream flowing into Greshams Lake because the lake provides significant water quality treatment prior to runoff from the owner's property reaching a Perry Creek a tributary to the Neuse River. Certainly this is not a typical situation in the Neuse River basin. The extent of the stream is approximately 200 feet, flows are estimated to be less than one gallon a minute and the stream enters a 1000-foot culvert. The water quality benefits this seep and buffer provide can be readily mitigated by water quality BMPs on the project. Economic Hardships If the variance request is not granted then retaining the existing 200 feet of stream and buffer will reduce significantly the economic value of the property. It is estimated that the square footage of lease space that can be built successfully leased will be reduced from 375,000 square feet to as little as 275,000 square feet. This reduction is based not just on available land but also on what the market will support in terms of access, roadway visibility, and tenant and spaced demands. H:\PN\000812\HKB\planatationvariancerequst.doc Part 3: Water Quality Protection .__ _... .......... _ . ..... ................. _ ........ . ......... _.......... .................. NOTE. This part of the application is to explain how the project meets criterion (c)• the general purpose and intent of the Rule would be preserved, water quality would be protected and substantial justice would be done if the variance were granted. 1.. Briefly summarize how water quality will be protected on this project. Also attach a detailed narrative (1-2 pages) describing the nonstructural and structural measures that will be used for protecting water quality and reducing nitrogen inputs to surface water. An extended detention stormwater wetland will be.used as a structural Best Management Practices to ensure both the quantity and quality of storm-water runoff after maximum-project . buildout. The extended stormwater wetland will be designed and constructed to the guidelines set forth in the.Stormwater BMP, NCDENR manual, version April 1999. This will ensure the- achievement of the 85% TSS removal standard, while reducing nitrogen loading rates to below l0lb/ac/yr per the Neuse Stormwater Rule (15A NCAC 2B 0235). The additional total nitrogen reduction from 10lb/ac/yr to the required 3.6lb/ac/yr will be through the one time offset payment of $330.00/lb. Stormwater wetlands serve several purposes: improving water quality, improving flood control, enhancing wildlife habitat, and providing education and recreation. Stormwater wetlands use several mechanisms to remove more pollutants, sediment, nutrients; metals and chemicals, and even bacteria than any other structural BMP. These mechanisms include sedimentation, filtration, adsorption, microbial activity, and plant intake. The intent of a stormwater wetland is to create a shallow matrix of sediment, plants, water and detritus that collectively removes multiple pollutants through a series of physical, chemical, and biological pathways. This BMP structure creates an environment that provides ideal conditions for particle settling. Because stormwater wetlands are efficient in removing sediment from the water column, they are also efficient at removing those pollutants, such as phosphorus, trace metals, and hydrocarbons, that may be absorbed to the surfaces of suspended particles. The plants that inhabit a stormwater wetland play a significant role in helping stabilize the sediments that settle while also providing aesthetic advantages. Located south of the property, Greshams Lake provides additional water quality and quantity benefits to the runoff created by the Plantation Point site and watershed, which makes the design of a stormwater wetland on this site ideal. The design of a stormwater wetland is very similar to that of a wet detention basin. In fact, the permanent pool of water for the extended detention wetland was sized using Table 1.1 (Stormwater BMP manual, April 1999), the table also used for sizing wet detention basins. The stormwater wetland was designed to detain the runoff from the 1" storm for a period of 2 to 5 days. A forebay will also be included in the overall design (Exhibit ?). The design criteria included a 75% maximum impervious area, a 48.5-acre drainage basin, and a permanent pool depth range of 0 to 1.5 feet that will ensure an 85% TSS and 40% nitrogen removal efficiency. The installation of this stormwater management facility will significantly improve the water quality of the watershed site. Project: Plantation Point Kimley-Horn Plantation Point, US-Iat I-540 and Associates, Inc. Title: Variance Request Prepared by: Nghi Thieu Job Number: 0111660.01 Sheet I of 5 Photo 1. Drainageway leading to pond area. Photo 2. Drainage entrance into pond. puod olui nouealuo a'DvuiejCj 'Z 0104d S to I joaus 10,0991110 'aagwnN qop noigl igDN :Aq paaudaad jsonbng noueuen •ou! 'salu!oossy pue „? ObS-I leI -Sfl `luiod uotleluejd :811!1 uaoH-AOIw!?{ M -.A zutod uolleluejd :loafoJd 'enJe puod of Duipenj A72moDeuiuiG - I 01ogd 1 Project: Plantation Point Prepared by: Nghi Thieu CIS„ Kimley-Horn Title: Plantation Point, US-Iat I-540 Job Number: 0111660.01 and Associates, Inc. Variance Request Sheet 2 of 5 Photo 3. Overview of drainage pond and I-540 construction. Photo 4. 1-540 construction and dam drain system. Project: Plantation Point Prepared by: Nghi Thieu /'M„ Kimley-Horn Title: Plantation Point, US-lat I-540 Job Number: 0111660.01 111111kh- M and Associates, Inc. Variance Request Sheet 3 of 5 1 FM' JAC ' '?'? ?? ?? ? err,.. iei ..tr`.r Y •?y ? ? ?,??? - r `, 'k N Photo 5. Drained pond bed. Photo 6. Drained pond bed and 1-540 construction Project: Plantation Point Prepared by: Nghi Thieu PP', M„ Kimley-Horn Title: Plantation Point, US-1 at I-540 Job Number: 0111660.01 and Associates, Inc. Variance Request Sheet 4 of 5 Photo 7. Temporary pond drain system. i Project: Plantation Point PPI iM Kimley-Horn Title: Plantation Point, US-Iat I-540 and Associates, Inc. Variance Request Prepared by: N11 i Thieu Job Number: 0111660.01 Sheet 5 of 5 Photo 8. I-540 culvert below existing dam .? ?. f 1 n L ? ? ? J ' I ? ?,?--?o? ? 5 <_./ IBS ??`?V-?J ? `• ?? i`? ?'? I ,t??/ ?I J ? 1 ?` ? j ? J' ?`, \ 1 . 1 "Ai be. ?. is ?, ? , -,;, ? ? f ;; ? 4 + ?? ??• ? t ' ^ ? .' +r J } , i '?,t • - i X10 ?"-- ( 4 , t' {.%' d fn i f / ? X / G S i Pro ect Area A o JPiKE FO 10 S / ! L_w Title: Location Ma USGS Quad Ma ? ? ? Project: Plantation Point Ki l H i h NC R l m ey- orn g , a e And Associates, Inc. Date: Scale: Project No. Figure: 11/17/00 N/A 011166001 1 M1 FIG" VIEW of, r d R 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 n 8 Mainlanapm 7 pool ?+ C Ci1W".Pi Area , % IL .4 Iti, W n+arsh-^ r ff*r hi mal bh Stormwater Wetland System Kimley-Horn And Associates, Inc. Project: Plantation Point Raleigh, NC re: i First-Flush Storage (1" Runoff). J AMU Kimley-Horn And Associates, inc. Weir Crest Project: Plantation Poirit Raleigh, NC Date: Scale: Project No. Figure: 11/20/00 N/A 011166001 3 Drawdown Orifice (2-5 Day Drawdown) p 8 1 VIci bMISV'^ ' °2x Ea_ K c c a? 36 b R Q : YI 4r a vsl o 9 a ° L n a 0 o s ?UI(OJp? l.?'}JO?( 'l,??le?(p? ,° SoE°a cis s ?y! N r \ z? r CAPITAL BLVD \ ( C)I!E r I M ? r ? r I w -.-L-1. zu 11-D L i +o a _ w r 91 - cjo? ? / ` - ? Grr ? I I \ I vI ? I i ? / \ ?? ?Qaz I I (? F ? ff ff j >>til ttN -' \\ ? ? \ ;? ? a i 1 1 / tN / / T aAjjVUJajjV o" I 1'17'mlc??P??I? O ^s ?d E.s _ 4-o I I; = we 8l^,Qo x Z ? BLVD •- CAPITAL r ? ? '? ?,? , r' , r+¦ , rte' ? 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