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Home My WebLink About20140822 Ver 1_Add Info WQC Mtg_20140507Sti morel 9; V September 27, 2013 April 10, 2014 (Appended) Town of Kernersville P.O. Drawer 728 Kernersville, NC 27285 Attn: Russell Radford, PE, Town Engineer Subject: Request for Variance for Stormwater Management Requirement in the Pre - Developed Condition Blue Diamond Property adjacent to the Proposed Veterans Administration Hospital Dear Russell, I am writing this letter on behalf of Blue Diamond Investments to request a variance in the timing of installation of stormwater management BMP's for the subject property. The Veterans Administration (VA) Hospital site lies downslope of the Blue Diamond Investments property. The VA site will have its own stormwater management system, sized to treat runoff from its site only, therfore a stormwater bypass system must be constructed to convey stormwater runoff from the Blue Diamond property around or through the VA site to keep runoff from Blue Diamond property separate from that of the VA site. The bypass system discharge point falls within the West Fork Deep River buffer which is a tributary within the Randleman Lake Water Supply Watershed. A rip rap lined channel will be provided through the buffer from the discharge point to the river. The Randleman Rules require that concentrated runoff from manmade conveyances be converted to diffuse flow before the runoff enters Zone 2 of the buffer, unless stormwater management is provided for the runoff. The State's Stormwater BMP Manual requires 50 linear feet of level spreader per cfs of flow to provide diffuse flow from a concentrated discharge point. For the 1.0 in. /hr. rainfall, 1,778 linear feet of level spreader is required for the flow from the bypass line. A second requirement for level spreaders per the State Manual is that the maximum flow that can be directed to a single level spreader is 2 cfs. With this limitation, the flow from the bypass line would have to be split into 18 discrete level spreaders. Additionally, flows that exceed the 2 cfs capacity of the level spreaders are required to be diverted away from the level spreaders. These higher rate flows would have to be channelized through the buffer to the stream as currently planned, which is what the developer is requesting approval of. Given these constraints, it is impractical to convert concentrated flow from the bypass line to diffuse flow. Since sufficient space to convert discharge from the bypass system to diffuse flow is not available outside the buffer, a stormwater BMP is required by the Rules. Given the topographic characteristics of the Blue Diamond property and other upslope properties, Blue Diamond Investments is requesting a variance to delay installation of the BMP until such time as development of the Blue Diamond property begins. A development plan has not been prepared for the Blue Diamond property. Designing and building a stormwater BMP without a development plan in place causes the development to be designed around the BMP, which may not yield the best and highest use of the property. The topography of the Blue Diamond property upslope of the VA site forms two drainage basins. Providing stormwater management for the property prior to development would require two BMP's to be constructed, or the majority of the property to be graded to drain to a central location. If BMP's are constructed at the current drainage collection points prior to development, these locations may not work with the final development plan and would have to be moved. This would certainly be the case for the drainage feature adjacent to Kernersville Medical Parkway, as the road frontage will be the most valuable property from a development perspective. Either of these scenarios, mass grading or building BMP's represents a significant financial burden to the developer prior to development activity commencing. 60,11 fit, Trade Streal Suite, 2114 ffim t n Sotern„ NC 2711011.2916 R 336723,1067 F: 336323 1069 Blue Diamond Property Stormwater Management Variance Request September 27, 2013 Page 2 What are the impacts to the VA site if their BMP is upsized to treat post - developed runoff from the Blue Diamond property ?: As the attached VA storm drainage plan reflects, there is little to no room to expand the stormwater pond. We have consulted with the VA's Civil Engineering consultant regarding upsizing their pond to accommodate runoff from the Blue Diamond and upslope residential properties in a developed condition. The VA's consultant looked at this during the design phase of the project and a pond of that size would not fit within the available space on the property. What are the impacts to the VA site if their BMP is upsized to treat pre - developed runoff from the Blue Diamond property, then bypass Blue Diamond runoff in the post - developed condition ?: Although not specifically studied, it is possible that the VA pond as designed could accommodate the area draining to the bypass system in the pre - developed condition, however when the Blue Diamond property develops, the bypass system would have to be disconnected from the VA pond and extended to the Deep River, causing significant disruption and damage to the VA site. Given this, it is unlikely that the VA and the site developer would agree to this arrangement. What are the impacts to water quality in the Deep River if pre - developed runoff from the Blue Diamond property is not treated ?: The total basin area draining to the bypass system is approximately 48 acres. The Blue Diamond property (28.8 acres) is undeveloped, with 0% built upon area (BUA). The remaining drainage area (19.2 acres) upslope of the Blue Diamond property is very sparsely developed as large lot residential. The upslope area currently has approximately 7% BUA. The aggregate BUA of all properties upslope of the VA site is 2.79 %. Runoff from this area flows overland through wooded areas and vegetated conveyances to the point where the bypass system through the VA site would intercept this water. The shortest flow path from the nearest rooftop is at least 700 feet from the bypass system inlet point. Given the extremely low BUA of the upslope properties and the length of the vegetated conveyances, we believe that adequate treatment is already being provided within the natural system without having to build an engineered BMP prior to development of the property. Untreated stormwater runoff from the Blue Diamond property discharged into the buffer from the bypass system will have the same characteristics in terms of quality as untreated runoff from the same area discharged into the buffer through the natural system that existed prior to development of the VA site. We believe that water quality will not be compromised by deferring installation of the Blue Diamond stormwater management BMP until development of that property occurs, and that the intent of the Randleman Rules will be satisfied. Blue Diamond Investments understands that stormwater management will be required for their development. They are simply requesting that final design and construction of the stormwater BMP be deferred until development of their property begins. The specific time frame anticipated for development of the property to begin moving forward is unknown, however we believe that completion of the Kernersville Medical Parkway in the fourth quarter of 2013 will be a primary catalyst for development in this area. We believe that granting this variance request is justifiable for the following reasons: • It is a minor deviation from the requirements of the Randleman Rules, since it only requests that implementation of the stormwater management plan be deferred until development of the Blue Diamond property. • Deferring implementation of the stormwater management plan will not negatively impact surface waters. • The requirement for implementation of the stormwater management plan prior to development of Blue Diamond property is not due to actions of Blue Diamond Investments, but rather due to development of the adjacent VA property. • The requirement for implementation of stormwater management prior to development of property is rare, and in this case only applies to Blue Diamond Investments and not to the upslope residential property owners, which are Blue Diamond Property Stormwater Management Variance Request September 27, 2013 Page 3 also contributors of runoff to the bypass system. It is in harmony with the general purpose and intent of the State's riparian buffer protection requirements and the Town's Ordinance and preserves its spirit. The public safety and welfare have been assured, water quality has been protected and substantial justice has been done. Thank you for your consideration of this variance request. Please contact me if you require additional information. Sincerely, J. Neal Tucker, PE Stimmel Associates, PA Cc: Jeff Hunter, Pope Companies Ana Jaramillo, Town of Kernersville +""1,11i lfiF l l(�l r�rrr�r % \ \� •X r SEAL r' i 14985 �4 I �` April 16, 2014 Ms. Jennifer Burdette 401 /Buffer Coordinator 401 & Buffer Permitting Unit Wetlands Branch NCDENR — DWR 1650 Mail Service Center Raleigh, NC 27699 -1650 Subject: Answers to Questions from the Water Resources Committee Regarding the Blue Diamond, LLC Variance Request Dear Ms. Burdette, Stimmel Associates, P.A. is working as an engineering consultant to Blue Diamond Investment Company, LLC for their property east of the Veterans Administration Hospital in Kernersville. The purpose of this letter is to address questions from the Water Quality Committee outlined in your e -mail to Ana Jaramillo with the Town of Kernersville dated April 7, 2014. The questions / additional information requested and answers are as follows: 1. Conceptual plan of BMP on the VA site to handle all stormwater from upslope. A: A conceptual plan of a BMP located on the VA Hospital site sized to handle all stormwater from both the VA site plus all upslope properties is not available. There was never a consideration to build a single BMP to handle all stormwater runoff for a number of reasons. Building a single BMP sized to handle all runoff places a financial burden on the VA Hospital due to the need to purchase more land to accommodate a larger BMP. There are difficulties with having multiple owners responsible for constructing and managing a single BMP, such as how are the construction costs and maintenance costs for each party equitably determined, and in situations where liabilities arise, such as a drowning, how are the liabilities shared. Building a single BMP sized to handle all runoff could pose a greater threat to water quality in the event of a failure of the BMP by 1) releasing a greater volume of sediment into the Deep River at the time of failure, and 2) stormwater from the drainage area would receive no treatment at all while the BMP is being repaired. Building a single BMP sized to handle all runoff could pose a greater threat to stream degradation at the point if discharge into the Deep River, since flows from the combined drainage area would likely be at a higher flow rate and velocity, and for a longer duration. Discharges from two BMP's would enter the stream at different points, at lower flow rates and velocities, and for shorter durations. A single, larger BMP would be more difficult and expensive to clean and maintain than two smaller BMP's. It is generally accepted that stormwater treatment is more efficiently provided closer to the source of the pollution (in this case sediment) than further from the source. 2. Cost difference between the VA treating only their stormwater vs. treating all stormwater from upslope. A: Since there was never a consideration for combining stormwater treatment into a single BMP for all properties draining to the VA site, the cost difference of providing combined treatment versus separate treatment was not determined. 3. Conceptual plan and design of BMP for Blue Diamond site including calculations used to size the BMP. A: See the attached Drainage Area Map by Stimmel Associates with backup calculations. This drawing 601 N, Trade Street Suite 200 Winston: Salerno, NC 27101.2916 P' 336 723 1067 P° 336 723.1069 Blue Diamond Property Stormwater Management Variance Request September 27, 2013 Page 2 represents a single wet detention pond to handle runoff in the developed condition. The pond is sized to provide 90% TSS removal. Per the NCDENR BMP's Manual, the pond will also provide some nutrient removal (25% total nitrogen, 40% total phosphorus), however nutrient removal is not required by the Randleman Watershed Rules. The plan does not represent the two separate BMP's that would be required for the pre - developed condition due to the site topography. Providing two BMP's would represent higher initial construction cost as well as higher maintenance cost. It is unlikely that both the BMP's would work in the developed condition, therefore one of the BMP's would have to be phased out and filled and the other would have to be increased in size, or relocated. 4. A complete site plan for the BMP on the VA site. A: See the attached Overall Storm Drainage Plan by Littlejohn Engineering, and annotated by Stimmel Associates. 5. Ownership history. A: See letter from Jeff Hunter with Pope Companies, partner in Blue Diamond Investment Company, LLC, addressing ownership history. 6. Determination if EO 13514 applies to the VA Hospital. If yes, then what provisions will be taken to comply with the Executive Order. A: The VA's Solicitation For Offers (SFO) did not specifically mention Executive Order 13514, although it did mention other EOs. Although EO 13514 was not mentioned, most of the pertinent goals of EO 13514 were requirements of the SFO, including sustainable design. In fact, the proposed facility has been designed to be certified as LEED Silver, possibly Gold. The areas of concentration include water efficiency, energy efficiency, recycling and reuse of demolition and building materials, green roofs, preferred parking spaces for energy efficient and alternative fuel vehicles, preferred parking spaces for carpool vehicles, and stormwater management measures. Please contact me if you require additional information. Sincerely, J. Neal Tucker, PE Stimmel Associates, PA Attachments Cc: Jeff Hunter, Pope Companies Ana Jaramillo, Town of Kernersville ,•'_ L SEAL - 14985 S 1 v !!lll lit* us® 0' Vo aat -.L dVW VA�jV 3JVNIV8G rLl CA EtOZILLJ6 ail S1N3W1S3nNl nNOwmO 3me m —n�W ZOr m CO C F Y-iyv Z�mm 3D0 Dmv M z C � 'a CA Z —1 a M G) m Z E M $�1•16�� MIT s� gd'sa }enaassq lawwil5 Jgww1}S Lo:a3ewnN 3nanO 031H013M .e.:anoa svos �oonoaaeN as:aaewnN3nanO Ov e ee v3av snOlna3awl —no 49 WO W aa S Oa Lr bt ro3OO1—d Ina3d sT+TOl 86'a38WON 3nan0 Oa rV'Et'a3aa Sn01n A3 m L9 :via vsnom n0 Oa aL 5tl3aa SOOina3a 3115130 W*ea WON—n0 Oa, bmysnolM -1 La alewnN anano Ov aae.tl3aysnolna3a 3115N0 SNOI110N00 03dO13n30150d se.aaewnN anano Oa re Lvaaysnon kiwi Is a3awnN 3na Otl 8a'1 L .v3av 5(101-93 d 311 Ud1O a6 .MN 3ntln0 0vto'oro. Sn.inaddwi ` N39MN 3nan0 Ov LL Vs W. Sn0 .Jd aASNO SNOI100N0003dO13n30 -- d 31V3S O1 ION m r 3115 oa ao wavd TnaLSnaNI ; - 1 I "Al1NVOUN91S 30NVH0 AVW SNOIl10NO0 '0- mc,NOO N338 SVH H0dV3338 311S ON *inOAVl 311S "IVN131O31d3N ION AVW 3HO33H3H10NV NOI1VVY8OdN1 313ldWOONI NO 03SV3 NVld 3115 A'dVNIW1'13Hd V SI SIHl r fi" Oa voar va � Z.s y IV11cIS h / +.41'\ r � 4�4 tit 1 0 r- � s�aOa rasa A \ ! / �re'� -'r�ws .N4 -,_ -.._ l , I /1 3 S "✓�! i. '� - '•artybl �_ e6 I'A�� v� 1 j %1�tl }: V,,w1, J / / .SS l �H1d30 /As 9/9'98 u d'1001 0Nbd I AS LZY09 Y3aa 30VJNnS % X94 v3dv sn0Na3d � Z.s y IV11cIS h / +.41'\ r � 4�4 tit 1 0 r- � s�aOa rasa A \ ! / �re'� -'r�ws .N4 -,_ -.._ l , I /1 3 S "✓�! i. '� - '•artybl �_ e6 I'A�� v� 1 j %1�tl }: V,,w1, Project : Kernersville Medical Parkway Sheet : 1 Project No.: 08 -032 Date : 4/16/2014 Designed by: BMH Checked by: JNT Blue Diamond Property - Option 5 East Pond Drainage Area SCS RUNOFF CURVE NUMBERS PRE - DEVELOPED CONDITIONS BASIN LAND USE SOIL NAME HYDROL. GROUP AREA (AC.) AREA ( %) CURVE NO (CN) CN x AREA Onsite - Pervious CiB* B 19.06 76.95% 61 1163 Onsite - Impervious CiB* B 0.00 0.00% 98 0 Offsite - Pervious CiB* B 5.34 21.56% 61 326 Offsite - Impervious CiB* B 1 0.37 1.49% 98 36 TOTALS 24.77 100.0% 1525 WEIGHTED CN (PRE - DEVELOPED) = 62 POST - DEVELOPED CONDITIONS - Onsite Developed Only BASIN LAND USE SOIL NAME HYDROL. GROUP AREA (AC.) AREA ( %) CURVE NO (CN) CN x AREA Onsite - Pervious CiB* B 5.72 23.08% 61 349 Onsite - Impervious CiB* B 13.34 53.86% 98 1308 Offsite - Pervious CiB* B 5.34 21.56% 61 326 Offsite - Impervious CiB* B 1 0.37 1.49% 98 36 POST - DEVELOPED CONDITIONS TOTALS 24.77 100.0% 2018 WEIGHTED CN (DEVELOPED) = 81 - Onsite & Offsite Developed BASIN LAND USE SOIL NAME HYDROL. GROUP AREA (AC.) AREA ( %) CURVE NO (CN) CN x AREA Onsite - Pervious CiB* B 5.72 23.08% 61 349 Onsite - Impervious CiB* B 13.34 53.86% 98 1308 Offsite - Pervious CiB* B 1.71 6.92% 61 104 Offsite - Impervious CiB* B 1 4.00 16.14% 98 392 TOTALS 24.77 100.0% 2153 WEIGHTED CN (DEVELOPED) = 87 * Various soils present - CiB, FaB, FaC, FcB2, FcC2, FcE3, Gu, HaA Dominant hydrologic soil group is B Project: Novant- Kernersville Project No.: 13 -114 Designed By: BMH Checked By: JNT Date: 8/5/2013 Revised: 4/16/2014 WATER QUALITY POND DESIGN (Option 6 On -Site Drainage Area to Pond = 28.84 acres On -Site Proposed Impervious Area = 20.19 acres On -Site Future Impervious Area = 0.00 acres Total On -Site Impervious Area = 20.19 acres Total Project Site Area = 28.84 acres Offsite Drainage Area to Pond = Offsite Impervious Area = Offsite Future Impervious Area = Total Offsite Impervious Area = WATERSHED INFORMATION Watershed = West Fork Deep River Classification = WS -IV 70.00% Drainage Area Impervious Percentage 70.00% Project Area Impervious Percentage 19.20 acres 1.35 acres 0.00 acres 1.35 acres 7.03% Drainage Area Impervious Percentage Total Watershed Area to Pond = 48.04 acres Graded Area to Pond = 20.19 acres Temporary Sediment Storage Used = n Temporary Sediment Storage = Permanent Sediment Storage = Current Composite Impervious Percentage = Maximum Impervious Percentage = Permanent Water Quality Pool Depth (3'min.) _ Surface Area / Drainage Area Ratio = Temporary Water Quality Depth to be Controlled = Elevation at Bottom of Pond = 911.50 Elevation at Bottom of PSS = 911.50 Elevation at Bottom of PWQ = 912.50 Elevation at Bottom of TWQ = 916.00 Elevation at Top of TWQ = 917.35 Elevation at Emergency Spillway = 0.00 Elevation at Top of Dam = 920.00 Invert of Barrel = 911.50 Elevation at Bottom of Pond = 911.50 Elevation at Bottom of TWQ = 916.00 0.50 ac -in. 0.125 ac -in. 44.84% 45.00% 3.00 FT 2.800% 1.0 Inch Surface Area = 45,381 SF Surface Area = 45,381 SF Surface Area = 47,904 SF Surface Area = 60,427 SF Surface Area = 71,435 SF Surface Area = 45381 Square Feet Surface Area = 60427 Square Feet Allow 75% of Basin Volume To Water Quality Orifice = 30�D Woot Fourth Street, Suite 1 -A Phone (33(b) 723 -1067 Stimmel A000ciateo, F.A. Winston Salem, NC 27101 Fax (330) 723 -1009 Elevation at Bottom of PSS = 911.50 Elevation at Middle of PSS = 912.00 Elevation at Bottom of PWQ = 912.50 Surface Area = 45381 Square Feet Surface Area = 46643 Square Feet Surface Area = 47904 Square Feet Volume Provided = PERMANENT WATER QUALITY SURFACE AREA REQ'D 58600 Square Feet Normal Pool Elevation = 916.00 Surface Area Provided = 60427 Square Feet OK Rv= 0.455 in /in (Based on Max Imp. %) Elevation at Bottom of TWQ = 916.00 Surface Area = 60427 Square Feet Elevation at Top of TWQ = 917.35 Surface Area = 71435 Square Feet Volume Provided = Elevation at Top of Riser = 917.35 Elevation at Bottom of Water Quality Release Hole = 916.00 Maximum Release Rate = 2 Days Minimum Release Rate = 5 Days Maximum Hole Size = 0.168767956 5.56 in. dia. Minimum Hole Size = 0.067507183 3.52 in. dia. Orifice Size Chosen = 4.00 in. dia. Orifice Coefficient = 0.60 Orifice Area = 0.087 SF Maximum Release Rate = 0.49 CFS WQ Drawdown Time = 4.22 Days Elevation at Normal Pool = Elevation at Bottom Of Pond = Release Rate = Minimum Hole Size = 916.00 911.50 3 Day 0.205417815 6.14 in. dia. 30�D Woot Fourth Street, Suite 1 -A Phone (330) 723 -1007 Stimmel A000ciateo, F.A. Winston Salem, NC 27101 Fax (330) 723 -1009 PROJECT: KERNERSVILLE MEDICAL PARKWAY PROJ. NO.: 08 -032 SHEET: 1 DESIGNED BY BMH DATE: 04/16/14 CHECKED BY JNT DATE: LOCATION / DESCRIPTION BLUE DIAMOND PROPERTY SWM POND IMPOUNDMENT VOLUMES BY INTERPOLATION INPUT DATA BEGIN DATA INPUT AT LOWEST CONTOUR 911.5 0 FOREBAY MAIN BODY TOTAL POND 12" CONTOUR CONTOUR CONTOUR CONTOUR INCR. CUMUL. STAGE ELEVATION AREA AREA AREA VOLUME VOLUME (FT) (FT) (SF) (SF) (SF) (C F) (C F) 0.00 911.5 0 45,381 45,381 0 0 1.00 912.5 0 47,904 47,904 46,643 46,643 4.00 915.5 0 55,814 55,814 155,576 202,219 4.50 916.0 0 60,427 60,427 29,060 231,279 5.00 916.5 0 65,198 65,198 31,406 262,685 8.50 920.0 0 75,729 75,729 246,622 509,307 Volume Query by Elevation Element Elevation Cumul_ Volume Surface Area Stane Perm. Sedim. Stor. 912.50 46,643 47,904 1.00 Perm. Pool 916.00 231,279 60,427 4.50 Top Temp WQ 917.24 310,901 70,758 5.74 Top Riser 917.35 318,271 71,435 5.85 Top of Dam 920.00 509,307 75,729 8.50 Bot of Shelf 915.50 202,219 55,814 4.00 Elevation Query by Volume Element Cumul_ Volume Elevation Surface Area Stane Perm. Sedim. Stor. 46,643 912.50 47,904 1.00 Perm. Pool 231,279 916.00 60,427 4.50 Temp. WQ 310,633 917.24 70,987 5.74 P. Pool Depth= 3.50 Ft. Average Depth = 3.27 Ft. Avg. depth calculated by Option 2 method. NCDENR BMP Manual 1" Storm Ooo -0 r0 >�� DOD v O-n z �z ' Z9 D K zcn ° lmm �� w n z cnm� M n� Dm m zz �� C lb ...,.......E i Ooo -0 r0 >�� DOD v O-n z �z ' Z9 D K zcn ° lmm �� w n z cnm� M n� Dm m zz �� C lb eo CL eo CO a - _=0 Tc- - m a _ � _ o �o- cmn s �0 3y z s o r � ro m � m z � � z >a m a7 O e to v N 0 D D n ®®®® ® ® m® 91mm1m9m919199999m - ®® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ® ®® ®mill®® ® ® ® ®1mm ® ®91111m11m9 ® Banco ® ®a self® ®e® 199�m199919 ®991119199 ®1999991111111® 999�IIIIIIIIII��III9IIII�IIII��I9IIIIII��9��I�III�I� ' 9I9I��9�III��IIIII�II9IIIIII� COMPANIES INDUSTRIAL • COMMERCIAL • LAND DEVELOPMENT 1349 -C SOUTH PARK DRIVE KERNERSVILLE, NC 27284 (336) 996 -5000 Fax (336) 996 -3858 VIA EMAIL: Jennifer.Burdettegncdenr. ov April 14, 2014 Ms. Jennifer Burdette 401 Buffer Coordinator Wetlands Branch NCDENR -- Division of Water Resources Water Quality Programs 1650 Mail Service Center Raleigh, NC 27699 -1650 Re: Blue Diamond Variance Dear Ms. Burdette: Please allow this letter to clarify the relationship between Blue Diamond Investment Company, LLC and Lend Lease (US) Healthcare Development LLC. Blue Diamond sold 39 acres to Lend Lease for the development of the new VA hospital. Blue Diamond has no interest in the land or development of the VA hospital. Sincerely, tiunter cc: Neal Tucker, Stimmel Associates, PA (via email: NTucker(2stimmelpa.com)