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HomeMy WebLinkAboutSDP200900036 Calculations 2009-04-30 GLOECKNER ENGINEERING/SURVEYING, INC. Engineers—Surveyors—Land Planners Kurt M.Gloeckner,P.E.,P.L.S. President April 30, 2009 Amy Pflaum, Engineer County of Albemarle 401 McIntire Road Charlottesville, Virginia 22902 Re: Synthetic Turf Field Post Development Run-off Coefficient Dear Amy Enclosed are copies of data supplied by the proposed supplier of the field to be installed at Saint Annes—Belfield. The Springfield data is the closest model data. The use of a post construction run-off coefficient of 0.4 is realistic for this area. In the 40 years of computing coefficients, post development for grass fields would be worse than the penetration through the artificial turf with gravel and sand bases. The enclosed study proves the storage capacity of this type of field. For my minor amendment for the turf field I am not going to claim any storage but will use 0.4 as my post construction run-off coefficient. The existing sand filters I have under the practice field and in front of the parking lot have the treatment/detention volume to handle the additional post development volumes. If necessary, I will be glad to discuss this further. Thank you for your interest. Sincerely, Kurt M. Gloeckner, P.E., P.L.S. President KMG:tpm 508 Dale Avenue,Suite A • Charlottesville,Virginia 22903 • Tel:(434)971-1591 • Fax:(434)293-7612 9 T (41)CZW T - a AU ? L - m zo IiUUoiaiaion0iooa -13 2 o a a a a a a a o o a o f01 D A V} +n :D O N O A N V :,' O W .9 7�737 W w rD ry O W O N D Z m(n+r0o000000000 0 0 0 = AO T ^ T /� T i T v 0 0 000 0 0 0 0 000 Z mo — 0 w N o m 0Q EC FA $ N m a a Ln S D 00 - 0 C 0,�J 0 0 0 0 0 0 0 0 0 CDi Zm :4 E 7....„...) N W O A (p V A W N 00 IND CA A C• /'�X _ o=, II (---------,:, N (T N (T (JT ST (T U cm N N Ir N z m , Z C O O 0 0 0 O O O O O O O �. a $ C-- V v ti v v 0 v V V v V V 0 Z a z .,X A 0 N '''I N N N N N N N N N = T O :.71V V V V V V V V V V V V i (D > D ( r -'I-13 r. 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W a N N V N Lo V a m t WEST SPRINGFIELD DRAWN BY VGY HIGH SCHOOL FIELDTURF TARKETT SCALE, BA ASYSHOWN S[ORM COMPUTATIONS UNITED IN SPORT FIELD AREA, 65,550 SQUARE FEET DATE=RAY 5,2006 ISSUE: 1 SHEET - nil Rights Reserved. Confidential Infornatlon. No portion of these drowings nay be disclosed,used,modified or shown without prior written consent of Fieldiurf. ELA Group, Inc. 743 South Broad Street Litt, PA 17543 (717) Engineers & Landscape Architects Phone: 62e-7271 Far (717)6264040 Fax To: Vincent Yoos From: Craig Smith Finn. Field Turf Date: October 2.2007 Fax (412)220-5308 Pages,: 13 Phone: (412)220-5304 CC: Re: Field Turf Study --- CI Urgent 0 For Review 0 Please Comment U Please Reply ..Comments: Hey Vincent. Here is the testing,procedure,and conclusion section of a study we did on a grass field converted to a synthetic turf field for Coatesville High School. Basically we just monitored rainfall and then recorded flow rates through a junction point between multiple underground drainage pipes The same procedure was then performed once the grass held was converted into a synthetic turf field. If you look at Table C. we averaged the results based on the rainfall amounts,and compared the results between the pre and tne post condition. It you look at the Average Peak Flow Column,at least for this study, a decrease by almost 50/0 was observed in the peak runoff flow rate. The total volume was increased in the post condition. which is probably justifiable by the fact that there is no longer natural grass to evapotranspirate the water. I'm not sure how much ground water recharge would actually occur once a synthetic turf field is installed, as a result of the original subgrade being compacted pnor to installation , of stone and sand sub--base,in preparation of the synthetic turf. What are your thoughts? Thanks Craig Smith. E.I.T ctsmith ,z)elagroup.corn NOTE: THIS MESSAGE iS iN(ENDED ONLY r-,01-it THE INDIVIDUAL 10 WHOM IT IS ADDRESSED. INFORMATION CONTAINED IN THIS DOCUMENT IS PROTECTED BY LAW DISCLOSURE, COPYING, DISTRIBUTION,OR USE OF THE CONTENTS OTHER THAN EP(RECIPIENT IS PROHIBITED_ IF YOU RAVE RECEIVED THIS DOCUMENT IN ERROR,PLEASE CONTACT RA GROUP,INC.AT(717)626-7271 eirast)s‘voi11,Data,337-RLPS\337,01.ci MOS'402 CiviltStormwutet\Conettpoirdentv.\Fax tu Fieki Turklot; -- ------ Coatesville H gh`,z"�oui A ttk Itc Fi.gs__.__�_W i 03070 rf TESTING EQUIPMENT, DATA, AND PROCEDURE is FIA Cai:tip,Inc Lititz.PA O. 1 1 Synthettg Turf Fteld TeAL _ _.1 j.34370. _____.... Ai 1 - TESTING EQUIPMENT DATA, AND PROCEDURE :14 — The testing was completed by installing a Greyline STINGRAY Level-Velocity Logger with 0Z02 submersible ultrasonic Level-Velocity Sensor into the 24 RCP storm sewer 1 that collects stormwater runoff from the site, Please see the Appendix for the specifications for the STINGRAY. The same STINGRAY unit with serial number 23(31 l . was used for the pre and post-construction testing. The STINGRAY was installed on i. April 27. 2006 and collected data until June 1, 2006 for the pre-construction condition I -14 Then the STINGRAY was installed on September 22, 2006 and collected data until November 3, 2006 for the post-construction condition. I he data that the STINGRAY collects includes the time of the data entry (typically every 30 to 60 seconds), level of the 1 stormwater in the storm sewer pipe, and finally the velocity of the stormwater. Software 1 Afor the STINGRAY computed the flow through the pipe using the level and velocity of the stormwater Data from the STINGRAY is shown in graph form on the following pages. 'AA I The data collected by the STINGRAY was then compared to the amount of rainfall that occurred Rainfall amounts were determined by using the U.S. Department of 1 Commerce's NOAA National Weather Service The NOAA provides copies of collected .--, .--1 weather data from sites all over the country The Coatesville 2 W 1983-02 . 2006-11 ''!.1 (361591) COOP Station was used to obtain results that since it is the closest official location to the Site. Please see the Record of River and Climatological Observations I A, sheets in the Appendix. 1 I 1 1 1 1 AA 1 ei 4 1 I .=_ ,—. [LA Group.Inc btitz,P4 1 I 1 i A A I 1 0, ------- - --1--- . i c •-• 1 -- • 43 ••• • •Ip ___ ki)41,,--- •si. .__. -1. 0- ... .. ..., •.. ..... ta - = '.-:.• L • trel — • -1 CO or C:,rar; . 1 I X 0.4 — 1 CP Ire ..• .... ._ ; 1-- . . 65 1 - a.) ...., usmi-1 esi ' I ›* es 1... on t- i es" z4. I -II Z a. i t . __ . _ t,_ 1 •-•- 1... ...-- , . C !NM *NO '05 I '''' 0 CL a'l I 0 i ti! 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EXPLANATION OF DATA CHARTS Tables A and 13 on the next page represent the data downloaded from the STINGRAY and the NOAA data sheets for the Coatesville Station. The following are definitions for the terms used in the following charts: • Amount of Rainfall: This value is taken directly from the NOAA data sheet and represents the total accumulation of rainfall for each event in inches. • Aneroximate Storm DurationEach NOAA data sheet gives a general time of duration for a storm event by crossing a line through the hours that precipitation was detectable. The duration of each storm was taken from this information, • ae_roxLeials.Lkitensily: This value represents the average rainfall intensity of each storm event and is calculated by dividing the Amount of Rainfall by the Approximate Storm Duration. • Beginning of Runoff Data: The STINGRAY logs flow data in time increments of 30 to 60 seconds: this is the first logging of a storm event (i.e. the first detection of flow in the pipe after a period of zero flow). • End of Runoff Datw The STINGRAY logs flow data in time increments of 30 to 60 seconds: this is the last logging of a storm event (i.e. the last detection of flow in the pipe prior to a period of zero flow). • k.)pration of_Runoff. This value represents the length of time flow that was detected within the pipe for each storm event and is calculated by subtracting the End of Runoff Data minus the Beginning of Runoff Data. This value can be used to show if storrnwater detention occurs within a watershed. • Peak How The STINGRAY logs velocity and level of the storrnwater passing through the storm sewer at determined intervals. The STINGRAY software then determines the flow at each of the time intervals. The peak flow is the largest logged flow rate through the storm sewer pipe for each storm event. • Volume of Runoff, This value represents the generalized volume of a give storm event. The instantaneous flow for each time increment in a storm event was added together arid then multiplied by 30 seconds, which was the interval between each data log Table C. The Comparison of Averages chart, on the next page takes the storm data from Tables A& 13 and breaks them into two subsets of storm ranges based on the amount of rainfall for each stone event. The two ranges, 0,00 to 0.60 inches and 0.61 to 1 20 inches, were chosen as means to show more representative average value sets that were not skewed in either direction This chart will help determine if the peak flow from the site increases after the construction of the synthetic turf field or if the synthetic turf field decreases the peak runoff from the Site and there by acts as a stormwater management detention facility. ELA Group,In !Adz Pit 7 0 '. CV D up c+. QO TccCW 11,1. in Nt j t Cr `ct +"' • 40 N ON el N s- r > c•7 •.- N r. 0.1N au000u 'F5 pUvc> ovoc) S' V- N 4/ 0) Ch N 07 CO lL. Y (C) 47 (0 CO r (y t•^) •7' CV UD Cc) Il') r- co ICS n- C7 C7 .-• r pp 01 V) Q Cq to r O(1 CU to C04 o w- to N s C aC700000o a0 oa6 .- o a. b ' p q E e U U o r 0 0 e e. 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I ••, v.; c) C 7 as l3 :!tic arc._ Coatesville High School Athletic;Fields 1U3-0A) CONCLUSION t.I 1(liotip Inc l Utr.PA 4 ° ^ ~ —. ________-==�`` CONCLUSION OF FIELD DATA The Average Rainfall column in Table C shows that the comparison of storm events is not exact since both of the post-construction ranges for the average are higher then the pre-construction values. thus being larger rain events. This must be kept in mind when comarinq the other columns The Average Duration of Runoff column in Table C clearly shows that the synthetic turf field is detaining stormwater The time that is takes before the runoff is complete is three to five times as long as in the pre-coristruction condition The prolonged detention time will help prevent downstream flooding and verifies that the reduction in the Average Peak flow in the post—construction condition is correct The Average Intensity column in Table C shows that the comparison of storm events is not exact since both of the pre-construction ranges for the average are higher then the post-construction values, thus being different shaped hydrographs and effecting the runoff response time in the watershed, This must also be kept in mind when comparing the other columns, The Average Peak Flow column in Table C shows that the synthetic turf field system is detaining stormwater as aforementioned The peak flow in the post-construction condition is reduced by half or more from the pre-constructiori condition. This reduction is even more significant when considering that the post-construction storm events were larger then the pre-construction events in total inches of accumulated rainfall. Fina|/ytheAvereQuVu|un`eo| Runoffco|umninTobiaCahowaanmc/eaaeinthepost- construction Condibon, huwever, this can be expected due to the increase in impervious area within the watershed and due to the Average Rainfall being larger in the post- construction condition This further proves that the synthetic turf field can be used as a stormwater management facility for detention, The increase volume should directly relate to a higher peak flow if the system was not detaining stormwater runoff. ConmaquonUy. the peak flow is |nvver, which means the synthetic turf field is storing the stormwater onsite and releasing it Slowly. Thus the data proves that the synthetic turf held system can be calculated as a stormwater management facility Until a larger subset of data can be collected that can match storm events in the pre-development condition in rainfall amount and average intensity it would be difficult to determine the amount of stormwater recharge that occurs within the system and what runoff coefficient should be used to model the synthetic turf field system. Other studies for other test sites are still on going and will thus allow for more accurate modeling in the future • pt A Group.Inc --------