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Preliminary Drainage Study Page 1 of 2 XO MARRIAGE TODAY – PRELIMINARY DRAINAGE STUDY CITY OF SOUTHLAKE, TARRANT COUNTY, TEXAS APRIL 26, 2021 Prepared for: Department of Planning & Development Services City of Southlake 1400 Main Street, Suite 310 Southlake, Texas 76092 Prepared by: Parkhill 255 N. Center Street Suite 200 Arlington, Texas 76011 817.649.3216 Page 2 of 2 1.0 INTRODUCTION XO Marriage Today is a proposed office building located on a 5.0-acre site along Kirkwood Boulevard and Grace Lane. The purpose of this report is to analyze any drainage impacts that changing the use for this property would have on-site or adjacent properties. 2.0 HYDROLOGY Parkhill has completed a drainage analysis for the existing and developed site to determine the additional runoff produced by the proposed improvements. The rational method was used to compute the total runoff values. Runoff coefficients and intensities are based on the 2020 iSWM Hydrology Technical Manual and a minimum time of concentration of 10 minutes was used for the developed condition. EXISTING CONDITIONS HYDROLOGY The site currently holds detention from a neighboring site, The Westin Hotel, in a detention channel that drains to a culvert under Kirkwood Boulevard. See the attached ‘Detention Plan’ (Table 2, Step 1) for pre-development 100-year runoff values for the XO Marriage Today site and Westin Hotel site. PROPOSED CONDITIONS HYDROLOGY See attached ‘Drainage Area Map’ (Table 1) for proposed hydrology calculations for the site. The hydrology calculations shown account for the ultimate development of this site. The runoff that exceeds pre-development flow will be detained on-site to prevent overloading the downstream drainage system. See attached ‘Detention Plan’ for post-development 100-year runoff values (Table 2, Step 2) for the XO Marriage Today site and required detention volume (Table 2, Step 3). 6206 2 0 620 625 6 3 0 6 3 0 630 635 635 635 6 3 5 6 3 5 635 635 6 4 0 640 640 6 4 0 6 4 0 640 640 645645 6 4 5 645 645 62162 2 623624 626627 62 8 6 2 8 628 6 2 9 6 2 9 629 6 3 1 6 3 1 631 632 632 6 3 2 6 3 2 632 633 633 6 3 3 6 3 3 633 633 633 634 634 634 634 6 3 4 63 4 634 636 636 6 3 6 6 3 6 636 636 636637 637 6 3 7 637 637 6 3 7 63 7 6 3 8 638 638 6 3 8 6 3 8 638 638 639 6 3 9 639 639 6 3 9 6 3 9 639 641 641 641 64 1 6 4 1 641 6 4 1 642 642 6 4 2 6 4 2 642 643 643 6 4 3 643 643 6 4 3 643 644 644 644 644 6 4 4 6 4 6 646 64 6 6 4 7 647 647648649 640 64 5 645 637638639641 64 2 642 64 3 643 64 4 644 64 6 6 4 6 64 5 640 635 645 6 3 5 6 3 0 F I N I S H E D F L O O R E L E V A T I O N 6 4 6 . 5 0 6 4 0 6 3 5 6 3 0 6 3 0 6 3 5 6 4 0 6 3 5 6 3 5 6 4 0 6 4 0 6 4 5 6 4 5 6 4 5 LP LP LP LP LPLP LPLP LP LPLP LP LP LP LP LP LP X ICVICVICVICV ICV ICV ICV ICV ICV ICV WV WV WV WV SSMH SDMH SDMHSDMH SDMH WMFH FH W W W W S S S S S S S S W W W W W W W W W W WWWW N A-10.17 ac G R A C E L A N E KIRKWOOD BOULEVARD A - 4 0 . 9 7 a c A - 3 0 . 1 3 a c A - 2 0 . 1 6 a c B - 1 0 . 2 5 a c B - 2 0 . 1 1 a c B - 3 0 . 4 3 a c C - 1 0 . 3 7 a c C - 2 0 . 6 7 a c D - 1 2 . 8 0 a c D-21.66 acPROPERTY LINE P R O P E R T Y L I N E FILE NAME: X:\2019\8555.19\03_DSGN\01_DWG\050_CIVIL\C-100 DRAINAGE AREA MAP.dwg LAYOUT NAME: C100 PRINTED: Wednesday, April 21, 2021 - 6:28pm USER: CHadsall P a r k h i l l . c o m P R O J E C T N O . C L I E N T # D A T E D E S C R I P T I O N K E Y P L A N 1 5 4 3 21 A B C D 2 3 4 5 XO MARRIAGE CENTER X O M A R R I A G E S O U T H L A K E , T X 7 6 0 9 2 8 5 5 5 . 1 9 - 0 3 / 1 9 / 2 0 2 1 5 0 % C D P A C K A G E T H I S D O C U M E N T I S R E L E A S E D O N A P R . 2 6 , 2 0 2 1 F O R T H E P U R P O S E O F I N T E R I M R E V I E W U N D E R T H E A U T H O R I T Y O F L A R R Y D . S T O N E , P . E . , T E X A S L I C E N S E # 4 2 2 5 2 . I T I S N O T T O B E U S E D F O R R E G U L A T O R Y A P P R O V A L , C O N S T R U C T I O N , B I D D I N G O R P E R M I T P U R P O S E S . P A R K H I L L S M I T H & C O O P E R , I N C . F - 5 6 0 D r a i n a g e A r e a M a p C - 1 0 0 4 0 ' 8 0 ' 0 iSWM Hydrology Calculations - Marriage Today SouthlakeD.A.Areacc25c100tcI5I25I100Q5Q25Q100No.ac.(includes cf)minin/hrin/hrin/hrcfscfscfsA-10.170.951.001.00105.5147.7829.7620.891.321.66A-20.160.350.390.44105.5147.7829.7620.310.480.68A-30.130.951.001.00105.5147.7829.7620.681.011.27A-40.970.700.770.88105.5147.7829.7623.745.818.29B-10.250.350.390.44105.5147.7829.7620.480.751.07B-20.110.951.001.00105.5147.7829.7620.580.861.07B-30.430.800.881.00105.5147.7829.7621.902.944.20C-10.370.800.881.00105.5147.7829.7621.632.533.61C-20.670.800.881.00105.5147.7829.7622.964.596.54D-12.800.350.390.44105.5147.7829.7625.408.3911.96D-21.660.350.390.44105.5147.7829.7623.204.977.09SITE TOTAL7.7221.7733.6647.44Notes:1) A minimum time of concentration of tc= 10 min was used2) Intensities from Tarrant County Rainfall Data - 2020 iSWM Hydrology Technical Manual 625 630630 630 635 635 635 635 6 3 5 635635640 640 640 6 4 0 640 645645 645 6 4 5 645 626627 628628 628 629629 629 631 631 631 632 632 632 6 3 2 632 633 633 633 6 3 3 633 633 633 634 634 634 634 634 63 4 634 636 636 636 6 3 6 636 636 636637 637 637 637 637 6 3 7 637638 638 638 6 3 8 638638 638 639 639 639 639 6 3 9 639 639 641 641 641 641 642 642 642 643 643 643 643 644 644 644 644 6 4 6 646646647647640 64 5 645 637638639641 64 2 642 64 3 643 64 4 644 64 6 646 LP LP LP LP LP LPLPLPLP LP LP LPLP LP LP ICV ICV ICV ICV WV WV SDMHSDMH WMFHFH FH W W W W W W W W WWWWGRACE LANE KIRKWOOD BOULEVARD645640635 645 635 630 6 4 0 6 3 5 6 3 0 6 3 0 6 3 5 6 4 0 6 3 5 6 3 5 6 4 0 6 4 0 6 4 5 6 4 5 6 4 5 D E T E N T I O N C H A N N E L V = 1 1 8 , 4 0 0 C F ( W I T H 1 ' F R E E B O A R D ) PROPERTY LINE P R O P E R T Y L I N E FILE NAME: X:\2019\8555.19\03_DSGN\01_DWG\050_CIVIL\C-101 DETENTION PLAN.dwg LAYOUT NAME: C-101 PRINTED: Wednesday, April 21, 2021 - 6:42pm USER: CHadsall P a r k h i l l . c o m P R O J E C T N O . C L I E N T # D A T E D E S C R I P T I O N K E Y P L A N 1 5 4 3 21 A B C D 2 3 4 5 XO MARRIAGE CENTER X O M A R R I A G E S O U T H L A K E , T X 7 6 0 9 2 8 5 5 5 . 1 9 - 0 3 / 1 9 / 2 0 2 1 5 0 % C D P A C K A G E T H I S D O C U M E N T I S R E L E A S E D O N A P R . 2 6 , 2 0 2 1 F O R T H E P U R P O S E O F I N T E R I M R E V I E W U N D E R T H E A U T H O R I T Y O F L A R R Y D . S T O N E , P . E . , T E X A S L I C E N S E # 4 2 2 5 2 . I T I S N O T T O B E U S E D F O R R E G U L A T O R Y A P P R O V A L , C O N S T R U C T I O N , B I D D I N G O R P E R M I T P U R P O S E S . P A R K H I L L S M I T H & C O O P E R , I N C . F - 5 6 0 N D e t e n t i o n P l a n C - 1 0 1 4 0 ' 8 0 ' 0 M o d i f i e d R a t i o n a l M e t h o d D e t e n t i o n P o n d D e s i g n - M a r r i a g e T o d a y S o u t h l a k e ( S i t e O n l y ) S t e p D r a i n a g e A r e a T c ( m i n ) I 1 0 0 ( i n / h r ) C A ( a c r e ) Q 1 0 0 ( c f s ) S u b t o t a l Q 1 0 0 ( c f s ) T o t a l 1 P r e - D e v e l o p m e n t A L L 1 5 8 . 0 2 0 . 3 0 7 . 7 2 1 8 . 5 7 1 8 . 5 7 2 P o s t - D e v e l o p m e n t A - 1 1 0 9 . 7 6 1 . 0 0 0 . 1 7 1 . 6 6 4 7 . 4 4 A - 2 1 0 9 . 7 6 0 . 4 4 0 . 1 6 0 . 6 9 A - 3 1 0 9 . 7 6 1 . 0 0 0 . 1 3 1 . 2 7 A - 4 1 0 9 . 7 6 0 . 8 8 0 . 9 7 8 . 2 9 B - 1 1 0 9 . 7 6 0 . 4 4 0 . 2 5 1 . 0 7 B - 2 1 0 9 . 7 6 1 . 0 0 0 . 1 1 1 . 0 7 B - 3 1 0 9 . 7 6 1 . 0 0 0 . 4 3 4 . 2 0 C - 1 1 0 9 . 7 6 1 . 0 0 0 . 3 7 3 . 6 1 C - 2 1 0 9 . 7 6 1 . 0 0 0 . 6 7 6 . 5 4 D - 1 1 0 9 . 7 6 0 . 4 4 2 . 8 0 1 1 . 9 6 D - 2 1 0 9 . 7 6 0 . 4 4 1 . 6 6 7 . 0 9 3 T d ( m i n ) C w I ( i n / h r ) A ( a c r e ) Q a ( c f s ) V p r e l i m ( f t 3 ) P 1 8 0 P t d V r e q ( f t 3 ) V r e q ( a c r e - f t ) 3 9 . 7 6 0 . 6 3 9 . 7 6 7 . 7 2 1 8 . 5 7 3 0 , 5 4 0 5 . 3 6 3 . 0 3 5 4 , 0 3 4 1 . 2 4 M o d i f i e d R a t i o n a l M e t h o d D e t e n t i o n P o n d D e s i g n - M a r r i a g e T o d a y S o u t h l a k e ( S i t e & H o t e l S i t e ) S t e p D r a i n a g e A r e a T c ( m i n ) I 1 0 0 ( i n / h r ) C A ( a c r e ) Q 1 0 0 ( c f s ) S u b t o t a l Q 1 0 0 ( c f s ) T o t a l 1 P r e - D e v e l o p m e n t - S I T E A L L 1 5 8 . 0 2 0 . 3 0 7 . 7 2 1 8 . 5 7 6 1 . 4 5 P r e - D e v e l o p m e n t - H O T E L F L O W V A L U E F R O M 2 0 1 7 W E S T I N C I V I L P L A N S 4 2 . 8 8 2 P o s t - D e v e l o p m e n t - S I T E A - 1 1 0 9 . 7 6 1 . 0 0 0 . 1 7 1 . 6 6 1 2 1 . 5 2 A - 2 1 0 9 . 7 6 0 . 4 4 0 . 1 6 0 . 6 9 A - 3 1 0 9 . 7 6 1 . 0 0 0 . 1 3 1 . 2 7 A - 4 1 0 9 . 7 6 0 . 8 8 0 . 9 7 8 . 2 9 B - 1 1 0 9 . 7 6 0 . 4 4 0 . 2 5 1 . 0 7 B - 2 1 0 9 . 7 6 1 . 0 0 0 . 1 1 1 . 0 7 B - 3 1 0 9 . 7 6 1 . 0 0 0 . 4 3 4 . 2 0 C - 1 1 0 9 . 7 6 1 . 0 0 0 . 3 7 3 . 6 1 C - 2 1 0 9 . 7 6 1 . 0 0 0 . 6 7 6 . 5 4 D - 1 1 0 9 . 7 6 0 . 4 4 2 . 8 0 1 1 . 9 6 D - 2 1 0 9 . 7 6 0 . 4 4 1 . 6 6 7 . 0 9 P o s t - D e v e l o p m e n t - H O T E L F L O W V A L U E F R O M 2 0 1 7 W E S T I N C I V I L P L A N S 7 4 . 0 8 3 T d ( m i n ) C w I ( i n / h r ) A ( a c r e ) Q a ( c f s ) V p r e l i m ( f t 3 ) P 1 8 0 P t d V r e q ( f t 3 ) V r e q ( a c r e - f t ) 3 1 . 8 8 0 . 6 8 9 . 7 6 1 8 . 2 1 6 1 . 4 5 5 8 , 3 7 5 5 . 3 6 2 . 8 1 1 1 1 , 3 4 8 2 . 5 6