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HomeMy WebLinkAbout6.13_Gallatin Subaru_Civil Engineering Report App B_Hydrologic Calculations_5-22-2020Im p e r v i o u s 0 . 9 0 Un d i s t u r b e d 0 . 2 0 Pr e - D e v e l o p m e n t : E x i s t i n g C o n d i t i o n We i g h t e d C - V a l u e ( C w ) Ar e a R u n o f f (A C ) Co e f f i c i e n t Ca l c u l a t i o n s Im p e r v i o u s 0. 0 0 0 . 9 0 0 . 0 0 Un d i s t u r b e d 4. 2 4 0 . 2 0 0 . 8 5 To t a l s 4. 2 4 0 . 8 5 C w = 0. 2 0 Po s t - D e v e l o p m e n t : E x i s t i n g C o n d i t i o n We i g h t e d C - V a l u e ( C w ) Ar e a R u n o f f (A C ) Co e f f i c i e n t Ca l c u l a t i o n s Im p e r v i o u s 3. 4 6 0 . 9 0 3 . 1 1 Un d i s t u r b e d 0. 7 8 0 . 2 0 0 . 1 6 To t a l s 4. 2 4 3 . 2 7 C w = 0. 7 7 BO Z E M A N S U B A R U WE I G H T E D C - V A L U E L: \ 1 9 3 2 9 0 \ C o m p u t a t i o n s \ S t o r m w a t e r \ S T O R M W A T E R C A L C U L A T I O N S Existing Situation Land Use Open Land Area 4.24 Acres Slope 1 % C= 0.20 Overland Flow Distance 336 ft Time of Concentration 31 min Design Storm Frequency 10 year (Table I-3) Intensity at Tc 0.99 in/hr (Figure I-3) Peak Runoff Rate 0.84 cfs Proposed Situation Land Use Commercial Area 4.24 Acres Slope 2 % C= 0.77 Overland Flow Distance 387 ft Time of Concentration 10 min Design Storm Frequency 10 year (Table I-3) Intensity at Tc 2.10 in/hr (Figure I-3) Peak Runoff Rate 6.86 cfs Percent Inpervious 82% Runoff Treatment Volume 6064 cf (RTV) BOZEMAN SUBARU DETENTION RELEASE RATE L:\193290\Computations\Stormwater\STORMWATER CALCULATIONS Ex i s t i n g S i t u a t i o n Mi n i m u m V o l u m e La n d U s e O p e n L a n d Ar e a 1 . 1 1 A c r e s St o r m Du r a t i o n In t e n s i t y F u t u r e R u n o f f Ra t e Ru n o f f Vo l u m e Re l e a s e Ra t e Release VolumeRequired Storage Sl o p e 1 . 0 % (M i n u t e s ) ( i n / h r ) Q = C i A ( c f s ) ( c f ) ( c f s ) ( c f ) ( c f ) C= 0 . 2 0 12 1 . 8 2 1 . 5 6 11 2 1 0 . 0 0 9 7 1 1 1 5 Ov e r l a n d F l o w D i s t a n c e 2 2 8 f t 14 1 . 6 5 1 . 4 1 11 8 3 0 . 0 0 9 8 1 1 7 6 Tim e o f C o n c e n t r a t i o n 25 min 16 1 . 5 1 1 . 2 9 12 4 0 0 . 0 0 9 9 1 2 3 1 De s i g n S t o r m F r e q u e n c y 1 0 y e a r ( T a b l e I - 3 ) 18 1 . 4 0 1 . 2 0 12 9 2 0 . 0 0 9 1 0 1 2 8 2 In t e n s i t y a t T c 1 . 1 2 i n / h r ( F i g u r e I - 3 ) 20 1 . 3 1 1 . 1 2 13 4 1 0 . 0 0 9 1 1 1 3 3 0 Pe a k R u n o f f R a t e 0 . 2 4 8 c f s 22 1 . 2 3 1 . 0 5 13 8 6 0 . 0 0 9 1 2 1 3 7 4 24 1 . 1 6 0 . 9 9 14 2 9 0 . 0 0 9 1 3 1 4 1 6 Pr o p o s e d S i t u a t i o n 26 1 . 1 0 0 . 9 4 14 7 0 0 . 0 0 9 1 4 1 4 5 5 La n d U s e C o m m e r c i a l 28 1 . 0 5 0 . 9 0 15 0 8 0 . 0 0 9 1 5 1 4 9 3 Ar e a 1 . 1 1 A c r e s 30 1 . 0 0 0 . 8 6 15 4 5 0 . 0 0 9 1 7 1 5 2 8 Sl o p e 2 . 0 % 32 0 . 9 6 0 . 8 2 15 8 0 0 . 2 4 8 3 0 1 5 5 1 C= 0 . 7 7 34 0 . 9 3 0 . 7 9 16 1 4 0 . 2 4 8 6 0 1 5 5 5 Ov e r l a n d F l o w D i s t a n c e 3 0 0 f t 36 0 . 8 9 0 . 7 6 16 4 7 0 . 2 4 8 8 9 1 5 5 7 Tim e o f C o n c e n t r a t i o n 10 min 38 0 . 8 6 0 . 7 4 16 7 8 0 . 2 4 8 1 1 9 1 5 5 9 De s i g n S t o r m F r e q u e n c y 1 0 y e a r ( T a b l e I - 3 ) 40 0 . 8 3 0 . 7 1 17 0 9 0 . 2 4 8 1 4 9 1 5 6 0 * * * 42 0 . 8 1 0 . 6 9 17 3 8 0 . 2 4 8 1 7 9 1 5 5 9 In t e n s i t y a t T c 2 . 0 5 i n / h r 1 0 - y r ( F i g u r e I - 3 ) 44 0 . 7 8 0 . 6 7 17 6 7 0 . 2 4 8 2 0 9 1 5 5 8 3. 3 5 i n / h r 1 0 0 - y r ( F i g u r e I - 3 ) 46 0 . 7 6 0 . 6 5 17 9 4 0 . 2 4 8 2 3 8 1 5 5 6 48 0 . 7 4 0 . 6 3 18 2 1 0 . 2 4 8 2 6 8 1 5 5 3 Pe a k R u n o f f R a t e 1 . 7 5 c f s 1 0 - y r 50 0 . 7 2 0 . 6 2 18 4 7 0 . 2 4 8 2 9 8 1 5 4 9 2. 8 7 c f s 1 0 0 - y r 52 0 . 7 0 0 . 6 0 18 7 3 0 . 2 4 8 3 2 8 1 5 4 5 54 0 . 6 9 0 . 5 9 18 9 8 0 . 2 4 8 3 5 8 1 5 4 0 Pe r c e n t I n p e r v i o u s 82 % 56 0 . 6 7 0 . 5 7 19 2 2 0 . 2 4 8 3 8 7 1 5 3 5 58 0 . 6 5 0 . 5 6 19 4 6 0 . 2 4 8 4 1 7 1 5 2 9 Ru n o f f T r e a t m e n t V o l u m e 15 8 8 c f 60 0 . 6 4 0 . 5 5 19 6 9 0 . 2 4 8 4 4 7 1 5 2 2 (R T V ) 62 0 . 6 3 0 . 5 4 19 9 2 0 . 2 4 8 4 7 7 1 5 1 5 64 0 . 6 1 0 . 5 2 20 1 4 0 . 2 4 8 5 0 7 1 5 0 8 Or i f i c e F l o w r a t e 0 . 0 0 9 c f s 66 0 . 6 0 0 . 5 1 20 3 6 0 . 2 4 8 5 3 6 1 5 0 0 Or i f i c e S i z e 0. 5 i n c h e s 68 0 . 5 9 0 . 5 0 20 5 7 0 . 2 4 8 5 6 6 1 4 9 1 70 0 . 5 8 0 . 4 9 20 7 8 0 . 2 4 8 5 9 6 1 4 8 2 We i r F l o w r a t e 0. 2 4 8 c f s 72 0 . 5 7 0 . 4 9 20 9 9 0 . 2 4 8 6 2 6 1 4 7 3 We i r W i d t h 1 2 . 0 i n c h e s 74 0 . 5 6 0 . 4 8 21 1 9 0 . 2 4 8 6 5 6 1 4 6 4 ** * 1 0 - y r D e t e n t i o n V o l u m e R e q u i r e d = 15 5 9 . 6 9 BO Z E M A N S U B A R U DE T E N T I O N R E L E A S E R A T E Po n d A L:\ 1 9 3 2 9 0 \ C o m p u t a t i o n s \ S t o r m w a t e r \ S T O R M W A T E R C A L C U L A T I O N S Ex i s t i n g S i t u a t i o n Mi n i m u m V o l u m e La n d U s e O p e n L a n d Ar e a 1 . 1 8 A c r e s St o r m Du r a t i o n In t e n s i t y F u t u r e R u n o f f Ra t e Ru n o f f Vo l u m e Release RateRelease VolumeRequired Storage Sl o p e 1 . 0 % (M i n u t e s ) ( i n / h r ) Q = C i A ( c f s ) ( c f ) ( c f s ) ( c f ) ( c f ) C= 0 . 2 0 12 1 . 8 2 1 . 6 6 11 9 2 0 . 0 1 0 7 1 1 8 5 Ov e r l a n d F l o w D i s t a n c e 2 4 3 f t 14 1 . 6 5 1 . 5 0 12 5 8 0 . 0 1 0 8 1 2 4 9 Tim e o f C o n c e n t r a t i o n 26 min 16 1 . 5 1 1 . 3 7 13 1 8 0 . 0 1 0 1 0 1 3 0 8 De s i g n S t o r m F r e q u e n c y 1 0 y e a r ( T a b l e I - 3 ) 18 1 . 4 0 1 . 2 7 13 7 4 0 . 0 1 0 1 1 1 3 6 3 In t e n s i t y a t T c 1 . 1 0 i n / h r ( F i g u r e I - 3 ) 20 1 . 3 1 1 . 1 9 14 2 5 0 . 0 1 0 1 2 1 4 1 3 Pe a k R u n o f f R a t e 0 . 2 5 9 c f s 22 1 . 2 3 1 . 1 2 14 7 4 0 . 0 1 0 1 3 1 4 6 0 24 1 . 1 6 1 . 0 5 15 1 9 0 . 0 1 0 1 5 1 5 0 5 Pr o p o s e d S i t u a t i o n 26 1 . 1 0 1 . 0 0 15 6 2 0 . 0 1 0 1 6 1 5 4 6 La n d U s e C o m m e r c i a l 28 1 . 0 5 0 . 9 5 16 0 3 0 . 0 1 0 1 7 1 5 8 6 Ar e a 1 . 1 8 A c r e s 30 1 . 0 0 0 . 9 1 16 4 2 0 . 0 1 0 1 8 1 6 2 4 Sl o p e 1 . 5 % 32 0 . 9 6 0 . 8 7 16 8 0 0 . 2 5 9 1 9 1 6 6 1 C= 0 . 7 7 34 0 . 9 3 0 . 8 4 17 1 6 0 . 2 5 9 3 1 1 6 8 5 Ov e r l a n d F l o w D i s t a n c e 3 1 6 f t 36 0 . 8 9 0 . 8 1 17 5 1 0 . 2 5 9 6 2 1 6 8 9 Tim e o f C o n c e n t r a t i o n 10 min 38 0 . 8 6 0 . 7 8 17 8 4 0 . 2 5 9 9 3 1 6 9 1 De s i g n S t o r m F r e q u e n c y 1 0 y e a r ( T a b l e I - 3 ) 40 0 . 8 3 0 . 7 6 18 1 6 0 . 2 5 9 1 2 4 1 6 9 2 42 0 . 8 1 0 . 7 3 18 4 8 0 . 2 5 9 1 5 5 1 6 9 3 * * * In t e n s i t y a t T c 2 . 1 1 i n / h r 1 0 - y r ( F i g u r e I - 3 ) 44 0 . 7 8 0 . 7 1 18 7 8 0 . 2 5 9 1 8 6 1 6 9 2 3. 4 5 i n / h r 1 0 0 - y r ( F i g u r e I - 3 ) 46 0 . 7 6 0 . 6 9 19 0 8 0 . 2 5 9 2 1 7 1 6 9 0 48 0 . 7 4 0 . 6 7 19 3 6 0 . 2 5 9 2 4 8 1 6 8 8 Pe a k R u n o f f R a t e 1 . 9 2 c f s 1 0 - y r 50 0 . 7 2 0 . 6 5 19 6 4 0 . 2 5 9 2 7 9 1 6 8 5 3. 1 4 c f s 1 0 0 - y r 52 0 . 7 0 0 . 6 4 19 9 1 0 . 2 5 9 3 1 0 1 6 8 1 54 0 . 6 9 0 . 6 2 20 1 8 0 . 2 5 9 3 4 1 1 6 7 6 Pe r c e n t I n p e r v i o u s 85 % 56 0 . 6 7 0 . 6 1 20 4 3 0 . 2 5 9 3 7 2 1 6 7 1 58 0 . 6 5 0 . 5 9 20 6 9 0 . 2 5 9 4 0 3 1 6 6 5 Ru n o f f T r e a t m e n t V o l u m e 17 4 5 c f 60 0 . 6 4 0 . 5 8 20 9 3 0 . 2 5 9 4 3 4 1 6 5 9 (R T V ) 62 0 . 6 3 0 . 5 7 21 1 8 0 . 2 5 9 4 6 5 1 6 5 2 64 0 . 6 1 0 . 5 6 21 4 1 0 . 2 5 9 4 9 6 1 6 4 5 Or i f i c e F l o w r a t e 0 . 0 1 0 c f s 66 0 . 6 0 0 . 5 5 21 6 4 0 . 2 5 9 5 2 8 1 6 3 7 Or i f i c e S i z e 0. 5 i n c h e s 68 0 . 5 9 0 . 5 4 21 8 7 0 . 2 5 9 5 5 9 1 6 2 9 70 0 . 5 8 0 . 5 3 22 0 9 0 . 2 5 9 5 9 0 1 6 2 0 We i r F l o w r a t e 0. 2 5 9 c f s 72 0 . 5 7 0 . 5 2 22 3 1 0 . 2 5 9 6 2 1 1 6 1 1 We i r W i d t h 6 . 0 i n c h e s 74 0 . 5 6 0 . 5 1 22 5 3 0 . 2 5 9 6 5 2 1 6 0 1 ** * 1 0 - y r D e t e n t i o n V o l u m e R e q u i r e d = 16 9 2 . 5 8 BO Z E M A N S U B A R U DE T E N T I O N R E L E A S E R A T E Po n d B L:\ 1 9 3 2 9 0 \ C o m p u t a t i o n s \ S t o r m w a t e r \ S T O R M W A T E R C A L C U L A T I O N S Ex i s t i n g S i t u a t i o n Mi n i m u m V o l u m e La n d U s e O p e n L a n d Ar e a 1 . 9 5 A c r e s St o r m Du r a t i o n In t e n s i t y F u t u r e R u n o f f R a t e R u n o f f Vo l u m e Re l e a s e RateRelease VolumeRequired Storage Sl o p e 1 . 0 % (M i n u t e s ) ( i n / h r ) Q = C i A ( c f s ) ( c f ) ( c f s ) ( c f ) ( c f ) C= 0 . 2 0 12 1 . 8 2 2 . 7 4 19 7 0 0 . 0 1 6 1 2 1 9 5 8 Ov e r l a n d F l o w D i s t a n c e 3 7 1 f t 14 1 . 6 5 2 . 4 7 20 7 9 0 . 0 1 6 1 4 2 0 6 5 Tim e o f C o n c e n t r a t i o n 32 min 16 1 . 5 1 2 . 2 7 21 7 8 0 . 0 1 6 1 6 2 1 6 3 De s i g n S t o r m F r e q u e n c y 1 0 y e a r ( T a b l e I - 3 ) 18 1 . 4 0 2 . 1 0 22 7 0 0 . 0 1 6 1 8 2 2 5 2 In t e n s i t y a t T c 0 . 9 5 i n / h r ( F i g u r e I - 3 ) 20 1 . 3 1 1 . 9 6 23 5 5 0 . 0 1 6 2 0 2 3 3 6 Pe a k R u n o f f R a t e 0 . 3 7 2 c f s 22 1 . 2 3 1 . 8 4 24 3 5 0 . 0 1 6 2 2 2 4 1 3 24 1 . 1 6 1 . 7 4 25 1 0 0 . 0 1 6 2 4 2 4 8 7 Pr o p o s e d S i t u a t i o n 26 1 . 1 0 1 . 6 5 25 8 2 0 . 0 1 6 2 5 2 5 5 6 La n d U s e C o m m e r c i a l 28 1 . 0 5 1 . 5 8 26 4 9 0 . 0 1 6 2 7 2 6 2 2 Ar e a 1 . 9 5 A c r e s 30 1 . 0 0 1 . 5 1 27 1 4 0 . 0 1 6 2 9 2 6 8 5 Sl o p e 2 % 32 0 . 9 6 1 . 4 5 27 7 6 0 . 3 7 2 4 5 2 7 3 2 C= 0 . 7 7 34 0 . 9 3 1 . 3 9 28 3 6 0 . 3 7 2 8 9 2 7 4 6 Ov e r l a n d F l o w D i s t a n c e 4 1 1 f t 36 0 . 8 9 1 . 3 4 28 9 3 0 . 3 7 2 1 3 4 2 7 5 9 Tim e o f C o n c e n t r a t i o n 10 min 38 0 . 8 6 1 . 2 9 29 4 8 0 . 3 7 2 1 7 9 2 7 7 0 De s i g n S t o r m F r e q u e n c y 1 0 y e a r ( T a b l e I - 3 ) 40 0 . 8 3 1 . 2 5 30 0 2 0 . 3 7 2 2 2 3 2 7 7 8 42 0 . 8 1 1 . 2 1 30 5 3 0 . 3 7 2 2 6 8 2 7 8 5 In t e n s i t y a t T c 2 . 0 6 i n / h r 1 0 - y r ( F i g u r e I - 3 ) 44 0 . 7 8 1 . 1 8 31 0 4 0 . 3 7 2 3 1 3 2 7 9 1 3. 3 7 i n / h r 1 0 0 - y r ( F i g u r e I - 3 ) 46 0 . 7 6 1 . 1 4 31 5 2 0 . 3 7 2 3 5 8 2 7 9 5 48 0 . 7 4 1 . 1 1 32 0 0 0 . 3 7 2 4 0 2 2 7 9 7 Pe a k R u n o f f R a t e 3 . 0 9 c f s 1 0 - y r 50 0 . 7 2 1 . 0 8 32 4 6 0 . 3 7 2 4 4 7 2 7 9 9 5. 0 6 c f s 1 0 0 - y r 52 0 . 7 0 1 . 0 5 32 9 0 0 . 3 7 2 4 9 2 2 7 9 9 * * * 54 0 . 6 9 1 . 0 3 33 3 4 0 . 3 7 2 5 3 6 2 7 9 8 Pe r c e n t I n p e r v i o u s 83 % 56 0 . 6 7 1 . 0 1 33 7 7 0 . 3 7 2 5 8 1 2 7 9 6 58 0 . 6 5 0 . 9 8 34 1 9 0 . 3 7 2 6 2 6 2 7 9 3 Ru n o f f T r e a t m e n t V o l u m e 28 2 1 c f 60 0 . 6 4 0 . 9 6 34 5 9 0 . 3 7 2 6 7 0 2 7 8 9 (R T V ) 62 0 . 6 3 0 . 9 4 34 9 9 0 . 3 7 2 7 1 5 2 7 8 4 64 0 . 6 1 0 . 9 2 35 3 8 0 . 3 7 2 7 6 0 2 7 7 9 Or i f i c e F l o w r a t e 0 . 0 1 6 c f s 66 0 . 6 0 0 . 9 0 35 7 7 0 . 3 7 2 8 0 4 2 7 7 2 Or i f i c e S i z e 0. 7 5 i n c h e s 68 0 . 5 9 0 . 8 9 36 1 4 0 . 3 7 2 8 4 9 2 7 6 5 70 0 . 5 8 0 . 8 7 36 5 1 0 . 3 7 2 8 9 4 2 7 5 7 We i r F l o w r a t e 0. 3 7 2 c f s 72 0 . 5 7 0 . 8 5 36 8 7 0 . 3 7 2 9 3 9 2 7 4 9 We i r W i d t h 12 . 0 in c h e s 74 0 . 5 6 0 . 8 4 37 2 3 0 . 3 7 2 9 8 3 2 7 4 0 ** * 1 0 - y r D e t e n t i o n V o l u m e R e q u i r e d = 27 9 8 . 8 5 BO Z E M A N S U B A R U DE T E N T I O N R E L E A S E R A T E Po n d C L:\ 1 9 3 2 9 0 \ C o m p u t a t i o n s \ S t o r m w a t e r \ S T O R M W A T E R C A L C U L A T I O N S