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Home My WebLink AboutDrainage Reports - 02/11/2025JANUARY 9, 2025 City of Fort Collins Approved Plans Approved by: Date: 1/9/2025 North East College Corridor Outfall (NECCO) Design Report North East College Corridor Outfall (NECCO) Design Report North East College Corridor Outfall (NECCO) Design Report North East College Corridor Outfall (NECCO) Design Report Urban Storm Drainage Criteria Manual Detained and Undetained Areas Project Site Area (acres) 11.08 Area of Undetained Area (acres) 1.71 Area of Detained Runoff (acres) 9.36 Max. Release Rate (cfs) 1.87 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 8 Table 3.4-1. IDF Table for Rational Method Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) 5 2.85 4.87 9.95 39 1.09 1.86 3.8 6 2.67 4.56 9.31 40 1.07 1.83 3.74 7 2.52 4.31 8.80 41 1.05 1.80 3.68 8 2.40 4.10 8.38 42 1.04 1.77 3.62 9 2.30 3.93 8.03 43 1.02 1.74 3.56 10 2.21 3.78 7.72 44 1.01 1.72 3.51 11 2.13 3.63 7.42 45 0.99 1.69 3.46 12 2.05 3.50 7.16 46 0.98 1.67 3.41 13 1.98 3.39 6.92 47 0.96 1.64 3.36 14 1.92 3.29 6.71 48 0.95 1.62 3.31 15 1.87 3.19 6.52 49 0.94 1.6 3.27 16 1.81 3.08 6.30 50 0.92 1.58 3.23 17 1.75 2.99 6.10 51 0.91 1.56 3.18 18 1.70 2.90 5.92 52 0.9 1.54 3.14 19 1.65 2.82 5.75 53 0.89 1.52 3.10 20 1.61 2.74 5.60 54 0.88 1.50 3.07 21 1.56 2.67 5.46 55 0.87 1.48 3.03 22 1.53 2.61 5.32 56 0.86 1.47 2.99 23 1.49 2.55 5.20 57 0.85 1.45 2.96 24 1.46 2.49 5.09 58 0.84 1.43 2.92 25 1.43 2.44 4.98 59 0.83 1.42 2.89 26 1.4 2.39 4.87 60 0.82 1.4 2.86 27 1.37 2.34 4.78 65 0.78 1.32 2.71 28 1.34 2.29 4.69 70 0.73 1.25 2.59 29 1.32 2.25 4.60 75 0.70 1.19 2.48 30 1.30 2.21 4.52 80 0.66 1.14 2.38 31 1.27 2.16 4.42 85 0.64 1.09 2.29 32 1.24 2.12 4.33 90 0.61 1.05 2.21 33 1.22 2.08 4.24 95 0.58 1.01 2.13 34 1.19 2.04 4.16 100 0.56 0.97 2.06 35 1.17 2.00 4.08 105 0.54 0.94 2.00 36 1.15 1.96 4.01 110 0.52 0.91 1.94 37 1.16 1.93 3.93 115 0.51 0.88 1.88 38 1.11 1.89 3.87 120 0.49 0.86 1.84 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 9 Figure 3.4-1. Rainfall IDF Curve – Fort Collins 0.00 5.00 10.00 15.00 20.00 25.00 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice 0.00 5.00 10.00 15.00 20.00 25.00 30.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice 0.00 10.00 20.00 30.00 40.00 50.00 60.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 5.00 10.00 15.00 20.00 25.00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice Project: Inlet ID: Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =2.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.020 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.020 Height of Curb at Gutter Flow Line HCURB =6.00 inches Distance from Curb Face to Street Crown TCROWN =14.0 ft Gutter Width W =2.00 ft Street Transverse Slope SX =0.060 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.000 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =14.0 14.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 6.0 inches Check boxes are not applicable in SUMP conditions MINOR STORM Allowable Capacity is not applicable to Sump Condition Minor Storm Major Storm MAJOR STORM Allowable Capacity is not applicable to Sump Condition Qallow =SUMP SUMP cfs ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Crowne at Suniga Inlet H6 1 Design Information (Input)MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a' from above)alocal =3.00 3.00 inches Number of Unit Inlets (Grate or Curb Opening)No =1 1 Water Depth at Flowline (outside of local depression)Ponding Depth =6.0 6.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) =N/A N/A feet Width of a Unit Grate Wo =N/A N/A feet Open Area Ratio for a Grate (typical values 0.15-0.90)Aratio =N/A N/A Clogging Factor for a Single Grate (typical value 0.50 - 0.70)Cf (G) =N/A N/A Grate Weir Coefficient (typical value 2.15 - 3.60)Cw (G) =N/A N/A Grate Orifice Coefficient (typical value 0.60 - 0.80)Co (G) =N/A N/A Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) =5.00 5.00 feet Height of Vertical Curb Opening in Inches Hvert =6.00 6.00 inches Height of Curb Orifice Throat in Inches Hthroat =6.00 6.00 inches Angle of Throat Theta =63.40 63.40 degrees Side Width for Depression Pan (typically the gutter width of 2 feet)Wp =2.00 2.00 feet Clogging Factor for a Single Curb Opening (typical value 0.10)Cf (C) =0.10 0.10 Curb Opening Weir Coefficient (typical value 2.3-3.7)Cw (C) =3.60 3.60 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70)Co (C) =0.67 0.67 Low Head Performance Reduction (Calculated)MINOR MAJOR Depth for Grate Midwidth dGrate =N/A N/A ft Depth for Curb Opening Weir Equation dCurb =0.33 0.33 ft Grated Inlet Performance Reduction Factor for Long Inlets RFGrate =N/A N/A Curb Opening Performance Reduction Factor for Long Inlets RFCurb =1.00 1.00 Combination Inlet Performance Reduction Factor for Long Inlets RFCombination =N/A N/A MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition)Qa =5.4 5.4 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q Peak)Q PEAK REQUIRED =0.9 3.4 cfs CDOT Type R Curb Opening INLET IN A SUMP OR SAG LOCATION 1 0.00 5.00 10.00 15.00 20.00 25.00 30.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice 0.00 0.50 1.00 1.50 2.00 2.50 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice 0.00 10.00 20.00 30.00 40.00 50.00 60.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 0.50 1.00 1.50 2.00 2.50 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice 0.00 5.00 10.00 15.00 20.00 25.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 Stage (ft) Stage - Discharge Curves Series1 Series2 0.00 0.50 1.00 1.50 2.00 2.50 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Stage (ft) Stage - Discharge Curves Shallow Weir Orifice Project Title Date: Project Number Calcs By: City Basins 0.8 WQCV = Watershed inches of Runoff (inches)79% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = Iwq/100)0.258 in A =9.36 ac V = 0.2413 ac-ft V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) 10509 cu. ft. Drain Time a = i = WQCV = Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event The Crowne at Suniga March 25, 2024 1893-001 F. Wegert Fort Collins Stormtech LID Pond 0.278 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Total Imperviousness Ratio (i = Iwq/100) Water Quality Capture Volume 6 hr 12 hr 24 hr 40 hr Pond No : Stormtech Pond WQ 0.81 5.00 min 7668 ft3 9.36 acres 0.18 ac-ft Max Release Rate =1.81 cfs Time (min) Ft Collins WQ Intensity (in/hr) Inflow Volume (ft3) Outflow Adjustmen t Factor Qav (cfs) Outflow Volume (ft3) Storage Volume (ft3) 5 1.425 3241 1.00 1.81 542 2699 10 1.105 5027 1.00 1.81 1084 3943 15 0.935 6380 0.67 1.20 1084 5296 20 0.805 7324 0.63 1.13 1355 5969 25 0.715 8131 0.60 1.08 1626 6505 30 0.650 8870 0.58 1.05 1897 6974 35 0.585 9314 0.57 1.03 2168 7146 40 0.535 9735 0.56 1.02 2439 7296 45 0.495 10133 0.56 1.00 2710 7423 50 0.460 10463 0.55 0.99 2981 7482 55 0.435 10883 0.55 0.99 3252 7632 60 0.410 11190 0.54 0.98 3523 7668 65 0.385 11384 0.54 0.97 3794 7590 70 0.365 11623 0.54 0.97 4065 7558 75 0.345 11770 0.53 0.96 4336 7435 80 0.330 12009 0.53 0.96 4607 7403 85 0.315 12180 0.53 0.96 4878 7302 90 0.305 12487 0.53 0.95 5149 7338 95 0.290 12532 0.53 0.95 5420 7113 100 0.280 12737 0.53 0.95 5691 7046 105 0.270 12896 0.52 0.95 5962 6935 110 0.260 13010 0.52 0.94 6233 6777 115 0.255 13340 0.52 0.94 6504 6836 120 0.245 13374 0.52 0.94 6775 6599 *Note: Using the method described in FCSCM Chapter 6 Section 2.3 A = Tc = Project Location : Design Point C = Design Storm WATER QUALITY CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Input Variables Results Required Detention Volume Fort Collins, Colorado 1893-001 The Crowne at Suniga Project Number : Project Name : Stormtech LID Pond Page 2 of 4 1893-001 LID Chamber Sizing FSW.xlsx Va u l t I D To t a l Re q u i r e d WQ V o l u m e (c f ) Fl o w , WQ (c f s ) Ch a m b e r Ty p e Ch a m b e r R e l e a s e Ra t e a (c f s ) Ch a m b e r Vo l u m e b (c f ) In s t a l l e d C a m b e r w/ A g g r e g a t e c (c f ) Mi m i m u m N o . of C h a m b e r s d To t a l R e l e a s e Ra t e e (c f s ) Re q u i r e d St o r a g e Vo l u m e b y FA A M e t h o d (c f ) Mi m i m u m No . o f Ch a m b e r s f St o r a g e Pr o v i d e d wi t h i n t h e Ch a m b e r s g (c f ) Mi n i m u m To t a l In s t a l l e d Sy s t e m Vo l u m e h (c f ) St o r m t e c h L I D P o n d 1 0 5 0 9 1 1 . 4 3 M C - 7 2 0 0 0 . 0 4 5 1 7 5 . 9 0 2 6 7 . 3 0 4 0 1 . 8 1 7 6 6 8 44 77 4 0 1 1 7 6 1 a. R e l e a s e r a t e p e r c h a m b e r , l i m i t e d b y f l o w t h r o u g h g e o t e x t i l e w i t h a c c u m u l a t e d s e d i m e n t . b. V o l u m e w i t h i n c h a m b e r o n l y , n o t a c c o u n t i n g f o r v o i d s p a c e s i n s u r r o u n d i n g a g g r e g a t e . c. V o l u m e i n c l u d e s c h a m b e r a n d v o i d s p a c e s ( 4 0 % ) i n s u r r o u n d i n g a g g r e g a t e , p e r c h a m b e r u n i t . d. N u m b e r o f c h a m b e r s r e q u i r e d t o p r o v i d e f u l l W Q C V w i t h i n t o t a l i n s t a l l e d s y s t e m , i n c l u d i n g a g g r e g a t e . e. R e l e a s e r a t e p e r c h a m b e r t i m e s n u m b e r o f c h a m b e r s . f. N u m b e r o f c h a m b e r s r e q u i r e d t o p r o v i d e r e q u i r e d F A A s t o r a g e v o l u m e s t o r e d w i t h i n t h e c h a m b e r o n l y ( n o a g g r e g a t e s t o r a g e ) . g. V o l u m e p r o v i d e d i n c h a m b e r s o n l y ( n o a g g r e g a t e s t o r a g e ) . T h i s n u m b e r m u s t m e e t o r e x c e e d t h e r e q u i r e d F A A s t o r a g e v o l u m e . h. S y s t e m v o l u m e i n c l u d e s t o t a l n u m b e r o f c h a m b e r s , p l u s s u r r o u n d i n g a g g r e g a t e . T h i s n u m b e r m u s t m e e t o r e x c e e d t h e r e q u i r e d W Q C V . Ch a m b e r C o n f i g u r a t i o n S u m m a r y P: \ 1 8 9 3 - 0 0 1 \ D r a i n a g e \ L I D \ 1 8 9 3 - 0 0 1 L I D C h a m b e r S i z i n g F S W . x l s x Chamber Dimensions SC-160 SC-310 SC-740 MC-3500 MC-7200 Width (in)34.0 34.0 51.0 77.0 100.0 Length (in) 85.4 85.4 85.4 90.0 83.4 Height (in) 16.0 16.0 30.0 45.0 60.0 Floor Area (sf) 20.2 20.2 30.2 48.1 57.9 Chamber Volume (cf) 6.9 14.7 45.9 109.9 175.9 Chamber/Aggregate Volume (cf) 29.3 29.3 74.9 175.0 267.3 Flow Rate* 0.35 gpm/sf 1 cf =7.48052 gal 1 gallon =0.133681 cf 1 GPM = 0.002228 cfs *Flow rate based on 1/2 of Nov 07 QMAX in Figure 17 of UNH Testing Report SC-160 SC-310 SC-740 MC-3500 MC-7200 Flow Rate/chamber (cfs) 0.015724 0.015724 0.023586 0.037528 0.045164 end caps have a volume of 115.3 cu. ft. StormTech Chamber Data Chamber Flow Rate Chamber Flow Rate Conversion (gpm/sf to cfs) end caps have a volume of 45.1 cu. ft. P:\1893-001\Drainage\LID\1893-001 LID Chamber Sizing FSW.xlsx De s i g n P o i n t ( B a s i n I D ) 1 To t a l A r e a (a c ) T r e a t m e n t M e t h o d A r e a T r e a t e d ( a c ) Pe r c e n t Im p e r v i o u s (% ) Ar e a o f Im p e r v i o u s (a c ) 2 Re q u i r e d L I D (c u . f t . ) Pe r c e n t o f Im p e r v i o u s Ar e a Pr o v i d e d L I D (c u . f t . ) Ma j o r B a s i n S C 9. 3 6 St o r m t e c h C h a m b e r s 9. 3 6 79 % 7. 3 9 13 , 4 3 4 98 % 11 , 7 6 1 Ma j o r B a s i n O S C 1. 7 1 N/ A N/ A 10 % 0. 1 7 N/ A 2% 0 1. R e f e r t o R a t i o n a l C a l c u l a t i o n s f o r a d d i t i o n a l c l a r i f i c a t i o n . 2. C a l c u l a t e d b y m u l t i p l y i n g t h e p e r c e n t i m p e r v i o u s b y a r e a t r e a t e d LI D S u m m a r y T a b l e B2 100-yr 1.00 5.00 min Storage 133324 ft3 11.08 acres Max Release Rate =1.87 cfs 3.06 ac-ft Time (min) Ft Collins 100-yr Intensity (in/hr) Inflow Volume (ft3) Outflow Adjustment Factor Qav (cfs) Outflow Volume (ft3) Storage Volume (ft3) 5 9.950 33074 1.00 1.87 561 32513 10 7.720 51323 1.00 1.87 1122 50201 15 6.520 65017 1.00 1.87 1683 63334 20 5.600 74458 1.00 1.87 2244 72214 25 4.980 82768 1.00 1.87 2805 79963 30 4.520 90147 1.00 1.87 3366 86781 35 4.080 94933 1.00 1.87 3927 91006 40 3.740 99454 1.00 1.87 4488 94966 45 3.460 103509 1.00 1.87 5049 98460 50 3.230 107365 1.00 1.87 5610 101755 55 3.030 110789 1.00 1.87 6171 104618 60 2.860 114080 1.00 1.87 6732 107348 65 2.720 117537 1.00 1.87 7293 110244 70 2.590 120528 1.00 1.87 7854 112674 75 2.480 123653 1.00 1.87 8415 115238 80 2.380 126578 1.00 1.87 8976 117602 85 2.290 129403 1.00 1.87 9537 119866 90 2.210 132229 1.00 1.87 10098 122131 95 2.130 134522 1.00 1.87 10659 123863 100 2.060 136949 1.00 1.87 11220 125729 105 2.000 139608 1.00 1.87 11781 127827 110 1.940 141868 1.00 1.87 12342 129526 115 1.890 144494 1.00 1.87 12903 131591 120 1.840 146788 1.00 1.87 13464 133324 *Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. DETENTION VOLUME CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Input Variables Results Required Detention Volume Fort Collins, Colorado 1893-001 The Crowne at Suniga Project Number : Project Name : Stormtech System - Detention A = Tc = Project Location : Design Point C = Design Storm Storage System : Page 1 of 1 1893-001_Pond_FAA_Fort Collins_Detention Volume.xls Project:Crowne at Suniga Project Number:1893-001 Date:3/25/2024 By:B. Mathisen MC-7200 StormTech Cambers & End Caps volume/part (CF)Quantity Total (CF) Required/Provided LID 1 267.3 44 11,761.20 Installed LID (Including Endcaps) See Table Below 86 Chambers 4 End Caps 2 22,914.40 Required Detention N/A N/A 133,324 Installed Detention Chamber Storage Not In Isolator Row 267.3 444 118,681.20 Installed Detention Chamber Storage In Isolator Row 267.3 42 11,226.60 Installed Detention Endcap Storage 115.3 60 6,918.00 Total Installed Detention Storage See Below 136,825.80 145,085.20 148,513.60 Notes: 1. Refer to the "Stormtech LID Pond" Calculations 4. The red numbers indicates what was summed to calculate the Required combined LID and Detention volumes. 5. The blue numbers indicate what was summed to calculate the installed combined LID and Detention volumes. 3. Total Installed Detention Storage is a sum of 444 non isolator row chambers plus 32 isolator chambers plus 64 end caps. (118,681.20 + 8,553.60 + 6,918.00 = 134,152.80 cf) Required combined LID and Detention Volumes Summary MC-7200 Stormtech Volume Specifications LID Detention 2. The two isolator rows are comprised of 84 chambers and 4 end caps. Only 54 chambers and 0 endcaps are required to provide the the required LID volume. Therefore, a portion of the isolator rows (32 chambers [86-54 = 32]) will be utilized for detention. Additionally, the end caps associated with the isolator rows (4) will be utilized for detention. Installed combined LID and Detention Volumes Pr o j e c t : Cr o w n e a t S u n i g a Pr o j e c t N u m b e r : 18 9 3 - 0 0 1 Da t e : 3/ 2 5 / 2 0 2 4 By : B. M a t h i s e n Bo r i n g # Ex i s t i n g Su r f a c e E l e v . (F T ) Pr o p o s e d Su r f a c e E l e v . (F T ) GW S E L ( F T ) Su b g r a d e El e v a t i o n (F T ) Se p e r a t i o n b e t w e e n P r o p o s e d an d G W ( F T ) Se p e r a t i o n b e t w e e n Su b g r a d e a n d G W ( F T ) SB - 5 51 . 0 3 54 . 9 3 43 . 1 0 45 . 1 11 . 8 3 2 SB - 6 5 0 . 1 3 5 8 . 0 5 4 1 . 8 8 4 4 . 2 4 1 6 . 1 7 2 . 3 6 No t e s : 1. 8 " p a v e m e n t d e p t h a s s u m e d . 2. R e f e r t o S u b g r a d e P l a n i n U t i l i t y P l a n s f o r a d d i t i o n a l i n f o r m a t i o n 3. R e f e r t o B o r i n g E x h i b i t i n U t i l i t y P l a n s f o r a d d i t i o n a l i n f o r m a t i o n 4. R e f e r t o S t o r m t e c h D e t a i l s i n U t i l i t y P l a n s f o r a d d i t i o n a l i n f o r m a t i o n 5. G W S E L = G r o u n d w a t e r S u r f a c e E l e v a t i o n 7. S u b g r a d e e l e v a t i o n s b a s e d o n s e p e r a t i o n f r o m g r o u n d w a t e r . A d d i t i o n a l r o c k b e l o w s u b g r a d e e l e v a t i o n i s re q u i r e d t o m a i n t a i n s t r u c t u r a l s t a b i l i t y w i t h i n t h e n a t i v e s o i l s . Pr o p o s e d S u r f a c e E l e v a t i o n , S t o r m t e c h S u b g r a d e E l e v a t i o n , a n d G r o u n d w a t e r E l e v a t i o n S u m m a r y 6. G r o u n d w a t e r e l e v a t i o n s c o m e f r o m " S u p p l e m e n t a l G e o t e c h n i c a l S u b s u r f a c e E x p l o r a t i o n Re p o r t " b y E a r t h E n g i n e e r i n g C o u n s u l t a n t s , L L C D a t e d J u n e 7 , 2 0 2 3 Stormwater Facility Name: Facility Location & Jurisdiction: User Input: Watershed Characteristics User Defined User Defined User Defined User Defined Selected BMP Type = EDB Stage [ft] Area [ft^2] Stage [ft]Discharge [cfs] Watershed Area = 11.08 acres 0.00 17,538 0.00 0.00 Watershed Length =1,000 ft 1.00 17,538 1.00 0.68 Watershed Length to Centroid = 300 ft 2.00 17,538 2.00 0.97 Watershed Slope =0.020 ft/ft 3.00 17,538 3.00 1.18 Watershed Imperviousness = 71.0%percent 4.00 17,538 4.00 1.37 Percentage Hydrologic Soil Group A = 0.0%percent 5.00 17,538 5.00 1.53 Percentage Hydrologic Soil Group B = 0.0%percent 6.00 17,538 6.00 1.67 Percentage Hydrologic Soil Groups C/D = 100.0%percent 7.00 17,538 7.00 1.81 Target WQCV Drain Time = 40.0 hours 7.60 17,538 7.60 1.88 User Input After completing and printing this worksheet to a pdf, go to: https://maperture.digitaldataservices.com/gvh/?viewer=cswdif Create a new stormwater facility, and attach the PDF of this worksheet to that record. Routed Hydrograph Results Design Storm Return Period =WQCV 2 Year 5 Year 10 Year 50 Year 100 Year One-Hour Rainfall Depth =N/A 0.98 1.36 1.71 2.31 2.91 in CUHP Runoff Volume =0.258 0.600 0.928 1.247 1.822 2.405 acre-ft Inflow Hydrograph Volume =N/A 0.600 0.928 1.247 1.822 2.405 acre-ft Time to Drain 97% of Inflow Volume =25.3 26.3 27.3 28.7 31.2 33.7 hours Time to Drain 99% of Inflow Volume =33.2 34.2 35.3 36.6 39.1 41.6 hours Maximum Ponding Depth =0.64 1.25 1.98 2.71 4.06 5.44 ft Maximum Ponded Area =0.40 0.40 0.40 0.40 0.40 0.40 acres Maximum Volume Stored =0.258 0.501 0.796 1.091 1.634 2.188 acre-ft Once CUHP has been run and the Stage-Area-Discharge information has been provided, click 'Process Data' to interpolate the Stage-Area-Volume-Discharge data and generate summary results in the table below. Once this is complete, click 'Print to PDF'. Stormwater Detention and Infiltration Design Data Sheet Crowne at Suniga - Stormtech System Detention Fort Collins, CO Location for 1-hr Rainfall Depths (use dropdown): After providing required inputs above including 1-hour rainfall depths, click 'Run CUHP' to generate runoff hydrographs using the embedded Colorado Urban Hydrograph Procedure. Stormtech Detention_SDI_Design_Data_v2.00 (State Compliance Time).xlsm, Design Data 3/25/2024, 12:09 PM Booleans for Message Booleans for CUHP Watershed L:W 1 CUHP Inputs Complete Watershed Lc:L 1 CUHP Results Calculated Watershed Slope FALSE Time Interval RunOnce 1 CountA 1 Draintime Coeff 1.0 User Precip 1 Equal SA Inputs 1 Equal SD Inputs 1 Stormwater Detention and Infiltration Design Data Sheet 0 10 20 30 40 50 60 0.1 1 10TIME [hr] 100YR IN 100YR OUT 50YR IN 50YR OUT 10YR IN 10YR OUT 5YR IN 5YR OUT 2YR IN 2YR OUT WQCV IN WQCV OUT 0 1 2 3 4 5 6 0.1 1 10 100 DRAIN TIME [hr] 100YR 50YR 10YR 5YR 2YR WQCV Stormtech Detention_SDI_Design_Data_v2.00 (State Compliance Time).xlsm, Design Data 3/25/2024, 12:09 PM 4396 G REENFIELD D RIVE W INDSOR , C OLORADO 80550 (970) 545-3908 FAX (970) 663-0282 www.earth-engineering.com June 7, 2023 Crowne Partners, Inc. 505 North 20th Street – Suite 1150 Birmingham, AL 35203 Attn: Mr. Oaky Dover (odover@crownepartners.com) Re: Supplemental Geotechnical Subsurface Exploration Report Proposed Apartment Complex Development – Crowne at Suniga Approximate 11-Acre Parcel – Northeast Corner of 9th Street and Suniga Road Fort Collins, Colorado EEC Project No. 1222009 Mr. Dover: Earth Engineering Consultants, LLC (EEC) personnel have completed the supplemental geotechnical subsurface exploration as requested for the approximate 11-acre parcel – proposed Crowne at Suniga apartment complex development located at the northeast corner of 9th Street and Suniga Road in Fort Collins, Colorado. In the summer of 2022, Earth Engineering Consultants, LLC (EEC) conducted a subsurface exploration for the referenced project by drilling a total of twenty-one (21) test borings throughout the property using a Geo- Probe drill rig in lieu of a more conventional CME – 75 rig due to the previous property owner’s concerns of potential “crop/terrain” damage. Unfortunately, the Geo-Probe utilized did not have the torque capacity to turn the hollow stem augers through the very dense cobble zones encountered across the site and the borings terminated at approximate depths of 5 to 10 feet below existing site grades. EEC prepared an appropriate project-specific Geo-Report for foundation, slab, and pavement support; however, the civil design team required greater depths of borings to assist in their utility design approach for the project. EEC hereby confirms that all of the recommendations provided in the preceding subsurface exploration/report are valid and those results were confirmed by the findings of this supplemental exploration/report. For further information and recommendations based on the 21 shallow borings, please refer to our “Subsurface exploration Report”dated June 9, 2022, EEC Project No. 1222009. For this supplemental subsurface exploration, EEC completed eight (8) additional test borings across the site at pre-selected locations determined by the design team, using a conventional CME-75 drill rig to approximate depths of 20 to 25 feet below the existing site grades at DATE: RIG TYPE: CME-75 FOREMAN: DG AUGER TYPE: 4" HAS SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET)(BLOWS/FT)(PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF VEGETATION AND TOPSOIL _ _ 1 SILTY/CLAYEY SAND (SM-SC) _ _ brown, dry, medium dense 2 _ _ WELL GRADED SAND WITH SILT AND GRAVEL (SW-SM)3 white/brown/rust/black, dry to moist to wet _ _ very dense 4 _ _ SS 5 50/11" 1.9 8.7 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SS 10 50/9" 9.5 _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ 15 _ _ 16 _ _ 17 _ _ 18 _ _ CLAYSTONE 19 gray _ _ hard CS 20 50/7" 9000+ 15.2 117.1 BOTTOM OF BORING DEPTH 20' _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC GRAHAM PROPERTY APARTMENT COMPLEX PROJECT NO: 1222009 LOG OF BORING SB-5 JUNE 2023 FORT COLLINS, COLORADO SHEET 1 OF 1 WATER DEPTH START DATE 5/3/2023 WHILE DRILLING 8.5' SURFACE ELEV N/A CHECKED 5/24/23 8' FINISH DATE 5/3/2023 CHECKED 5/18/23 8' A-LIMITS SWELL DATE: RIG TYPE: CME-75 FOREMAN: DG AUGER TYPE: 4" HAS SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET)(BLOWS/FT)(PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF VEGETATION AND TOPSOIL _ _ 1 SANDY LEAN CLAY / CLAYEY SAND (CL / SC) _ _ brown, dry, medium stiff/medium dense 2 _ _ SAND WITH SILT AND GRAVEL (SP-SM) 3 white/brown/rust/black, dry to moist to wet _ _ dense 4 _ _ SS 5 50 1.0 8.7 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SS 10 50 11.8 _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ 15 _ _ 16 _ _ 17 _ _ CLAYSTONE 18 gray _ _ hard 19 _ _ SS 20 50/8" 6000 16.9 _ _ BOTTOM OF BORING DEPTH 20.5' 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC GRAHAM PROPERTY APARTMENT COMPLEX PROJECT NO: 1222009 LOG OF BORING SB-6 JUNE 2023 FORT COLLINS, COLORADO SHEET 1 OF 1 WATER DEPTH START DATE 5/3/2023 WHILE DRILLING 9' SURFACE ELEV N/A CHECKED 5/24/23 8' 3" FINISH DATE 5/3/2023 CHECKED 5/18/23 8' 3" A-LIMITS SWELL GEOTECHNICAL SUBSURFACE EXPLORATION REPORT PROPOSED APARTMENT COMPLEX DEVELOPMENT - GRAHAM PROPERTY NORTHEAST CORNER OF 9TH STREET AND SUNIGA ROAD FORT COLLINS, COLORADO EEC PROJECT NO. 1222009 Prepared for: Crowne Partners, Inc. 505 North 20th Street - Suite 1150 Birmingham, AL 35203 Attn: Mr. Cary Levow (clevow@crownepartners.com) Prepared by: Earth Engineering Consultants, LLC 4396 Greenfield Drive Windsor, Colorado 80550 4396 G REENFIELD D RIVE W INDSOR , C OLORADO 80550 (970) 545-3908 FAX (970) 663-0282 June 1, 2022 Crowne Partners, Inc. 505 North 20th Street - Suite 1150 Birmingham, AL 35203 Attn: Mr. Cary Levow (clevow@crownepartners.com) Re: Geotechnical Subsurface Exploration Report Proposed Apartment Complex Development Graham Property Approximate 11-Acres Parcel Northeast Corner of 9th Street and Suniga Road Fort Collins, Colorado EEC Project No. 1222009 Mr. Levow: Enclosed, herewith, are the results of the geotechnical subsurface exploration completed by Earth Engineering Consultants, LLC (EEC) for the proposed multi-family apartment complex planned for construction in Fort Collins, Colorado. For this exploration, EEC personnel advanced twenty- one (21) soil borings to depths of approximately 4 to 13 feet below present site grades at pre- selected locations within the various proposed building footprints and associated on-site pavement improvements. This exploration was completed in general accordance with our proposal dated January 17, 2022. In summary, the subsurface conditions encountered beneath the surficial vegetation/fescue grass generally consisted of cohesive to slightly cohesive lean clay with sand to silty/clayey sand soils extending to granular gravel/sand with silt/clay soils at depths of approximately ½ to 8 feet. The cohesive soils were generally dry to moist and soft/very loose to stiff/dense and exhibited nil to low with an occasional high swell potential (at boring B-15) and slight tendency to hydro- compact at current moisture and density conditions. Gravel/sand with silt/clay soils were encountered below the cohesive to slightly cohesive soils and extended to the depths explored at approximately 4 to 13 feet below the site grades. Zones of larger cobbles were also encountered in the gravel/sand soils. The gravel/sand soils were generally dry to moist and medium dense to very dense. Groundwater was observed in the two deepest borings; B-14 and B-20 which advanced to depths of approximately 13 and 10 feet below the site grades at depths of approximately 7 to 9 feet, respectively. Groundwater was not observed in the rest of the borings advanced to maximum depths of approximately 7 feet below the ground surface at the time of drilling. very dense. Groundwater was observed in the two deepest borings; B-14 and B-20 which advanced to depths of approximately 13 and 10 feet below the site grades at depths of approximately 7 to 9 feet, respectively. Groundwater was not observe advanced to maximum depths of approximately 7 to 9 feet, respapproximately 7 to 9 feet, resp LE G E N D DR A I N A G E B A S I N BA S I N N U M B E R BA S I N A R E A ( A C R E S ) EX H I B I T 4 . 2 FU T U R E D E T E N T I O N A N D W A T E R Q U A L I T Y R E Q U I R E M E N T S RE S T R I C T A M O U N T O F R U N O F F TO E X I S T I N G C O N D I T I O N S I F RE - D E V E L O P E D . W A T E R Q U A L I T Y PR O V I D E D I N R E D W O O D P O N D RE Q U I R E F U T U R E O N - S I T E DE T E N T I O N & W A T E R QU A L I T Y . R E L E A S E R A T E @ 0 . 2 0 c f s / a c r e RE Q U I R E F U T U R E O N - S I T E DE T E N T I O N . WA T E R Q U A L I T Y P R O V I D E D IN R E G I O N A L P O N D . FU T U R E R E - A L I G N E D V I N E DR I V E . W A T E R Q U A L I T Y PR O V I D E D W I T H S N O U T S . DI S C H A R G E I N T O RE G I O N A L P O N D W I T H O U T FU T U R E D E T E N T I O N O R WA T E R Q U A L I T Y . 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