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Home My WebLink About16 - Design Report - Swissdetail Lot 3, Block 4 Cattail Creek Ph 1 - Stormwater STORMWATER DESIGN REPORT for SWISSDETAIL LOT 3, BLOCK 4, CATTAIL CREEK SUBDIVISION, PHASE 1 BOZEMAN, MONTANA Prepared for: Pam Shontz 7 Sweetgrass Ave. Bozeman, MT 59718 Prepared by: C & H Engineering and Surveying, Inc. 1091 Stoneridge Drive Bozeman, MT 59718 (406) 587-1115 If f �� . Project No.: 16180 APRIL 2016 INTRODUCTION Design Report-Page 2 of 2 Lot 3,Block 4,Cattail Creek Subdivision,Phase 1 is located east of N. 271h Ave. and north of Cattail Street in Bozeman, Montana. The project address is 3230 N. 271h Ave, Bozeman, MT 59718. This project will include the construction of a 7,200 square foot car detailing shop, a parking lot, and associated infrastructure. The west part of the parking lot and sidewalks (Drainage Area#2)will be graded using curb and gutter to direct stormwater runoff to flow off site to N. 27th Ave., at which point it will travel to the regional detention pond for Cattail Creek Subdivision,Phase 1. The portion of the parking lot and paved areas lying south of the building and the south half of the roof drainage (Drainage Area#1) will be retained on site using a retention pond with a capacity of 924 cubic feet, to retain the 10-year, 2-hour storm. CATTAIL CREEK SUBDIVISION, PRASE 1 — STORMWATER BACKGROUND INFORMATION Cattail Creek Subdivision, Phase, 1 included the construction of 3 detention ponds that handle the entire Phase 1 runoff by curb and gutter and underground stormwater infrastructure designed by TD&H Engineering. Lot 3, Block 4 was assigned a Rational Method Runoff Coefficient of 0.8 in that original design (see supporting materials in Appendix Q. A Runoff Coefficient of 0.8 is assuming the entire lot is being developed. Since only a part of the lot is being developed at this time,the actual Runoff Coefficient for the proposed Swissdetail shop on Lot 3, Block 4 is 0.42 (See Appendix B for calculations). This difference in weighted runoff coefficients shows the regional detention ponds for Phase 1 are adequate to handle the entire runoff contribution of Lot 3, Block 4 as proposed. LOT 3,BLOCK 4 STORMWATER DESIGN Even though the subdivision's stormwater infrastructure is designed to handle this lot's proposed development, a retention pond is proposed on site. Due to the project layout, it was not practical to direct all the runoff from the site to the street. The parking lot grading that worked best includes a grade break near the southwest corner of the building. This meant that a small retention pond capable of storing runoff from the Drainage Area #1 was required. The pond was sized for the 10- year, 2-hour storm and has a design depth of 1.5 feet and storage volume of 924 cubic feet. The remaining portion of the development on the lot (Drainage Area #2) flows to two curb cuts in the northwest corner of the parking lot and flows via a swale to a concrete storm drainage chase in the sidewalk, which drains into N. 27th Avenue. A drainage area map clearly identifying the site's proposed drainage patterns is found in Appendix A. All calculations can be found in Appendix B and supporting materials in Appendix C. DRAINAGE AREA MAP EXHIBIT DRAINAGE AREA MAP SWISSDETAIL STORM (DRAINAGE AREA BOUNDARY RAINAGE CHASE I CURB CUT [S89°46 08,�E] 400.00 090°13'52" QD URB C J i -1 F- ROPOSED SHOP Ul .. Of v ' c W Y - PREP ❑ J . COD p,G� -� DRP� — I II IN ALL RETENTION POND TJ.P. ELEV.=82.6' VOLUMEP. p 1.80.W O.P. ELEV.— 5' WATER DEPTH 924 C.F. ----- r y _ _J I DRAINAGE AREA BOUNDARY [N89°46'08"W] CATTAIL ST. Scale In Feet 50 0 50 ( 15 0 15 Engineering and Surveying Inc. 1091 Stoneridge Drive°Bozeman,MT 59718 Scale In Meters Phone(4061 5B7-1115°Fax(406)587-9768 Contour Intervals: FOOL va Chengineers.com°info@chengineers.com Sheet I Of ' #16180 STORMWATER CALCULATIONS Calculate entire Lot 3, Block 4 C Factor Site Area (Sq. Ft.) Area (acre) C FACTOR Pavement/Roof 26112 0.599 0.95 Open Space/landscape 23115 0.531 0.10 Undeveloped land 54881 1.260 0.30 Total 2.390 Weighted C= The entire lot's runoff from the 10-year 2-hour storm could be discharged into the street if necessary because the existing regional detention pond was sized using a C-factor of 0.8 Determine size of retention pond Calculate required volume Q=CiA V=7200Q Calculate C Factor for Drainage Area#9 Site Area(Sq. Ft.) Area(acre) C FACTOR Pavement/Roof 13518 0.3103 0.95 Open Space/landscape 7814 0.1794 0.10 Total 81850 0.4897 Weighted C= Retention Pond Summary Total Area= 0.490 acres Weighted C= 0.64 Rainfall intensity= 0.41 in./hr. (From C.O.B. Design Standards for 10-year, 2-hr storm) Runoff, Q= 0.1 cfs Volume,V= 923 ft The proposed retention pond is sized at 924 ft3,with a design depth of 1.5 feet and a total pond depth of 2 feet to allow for 6 inches of freeboard. Determine size of sidewalk chase Calculate C Factor for Drainage Area#2 Site Area(Sq. Ft.) Area (acre) C FACTOR Pavement/Roof 12596 0.2892 0.95 Open Space/landscape 26886 0.6172 0.1 Total 39482 0.9064 Weighted C= Calculate Max T c from Contributing Drainage Area (from grade break in middle of parking lot, through curb cut and swale) T,Overland Flow T°= 1.87 (1.1-CCf)D1/2/5113 Storm S = Slope of Basin (%) 0.015 Return (yrs) Cf C = Rational Method Runoff Coefficient 0.37 2 to 10 1 Cf= Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft) 164 26'to 50 1.2 51 to 100 1.25 T,Overland Flow(minutes) 14.37 mins (5 minute minimum) T,Overland Flow(hours) 0.24 hrs T,open channel flow(through swale) T,=LN/60 V= (1.486/n)R213 S12 n = Mannings Coefficient 0.03 A=cross sectional area (ft) 2.0 P=wetted perimeter 2.41 R = Hydraulic Radius A/P (ft) 0.83 S =slope(ft/ft) 0.0 L= length of swale (ft) 46 V= mean velocity(ft/s) 6.4 T,swale flow(minutes) = 0.12 min T,swale flow(hours) = 0.002 hours Tc TOTAL(minutes) = 14.48 mins Tc TOTAL(hours) = 0.24 hours Calculate Rainfall Intensity(Duration =Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. 1-3, COB Design Standards) x=storm duration (hrs) 0.24 (calculated above) i= rainfall intensity(in./hr.) 1.95 Calculate 25-yr Flow Rate Q =CiA C = Rational Method Runoff Coefficient 0.37 (calculated above) i = rainfall intensity(in./hr.) 1.95 (calculated above) A=Area (acres) 0.91 (calculated above) Q=25-yr Pond Outflow Rate (cfs) 0.66 Calculate stormwater chase capacity Chase depth (feet) 0.5 Chase width (feet) 1.0 Mannings#, n (for concrete) 0.013 X-sect. area (ft) 0.5 Perimeter(ft) 2 Hydr. Radius, R (ft) 0.25 slope (ft/ft) 0.015 Qf„u(cfs) 2.80 The stormwater chase as speficied on sheet C2.0 is sufficient to handle the 25-year storm. 2.80cfs>0.66cfs. The dimensions of the chase are 0.5'deep by 1.0'wide. SUPPORTING MATERIALS 4/11/2016 Manning's n Values Show Manning's n Values Reference tables for Manning's n values for Channels, Closed Conduits Flowing Partially Full, and Corrugated Metal Pipes. Manning's n for Channels (Chow, 1959). [- Type of Channel and Description Minimum Normal I Maximum] Natural streams -minor streams (top width at floodstage < 100 ft) 1. Main Channels �- rt E a clean, straight, full stage, no rifts or deep pools I 0.025 0.030 0.033 C b same as above, but more stones and weeds 0.030 0.035 0.040 c. clean, winding, some pools and shoals 0.033 0.040 0.045 d.d. same as above, but some weeds and stones i 0.035 € 0.045 i i 0.050 e. same as above, lower stages, more ineffective 0.040 0.048 0.055 slopes and sections f. same as "d" with more stones 0.045 0.050 0.060 g. sluggish reaches, weedy, deep pools j 0.050 0.070 �° -0.080- E h. very weedy reaches, deep pools, or floodways f with heavy stand of timber and underbrush 0.075 0.100 0.150 i 2. Mountain streams, no vegetation in channel, banks usually steep, trees and brush along I banks submerged at high stages a. bottom: gravels, cobbles, and few boulders I0.030 _ 0.040 0.050 s b. bottom: cobbles with large boulders -�0.040 0.050 0.070 3 Floodplains a. Pasture, no brush I 1.short grass _ - 0.025 0.030 0.035 2. high grass _... � 0.030 0.035 � 0.050 b. Cultivated areas 1. no crop 0.020 0.030 0.040 �.. 2. mature row crops 0.025 0.035 -0.045 3 mature field crops I 0.030 0.040 0.050 _.._.._ .__ c. Brush 1. scattered brush, heavy weeds - - 0.035 1 0.050 - 0.070 2. light brush and trees, in winter 0.035 0.,050 0.060 3. light brush and trees, in summer 0.040 0.060 0.080 4. medium to dense brush, in winter 0.045-� m0.070 -00110_ 5 medium to dense brush, in summer 0.070 0.100 0.160 d. Trees 1. dense willows, summer, straight _ 0.110 f 0.150 0.200 http://www.fsl.orst.edu/geowater/FX3/helptELHydraulic Reference/Mannings n_Tabies.htm 1/5 4/11/2016 Manning's n values i 2. cleared land , h tree stum s, n o s routs I 0.'!- _ p _ _ _L__ 0.040 f 0.050 3. same as abovtj, but with heavy growth of 0.050 0.060 i s prouts ► 0.080 4. heavy stand of timber, a few down trees, little I0.080 0.100 ~ 'vu0.120 - undergrowth, flood stage below branches 5. same as 4. with flood stage reaching branches ; 0.100 0.120 0.160 4. Excavated or Dredged Channels 1 a. Earth, straight, and uniform ____-------- 1 clean, recently completed 0.016 0.018 0.020 2 clean, after weathering _- `� 0.018 0.022 I 0.025 3. gravel, uniform section, clean 0.022 0.025 0.030 4 with short grass, few weeds 0.022 0.027 0.033 b. Earth winding and sluggish � 1. no vegetation ��- g 0.023 0.025 0.030 2 grass, some weeds _ _ _ i 0.025 0.030 f 0A33 3 dense weeds or aquatic plants in deep channels 0.030 0.035 0.040� 4. earth bottom and rubble sides 0.028 0.030 0.035 5. stony bottom and weedy banks 0.025 I 0.035 0.040 - ' 6. cobble bottom and clean sides 0.030 i 0.040 0.050 c. Dragline-excavated or dredged 1. no vegetation 0.025 i 0.028 0.033 2 light brush on banks0.035 �� ✓ _ 0.050 0.060 d. Rock cuts 1. smooth and uniform 0.025 0.035 0.040 a ged and irreular _ � 0.035 0.040 � 0.050 e. Channels not maintained, weeds and brush uncut 1. dense weeds, high as flow depth i 0.050 0.080 0.120 2. clean bottom, brush on sides 0.040 0.050 0.080 3. same as above, highest stage of flow 0.045 0.070 0.110 4. dense brush, high stage ` 0.080 0.100 0.140 5. Lined or Constructed Channels a. Cement 1. neat surface 0.010 ( 0.011 ° 0.013 2. mortar 0.011 0.013 0.015 �_.b-Wood 3 1. planed, untreated 0.010 0.012 1 0.014 2. planed, creosoted 0.011 0.012� i� 0.015 3. unplaned 0.011 0.013 i 0.015 4. plank with battens v 0.012 0.015 0.018 5. lined with roofing paper 0.010 0.014 0.017 c. Concrete 1. trowel finish 0.011 _ F0.013 0.015 http://www.fsl.orst.edulgeowater/FX3/helpt8 Hydraulic_ReferencetMannings n Tables.htm 26 4/11/2016 Manning's n Values 2. float finish 0.0' 1 0.015 0.016 _ - 3. finished, with gravel on bottom 0.015 0.017 0.020 4. unfinished 0.014 0.017 0.020 --5. gunite, good section 0.016 0.019 0.023 6. gunite, wavy section 0.018 0.022 0.025 - - -- - ------ --- ----- -----._- 7. on good excavated rock 0.017 0.020 8. on irregular excavated rock 0.022 0.027 d. Concrete bottom float finish with sides of: 1. dressed stone in mortar_ _ -0.015 �0.017 0.020 2. random stone in mortar - -- - 0.017 0.020 0.024 3. cement rubble masonry, plastered 0.016 0.020 0.024 --- - ------------ 4. cement rubble masonry 0.020 0.025 0.030 5. dry rubble or riprap 0.020 0.030 0.035 e. Gravel bottom with sides of: - -- 1. formed concrete 0.017 0.020 0.025 2. random stone mortar 0.020 0.023 0.026 3. dry rubble or riprap 0.023 0.033 0.636 _ f. Brick 1. glazed 0.011 0.013 I 0.015 2. in cement mortar 0.012 0.015 0.018 g. Masonry - 1. cemented rubble ----------_---- --_------- 0.017 0.025 0.030 --- 2. dry rubble 0.023 0.032 0.035 h. Dressed ashlar/stone paving _ -- _ -0.013 0.015 0.017 i. Asphalt - ----- 1. smooth - - 0.013 0.013 2. rough_ 0.016 0.016 - j. Vegetal lining - 0.030 0.500 - . _Manning's n for Closed Conduits_Flowing Partly Full (Chow, 1959). _ Type of Conduit and Description __---- ( Minim_um _Normal_ Maximum_ 1. Brass, smooth:-- 0.009 0.010 - 2. Steel: - ---- ----- -- -- 0.013-- --� Lockbar and welded- -- - 0.010 - 0.012 _ 0.014_ 0.013 0.016 _ -0.017 - 3. Cast Iron: - 6 - 017 Coated - `- -- - 0.010 0.013 0.014 u ncoated - 0.011 0.014 0.016 4. Wrought Iron: - - ---- --Black ------_- --- -- 0.012 0.014 - 0.015 _ Galvanized _ _ 0.013 _ 0.016 _ _0.017 5. Corrugated Metal: - - - - Subdrain _ - 0.017 0.019 0.021 Stormdrain 0.021 0.024 0.030 http://www.fsl.orst.edu/geowater/FX31help/8_Hydraulic_Reference/Mannings_n Tables.htm -- 3/5 4/11/2016 Manning's n Values 6. Cement Neat Surface 0.010 � 0.011 i 0.013 Mortar 0.011 0.013 0.015 7. Concrete: ( i Culvert, straight and free of debris 0.010 0.011 0.013 ( Culvert with bends, connections, and some debris 0.011 i 0.013 0.014 __7 _ _0._011 � 0.012 0.014 Sewer with manholes, inlet, etc., straight - 0.013 O.Q15 0.017 I Unfinished, steel form _ 0.012 .; 0013 ° 0.014 `. . _. Unfinished, smooth wood form_ _ i� 0.012 0.014 0.016 Unfinished, rough wood form i 0.015 0.017 0.020 f 8. Wood -_�__T__ Stave _0.010 0.012 0.014 _ Laminated, treated 0.020 1 9. _Clay: _-_ - Common drainage the �6 0.Q11 7 0 013 0.017 Vitrified_se_wer �.__ d --_ _ 1 _0.011 0.014 0.017 { � Vitrified sewer with man_h-of es_, inlet__, e_tc. 0.013 0.015 0 0171 ( Vitrified Subdrain with open joint 0.014 1�-0.016 _ 0 018 --_ _-_ _ _ 10. Brickwork: Glazed 0.011 _j 0.013_e__ 0.015 Lined with cement mortar - - OAl2 0.015 4 0.017 Sanitary sewers coated with sewage slime 1 with bends and connections 0.012 0.013 S 0.016 Paved invert, sewer, smooth bottom - 0 016 0.019 , 0.020 Rubble monry cem as , ented 0.018 0 025V _ 0 030 Manning's_ n_for Corrugated Metal Pipe�(AISI, 1980). Type of Pipe, Diameter and Corrugation Dimension ! n s I. Annular 2.67 x 112 inch (all diameters) 0.024 2. Helical 1.50 x 1/4 inch 8" diameter 0 014 _ 3. Helical 2.67 x 1/2 inch ~ _ _ _ 12" diameter 0.011 I `18" diameter _ 0.014__ __�r�-_�_ 24" diameter 0.016 36" diameter _ 0.019 d 48" diameter 60"_dia meter �0.021 4. Annular 3x1 inch all diameters 5. Helical 3x1 inch -- � 48" diameter _ 54"mdiameter-� 0.023 60" diameter � 0.024 66" diameter _f__._.._ 0.025� 72" diameter _ _ 0.026 78" diameter and larger _ --_^ - 0.027� + 6. Corrugations 6x2 inches http://www.fsl.orst.edulgeowater/FX3/helpt8 Hydraulic_ReferencelMannings n Tables.htm 4/5 4/11/2016 Manning's n Values f 60" diameter ' 0.033 _ 72" diameter____ _ 120" diameter OA30 180____" _dia____met_. er _.______.___-- 0.028 FishXing Version 3.0 Beta,2006 http:Uwww.fsl.orst.edulgeowater/FX3ftipl8 Hydraulic_Reference/Mannings n Tables.htm 515 Table 3-1. Recommended Runoff Coefficients. Description of Area Runoff Coefficient Business Downtown 0.70 to 0.95 Neighborhood 0.50 to 0.70 Residential Single-family 0.30 to 0.50 20,000 sq ft 0.49 10,000 sq R 0.52 8,500 sq ft 0.57 Multi-units,detached 0.40 to 0.60 Multi-units,attached 0.60 to 0.75 Residential(suburban) 0.25 to 0.40 Apartment 0.50 to 0.70 Industrial Light 0.50 to 0.80 Heavy 0.60 to 0.90 Parks, cemeteries 0.10 to 0.25 Playgrounds 0.20 to 0.35 Railroad yard 0.20 to 0.35 Unimproved 0.10 to 0.30 Character of Surface Pavement Asphalt and Concrete 0.95 Brick 0.85 Roofs 0.95 Lawns, Sandy soil Flat,2% 0.05 to 0.10 Average,2 to 7% 0.10 to 0.15 Steep, 7%+ 0.15 to 0.20 Lawns, Heavy soil Flat, 2% 0.13 to 0.17 Average,2 to 7% 0.18 to 0.22 Steep, 7%+ 0.25 to 0.35 Source: Design and Construction of Sanitary and Stonn Sewers, ASCE and the Water Pollution Control Federation, 1969. Of hor P- 9cA 4 C4 C.,c fsz—.r--pof Ulz VIC ove 0&7 I Ike- S:�kt �teso 0- s 176) =7 5 Ali\ j @ CL-- (2 YT. -.7.4 0,4-9 t 11,s x 6 O-z- r".cog