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HomeMy WebLinkAboutDrainage Reports - 06/11/1999• w • ' DRAINAGE & EROSION CONTROL REPORT FOR 102 Peterson Street Fort Collins, Colorado 80521 Prepared by ADVANCED PROFESSIONAL ENGINEERING INC. P .0. Box 1391 Fort Collins, CO 80522 Phone 970-484-0533 Fax 970-484-5086 Project# 69-7N-12-32 May 20, 1999 .. • I ADVANCED PROFESSIONAL ENGINEERING INC. Roqi:.;/Oie d Profess io n a l En q ineer s P.O. l3ox 1391, Fort Collin s, CO 8052 2-13<J 1 PHONE 970-484 -0533 , FAX 970-484-5086 May 20, 1999 David Braley & Martha Roden 1967 Massachusetts Street Fort Collins, CO 80525 Re : Drainage Report for 102 Peterson Street. Dear David & Martha, E-MAIL apeinc@ frii .com This is the drainage and erosion control report for your house located at 102 Peterson Street, Fort Collins, Colorado. Also, known as Lot 19, Block 151 , City of Fort Collins . The site is bordered by Peterson Street, Mountain Avenue and River Side Avenue. The existing house is a one story frame house with a basement with a single car garage. The new proposed house is a two-story wood frame house and a two -car garage. Hydrology data and the hydraulic analysis are presented here to meet the City of Fort Collins "Storm Drainage Design Criteria," dated May 1984. Data and analysis are determined based on the historic ( existing) and proposed conditions . If you have any further questions or would like additional information, please feel free to call me at 970-484-0533. Sincerely, repare y MOHAMED S. WORAYETH Colorado Registered Professional Engineer P. E. # 23019 FOUNDATION DESIGN a INSPECTIONS . LAND DEVELOPMENT· DRAINAGE· ENVIRONMENTAL AUDITS, PHASE 1 a 2 PERCOLATION TEST!I • SEPTIC SYSTEM DESIGN • CON!JTUIIUCTED WETLANDS DESIGN TABLE OF CONTENTS Title 1-Drainage Report Introduction Site Location and Conditions Hydrology and Hydraulics Analysis Historic Conditions Historic Drainage Conditions Proposed Development Developed Drainage Conditions Discussion 11-Erosion Control Report Introduction Wind Erosion Control Rainfall Erosion Control Cost Estimate Page 1 1 1 1 2 2 3 3 5 6 6 6 7 8 • t • I 1-DRAINAGE REPORT INTRODUCTION This drainage and erosion control report provides the hydrology data using City of Fort Collins rainfall data. This report utilizes hydraulic analysis to determine historic and proposed drainage conditions for the proposed construction at 102 Peterson Street, Fort Collins, Colorado. Also, known as Lot 19, Block 151, City of Fort Collins. The site is bordered by Peterson Street, Mountain Avenue and River Side Avenue. The existing house is a one story frame house with a basement with a single car garage. The new proposed house is a two-story wood frame house and a two-car garage. Total area of the site is equal to 6,648.66 square feet, or 0.153 acres. This drainage report is prepared and compiled based on the following references: A-Storm Drainage Criteria, City of Fort Collins, dated May 1984, revised January 1997. B-Old Town Master Drainage Basin Plan for the City of Fort Collins, by RCE, dated January 7, 1993. C-Topographic map by Advanced Professional Engineering Inc., December 1998. D-Federal Emergency Management Agency, Flood Insurance Rate Map, Community -Panel #080102 0004C Map Revised March, 18, 1996. E-Site plan prepared by David Braley dated October 1998. SITE LOCATION AND CONDITIONS The site is located at the intersection of Peterson Street, Mountain Avenue and River Side Avenue. The project site is known as 102 Peterson Street, Fort Collins. Also, known as Lot 19, Block 151, situated in Southeast 1/4 of Section 12, Township 7 North , Range 69 West of the 6th P.M., City of Fort Collins, State of Colorado. The existing condition of the property consists of an existing one story frame house with a basement with a single car garage. Existing general topography of the site is relatively flat with an overall slope of 2 .0% to the east toward the alley. Total area of the site is 6,649 square feet, or 0 .15 acres . The access to the garage is through the alley. All three streets have curb, gutter and side walks . A storm drainage inlet is existing at southeast end of Peterson street and Mountain Avenue. A new landscaped area was built north of the site at the time when Mountain Avenue was realigned with Lincoln Avenue . HYDROLOGY DATA AND HYDRAULICS ANALYSIS This report will present and discuss the historic and proposed conditions. Total area of the site is equal to 6 ,649 square feet, or 0.15 acres . Since the area is far less than 5 acres, Rational Method to calculate the storm runoff quantity can be used . The site is part of Old Town Master Drainage Basin Plan for the City of Fort Collins . 1 .. ' -.. HISTORIC DRAINAGE CONDITIONS The historic drainage flow is toward the east to the alley . There is an inlet storm drainage at the northwest corner of the lot along the flow line of Peterson Street. The existing house area is 1, 195 square feet. The existing garage area is 335 square feet. The existing side walk and stone area is 1,057 square feet. The existing grass area is 4 ,062 square feet. The historic runoff is calculated for the site as follows: Estimated runoff quantity "Q" in cfs, under historic conditions for 2, 10 & 100- year storms, based on design storm frequencies for composite ground cover conditions will be: 1-The soil in the lawn area is Clay soil (heavy) with 2% slope and runoff coefficient of 0 .20. The average determined composite runoff coefficient for the total area of 6,648.66 square foot acres un _der historic conditions is equal to the following: Land Cover House & garage = Side walk & Stone = Landscape - Total Area = Area/sq.ft. % Of Total 1,530 SF . 23% 1,057 SF . 16% 4,062 SF . 61 % 6,649 SF . 100% 2-The average slope is= 2.0 % Runoff/Coef. 0.90 0.90 0.20 0 .50 3-Time of concentration: Length of Basin (L) = 70 feet of overland flow from the east side of the house to the alley with an average slope of 2.0%. Time of concentration= Tc min. S = Slope of basin S% = 2.0%. Cf= Frequency adjustment factor for 2 & 10 yr= 1.0 Cf= Frequency adjustment factor for 100 yr= 1.25 C = Rational Method Runoff Coefficient= 0.50 L = Length of Basin in feet= 70 feet For the 2 and 10-year storms : Tc = 1.87 x (1.1 -CxCf} x (L) ½ = 7.50 minutes 51/3 For the 100-year storm: Tc = 5.90 minutes 4-Determine precipitation in inches per hour using Rainfall Intensity Duration Curves for 2 year frequency from figure (3-1) Storm Water Manual : I = Rainfall intensity 2 . . I for 2-year storm = 2.46 inches/hour I for 10-year storm = 4 .20 inches/hour I for 100-year storm= 9.36 inches/hour 5-Runoff quantity for historical conditions: Q = C,CIA where Q = Flow quantity, cfs A = Total area of land = 0.15 acres C, = Frequency adjustment factor: = 1 . 0 for 2 and 1 0-year storms = 1.25 for 100-year storm C = Runoff coefficient = 0.50 I = Rainfall intensity = 1.0 X 0.50 X 2.46 X 0 .15 = 0.19 cfs = 1.0 x 0.50 x 4 .20 x 0.15 = 0 .32 cfs = 1.25x0.50x9.36x0.15=0.88cfs B-PROPOSED DEVELOPMENT The proposed construction is a new two story wood frame house and a two-car garage. The existing side walks will be wide. The new house is 1,777 square feet. The garage area is 924 square feet. The side walk area is 706 square feet. The alley will be improved with concrete surface. Developed Drainage Conditions The proposed developed drainage pattern will follow the historic. The east portion of the lot is drained toward the alley to the east. There is an inlet storm drainage at the northwest corner of the lot along the flow line of Peterson Street. The following is the site data: The soil in the lawn area is Clay soil (heavy) with 2% slope and runoff coefficient of 0.20. The average determined composite runoff coefficient for the total area of 6,649 square foot acres under historic conditions is equal to the following: Land Cover Area/sg.ft. % Of Total Runoff/Coef. House & garage = 2,701 SF. 40% 0.90 Sidewalk = 706 SF . 10% 0.90 Landsca12e = -:, :z-t l, 3;-a4z SF. 50% 0 .20 Total Area = 6,649 SF. 100% 0.55 2-The average slope is= 2.0 % 3 3-Time of concentration: Length of Basin (L) = 70 feet of overland flow from the east side of the house to the alley with an average slope of 2.0%. Time of concentration = Tc min. S = Slope of basin S% = 2.0%. Cf= Frequency adjustment factor for 2 & 10 yr= 1.0 Cf = Frequency adjustment factor for 100 yr = 1.25 C = Rational Method Runoff Coefficient= 0.55 L = Length of Basin in feet= 70 feet For the 2 and 10-year storms: Tc = 1.87 x (1 .1 -CxCf) x (L) ½ = 7 .50 minutes 5113 For the 100-year storm : Tc = 5 .90 minutes 4-Determine precipitation in inches per hour using Rainfall Intensity Duration Curves for 2 year frequency from figure (3-1) Storm Water Manual : I = Rainfall intensity I for 2-year storm = 2.46 inches/hour I for 10-year storm = 4 .20 inches/hour I for 100-year storm= 9.36 inches/hour 5-Runoff quantity for historical conditions : Q = C,CIA where Q = Flow quantity, cfs A = Total area of land = 0.15 acres C, = Frequency adjustment factor: = 1 . 0 for 2 and 1 0-year storms = 1.25 for 100-year storm C = Runoff coefficient= 0.55 I = Rainfall intensity = 1.0 X 0.55 X 2.46 X 0.15 = 0.20 cfs = 1.0 x 0.55 x 4.20 x 0 .15 = 0 .35 cfs 1.25 x 0.55 x 9 .36 x 0.15 = 0 .97 cfs 4 • I ., I Summary of Runoff Historic Developed Basin Area in sq.ft. = 6,649 6,649 Basin Area in acres = 0 .15 0 .15 Slope (S) % = 2 .0% 2 .0% Length of Basin (D), feet = 70 70 Runoff Coefficient = 0.50 0.55 Time of Concentration: Tc for 2 year per minutes = 7 .50 7 .50 Tc for 10 year per minutes = 7 .50 7.50 Tc for 100 year per minutes = 5 .90 5 .90 Precipitation for 2 year, in/hr = 2.46 2.46 Precipitation for 1 O year, in/hr = 4.20 4.20 Precipitation for 100 year, in/hr = 9.36 9.36 Runoff 0 2, cfs = 0 .19 0.20 Runoff 0 10 , cfs = 0 .32 0.35 Runoff 0 100 , cfs = 0.88 0 .97 DISCUSSION The following assumptions have been considered in determining the drainage conditions: 1-The historic and developed site has the same drainage pattern . The site is relatively flat. The lot has a slope of 2% to the east. The main drainage is toward the alley. 2-There is no off-site runoff from outside the property from the south, west, east nor from the north that entering the site. The northern landscape area does slope toward the south . However once the runoff reaches the side walk then it flows to the east or west. All the streets runoffs are contained in the gutter of each street. The alley is draining toward the north to River Side Avenue. 3-The difference between developed and historic runoff is very small. The difference between 100 year developed storm and 100 year historic storm is = Q 100O -Q 100H = 0.97 -0.88 = 0 .09 cfs. The difference between the 100 year developed storm and 2 year historic storm is = 0 1000 -Q2H = 0. 97 -0.19= 0 . 78 cfs : Based on the above-mentioned flow rates, and the Old Town Master Drainage Basin Plan for the City of Fort Collins a detention pond is not required. 4-Old Town Master Drainage Basin Plan for the City of Fort Collins, by RCE, dated January 7, 1993, in table 5 .1 defines the 10-year flood plain at 4,969.60 and 100-year flood plain at 4,969.90. However, in figure 5.7: Reach 5 & SB it shows the 10-year flood plain at 4,970.00 and 100-year flood plain at 4,970.50. This 5 . ·-. . report will consider the 100-year flood at 4,970.00. 5-The existing garage elevation is at 4,970.00. The proposed elevation for the garage is 4,971.50, which is 18-inches higher than the 100-year flood . 6-The existing house elevation is at 4,972 .35. The proposed home will be set at the same elevation of 4,972 .35, which is 2 .35 feet higher than the 100-year flood . II. EROSION CONTROL REPORT INTRODUCTION This erosion control report provides the wind and rainfall erosion control plan using the City of Fort Collins wind and rainfall data, for the proposed construction at 102 Peterson Street. The site is located at the intersection of Peterson Street, Mountain Avenue and River Side Avenue . The project site is known as Lot 19, Block 151 , situated in Southeast 1/4 of Section 12, Township 7 North, Range 69 West of the 6th P.M ., City of Fort Collins , State of Colorado. The existing condition of the property consists of an existing one story frame house with a basement with a single car garage. Existing general topography of the site is relatively flat with an overall slope of 2.0% to the east toward the alley. Total area of the site is 6,649 square feet, or 0.15 acres. The access to the garage is through the alley. All three streets have curb, gutter and side walks . A storm drainage inlet is existing at southeast end of Peterson street and Mountain Avenue. A new landscaped area was built north of the site at the time when Mountain Avenue was realigned with Lincoln Avenue . Wind and Rainfall Erosion Control According to Section 8.1 of Fort Collins Storm Drainage Design Criteria and Erosion Control Manual the wind erosion control is not needed for areas less than one acre. Since the site is 0 .15 acres then this erosion control plan , therefore, presents methods to control only rainfall erosion . An erosion control installation schedule is presented here for erosion control measures that are taking place when construction starts . The entire site is in a low wind erodibility zone . RAINFALL EROSION CONTROL PLAN According to Section 8 .1 of Fort Collins Storm Drainage Design Criteria and Erosion Control Manual the rainfall erosion control is not needed for areas less than 10,000 square feet, unless they are within 50 feet from flood plain areas . Since the site is only 6,649 square feet , then a measure to control the rainfall erosion is presented in this report . An erosion control installation schedule is presented here for erosion control measures that are taking place when construction starts . The entire site is in a low rainfall erodibility zone. 6 • r ., • Rainfall Performance Standard Rainfall zone 100% Low Area 0 .15 ac. Length, Lb Slope, Sb 70 ft 2.0 From Table 8-A of the Fort Collins Storm Water Manual: Performance Standard= 78.4% Performance Standard= 78.4%/0.85 = 92.2% Rainfall Erosion Control Effectiveness Land Cover Area/sg.ft. House & garage = 2,701 SF . Sidewalk = 706 SF . Landscape = 3,342 SF. -Total Area = 6,649 SF. EFF = (1 - C x P) x 100. where : for construction conditions for developed conditions % Of Total 40% 10% 50% 100% EFF =Effectiveness(%), C = C-Factor (cover factor), P = P-Factor (Practice factor) Erosion Control C-Factor P-Factor Method Value Value Established Grass 0 .08 1.00 Roads/Walks 0 .01 1.00 AsphalUConc. 0.01 1.00 Bare Soil 1.00 1.00 Gravel Filters 1.00 0.80 Silt Fence 1.00 0.50 Land Cover Area/Acres % Of Area C-factor P-factor House & garage = 0.062 AC . 40% 0.01 1.00 Side walk = 0.016 AC . 10% 0 .01 1.00 Landscape = 0.077 SF. 50% 0.08 1.00 -Total Area = 0.15 SF. 100% 0.05 1.00 Net C-Factor = 0.05, Net P-Factor = 1.00 EFF sbB = (1 -C X P) X 100 = (1 -(0.05 X 1.00)) X 100% = 95.0% 7 .. . Since the net EFF is greater than PS (95.0% > 78.4%), the proposed erosion control methods will meet the City of Fort Collins requirements. For developed conditions, the net effectiveness will be increased due to the new building , and thus will exceed the performance standard (95.0% > 92.3%). COST ESTIMATE FOR EROSION CONTROL PLAN A. The silt fence is proposed along the west, south and the north property lines. A 300 linear feet of silt fence x 4 feet high of 6 mills at $3.00/liner foot. $2.00 X 300 = $600.00. B. 12 pieces of concrete blocks and 3/4" gravel to be placed around one drainage inlet, 12 concrete blocks @ $1.5/each = $18.00 + $20 .00 gravel = $38.00. C . 3,342 square feet of landscaped at the end of project cost= 3,342 x $0.25 = $835.50 Total cost= $600.00 + $38.00 + $835 .50 = $1,473 .5.00. Then 150% of the cost = 1.5 x 1,473.50 = $2,210.25, which is more than the $1,000.00 minimum . 8 City of Fort Collins Rainfall Intensity-Duration-Frequency Table for using the Rational Method (5 minutes -30 minutes) Figure 3-1a Duration 2-year 10-year 100-year (minutes) Intensity Intensity Intensity (in/hr) (in/hr) (in/hr) 5.00 2.85 4.87 9 .95 6.00 2.67 4 .56 9.31 7 .00 2.52 4 .31 8.80 8 .00 2.40 4 .10 8.38 9 .00 2.30 3 .93 8 .03 10.00 2.21 3.78 7.72 11 .00 2.13 3.63 7.42 12.00 2.05 3.50 7.16 13 .00 1.98 . 3 .39 6.92 14 .00 1.92 3 .29 6 .71 15 .00 1.87 3.19 6 .52 16.00 1.81 3.08 6 .30 17.00 1.75 2.99 6.10 18.00 1.70 2.90 5.92 19.00 1.65 2 .82 5 .75 20 .00 1.61 2.74 5 .60 21.00 1.56 2.67 5.46 22.00 1.53 2 .61 5 .32 23.00 1.49 2.55 5.20 24.00 1.46 2.49 5.09 25.00 1.43 2.44 4.98. 26 .00 1.40 2 .39 4 .87 27 .00 1.37 2.34 4.78 28.00 1.34 2.29 4 .69 29.00 1.32 2 .25 4.60 30.00 1.30 2.21 4 .52 · City of Fort Collins Rainfall Intensity-Duration-Frequency Table for using the Rational Method (31 minutes -60 minutes) Figure 3-1b Duration 2-year 10-year 100-year (minutes) Intensity Intensity Intensity (in/hr) (in/hr) (in/hr) 31 .00 1.27 2.16 4.42 32.00 1.24 2.12 4.33 33.00 1.22 2 .08 4 .24 34 .00 1.19 2.04 4 .16 35 .00 1.17 2.00 4.08 36 .00 1.15 1.96 4.01 37.00 1.13 1.93 3.93 38 .00 1.11 1.89 3 .87 39 .00 1.09 1.86 3 .80 40.00 1.07 1.83 3.74 41.00 1.05 1.80 3 .68 42.00 1.04 1.77 3.62 43.00 1.02 1.74 3.56 44 .00 1.01 1.72 3.51 45 .00 0 .99 1.69 3.46 46.00 0.98 1.67 3.41 47.00 0 .96 1.64 3.36 48 .00 0 .95 1.62 3 .31 49.00 0.94 1.60 3.27 50.00 0 .92 1.58 3 .23 51.00 0.91 1.56 3 .18 52 .00 0 .90 1..54 3 .14 53.00 0.89 1.52 3.10 54 .00 0 .88 1.50 3.07 55 .00 0.87 1.48 3.03 56.00 0 .86 1.47 2 .99 57.00 0 .85 1.45 2 .96 58.00 0 .84 1.43 2 .92 59 .00 0.83 1.42 2 .89 60 .00 0 .82 1.40 2 .86 Table 5.1. Flood Frequ~ncy Elevation Discharge (continued). • Reach 4 (continued) 56 9700 4995.0 100 4996.6 180 4996.7 280 4996.8 500 4997.0 700 4997.3 57 9860 4997.0 100 4997.5 180 4997.6 280 4997.7 500 4997.9 700 4998.1 58 9970 4998.1 100 4998.4 180 4998.5 280 4998.6 500 4998.8 700 4998.8 59 10340 4998.1 100 4999.1 180 4999.2 280 4999.3 500 4999.5 700 I 4999.6 60 10650 4999.7 100 5000.0 180 5000.1 280 5000.2 500 5000.3 700 I 5000.4 Reach 5 (J'I Ii 61 o ~ 4965.8 80 4966.1 170 4966.1 250 4966.2 380 4966.3 600 4966.4 CX) 62 90 4966.8 1 4967.0 90 4967.1 190 4967.3 260 4967.4 430 4967.5 63 630 4969.0 80 4969.4 170 4969.6 250 4969.7 380 4969.9 500 4969.9 64 1000 4970.1 40 4971.1 90 4971.2 140 4971.3 230 4971.5 330 4971.6 65 1300 4972.9 40 4973.4 90 4976.7 130 4973.9 190 4974.0 260 4974.1 66 1610 4973.9 60 4975.0 130 4975.3 180 4975.5 280 4975.8 390 4976.0 67 1900 4976.8 50 4977.7 110 4978.0 150 4978.1 220 4978.2 310 4978.4 68 1950 4977.0 50 4977.9 110 4978.2 150 4978.3 220 4978.5 310 I 4978.6 69 2080 4979.1 80 4979.8 170 4980.0 240 4980.2 360 4980.3 500 I 4980.4 70 2160 4980.0 110 4980.5 240 4980.6 340 4980.7 500 4980.7 690 I 4980.8 -... .c -C ·--~ -·-Cl) C Q) -C 11.00 10.00 I 9.00 8.00 6.00 ,.: ~ Figure 3-1 City of Fort Collins, Colorado Rainfall Intensity-Duration-Frequency Curve City of Fort Collins Precipitation Frequency Analysis, 1999 (Regional Analsysls) ... ,~ ·I·· ; · J .--❖,· J <r-:-----c--l"-,.:T-; F·-Y -..._ I · I • I · I :,· ·. 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I.JJ·.;..~ I ... .,..,_.,.1_-.. ..., 1~, .. ~ ;.,....----.: 1--;.r.,, ,_.,-. t~•"' 100 120 100-year 50-year ---25-year -10-year • 5-year ___ -2-year • Figure 5. 7: REACH 5 & 5B FLOODED AREAS OLD TOWN MASTER DRAINAGE BASIN PLAN CITY of FORT COLLINS DECEMBER, 1992 REMINGTON ,- ·- NOTES: 1. For locnllon ol Mop, s oo lmJo ,c, Figura 5 . 1 2. For Prolilo, aoo Figura 5 .16 3. For Flood Elovnlfono, aoo Tobia 5 . 1 4. Basa Mnp trom Moy-July 1070 Aorlal Photographs by M&f Conaulllng Enoinocra ontJ from May 1904 Ac1lal Photograph:, by Arht C o rp. SCALE: 1 • • 200' LEGEND: ---® ~" 100 Yonr Flood Limit s 10 Yoar flood Limils Cross Section Location nnd ncro, cnco Uun\bcr Appro 1dmAle L oca tio n o f Shallow Flooding Less than 1.5' Deep 100 Yr . Flood Wator Surl1ee Contour•