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HomeMy WebLinkAboutDrainage Reports - 03/03/19931 1 1 1 1 1 1 Final Anrm�,O Report FINAL DRAINAGE AND EROSION CONTROL REPORT FOR SCHMIDTBERGER MINOR SUBDIVISION IN THE NW 1/4 OF SEC. 10, T7N, R69W CITY OF FORT COLLINS, COLORADO by ADVANCED PROFESSIONAL ENGINEER] P.O. Box 1391 Fort Collins, 00 80522 484-0533 Project A 69-7N-10-196 February 14, 1993 INC. ADVANCED PROFESSIONAL ENGINEERING ' COLORADO REGISTERED PROFESSIONAL ENGINEERS AND LAND SURVEYORS P.O. Box 1391, Fort Collins, CO 80522 Phone (303) 484-0533 February 14, 1993 ' Ernie Schmidtberger 825 Grouse Ct. Fort Collins, CO 80524 1 RE: Final Drainage and Erosion Control Report for Schmidtberger Minor Subdivision, 1900 Laporte Avenue, City of Fort Collins, ' Colorado. ' Dear Mr. Schmidtberger; Submitted herein is the final drainage and erosion control report ' that the City of Fort Collins had requested for Schmidtberger Minor Subdivision at 1900 Laporte Ave., in the City of Fort Collins Colorado. The hydrology data and the hydraulics analysis presented ' here are in compliance with .the City of Fort Collins " Storm Drainage Design Criteria", dated May 1984. ' The hydrology data and the hydraulics analysis is determined based on the historic and proposed conditions, and based on the Major Drainage way Plan for West Vine Drainage Basin, dated December 1980. As you can see from the Drainage way for West Vine Drainage ' Basin dated December 1980, there is no need for a detention pond. If you have any further questions or need more information please feel free to call me at 484-0533. Sincerely / hamed t. Worayeth olorado Reg. P.E. 23019 TABLE OF CONTENTS Title Page INTRODUCTION 1 SITE LOCATION AND CONDITIONS 1 EXISTING DRAINAGE CONDITIONS 2 PROPOSED CONSTRUCTION 3 LANDSCAPING 3 HYDROLOGY.AND HYDRAULICS ANALYSIS 3 SUMMARY 16 DISCUSSION 16 WIND & RAINFALL EROSION CONTROL 18 I 1 INTRODUCTION This drainage and erosion control report provides the final hydrology analysis using The City of Fort Collins rainfall data, ' and hydraulic investigation to determine the existing and the proposed drainage and erosion conditions, for Schmidtberger Minor ' Subdivision. It is proposed to divide into two lots. The existing parcel located in the SW 1/4 of the NW 1/4, Section 10, Township 7 North, Range 69 West, also known as 1900 Laporte Avenue, in the t City of Fort Collins, Colorado. The total area involved is 16.9595 acres. ' The new proposed lot, which is 1.550 acres, is located Southeast of Larimer Canal # 2. It is proposed that a new house will be ' built on the new lot. The second lot which is 15.4095 acres will remain without change except removing the old barn. This drainage report is prepared and compiled from the following references. ' 1- Storm Drainage Criteria, City of Fort Collins, May 1984. ' 2- Major Drainage -way Plan for West Vine Drainage Basin by EPI dated December 1980. ' 3- Topographic Maps, contour map prepared by Advanced ' Professional Engineering Inc. 1992. SITE LOCATION AND CONDITIONS The site is located on the North side of Laporte Avenue, about 1/4 mile East of the Taft Hill Road, also known as 1900 Laporte ' Avenue. There is an existing house which will remain in place, and a barn which will be removed. ' The property is divided physically into three sections (sub - basins) by the Larimer County # 2 Canal and by the New Mercer ' Canal. The first section will be called Sub -basin "A", which is located to the Northeast of the Larimer County # 2 Canal, the sub -basin area is 6.825 acres. The second section is located ' between the Larimer-County # 2 Canal and the New Mercer Canal. The basin area is equal to 9.904 acres, and will be known as sub - basin "B". ' 1 L ' The third section or sub -basin "C" is very small basin, with an area equal to 0.252 acres, which is located South of the New ' Mercer Canal and North of Laporte Avenue. Sub -basins "A" and "C" are not developed, and are covered with ' local, native, and wild weed and grasses. Some scattered trees are present along the two irrigation ditches. Sub -basin "B" t includes the irrigated landscaped lawn around the existing house and the barn, at the South portion of the property. ' EXISTING DRAINAGE CONDITIONS The property is part of the West Vine Drainage Basin. The ' original natural drainage of the whole area is a sheet flow type drainage to the North and the Northeast. However, the two irrigation ditches were cut and built through the property which ' created a physical boundary to the pattern of the natural drainage, and divided the property to three drainage sections ' (basins); Basin "A" drains by sheet flow to the Northeast onto adjacent ' undeveloped property. Basin "B" located between the Larimer County # 2 Canal and the New Mercer Canal, drains to the North and the Northeast into the Larimer County Canal # 2 by sheet ' flow. Basin "C" lies South of the New Mercer Canal and North of Laporte Avenue. This very small area drains to the North and into the New Mercer Canal through sheet flow. The drainage from the ' road (Laporte Avenue) is also draining into New Mercer Canal. ' All the existing drainage in Basin "B" drains onto Larimer Canal # 2 by sheet flow, however larger portions of the runoff is ' seeping through the ground. The first sub -basin in the Northeast section, sub -basin "A" is currently draining into the Northeast corner and into the adjacent property. A 100-year flood would cover the northern third of the property, according to the Major Drainage -way Plan of West Vine Drainage Basin. The high water elevation in the 100 year flood at the site is 5,048.00. '. 2 I PROPOSED CONSTRUCTION The proposed construction includes a new residential house to be ' located in Lot 1, a new gravel driveway with a cul-de-sac at the end, to connect the new house to Laporte Avenue as an access. The plan also calls for the removal of the existing barn. ' Landscaped area with grass and gravel will surround the new home building and the driveway. LANDSCAPING ' It is proposed that gravel and irrigated lawn would be planted around the new house building. All the finished grades around the new and existing buildings should be sloped away from the ' structure on all sides to provide positive drainage. A minimum of one foot fall in the first ten feet is recommended. Sprinkler ' systems should not be installed within ten (10) feet from the structure. Down -spouts ar.e recommended and should be arranged to carry drainage from the roof at least five (5) feet. Any low area ' between the two houses'should be sloped away to drain to the Northeast. ' HYDROLOGY AND HYDRAULICS ANALYSIS The total area involved in this drainage study is 738,755 square ' feet or 16.9595 acres gross. Since the area is far less than 200 acres, the Rational Method to calculate the storm runoff quantity ' can be used. The total developed area will be divided into three sub -basins "A", "B", and "C". The historical runoff will be calculated for each basin separate as follows; SUB -BASIN "A" ' I- Estimated runoff quantity "Q" in cfs, for 2 year initial storm, under historical (existing) conditions; ' The first basin "A" is located Northeast of Larimer County # 2 Canal. Using the rational Method to determine runoff storm ' drainage criteria for 2 year initial storm, the historical conditions are determined. The runoff coefficient for the undeveloped area under historical conditions will be determined ' as follows: ' 3 1 ' The total area of basin "A" is 297,277 square feet, or 6.83 acres. The average slope for basin "A" is 1.83% (S = 1.83%). From table 3-2 for (unimproved area) lawn with heavy soil, and ' flat to less than 2% slope, the runoff coefficient is equal to 0.20. ' 1- The length of basin (D) is equal to 600 feet, in which 500 feet is sheet flow, the last 100 feet is channel flow. ' 2- The average slope is 1.83% (S = 1.83%) ' determine time in 3- To of concentration minutes; ' Tc = 1.87 - f) Dl/2 Sl 3 Where ' Tc = Time of Concentration, minutes. S = Slope of basin 1.83% (S = 1.83%) C = Rational Method Runoff Coefficient = 0.2. Cf = Frequency adjustment factor = 1.0 for 2 year storm. ' D = Length of Basin is equal to 600 feet, which is sheet flow for 500 feet, with 100 feet of channelized flow. ' Time of concentration: Tr = Tlc + T2c where Tic is the time of sheet flow, which can obtained from the above equation; ' Tlc = 1.87 (1.1 - 0.2x1.0)(500)1/2 (1.83)1/3 ' Tlc = 30.8 minutes. T2c is the time of channelized flow where the velocity can ' be obtained from Figure # 3-2, based on slope = 1.83% and pasture/fallow type grass. The average velocity of 0.9 and t 0.6 is equal to 0.75 ft/sec., T2c = 100/(60xO.75) = 2.40 minutes. ' Then Tc = 30.8 + 2.4 = 33.20 minutes. ' 4 '. 4- Determine precipitation in inches per hour from figure (3- t1) Storm Drainage Design Manual, I2 = 1.38 inches/hour 5- Determine runoff quantity ' Q = CfCIA Where Q = Flow quantity, cfs A = Total are of basin = 6.83 acres Cf = Frequency adjustment factor = 1.0 C = Runoff coefficient = 0.20 ' I = Rainfall intensity = 1.38 inches/hour ' Then the allowable historical release rate under existing conditions is equal to; ' Q2 = 1.0 x 0.20 x 1.38 x 6.83 = 1.89 cfs SUB -BASIN "B" II- Estimated runoff quantity "Q" in cfs, for 2 year initial ' storm, under historical (existing) conditions; Basin "B" is located between the Larimer County # 2 Canal and New ' Mercer Canal. All of the existing drainage in Basin "B" drains onto Larimer Canal # 2 by sheet flow, however larger portions of the runoff is seeping through the ground. Using the rational ' Method to determine runoff storm drainage criteria for 2 year initial storm, the historical conditions are determined for the ' developed and undeveloped area of sub -basin "B". The composite runoff coefficient for the developed and undeveloped area under historical conditions will be determined as follows: ' The total area of basin "B" is 431,426 square feet, or 9.90 acres. The average slope for basin "B" is 2.0% (S = 2.0%). The ' total developed area is equal to 7,150 sq. ft., and the total undeveloped area is equal to 424,276 sq. ft. The area of an existing house is equal to 1,500 sq. ft. The area of an existing barn is equal to 1,650 sq. ft. The area of the existing gravel road entrance is 2,400 sq. ft. The area of the Existing parking ' lot between the old.house and the barn is 1,600 sq. ft. 1 5 I ' The runoff coefficient for roof is 0.95. The runoff coefficient for gravel road or driveway or gravel parking lot is 0.50. From table 3-2, the runoff coefficient for (undeveloped area which is ' equal to 424,276) lawn with heavy soil, and flat to less than 2% slope is equal to 0.20. ' 1- Determine composite runoff coefficient for the total area of 431,426 square feet is 0.208 = 0.21. 2- The length of basin (D) is equal to 550 feet, in which 500 feet is a sheet flow and 50 feet is channel flow. 3- The average slope is 2.0% (S = 2.0%) 4- To determine time of concentration in minutes; ' T, = 1.87 (1.1 - CxC[) D1/2 S1/3 Where TC = Time of Concentration, minutes. S = Slope of basin % = 2.0% ' C = Rational Method Runoff Coefficient = 0.21. Cf = Frequency adjustment factor = 1.0 for 2 year storm. ' D = Lenoth of Basin is equal to 550 feet, which is sheet flow for 500 feet, with 50 feet of channelized flow. 1 Time of concentration: TC = Tlc + T2c where Tj,, is the time of sheet flow, which can obtained from the above equation; Tlc = 1_87 (1_1 - 0.21x1.0)(500)1/2 (2.0)1 3 Tlc = 30.88 minutes. T2c is the time of channelized flow where the velocity can be obtained from Figure # 3-2, based on slope = 2.0% and pasture/fallow type grass. The average velocity of 1.0 and 0.65 is equal to 0.83 ft/sec., T2c = 50/(60x0.83) = 2r40 minutes. N 1 Then Tc = 30.88 + 1.01 = 31.89 minutes. ' 5- Determine precipitation in inches per hour from figure (3- ' 1) Storm Drainage Design Manual, I2 = 1.40 inches/hour 6- Determine runoff quantity Q = CfCIA where Q = Flow quantity, cfs A = Total are of basin = 9.90 acres ' Cf = Frequency adjustment factor = 1.0 C = Runoff coefficient = 0.21 I = Rainfall intensity = 1.40 inches/hour Then the allowable historical release rate under existing conditions is equal to; Q2 = 1.0 x 0.21 x 1.40 x 9.90 = 2.91 cfs SUB -BASIN "C" ' III- Estimated runoff quantity "Q" in cfs, for 2 year initial storm, under historical (existing) conditions; ' The third basin "C" lies South of the New Mercer Canal and North of Laporte Avenue, which is a very small tract of land. Using the rational Method to determine runoff storm drainage criteria for 2 year initial storm, the historical conditions are determined for ' the undeveloped area; The total area of basin "C" is 10,975 square feet, or 0.252 ' acres. The average slope for basin "C" is 3.33% (S = 3.33%). From table 3-2 for lawn with heavy soil, and more than 2% slope, the ' runoff coefficient is equal to 0.25. 1- The length of basin (D) is equal to 60 feet, which is all ' sheet flow. 2- The average slope is 3.33% (S = 3.33%) 1 7 3- To determine time of concentration in minutes; TC = 1.87 1.1.- CxCf) D1/2 S1/3 Where ' Tc = Time of Concentration, minutes. S = Slope of basin % =3.33% C = Rational Method Runoff Coefficient = 0.25. ' D = Length of Basin, 60 feet. Cf = Frequency adjustment factor = 1.0 for 2 year ' storm. Then TC = 8.26 minutes. ' 4- Determine precipitation in inches per house from figure (3- 1) Storm Drainage Design Manual, I 2 = 2.68 inches/hour ' 5- Determine runoff quantity ' Q = CfCIA ' Where Q = Flow quantity, cfs A = Total are of basin = 0.252 acres Cf = Frequency adjustment factor = 1.0 C = Runoff coefficient = 0.25 I = Rainfall intensity, = 2.68 inches/hour Then the allowable historical release rate under existing ' conditions is equal to; Q2 = 1.0 x 0.25 x 2.68 x 0.252 = 0.17 cfs ' Estimated Runoff Quantity "Q" In cfs, For 100 Year Major Storm Under The Proposed Conditions; To determine the runoff quantity "Q" in cfs, for 100 year major & 2 year storm design return period for the site, the whole ' property will be divided into three sub -basin called "A", and "C". The 100 year major storm runoff for the developed and undeveloped areas will be calculated for each basin separate as ' follows; 1 8 SUB -BASIN "A" ' IV- Estimated runoff quantity "Q" in cfs, for 100 year major ' storm, under both existing and proposed conditions; Using the rational Method to determine runoff storm drainage ' criteria for 100 year major storm, the proposed conditions for sub -basin "A" are not changed from the historic conditions. The runoff coefficient for the undeveloped area will be the same as for the minor 2 year storm, which is as follows: ' The total area of basin "A" is 297.277 square feet, or 6.83 acres. The average slope for basin "A" is 1.83% (S = 1.83%). From table 3-2 for (unimproved area) lawn with heavy soil, and flat to less than 2% slope, the runoff coefficient is equal to 0.20. ' 1- The length of basin (D) is equal to 600 feet, in which 500 feet is sheet flow, the last 100 feet is channel flow. 2- The average slope is 1.83% (S = 1.83%) ' 3- To determine time of concentration in minutes; TC = 1.87 (1.1 - CxCE) D1/2 S1/3 Where TC = Time of Concentration, minutes. S = Slope of basin 1.83% (S = 1.83%) C = Rational Method Runoff Coefficient = 0.2 ' D = Length of Basin, 600 feet ( 500 + 100 channel flow) ' Cf = Frequency adjustment factor = 1.25 for 100 year storm. ' Then Tc = 29.13 + 2.4 = 31.53 minutes. 4- Determine precipitation in inches per hour from figure (3- ' 1) Storm Drainage Design Manual, I100 = 3.95 inches/hour ' 5- Determine runoff quantity Q = CfCIA 1 9 Where Q = Flow quantity, cfs A = Total ate of basin = 6.83 acres ' CE = Frequency adjustment factor = 1.25 C = Runoff coefficient = 0.20 I = Rainfall intensity = 3.95 inches/hour ' Then the runoff quantity for 100 year major storm for basin ' "A" under proposed conditions is equal to: Q100 = 1.25 x 0.20 x 3.95 x 6.83 = 6.75 cfs ' Estimated runoff quantity "0" in cfs, for 100 year major storm under historical conditions for sub -basin "A: is the same as for ' the developed conditions, which is equal to 6.75 cfs. SUB -BASIN "B" V- Estimated runoff quantity "Q" in cfs, for 100 year major ' storm, under proposed conditions would be as follows; Using the rational Method to determine runoff storm drainage ' criteria for 100 year major storm, the proposed conditions are determined for the developed and undeveloped area for sub -basin "B", between the Larimer County # 2 Canal and the New Mercer ' Canal. The composite runoff coefficient for the developed and undeveloped area will be determined as follows: ' The total area of basin "B" is 431,426 square feet, or 9.90 acres. The average slope for basin "B" is 2.0% (S = 2.0%). The ' total developed area is equal to 16,358 sq. ft., and the total undeveloped area is equal to 415,068 sq. ft. The area of an existing house is equal to 1,500 sq. ft. The area of a proposed ' new home is equal to 1,800 sq. ft. The area of the new gravel road entrance with the cul-de-sac is 13,058 sq. ft. ' The existing gravel parking lot near the old house and the barn will remain. The runoff coefficient for roof is 0.95. The runoff ' coefficient for gravel road or driveway or gravel parking lot is 0.50. From table 3-3 the runoff coefficient for lawn with heavy soil, and flat to less than 2% slope, is equal to 0.20 for the ' undeveloped area which is equal to 415.068 sq. ft. 10 1- Determined composite runoff coefficient for the total area ' of 431,426 sq. ft is 0.22 ' 2- The length of basin (D) is equal to 550 feet, in which 500 feet is a sheet flow and 50 feet is channel flow. ' 3- The average slope is 2.0% (S = 2.0%) 4- To determine time of concentration in minutes; ' Tr = 1.87 (1.1 - CxCf) D1/2 S1�' ' Where TC = Time of Concentration, minutes. S = Slope of basin % =2.00% C = Rational Method Runoff Coefficient = 0.22. D = Length of Basin, 500 feet sheet flow & 50 feet ' channel flow. Cf = Frequency adjustment factor = 1.25 for 100 year storm. Then Tc = 27.95 + 1.01 = 28.96 minutes. 5- Determine precipitation in inches per hour from figure (3- 1) Storm Drainage Design Manual, Ilop = 4.25 inches/hour 5- Determine runoff quantity Q = CfCIA Where ' Q = Flow quantity, cfs A = Total are of basin = 9.90 acres Cf = Frequency adjustment factor = 1.25 ' C = Runoff coefficient = 0.22 I = Rainfall intensity = 4.25 inches/hour ' Then the runoff quantity for 100 year major storm for basin "B" under proposed conditions is equal to: 1.25 x 0.22 x 4.25 x 9.90 = 11.57 cfs 11 VI- Estimated runoff quantity "Q" in cfs, for 100 year major ' storm under historical conditions for sub -basin "B" would be as follows: ' The total area of basin "B" is 431,426 square feet, or 9.90 acres. The average slope for basin "B" is 2.0% (S = 2.0%). The total developed area is equal to 7,150 sq. ft., and the total undeveloped area is equal to 424,276 sq. ft. The area of an existing house is equal to 1,500 sq. ft. The area of an existing ' barn is equal to 1,650 sq. ft. The area of the new gravel road entrance is 2,400 sq. ft. The area of the existing parking lot ' between the old house and the barn is 1,600 sq. ft. The runoff coefficient for roof is 0.95. The runoff coefficient for gravel road or driveway or gravel parking lot is 0.50. From table 3-3 ' for lawn with heavy soil, and flat to less than 2% slope, is equal to 0.20 for the undeveloped area which is equal to 424,276 sq. ft. ' 1- Determined composite runoff coefficient for the total area ' of 431,426 sq. ft., is 0.208 = 0.21 2- The length of basin (D) is equal to 500 feet sheet flow and ' 50' channel flow. 3- The average slope is 2.0% (S = 2.0%) ' 4- To determine time of concentration in minutes; TG = 1,_87 �1, 1 - CxCf)__D1�2 S!' J Where T(, = Time of Concentration, minutes. S = Slope of basin % =2.00% ' C = Rational Method Runoff Coefficient = 0.21. D = Length of Basin, 550 feet. (500 feet sheet flow & ' 50 feet channel flow. Cf = Frequency adjustment factor = 1.25 for 100 year storm. 1 Then Tc = 28.23 + 1.01 = 29.24 minutes. 12 [1 ' S- Determine precipitation in inches per house from figure (3- 1) Storm Drainage Design Manual, I100 = 4.22 inches/hour 6- Determine runoff quantity ' Q = CfCIA Where Q = Flow quantity, cfs A = Total are of basin = 9.90 acres ' Cf = Frequency adjustment factor = 1.25 C = Runoff coefficient = 0.21 ' I = Rainfall intensity = 4.22 inches/hour Then the runoff quantity for 100 year major storm for basin ' "B" under existing conditions is equal to: ' 0100 = 1.25 x 0.21 x 4.22 x 9.90 = 10.97 cfs ' SUB -BASIN "C" VII- Estimated runoff quantity "Q" in cfs, for 100 year major ' storm, under proposed conditions would be; ' Using the rational Method to determine runoff storm drainage criteria for 100 year major storm, the proposed conditions for sub -basin "C" are not changed from the historic conditions for ' the undeveloped area. The runoff coefficient for the undeveloped area will be the same as for the minor 2 year storm, which is as follows: The total area of basin "C" is 10,975 square feet, or 0.252 acre. The average slope for basin "C" is 3.33% (S = 3.33%). From table ' 3-2 for lawn with heavy soil, and more than 20 slope, the runoff coefficient is equal to 0.25. ' 1- The length of basin (D) is equal to.6O feet, which is all sheet flow. ' 2- The average slope is 3.33% (S = 3.33%) ' 3- To determine time of concentration in minutes; 13 Where Tc. = 1_87 (1.1 - CxC_r) D1/2 Sli 3 Tc = Time of Concentration, minutes. s = Slope of basin % =3.33% C = Rational Method Runoff Coefficient = 0.25. D = Length of Basin, 60 feet. Cf = Frequency adjustment factor = 1.25 for 100 year storm. Then Tc = 8.47 minutes. 4- Determine precipitation in inches per house from figure (3- 1) Storm Drainage Design Manual, I100 = 7.0 inches/hour 5- Determine runoff quantity Q = CfCIA Where Q = Flow quantity, cfs A = Total are of basin = 0.252 acres Cf = Frequency adjustment factor = 1.25 C = Runoff coefficient = 0.25 I = Rainfall intensity = 7.0 inches/hour Then the runoff quantity for 100 year major storm for basin "C" under proposed conditions is equal to: Q100 = 1.25 x 0.25 x 7.0 x 0.252 = 0.55 cfs 14 1 1 1 1 1 i 1 1 1 RUNOFF FLOW SUMMARY Sub -Basin "A" "B" "C" Total area (Ac) 6.83 9.90 0.252 Slope (S) 1.83% 2.0% 3.33% Lenqth of Basin (D) 600 550 60 Runoff Coef. 2yr 0.20 0.21 0.25 Undeveloped Runoff. Coef 100 yr 0.20 0.22 0.25 Developed Time of Concen. T. Historic 2 yr 33.20 31.89 8.26 Time of Concen. Tr, Proposed 100 yr 31.53 28.96 8.47 Time of Concen. T, Historic 100 yr 31.53 29.24 8.47 Precipe. 2yr in In/fir Existing 1.38 1.40 2.68 Precipe. 100 yr in in/hr Proposed 3.95 4.25 7.00 Precipe. 100 yr in in/hr existing 3.95 4.22 7.00 Runoff Q100 proposed Cfs 6.75 11.57 0.55 Runoff Q ,; Existing cfs 6.75 10.97 0.55 Allow. Rel. (Qi)cfs. 1.89 2.91 0.17 Diff. Q100 - QZ c f s 4.86 8.66 0.38 15 I 1 I 1 46JVIWVt.13'1 The entire site is divided into three sub -basins "A", "B" and "C". The allowable historical release rate for the minor 2 year rainstorm, for the entire site is equal = QZ = QA + QB + QC = 1.89 + 2.91 + 0.17 = 6.97 cfs. The total runoff for the 100 year major rainstorm for the proposed condition for the three sub - basins "A" "B", and "C" are = Q100 = QA + QB + QC = 6.75 + 11.57 + 0.55 = 18.87 cfs. The total runoff for. the 100 year major rainstorm for the existing conditions for the three sub -basins "A", "B", and "C" are = Q100 = QA + QB + QC = 6.75 + 10.97 + 0.55 = 18.27 cfs. The total difference between the major storm runoff (Q100) for the proposed conditions and the existing conditions for the entire site is equal to = 0.60 cfs. A 100 year flood cover the middle third of the property, according to the Major Drainage -way Plan of West Vine Drainage Basin. The high water elevation in the 100 year flood at the site is 5,048.00. DISCUSSION 1- No other off site runoff is entering the proposed developed and the undeveloped areas, not including the 100 year flood. 2- The drainage characteristics of two sub -basins "A" and "C" will not change between the existing and the proposed conditions. The third sub -basin "B" has a slight change in the drainage characteristics as follows: ' UNDER HISTORICAL CONDITIONS The total area of basin "B" is 431,426 sq. ft., or 9.90 acres. ' The average slope of basin "B" is 2.0% (S = 2.0%). The total undeveloped area is equal to 424,276 sq.ft. The area of an existing house is equal to 1,500 sq. ft. The area of an existing barn is equal to 1,650 sq. ft. The area of the existing gravel road entrance is 2,400 sq. ft. 16 I h 1 1 The area of the existing parking lot between the old house and the barn is 1,600 sq. ft. Then the total developed area is equal to 7,150 sq.ft. The composite runoff coefficient is equal to 0.21 Then the runoff quantity for 100 year major storm for basin "B" under existing conditions is equal to Q100 = 10.97 cfs UNDER DEVELOPED CONDITIONS The total area of basin "B" is 431,426 square feet, or 9.90 acres The average slope for basin "B" is 2.0% (S = 2.0%). The total undeveloped area is equal to 415,068 sq. ft. The area of an existing house is equal to 1,500 sq. ft. The area of a new home is equal to 1,800. The area of the new gravel road entrance with the cul-de-sac is 13,058 sq. ft. Then the total developed area is equal to 16,358 sq. ft. The composite runoff coefficient is equal to 0.22. Then the runoff quantity for 100 year major storm for basin "B" under proposed conditions is equal to Q100 = 11.57 cfs. As shown above the difference.between the 100 year major rainstorm for the existing and proposed conditions is equal to 11.57 - 10.97 = 0.60 cfs, which is a minimal amount for the total area of sub -basin "B". 17 I t WIND AND RAINFALL EROSION CONTROL DURING CONSTRUCTION INTRODUCTION Schmidtberger Minor Subdivision is to divide the parcel into two lots. The total area involved in this drainage and erosion control study is 738,755 square feet or 16.9595 acres gross. The new proposed lot, which is 1.6405 acres, is located Southeast of Larimer Canal # 2• The new lot will have a single family house. The second lot which is 15.319 acres will remain the same without change except removing the old barn. The existing developed area is equal to 7,150 sq.ft. The total proposed developed area is equal to 16,358 sq. ft. The total proposed area to be under construction, which is the difference between the historic developed area and the proposed one, is equal to 9,208 square feet, which is about one percent (1%) of the total area involved. If we assumed that during construction the area that is subject to erosion is doubled in size of the proposed developed site, then the subject area is equal to 18,416 square feet, which is a two percent (2%) of the total area. The property is part of Major Drainage -way Plan for West Vine Drainage Basin, the original natural drainage of the whole area is a sheet flow type drainage to the North and the Northeast. The two irrigation ditches are considered as a physical boundary to the pattern of the natural drainage. This results into dividing the property to three drainage basins. The boundary of tl7e ba:.ins are the Larimer County # 2 Canal and New Mercer Canal. The first sub -basin "A" is located to the Northeast of Larimer County Canal and has an area .of 6.625 acres. The second sub -basin "B" is located between the Larimer County # 2 Canal and New Mercer Canal, the basin area is equal to 9.904 acres. The third sub -basin "C" is very small basin, the total area is equal to 0.252 acres, which is located South of the New Mercer Canal and North of Laporte Avenue. EI] Sub -basins "A" and "C" are not developed, the sub -basins will stay undeveloped under the new proposed Minor subdivision. These basins are covered with local, native, and wild weed and grasses. There are irrigated landscaped lawn areas around the existing house and the barn, at the South portion of the property. Some scattered trees are present along the two irrigation ditches. The trees and the irriaation ditches could be considered as a wind and rainfall erosion barrier. The middle one third of the property is under 100 year flood, according to Major Drainage -way Plan of West. Vine Drainage Basin. The high water elevation in the 100 year flood at the site is 5,048.00. PROPOSED CONSTRUCTION The new pronesed construction includes a new residential house to be located in Lot 1, a new compacted gravel driveway with a cul- de-sac at the end, to connect the new house to Laporte Avenue as an access. The new plan also calls for removal of the existing barn. Landscaped area with grass and gravel will surround the new home and the driveway. LANDSCAPING It is proposed that gravel and irrigated lawn would be planted around the new house. All finished grades around the new and the existing homes should be sloped away from the structure on all sides to provide positive drainage. A minimum of one foot fall in the first ten feet is recommended. WIND AND RAINFALL EROSION CONTROL The entire site is in a moderate wind and rainfall erodibility zone. The undeveloped portion of the site is covered with local, native and wild grass, weed, and trees. The developed portion will be covered with sod, irrigated lawn and gravel. All runoff flows from the new house or the new road, will drain toward the Larimer County # Ditch to the Northeast. From the drainage study, the following information was obtained; 19 I Sub-hasin A: Area (Asl,,) = 6.825 acres Average Slope (Ssbl) = 1.83% Flow plat (Lsbl) = 600 feet ' Sub -basin B: Area (A,bj) = 9.094 acres Average Slope (Ssbl) = 2.0% Flow plat (Lsbl) = 550 feet ' Sub -basin C: Area (Asbl) = 0.252 acres Average Slope (Ssbl) = 3.33% Flow plat (Lsbl) = 60 feet 1 RAINFALL WIND ' Sub -basin A 100% moderate 100% moderate Sub -basin B 100% moderate 100% moderate Sub -basin C 100% moderate 100% moderate ' RAINFALL PERFORMANCE STANDARD ' Sub -basins: Lb = sum (Lsb x A b)/sum Asb _ (60Ox6.83 + 550x9.9 + 60x0.252)/16.96 ' = 564 feet Sb = sum (Lsb x A s,b) / sum Asb = (1.83x6.83 + 2.Ox9.9 + 3.33x.252)/16.96 = 1.95% IPerformanc,-, Standard = 80.55% ( from table 8-A) RAINFALL EROSION CONTROL PLAN The existing drainaqe pattern which is primarily sheet flow drains into the irrigation ditches, should channels form at the irrigation canal sediment traps should be installed around the ' formed drainage outlet falling into the irrigation ditches, which Will reducing any erosion effect. These sediment traps can be consisted of hay bales to be placed around drainage outlet to pre nt erosion and sediments from entering the irrigation ditches. 20 There is irrigated landscaped lawn around the existing house and the barn, at the South portion of the property. Landscaped area with grass and gravel will surround the new home building and the driveway. A strip of 20' x 20'x 6" deep of gravel or crushed rocks, to be laid on the driveway at Laporte Avenue during construction to prevent sediment and deposits from the work site onto Laporte Avenue. RAINFALL EROSION CONTROL EFFECTIVENESS EFF = (1 - C r. P) x 100 where EFF = Effectiveness M C = C-Factor (cover factor) P = P-Factor (Practice factor) Erosion Control C-Factor P-Factor Method Value Value Comment Established Grass 0.0375 1.00 75% cover Gravel Road 0.51 0.90 for B only Bare Soil 1.00 1.00 25* cover Sub -basin n Local. native and wild weed and grass = 75%x6.83 ac. = 5.12 ac. Bare around = 6.83 - 5.12 = 1.71 acres. Net C-Factor. _ (5.12 x 0.0375 + 1.71 x 1.00)/6.83 = 0.28 (grass) (bare gr.) Net P-Factor. _ (5.12 x 1.0 + 1.71 x 0.90)0.80.5/6.83 = 0.39 (bales)(basin) (I. -C x P) x 100 (1 - (0.28 x 0.39) x 100 89% 21 ' Sub -basin "B" ' Local, native and wild weed and grass = 75%x9.9 ac. = 7.43 ac. Bare ground = 9.9 - 7.43 = 2.47 acres. Gravel road = 3% x 9.9 = 0.297 acres. ' Remaining ground = 2.47 - 0.297 = 2.17 acres. Net C-Factor = (7.43x0.0375 + 0.297x0.51 + 2.17x1.0)/9.9 = 0.29 ' (grass) (roads) (bare gr.) Net ^r-Factor =(7.43x1.0+0.297x0.90+2.17x1.0)x0.8x0.5/9.9 = 0.40 ' (bales)(basin) ' EFFsiil = (I. -C x P) x 100 (1 - (0.29 x 0.40) x 100 88% Sub -basin "C" ' Local., native and wild weed and grass = 75%x0.252 ac. = 0.19 ac. Bare ground = 0.252 - o.19 = 0.06 acres. Net C-F=tctor_= (0.19x0.0375 + 0.06x1.00)/0.252 = 0.27 (grass) (bare gr.) + O.00x0.9)x0.8x0.5/0.252 = 0.39 (bales)(basin) EFFyI,,, _ ( ]. -C, x P ) x 100 (1 - (0.27 x 0.39) x 100 ' = 89% The riot UP value ('or the entire 16.9595 acres basin is ' calculated as follow, EFFif,,; = sum (Elf sb x A sb) /sum A sb ' = (89%x6.83 + 88%x19.9 + 89%x0.252)/16.96 = 89% ' Since the net EFF is greater than PS (89% > 80.55%), the proposed erosion control methods will meet the City of Fort Collins requirements. 22 WIND EROSION CONTROL PLAN Sub -basin "B" The existing developed area in sub -basin "B" is equal to 7,150 sq.ft. The total proposed developed area is equal to 16,358 sq. ft. The rest of the site is covered with local, native, and wild weed and grasses. Some scattered trees are present along the two irrigation ditches which will remain. The trees and the irrigation ditches could be considered as a wind and rainfall erosion barrier. Due to the historic sheet flow drainage only in the event channels form would sediment traps be installed around the existing drainage outlet fails into the irrigation ditches, which will reduce any additional erosion effect. These sediment traps can be consisted of hay bales to be placed around drainage outlet (as shown in the drainage plan) to prevent erosion and sediments from entering the irri.aation ditches. Since the total area under construction is relatively flat with a slight slope to the Northeast, and since the subject area is equal to 18,416 square feet, which is two percent (2%) of the total area, then no additional erosion control methods will be required. 23 ' RAINFALL PERFORMANCE STANDARD EVALUATION PROJECT: STANDARD FORMA Schmidtberger Minor Subdivision COMPLETED BY: Advanced Professional Eng Inc. DATE: 1/5/92 LO DEVEPED ERODIBILITY Asb Lsb Ssb Lb Sb PS SUBBAgIN ZONE (ac) (ft) M (feet) M M B moderate 9.904 550 2.00. 564 1.95 80.55 ' MAHf H 1991 8-14 DESIGN CRITERIA EFFECTIVENESS CALCULATIONS PROJECT: Schmidtberger Minor Subdivision STANDARD FORM B COMPLETED BY: Advanced Professional Eng Inc. DATE: 1/3/93 Erosion Control C-Factor P-Factor Method Value Value Comment Established grass 0.0375 1.00 75Zcover Gravel Road 0..51 0.90 in subbasin B Bare Soil 1.00 1.00 MAJOR PS SUB AREA BASIN (t) BASIN (Ac) CALCULATIONS Entire Grass Area 752 x 6.83 - 5.12 acres Site 80.55% A 6.83 Bare Ground - 6.83 - 5.12 - 1.71 so. WTD C-Factor-(0.0375x5.12 + 1.Oxl.71)/6.83 - 0.28 WTD P-Factor-(1.Ox5.12 + 0.9xl.71)/6.83xO.80 ----- ------ - 0.39, EFF. - (1-0.28x0.39) - 0.89 --------------------------------------------- B 9.0 Grass Area 75% x 9.9 - 7.43 ac Bare Ground - 9.9 - 7.43 - 2.47 ac. Gravel Road - 32 x 9.9 - 0.297 ac. Remaining Ground ■ 2.47 - 0.297 - 2.17 ac. WTD C-Factor-(7.43x.0375+.297x.52+2.17x1)/9. - 0.29 WTD P-Factor-(1.Ox7.43+0.9x2.47)/9.9 - 97.52 - 0.975x0.8Ox0.50 - 0.39 ----- ------ EFF - (1-0.29x0.39) - 0.88 ------------------------------------ ---------- C 0.252 Grass Area 752 x 0.252 - 0.19 so. Bare Ground - 0.252•- 0.19 ■ 0.06 so. WTD C-Factor m(0.0375x0.19 + 1.Ox0.06)/0.252 - 0.27 WTD P-Factor-(1x0.19+0.9x0.06)x0.Bx0.5/0.252 -0.39 Eff. - (1-0.27x0.39) - 0.89 Total 16.96 --------------------------------------------- -(0.89x6.83+0.88x9.9+0.89xO.252)/16.96 -0.89 -89Z Which is -greater than 80.55% MARCH 1991 6 15 DESIGN [RITCRI4 CONSTRUCTION SEQUENCE �ROJECT: Schmidtberger Minor Sub - STANDARD FORM C SEQUENCE FOR 19 93 ONLY COMPLETED By: Advanced Professional Eng DATEil/5/93 �ndicate by use of a bar line or symbols when erosion control measures will be installed. ajor modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. YEAR MONTH I A I M I J I J IA IS IO I. N I I I I GRADING IND EROSION CONTROL Soil Roughening Perimeter Barrier Additional Barriers Vegetative Methods Soil Sealant other RAINFALL EROSION CONTROL ' STRUCTURAL: Sediment Trap/Basin Inlet Filters ' Straw Barriers Silt Fence Barriers Sand Saga ' Bare Soil Preparation Contour Furrows Terracing Asphalt/Concrete Paving ' Other ' VEGETATIVE: Permanent Seed Planting Mulching/Sealant ' Temporary Seed Planting Sod Installation Nettinge/Mate/Blankets Other RUCTURESs INSTALLED BY owner I VEGETATION/MULCHING CONTRACTOR tTE SUBMITTED 1/7/93 MAINTAINED BY owner owner APPROVED BY CITY OF FORT COLLINS ON ' +++r -yi 1•?^.1 d 16 GE�IGN CRITERIA o U) C) m. N � rt� O rt Qrt O S s CO I?1 f • K n r! rrl C) O p 0 r • O0 O > 7 l^ N N S_ r,° 3z� mo l l rt n T O C /1 v � 7 K ^s l ' O z 0 C a 0 �rf`ci rr 1R ..we/. W 1/4 Comer Section 10, T 7N. R69 W Scale '1�=�6.0� \ Pound 1/20 near � xK N 0 4'45 W b259• q Of r SUB—BAS C RClear W s 0.252Ans at e a a.90 Y.aD �� 29 J Q1S B A N B er.r a 9 OCE I aa�llr C W 0.3s2See .� r yearep N MCSayIiYn1 8 oyal IN ll Aa far If CFIT z all •q I A mnw u emrc "e a Crt 1/4 Comer Section 10 (ECEND • 1/2• neaw Nu• for1110Tu W 0 MNw mnm • I sN Ill labs A/ cm 1010 • turfor polar m a line radial conloun — -- proposed =onaury, sue Ill A [-7 ie Bosh B C� sd eaem C �.. IN nood El•w4m as W W NnOe BraMaY•WOY Plm Boundary for propaead SIB-0aaFe BonMmort HE Bor BN1 EYdydrmt 4 canna i.NoNe a Taft HIII elewtlm at 50112.40 i'e0 DRAINAGE PLAN for SCHMIDTBERGER SUBDIVISIOwhere- far "ll wher N oDyoW. w ewes (ro«..eA �+«aa I^wr+ yeaJ aw3 e \� \ 5 00.12.w" E 1323.nr — __/ )'&u W Stab Stmu . v / 11'Mw1ln�um a.Pm •... BNuetn � BekS STRAW BALE DIKE N�•a0' CHANNEL APPLICATION n •. oener*aiti, 1. µ flu, p.,anne"maiunmeun amity all,it Impact 10 0.25 acres per 100 3BWY)IIIM F,rmaud fide �clamar, ene,eplace 2 �� Ba► aryl the recall *net each Y1aYd Art 3. • ced after 12 molW Ename D �ewo br tinge nr Be1BY me r�,u III eI RWar 1r�il I cFAj*4sG.2wwew i 1 �. R1MbP nnW awNaltr A B c 918 BA9N Tom Pr•e (AC) aaa I.YD am Sate (s) 1.a]x 20.x a.aax wroa or slain (D) aoo 'Ao w Rs1eW CON. )y an am an shelter caN. IN W 0.21) an a.YS T1m of Cme VeiM Try Hmalc 2Y U." 211.1110 a.Y r M. of Donmt j Te Prwwee IN by afm 20.Ye 11.47 mme of loncminapn T, Hmmk IN F. ' IM 20.N e.47 I-� Preal) 2Y by Mn«/Tr EVMIF9 l.w 1.40 zu Preal IN Orlady"lr orpha 3.0 A2a 7.00 beaelp IN F Fdw/M aabtFO 3.ES 4.0 9.00 _"OR ales M ab Ill11.5) G." W Ole G !F9 Na 0.)3 10.117 a55 W IN (02 ) 1 Lea 191 0.44' DIN over Oa ah ♦M W am 4r show Bab S.r+loth 2 sulyq Bala all A e! Tr'"ne Bil Than STRAW BALE DIKE GENERAL INSTALLATION Gene jilKII1W Al r I Iropecl, ragas ens replace, ! (111u[nwryl the MISS alai each I I 2. little of man by replaced ever 12 Imo. Myr unleu approval la wanted by I 1 1N Enprm Inp wby bwn for anger u +, d d. o' �aa A BAN YIYW I RI SCHMIDTBERGER SUBDIVISION Part of the NW 1/4 Section 10, Township 7 North, Range 69 West of the 6th P.M.,City of Fort Collins, Larimer County, Colorado. W 1/4 Corner Section 10, T 7N, R69 W Found 1/2• rebor 16T won' 20 w 1' ,' II 8 Crt 1/4 Corner Section 10 1 a AIII)Mw S Cl SCHMIDTBERGE SUBDIVISION fire hydrant GRAPHIC SCALE (q pain ) IW—b R /// rand 1rr new drew wp to At 1/4 aan s rsyu ro31>o w �2 C� �w $8 x rov4.4e• w acres, lestwo N 0m0rW w eae.ae (Moral i4 \90'071uTY r s\—N new �a I ��. _ � w_ / au°ai zn� Feand 1/Y lees no cap 1 a r3aa, not, pa iarlmei ra z'{�x / � Hye S01 J Me w..nse y, 1 r count ak ]34 pope '/ zepert It ew �4Res over a'q, \\ 2W Utility Easement / o �\ �"4 olwwy \ / overlie postal\ NI MT 71430.0690 sq ti.. 1.6403 Acres 305e.er Eawn —rr so I swx,'4J's w24 s . e Wa 11F w \ LEGEND Seams 4 N 1/2' now w lo- Cap gaz40 w .0www en W 1/2' .war e/ pap Imw Ton xm seas \ %/ wmha point m a In, 'r M _ Lot 2 / 15.319 A res gross odor A 9aoe 1313 P", .1Q} Leon. Ccunlr S 001T00' E 1323.22' CURVE DATA FOR ROAD OWNER: Ernest M. and Ktlalen K. Schmidtberger- ©n-a4-4a'z3' 825 Grouse Cr. R - moo' T . 9.50' Fort Collins. CO 80524 L - 1613' 490-1710 1` ENGINEER Advanced Professional EngineeringMa R - zs.ar P.O. Box 1391 1391 T- Fort Collins, CO 80522 L - 28za.2Tzz 484-0533 ©a _ 6451FIT ZONING: R-L-P Low Density Planned Residential - 30. W'tlal T - late' L - 34.W DATE: Sept. 15, 1992 BEARINGS & DISTANCES FOR LARIMER COUNTY CANAL /_�z1NK7Ff M9-% ➢ [ L e' �Nffwj 17 .�lr .fi^�IIiG-SII7i1 r. NEW MERCER CANAL BEARINGS & DISTANCES FOR K 1 N 88 37'310 W 1 104 Ad! L I N 75 04'49- W 1 28,85- M 7'58- W 48.26' N N 76 12'01- W 1 148.15 8 f CERTIFICATION OF OWNERSHIP Know all men by these presents that Ernest M. and Kristen K. Schmidtberaer belno the of the NW 1/4 of to the Point of Beginning. Said Parcel contains 16.9595 acres more less gross. SUBJECT to all RIGHTS OF WAY, EASEMENTS and RESTRICTIONS as now in use or of record. have cahsed the same to be surveyed and subdivided into Iota, tracts, And private drives as shown on this plat to be known as Schmidtber9er Subdivision and is su=t to all easements as shown on this plat, and does hereby dedicated and convey to the City of Fort Col ns, Colorado, forever hereafter, the easements as are laid out and designated on this lat, rovided, however, that acceptance b the City of this scion [an of easements does not impose upon ythe City a duty to m4intain the a seine t so dedlcateQy Witness our hand and seals this �t—duy of a I' A.D., 199._ 1Ii 5r mess, cm i erie Kristen K 5. 5&midtNrgff NOTARY State of Colorado County o/ Larimer)) ____//��rl.V� day of., A.D. 19 � by Eland Kristen c erger My Commission expires r,,i 2'ai., / 1. R otary ubllc repro or Notmy F+ rT.Cc iN.rl1 8 SURVEYOR CERRFlCATE I, Joseph Surprenant A dui re isteretl land surv< r in the State of Colorado, do hereby carilfy hat this plat of Shmidtberger Subdivision truly and correctly represents the results of a survey made by me or under my direct supervision. Jo son A. SuWrenant Colorado Reg. LS. 10740 ATTORNEiY'S CERTIFICATE This Is to certify that on the day of 19_, 1 examined the title to the properly as described hereon and established that the owners and proprietors of record of the said property as construced In C.R.S. 1973. 31-23-111, are as shown herein as of said dote. I , , , . ('i,4.�=n,lL�. Fi,,n v12 rotor I Attorney cap Address Registration No. J`A c. t- APPROVED AS TO FORM Appravedas to form by the Director of Engineering of the City of Fart Collins, Colorado on —day of A.D. 19 I �„yam:ln�y APPROVE4 Apd by the Planning Director of th Cit of ForI CaPins, Colorado on the 14TA day of i City Clerk Planning Director LIEN ER Citizen imina Co a Cerromee rarmmUnn NOTARY Spore a"moo CoaMy of Lorimar —� Y of " AD. B by David W. Shafer MY co mission —expires � , ofary P bC 4daress