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Home My WebLink About20130043.tiffPreliminary Drainage, Erosion/Sediment Control and Water Quality Report For Baldridge P.U.D., First Filing, First Replat Weld County (Longmont), Colorado 0 Prepared for: Mountain View Fire Protection District 9119 County Line Road Longmont, Colorado 80501 Prepared by: SHEAR ENGINEERING CORPORATION Project No: 2608-04-12 Date: July, 2012 4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 Fax (970) 282-0311 www.shearcngineering.com "I hereby certi First Filing, with the pr at this report for the preliminary drainage design of "Baldridge P.U.D., Replat" was prepared by me (or under my direct supervision) in accordance ions of the W County storm drainage criteria for the owners thereof." Brian ' . Shear, P.E. Registered Professiongineer State of Colorado No: 20262 � O REG/6,4,, ',, . `�•20262� s`" t YY�Y„ uy.J 4836 S. College. Suite 12 Ft. Collins, CO 80525 (970) 226-5334 Fax (970) 282-0311 www.shearengineering.com r 0_ Q 5 >- I- 2 0 NOT TO SCALE TABLE OF CONTENTS Title Page Engineer's Statement Vicinity Map Table of Contents I. INTRODUCTION: 1 II. GENERAL LOCATION AND DESCRIPTION 1 A. Property location 1 B. Description of Property 1 C. 2 III. DRAINAGE BASINS AND SUB -BASINS 2 A. Major Basin Description 2 B. Sub -Basin Description 3 C. Historic Conditions 3 IV. DRAINAGE DESIGN CRITERIA S A. Regulations 5 B. Development Criteria Reference and Constraints 5 C. Hydrological Criteria 6 D. Hydraulic Criteria 6 V. DRAINAGE FACILITY DESIGN 6 A. General Concept 6 B. Specific Details — Runoff 7 C. Specific Details — Detention 7 VI. WATER QUALITY 9 A. General Concept 9 VII. EROSION CONTROL 10 A. General Concept 10 B. Specific Details 10 VIII. CONCLUSIONS 10 A. Compliance with Standards 10 B. Drainage Concept 10 IX. REFERENCES 11 Appendices APPENDIX I Runoff Detention APPENDIX II Table 3-4 — One Hour Point Rainfall of the WCSDC Table RO-3, Recommended Percentage Imperviousness Values, USDCM Section 2.1 Rational Formula, USDCM Section 3.2.3 Rational Formula -Based Modified FAA Procedure, USDCM Section 3.4.3.1 Orifices, USDCM Figure RA -15 Rainfall Intensity -Duration Curves, USDCM FIRM (Flood Insurance Rate Map) Community Panel Number 080266-0850-C (Panel 495 of 1075); Map Revised September 28, 1982. CertainTeed C900-RJ Dimensions APPENDIX Ill 1984 Historic Drainage Plan by Nelson Engineers Existing Conditions and Demolition Plan (for historic conditions and historic drainage data) Drainage Plan Erosion/ Sediment Control and Water Quality Plan Drainage, Erosion Control and Water Quality Details Page 1 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado I. INTRODUCTION: This report presents the pertinent data, methods, assumptions, and references used in analyzing and preparing the preliminary Drainage, Erosion/Sediment Control and Water Quality design for "Baldridge P.U.D., First Filing, First Replat". The site is currently developed with an existing detention pond located in the northeast corner of the site. No previous drainage reports were located in Weld County records or provided by Weld County personnel. The area of development consists of approximately 4.51 acres according to the final plat for Baldridge P.U.D., First Filing. Detention pond design with this project accommodates the existing 4.00 acre area tributary to the pond for this redevelopment only. Future potential development of the property to the west will require additional drainage studies and improvements to accommodate the potential development. II. GENERAL LOCATION AND DESCRIPTION A. Property location 1. Baldridge P.U.D., First Filing, First Replat is located in the South one-half (1/2) of Section 5 and North one-half (1/2) of Section 8, Township 2 North, Range 68 West of the 6th P.M., County of Weld, State of Colorado. 2. The property is bounded on the South by Vista View Drive, on the East by Weld County Road 5, on the North by Colorado State Highway No. 119, and on the West by Vista View Commercial Center Filing 1. 3. There are no major open channels, lakes, streams, irrigation or other water resource facilities within or adjacent to the proposed development. 4. Refer to the vicinity map located near the beginning of this report. B. Description of Property 1. Baldridge P.U.D., First Filing, First Replat has a platted area of approximately 4.51 acres. 2. The site was initially developed in 1984 according to Weld County Assessor records and included an existing 5,400 square foot Morton Building. The Morton Building was built in 1984 according to Weld County records and Morton Buildings, Inc. records. Page 2 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado 3. The site was redeveloped in 1991 by Donald and Adele Baldridge for Universal Transport, Inc. The 1991 redevelopment included the addition of a detention pond in the northeast corner of the site. There are no records of the 1991 drainage report. The 1991 Drainage and Landscaping Plan by Nelson Engineers is included with this report for immediate reference. 4. Existing developed site groundcover consists of approximately 79 percent gravel, 3 percent roof area, 1 percent concrete, and 17 percent turf. 5. There are no major open channels within or adjacent to the site. 6. The project is a replat of Lot 1, Baldridge P.U.D., First Filing and will create two (2) lots. The site will continue as a commercial use. Lot 1 will be a 2.04 acre lot and will be redeveloped as a fire station by the Mountain View Fire Protection District. Redevelopment will consist primarily of adding a parking lot and expanding the detention pond. Lot 2 will be a 2.47 acre lot and will remain primarily in its current condition as a gravel covered area. Lot 2 may redevelop in the future. III. DRAINAGE BASINS AND SUB -BASINS A. Major Basin Description 1. Weld County does not have any master drainage planning or delineated basins for this area. 2. City of Longmont does not have any master drainage planning or delineated basins for this area. 3. The Baldridge P.U.D., First Filing, First Replat site contains one single major basin and no sub -basins. The major basin area is approximately 3.96 acres. The basin area changes slightly with the redevelopment of the site due to the new access drives being provided on Weld County Road 5 and Vista View Drive. 4. Baldridge P.U.D., First Filing, First Replat is not within a defined FEMA floodplain. Reference FIRM (Flood Insurance Rate Map) Community Panel number 080266-0850-C (Panel 850 of 1075; Map Revised September 28, 1982). Page 3 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado Irk B. Sub -Basin Description 1. The Baldridge primary Basin is a sub -basin to the primary undefined drainage basin for the immediate area. 2. There are no sub -basins currently defined within the main Baldridge basin. Future development of Lot 2 may define additional sub -basins for future detention pond volume requirements. C. Historic Conditions 1. Pre -development historic conditions prior to the 1984 construction of the existing building were not researched with this report. Historic conditions presented here include current site developed conditions only. No previous drainage reports were located in Weld County records. 2. The existing terrain slopes from the northwest to the southeast at an average grade of 1.75%. Site runoff flows overland to an existing detention pond located at the northeast corner of the site. 3. The 4.00 acre drainage basin is 83 percent impervious, consisting of approximately 79 percent gravel, 3 percent roof area, and 1 percent concrete. a. The actual existing basin area was not well defined on the Baldridge Subdivision, First Filing Drainage and Landscaping Plan by Nelson Engineers. The basin area was defined based on a topographic and improvement survey for the site by Intermill Land Surveying (Loveland). 4. With an existing weighted runoff coefficient of 0.39, the peak flow of the 4 acre basin is approximately 10.93 cubic feet per second (cfs) based on the 100 -year storm criterion and a rainfall intensity of 7 inches per hour based on the Figure RA- 15 Rainfall Intensity -Duration Curves of the USDCM. 5. Refer to Appendix I- Runoff for all related runoff calculations and specifications. 6. The existing detention pond is approximately 7,151.56 square feet and detains a volume of approximately 5,913.50 cubic feet, summarized in the following stage -storage summary: Page 4 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat: Weld County (Longmont), Colorado STAGE - STORAGE SUMMARY Elevation Area Cumml Avg Vol Cumml Conic (ft.) (sf) (cubic feet) Volume ******* ******* ********* ********* 4895.9 0.08 0 0 4896.0 712.07 39.17 26.38 4897.0 4973.88 2882.14 2549.01 4897.5 7151.56 5913.50 5563.95 7. The existing detention pond outlet structure consists of a 4'x4' concrete box with a two stage release. The top of the box elevation is 4898.36. The existing grade of the berm immediately east of the outlet structure is set at elevation 4897.80. a. Note that stormwater overflows the berm (4897.80) to the east prior to entering the top of the existing outlet structure (4898.36). 8. The existing detention pond outlet structure restricts the release from the pond with a 4" PVC orifice opening (as verified in the field). The original drainage plan by Nelson Engineers specified a 3 5/8" orifice opening. Based on the actual existing 4" PVC orifice opening and a total detention pond outlet structure head of 2.3 feet (measured from the centroid of the opening to the top of the existing outlet structure), the restricted release rate is calculated to be 0.67 cfs. 9. There is an existing 8" PVC outlet pipe at the back (east) of the existing outfall structure that conveys additional runoff from the site that drops over the top of the existing outfall structure. All runoff exits this pipe to an existing rip rap bed to Weld County Road 5 and ultimately to the intersection of State Highway 119 and Weld County Road 5. The maximum discharge from the site is 4.78 cfs based on the capacity of the 8" PVC pipe for a hydraulic grade line slope of 13%. A manning's coefficient of 0.012 was assumed. 10. No water quality devices were provided with the original detention pond. 11. Refer to Appendix I- Runoff for all related calculations. 12. Refer to the following plans in the stuffer envelope in the back of this report: • Baldridge Subdivision, First Filing Drainage and Landscaping Plan; Nelson Engineers (Greeley, Colorado); March, 1991 • Existing Conditions and Demolition Plan (for historic conditions and historic drainage data) Page 5 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado IV. DRAINAGE DESIGN CRITERIA A. Regulations 1. Design criteria from the Weld County Storm Drainage Criteria Addendum to the Urban Storm Drainage Criteria Manuals Volumes 1. 2 and 3. October 2006 (WCSDC) and the Urban Storm Drainage Criteria Manuals Volumes 1. 2 and 3 (USDCM) were utilized. B. Development Criteria Reference and Constraints 1. No previous drainage reports were located in Weld County records or provided by Weld County personnel. All previous drainage concepts were taken from the Baldridge Subdivision, First Filing Drainage and Landscaping Plan; Nelson Engineers (Greeley, Colorado); March, 1991. 2. Generally, any additional development within the site will not redefine grades along the property boundaries. a. Colorado State Highway 119 exists to the north. A fifteen foot (15') utility easement is adjacent to the Colorado State Highway 119 south right-of-way. There is a drainage channel defined between the north side of the existing detention pond and the north boundary of the site. a. Weld County Road 5 exists to the east. Weld County Road 5 is paved. Weld County personnel have advised that there is little likelihood for Weld County Road 5 to widen. i. A fifteen foot (15') utility easement is adjacent to the Weld County Road 5 west right-of-way with existing electric facilities located within the easement. ii. Existing side road drainage swale and culverts will be maintained. b. Vista View Drive exists to the south. Vista View Drive is paved. i. A fifteen foot (15') utility easement is adjacent to the Vista View Drive north right-of-way. ii. Existing side road drainage swale and culverts will be maintained. p 3. Existing improvements on site will be maintained including the existing building, sanitary sewer service facilities (manhole and grease trap), electric facilities including a large vault, the detention pond outlet structure, and an existing gas service line. Page 6 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing. First Replat: Weld County (Longmont), Colorado 4. The primary design constraint was the existing detention pond outlet structure. The structure will remain and structure release components will continue to be utilized. C. Hydrological Criteria 1. Table 3.4 of the Weld County Strom Drainage Criteria October 2006 will be used to determine design rainfall amounts. One -hour point rainfall for 100 - year storm criteria is 2.78 inches. 2. Rational Method - The Rational Method will be used to determine peak runoff rates for the site for the sizing of detention pond volumes. a. Percentage imperviousness values were taken from Table RO-3, Recommended Percentage Imperviousness Values (See Appendix II). b. Runoff calculations were completed using the Rational Formula defined in Section 2.1 of the USDCM. D. Hydraulic Criteria 1. EPA SWMM 5 — EPA SWMM 5 will be used to route the CUHP hydrograph through the detention pond system. This model was chosen for its ability to model storage and to implement a variable head discharge curve as required by the WCSDC. 2. Pond discharge pipe capacities are based on the Manning's Equation. Pipe capacities will be determined using Flowmaster by Haestad Methods software. 3. The detention pond will consist of an outlet that will be composed of an existing outlet structure with a proposed water quality structure and a WQCV restrictor plate at the back of the front wall of the proposed water quality structure. There is a well -screen and frame at the front of the proposed water quality structure. V. DRAINAGE FACILITY DESIGN A. General Concept 1. The storm drainage systems are designed to safely convey the 100 -year storm event runoff by sheet flow regimes over concrete and vegetation across the site to the detention pond located in the northeast corner of the site. Page 7 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado Oft a. The detention pond will attenuate the developed condition 100 -year storm event runoff down to actual release rate determined for the existing detention pond structure release components. B. Specific Details — Runoff 1. The Rational Method was used to determine peak runoff rate for the 100 - year storm event for the entire 4.51 acre site. Please see the hydrology summary table and the hand calculations in the runoff section of Appendix I for the peak discharges of the basin within the project site. 2. The impervious calculations based on land use are included for the basin in Appendix I. a. Figure RO-3 of the USDCM was referred to compute percentage imperviousness for the site. 3. There is no off -site runoff conveyed through the site. a. Design point 1 is located at the detention pond outlet structure. r detention pond outlet structure. 4. Runoff from basin A is conveyed by sheet flow to design point 1 at the a. A total of 10.93 cfs is conveyed to the existing detention pond in the 100 -year storm event for historic conditions (as the site is currently developed). b. A total of 11.65 cfs is conveyed to the detention pond in the 100 -year storm event after site modifications are made with this project for the Mountain View Fire Protection District. c. The 0.72 cfs increase from the existing pond discharge is due to an increase in composite runoff coefficient from .39 to .42 primarily as a result of the addition of parking lot pavement. C. Specific Details — Detention 1. The detention pond is sized and will be expanded to accommodate on those developed conditions resulting after redevelopment of the site with this project only. The detention pond will not accommodate ultimate development of Lot 2. 2. Please refer to Historic Conditions of this report for detailed discussion concerning the existing detention pond and existing outlet structure. Because the existing outlet structure is not being modified (except for the water quality modification), some discussion will be repetitive. Page 8 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing. First Replat; Weld County (Longmont), Colorado 3. The detention pond outlet works will consist of the existing outlet structure box including orifice and discharge pipe and slight modification to the east berm to define an emergency overflow weir at an elevation higher than the elevation of the top of the detention pond outlet structure. a. The pond outlet structure will consist of the existing 4x4 outlet structure with a new water quality structure placed just west of the existing 4x4 outlet structure orifice. b. The top of the box elevation is 4898.36. This elevation was utilized as the 100 -year water surface elevation for purposes of establishing actual detention volume requirements. c. The actual detention pond release is restricted to 0.67 cfs with the existing 4" PVC orifice opening. d. The existing 8" PVC outlet pipe at the back (east) of the existing outfall structure will convey additional runoff from the site that drops over the top of the existing outfall structure. The maximum discharge from the site is 4.78 cfs based on the capacity of the 8" PVC pipe for a hydraulic grade line slope of 13%. A manning's coefficient of 0.012 was assumed. e. A portion of the existing berm on the east and the north sides of the existing detention pond will be slightly modified to the raise the berm to an elevation higher than the elevation of the top of the outlet strucutre box and to define an emergency overflow weir. The emergency overflow weir for the pond will have a crest length of 110 feet and a crest elevation set at 4898.50. Freeboard is provided up to elevation 4899.00. f. A new water quality restrictor plate will be provided at the back of the front wall of the proposed water quality structure. There will be a well - screen and frame at the front of the proposed water quality structure. The top of the water quality box is set at the required water quality surface elevation of 4896.90. g. There is existing riprap that was provided for the overflow weir bank. h. Please see the detail of the outlet on the construction plans. 4. The detention pond attains a maximum 100 -year water surface elevation of 4898.36. The required storage volume at this elevation is 24,347 cubic feet, summarized in the following stage storage summary: Page 9 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado STAGE - STORAGE SUMMARY Elevation Area Cumml Avg Vol Cumml Conic (ft.) (sf) (cubic feet) Volume ******* ******* ********* ********* 4895.89 2.88 0 0 4896.00 359.26 19.92 14.4577 4896.50 6433.87 1718.2 1400.04 4897.00 11479.61 6196.57 5817.96 4898.00 14225.92 19049.33 18646.21 4898.36 15204.44 24346.80 23942.7 5. Please see all of the detention design data in the detention section of Appendix I. VI. WATER QUALITY A. General Concept 1. The existing detention pond will serve as a siltation pond during overlot grading operations and sitework improvements. 2. Runoff is designed to flow as long as possible in sheet flow regimes over concrete and vegetation across the site promoting scrubbing of sediment and pollutants. a. Construction BMP's will consist of: i. Gravel vehicle tracking control pad at the proposed Weld County Road 5 entry to the site. ii. Wattles in the channels, area inlet and a detention pond outlet structure. iii. Surface roughening and re -vegetation. iv. Silt fence, preventing sediment in runoff leaving the site immediately bordering the extent. v. The detention pond will act as a sediment basin during overlot grading operations and sitework improvements. Page 10 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado VII. EROSION CONTROL A. General Concept 1. Erosion control will minimize the amount of sediment being transported from the site during and after construction. B. Specific Details 1. During construction, wattles will be placed along channel inverts and at the entrances to culverts to minimize the propagation of sedimentation prior to finished grading and landscaping being installed. 2. During construction, a riprap pad will be placed at the detention and water quality pond preventing erosion from flow discharges. 3. Silt fence will be installed all along the northerly and easterly edge of the Project site. 4. Permanent re -vegetation will be required for all disturbed earth. Please see the re -vegetation notes and seeding schedule on sheet 9 of 12 of the construction drawings titled "Erosion / Sediment Control and Water Quality Plan". This plan is also included in Appendix III of this report. VIII. CONCLUSIONS A. Compliance with Standards 1. The grading and drainage design for the Baldridge P.U.D., First Filing, First Replat will comply with the requirements of the Weld County Storm Drainage Criteria Addendum to the Urban Storm Drainage Criteria Manuals Volumes 1, 2 and 3, October 2006 (WCSDC). 2. All erosion control measures will comply with the Weld County Storm Drainage Criteria Addendum to the Urban Storm Drainage Criteria Manuals Volumes 1, 2 and 3, October 2006 (WCSDC) and generally accepted erosion control practices. B. Drainage Concept 1. The drainage design for Baldridge P.U.D., First Filing, First Replat will be adequate to safely convey onsite and offsite flows through the development. Page 1 1 Preliminary Drainage, Erosion/Sediment Control and Water Quality Report Baldridge P.U.D., First Filing, First Replat; Weld County (Longmont), Colorado IX. REFERENCES A. Weld County Storm Drainage Criteria Addendum to the Urban Storm Drainage Criteria Manuals Volumes 1.2 and 3. October 2006. B. Urban Storm Drainage Criteria Manual Volume 1; Urban Drainage and Flood Control District, Denver, Colorado. C. Urban Storm Drainage Criteria Manual Volume 2; Urban Drainage and Flood Control District, Denver, Colorado. D. Urban Storm Drainage Criteria Manual Volume 3, Best Management Practices; Urban Drainage and Flood Control District, Denver, Colorado. E. Baldridge Subdivision, First Filing Drainage and Landscaping Plan; Nelson Engineers (Greeley, Colorado); March, 1991 r APPENDIX I Runoff Detention r Runoff giof Coefficient- Calcuial•ors proud Cover .r. yarn Area,(S F) °/p lvr1 p61)1oUS 3$,5140-.(92_ WO ex istihq Cafes' impeYV/ays 4rea(5F) ,119. 0105 g��id'k19 5A30W `?) 5, 321 .i139 CoriOtt e h5V.12 .11 •12 -41(1q Turf 28, S2,2-- IS 20 i�mverVi ous arc.& Cweigh�ed t&tcu OS a e_DL a G21 -,g32./11.12 sv. I �l, 38(0. 05 Se -6o1,a,) impervious. 2. .41/i 2 0 39 �= o•39 Ac_ A1.o03W OLres L - -t.o inches/hour ( ioo\ ) Q-• CIA Co • 3Q) incinih() (Ai•DoVi acres i _ 10 .q3 CfS 25 Lnc h%hr 6 N N, ) cu1ta on16)z.ctiA =co•3a)(a•ZstnlhY)Czs,003li Ort-�1c2 �I o W C.� 1(.0. (� �1 c�s� � � ��' OutkX d Wa11 •t'h.m(rtCri A0 4 �i •$`� 2 3X13'') = q.l1 " 1rw.ox aim -nob( Q' 11' _ Tr (4_,)2- Tr(.1 u) Z _ l3.29 tih2 2- 100y - Dior o e1aU¢oo� i,on 1orr. of �, P c4tinou� ldio.hka4iy?(11Fcer-1.// 11 C° pLQ 0.0 9 2 -F -k 2- �' Q' co 2-9 Ho ` Co•(D)(0.09szK2-•3 rwf Proposed ,e Coect /rood Cooed _ Area ar) o5 (AI Proposed CCUcc °f(' kit) Arc (iF) Ai z, 2_•zco --4-53.1-• oft 15,10G•3(0 '4 438to• 30 91 0,1449-.09 ,�{S,�3q•�q 2-� 910 -•q98 Cwciglded vrnlperu . axca bum axeck c 1-3083.605 sE__. t'-c•1r 3 VP, o S S F tort(LQ.- lm h 13, I b 3. tQ S' . oced peaK r1-006 CCU CakaM Oh 3 9toogres -k/' .O nc.lvsihur Ctoogr G? •cLl\ (0•U2,)(1-•0 tinlhr)(39(204�)= I•�pc s I0ov\r 4.2S trdre/hour ( tow.) Ct o - (0.42)(At• tnivir) (3.9acf(F\ i-.oICfs lower r Detention pt 00 00 ) J (D CN [O ) l ) U) tr) CO _z 3 ) .. ) 0!' J Z a. to En S../ l\ 00 • o o, i \ _ / v NcCQ. / m �._ 0 cp 0 , E1.o 6. v ��' ay a.r 0 aL -0 C1 cc 0 I •o 0 0 U CO N W re') M Lr) .- ui (Y p 0 nn N 00 1O N In m 0 11 0I _ n N N J a O 5 "51 m a) LO' O N) / • / / 0/ 0 C 7O 0 om a / O) co D'• O U K EkiEREtl JUL Q 4 P tmp#1.txt #units=Elevation,ft,Area,ft2,volume,ft3,volume,ft3 # Elev Area Cumml Avg Cumml Conic # ft ft2 ft3 ft3 4897.5000 7151.5615 5913.5019 5563.9451 4897.0000 4973.8817 2882.1412 2549.0139 4896.0000 712.0651 39.1678 26.3823 4895.8900 0.0764 0.0000 0.0000qi r P Page 1 m m a • �JyT 7A f�'•7� M/ S �0, 1 AINQQ3 ��.LL la 41 Pc I; r /2"eoPe),swz, Po iva +—• 3 8fA544./e tmp#4.txt #units=Elevation,ft,Area,ft2,Volume,ft3,volume,ft3 # Elev Area cumml Avg Cumml Conic # ft ft2 ft3 ft3 4898.3600 15204.4429 24346.8003 23942.6966 4898.0000 14225.9243 19049.3342 18646.2069 4897.0000 11479.6088 6196.5677 5817.9613 4896.5000 6433.8658 1718.1990 1400.0350 4896.0000 359.2597 19.9176 14.4577 4895.8900 2.8793 0.0000 0.0000 Page 1 Ow J Worksheet for Circular Pipe - 9 Project Description Friction Method Solve For Input Data Roughness Coefficient Channel Slope Normal Depth Diameter Discharge Results Discharge Normal Depth Flow Area Wetted Perimeter Top Width Critical Depth Percent Full Critical Slope Velocity Velocity Head Specific Energy Froude Number Maximum Discharge Discharge Full Slope Full Flow Type GVF Input Data Downstream Depth Length Number Of Steps Manning Formula Full Flow Capacity SubCritical 0.012 0.13000 ft/ft 0.67 ft 0.67 ft 4.78 ft'/s 4.78 ft'/s 0.67 ft 0.35 ft2 2.10 ft 0.00 ft 0.67 ft 100.0 0.12501 ft/ft 13.57 ft/s 2.86 ft 3.53 ft 0.00 5.15 ft'/s 4.78 ft'/s 0.13000 ft/ft 0.00 ft 0.00 ft 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headless 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 100.00 Bentley Systems, Inc. Haeslad Methods Solution Center Bentley FlowMaster 108.01.071.00) 81312012 10:38:27 AM 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755.1666 Page 1 of 2 Worksheet for Circular Pipe - T GVF Output Data Downstream Velocity Upstream Velocity Normal Depth Critical Depth Channel Slope Critical Slope Infinity ft/s Infinity ft/s 0.67 ft 0.67 ft 0.13000 ft/ft 0.12501 ft/ft Bentley Systems, Inc. Haestad Methods Solution Center Bentley FlowMaster (08.01.071.00) 81312012 10:38:27 AM 27 Slemons Company Drivo Suite 200 W Watertown, CT 06795 USA +1-203-755.1666 Page 2 of 2 APPENDIX II Table 3-4 — One Hour Point Rainfall of the WCSDC Table RO-3 Recommended Percentage Imperviousness Values, USDCM. Section 2.1 Rational Formula, USDCM Section 3.2.3 Rational Formula -Based Modified FAA Procedure, USDCM Section 3.4.3.1 Orifices, USDCM Figure RA -15 Rainfall Intensity -Duration Curves, USDCM /` FIRM (Flood Insurance Rate Map) Community Panel number 080266-0850-C (Panel 850 of 1075); Map Revised September 28, 1982. CertainTeed C900-RJ Dimensions r TABLE 3.4 - ONE -HOUR POINT RAINFALL (INCHES) 2 -year 5 -year 10 -year 50 -year 100 -year 1.04 1.49 1.76 2.51 2.78 The IDF curves were developed by distributing the one -hour point rainfall values using the factors obtained from the NOAA Atlas as presented below. TABLE 3.4(1) - FACTORS FOR DURATIONS OF LESS THAN ONE HOUR Duration (minutes) 5 10 15 30 Ratio to 1 -hour Depth 0.29 0.45 0.57 0.79 The point values were then converted to intensities and plotted on Figure 3-1. The data are also presented in Tables 3-1, 3-2, and 3-3. Section 3— Page 4 r 0 DRAINAGE CRITERIA MANUAL (V. 1) Table RO-3—Recommended Percentage Imperviousness Values Land Use or Surface Characteristics Percentage Imperviousness Business: Commercial areas 95 Neighborhood areas 85 Residential: Single-family Multi -unit (detached) 60 Multi -unit (attached) 75 Half -acre lot or larger * Apartments 80 Industrial: Light areas 80 Heavy areas 90 Parks, cemeteries 5 Playgrounds 10 Schools 50 Railroad yard areas 15 Undeveloped Areas: Historic flow analysis 2 Greenbelts, agricultural 2 Off -site flow analysis (when land use not defined) 45 Streets: Paved 100 Gravel (packed) 40 Drive and walks 90 Roofs 90 Lawns, sandy soil 0 Lawns, clayey soil 0 RUNOFF * See Figures RO-3 through RO-5 for percentage imperviousness. CA = KA + (1.31i' -1.44i2 +1.1351- 0.12) for CA ≥ 0, otherwise Cif = 0 (RO-6) CCD =KCD+(0.858i'-0.786i2+0.7741+0.04) (RO-7) C,i _ \CA +CCD /I2 08/2006 Urban Drainage and Flood Control Dlslrict RO-9 DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF r 2.0 RATIONAL METHOD For urban catchments that are not complex and are generally 160 acres or less in size, it is acceptable that the design storm runoff be analyzed by the Rational Method. This method was introduced in 1889 and is still being used in most engineering offices in the United States. Even though this method has frequently come under academic criticism for its simplicity, no other practical drainage design method has evolved to such a level of general acceptance by the practicing engineer. The Rational Method properly understood and applied can produce satisfactory results for urban storm sewer and small on -site detention design. 2.1 Rational Formula The Rational Method is based on the Rational Formula: Q=CIA in which: Q = the maximum rate of runoff (cfs) (RO-1) C = a runoff coefficient that is the ratio between the runoff volume from an area and the average rate of rainfall depth over a given duration for that area I= average intensity of rainfall in inches per hour for a duration equal to the time of concentration, rC A = area (acres) Actually, Q has units of inches per hour per acre (in/hr/ac); however, since this rate of in/hr/ac differs from cubic feet per second (cfs) by less than one percent, the more common units of cfs are used. The time of concentration is typically defined as the time required for water to flow from the most remote point of the area to the point being investigated. The time of concentration should be based upon a flow length and path that results in a time of concentration for only a portion of the area if that portion of the catchment produces a higher rate of runoff. The general procedure for Rational Method calculations for a single catchment is as follows: 1. Delineate the catchment boundary. Measure its area. 2. Define the flow path from the upper -most portion of the catchment to the design point. This flow path should be divided into reaches of similar flow type (e.g., overland flow, shallow swate flow, gutter flow, etc.). The length and slope of each reach should be measured. 3. Determine the time of concentration, r., for the catchment. 06/2001 Urban Drainage and Flood Control District RO-3 DRAINAGE CRITERIA MANUAL (V. 2) STORAGE storage or sizing of on -site detention facilities, those guidelines should be followed instead. The empirical equations are as follows: I ; = K; A (SO -1) for the 100 -year: =(1.781 —0.00212 — 3.56) KI00 900 for the 10 -year: K1° 1,000 (0.951 —1.90) for the 5 -year: _ (0.771 — 2.65) KS 1,000 in which: (SO -2) (SO -3) (SO -4) I; = required volume where subscript i =100-, 10- or 5 -year storm, as appropriate (acre-feet) Kr = empirical volume coefficient where subscript i = 100-, 10- or 5 -year storm, as appropriate I = fully developed tributary catchment imperviousness (%) A = tributary catchment area (acres) Design Example 6.1 shows calculations of allowable release rate and storage requirement using empirical equations. 3.2.3 Rational Formula -Based Modified FAA Procedure. The Rational Formula -based Federal Aviation Administration (FAA) (1966) detention sizing method (sometimes referred to as the "FAA Procedure"), as modified by Guo (1999a), provides a reasonable estimate of storage volume requirements for on -site detention facilities. Again, this method provides sizing for one level of peak control only. The method may also be used for initial sizing of detention storage volumes whenever a detailed hydrograph routing design method is used. The input required for this Rational Formula -based FAA volume calculation procedure includes: A = the area of the catchment tributary to the storage facility (acres) 06/2001 Urban Drainage and Flood Control District SO -9 STORAGE DRAINAGE CRITERIA MANUAL (V. 2) C= the runoff coefficient Q!„ = the allowable maximum release rate from the detention facility based on Table SO -1 (cfs) Tc = the time of concentration for the tributary catchment (see the RUNOFF chapter) (minutes) P, = the 1 -hour design rainfall depth (inches) at the site taken from the RAINFALL chapter for the relevant return frequency storms The calculations are best set up in a tabular (spreadsheet) form with each 5 -minute increment in duration being entered in rows and the following variables being entered, or calculated, in each column: 1. Storm Duration Time, T(minutes), up to 180 minutes. 2. Rainfall Intensity, 1 (inches per hour), calculated using Equation RA -3 from the RAINFALL chapter. 3. Inflow volume, v, (cubic feet), calculated as the cumulative volume at the given storm duration using the equation: Y,. = CIA (60T) (SO -5) 4. Outflow adjustment factor m (Guo 1999a): m= 1 1+T` 2 T p.5≤r»≤1 and T≥TT (SO -6) 5. The calculated average outflow rate, Q,,,, (cfs), over the duration T: Q,,,• _ »f Qpo (SO -7) 6. The calculated outflow volume, 1',(cubic feet), during the given duration and the adjustment factor at that duration calculated using the equation: Vo = Q.„ (60T) (SO -8) '7. The required storage volume, VS (cubic feet), calculated using the equation: Vs = V — f o (SO -9) The value of V, increases with time, reaches a maximum value, and then starts to decrease. The maximum value of Vs is the required storage volume for the detention facility. Sample calculations using SO -10 06/2001 Urban Drainage and Flood Control District DRAINAGE CRITERIA MANUAL (V. 2) STORAGE 3.4.2 Initial Shaping. The initial shaping of the storage basin provides a starting point for defining the stage -storage relationship. The stage -storage relationship will be refined during preliminary and final design phases of the project. The initial shaping is easiest when regular geometry (such as a triangle or rectangle) is used for approximation. The detention volume needed for any specific design storm is combined with site constraints (e.g., size or depth limitations, number of control stages, etc.) and the simplified formulas describing the basin geometry in order to develop an initial depth, length, and width for the basin. Design spreadsheets can be used to assist in preliminary shaping of the storage facility. The District does not encourage the use of storage facilities with uniform, geometric properties. To the contrary, the District encourages designers to collaborate with landscape architects to develop storage facilities that are attractive visually, fit into the fabric of the landscape, and enhance the overall character of an area. However, using regular geometry can approximate initial shaping of a non -uniformly shaped facility. 3.4.3 Outlet Works Design. Outlet works are structures that control the depth of water and release rates from storage facilities. There are numerous types of designs that have been used successfully in the Denver area. Figure SO -2 (duplicated from Volume 3 of the Manual) shows a typical design that may be used in combination with the control of the WOCV. It includes an orifice plate for release of the water quality storm. The 2- to 10 -year storm release is controlled by the size of the orifice at the bottom of the drop box. The trash rack at the top of the drop box can be sized using Figure SO -3. Either the outlet at the bottom of a second drop box or the configuration of the spillway limits the 100 -year storm release. The hydraulic capacity of the various components of the outlet works (orifices, weirs, pipes) can be determined using standard hydraulic equations. The discharge pipe of the outlet works functions as a culvert. See the CULVERTS chapter of the Manual for guidance regarding the calculation of the hydraulic capacity of outlet pipes. The following discussion regarding weirs and orifices is adapted from Urban Drainage Design Manual, Hydraulic Engineering Circular No. 22 (Brown, Stein, and Warner 1996). A rating curve for the entire outlet can be developed by combining the rating curves developed for each of the components of the outlet and then selecting the most restrictive element that controls a given stage for determining the composite total outlet rating curve. Design aids for outlet works hydraulic calculations are provided on several worksheets in the UD- Detention Spreadsheet. 3.4.3.1 Orifices. Multiple orifices may be used in a detention facility, and the hydraulics of each can be superimposed to develop the outlet -rating curve. For a single orifice as illustrated in Figure SO -3a, orifice flow can be determined using Equation SO -11. Q = Cp Ap (2gH0)o.s (SO -11) 06/2001 Urban Drainage and Flood Control District SO -17 STORAGE in which: DRAINAGE CRITERIA MANUAL (V. 2) Q = the orifice flow rate (cfs) C„ = discharge coefficient (0.40 - 0.60) A.= area of orifice (ft2) H.= effective head on the orifice measured from the centroid of the opening (ft) g = gravitational acceleration (32.2 ft/sec2) If the orifice discharges as a free outfall, the effective head is measured from the centroid of the orifice to the upstream water surface elevation. If the orifice discharge is submerged, then the effective head is the difference in elevation of the upstream and downstream water surfaces. This latter condition of a submerged discharge is shown in Figure SO -3b. For square -edged, uniform orifice entrance conditions, a discharge coefficient of 0.6 should be used. For ragged edged orifices, such as those resulting from the use of an acetylene torch to cut orifice openings in corrugated pipe, a value of 0.4 should be used. 3.4.3.2 Weirs. Relationships for sharp -crested, broad -crested, V -notch, and proportional weirs are provided below: Sharp -Crested Weirs: Typical sharp -crested weirs are illustrated in Figures SO -4a through SO -4d. Equation SO -12 provides the discharge relationship for sharp -crested weirs with no end contractions (illustrated in Figure SO -4a): Q = C.L1-i' 5 (SO -12) in which: Q = discharge (cfs) L = horizontal weir length (ft) H = head above weir crest excluding velocity head (ft) = 3.27 + 0.4 (HIHH), where N1 is the height of the weir crest (ft) As indicated above, the value of the coefficient Csor is known to vary with the ratio H/H( (see Figure SO - 4c for definition of terms). For values of the ratio HIH, less than 0.3, a constant Csc„ • of 3.33 is often used. Equation SO -13 provides the discharge equation for sharp -crested weirs with end contractions (illustrated in Figure SO -4b). The value of the coefficient Cscu• is known to vary with the ratio HIH„ (see Figure SO -4c for definition of terms). For values of the ratio H/H1 less than 0.3, a constant C.s.cw of 3.33 is often used. SO -18 06/2001 Urban Drainage and Flood Control District DRAINAGE CRITERIA MANUAL (V. 1) RAINFALL Rainfall Intensity (inches per hour) 10 9 7 6 5 4 3 2 1 0 ,. 100-yr rainf all = 2.6 inch . \ ` , '' ., 10-yr rainfall = 1.55 inch 2-yr rainfall = 0.95 inch ` 1 — - — - ~ - 0 10 20 30 Time (minutes) 40 FIGURE RA -15 Rainfall Intensity -Duration Curves 50 60 06/2001 RA -27 Urban Drainage and Flood Control District ..•10' Cerka seed Cgoo/Q1- Dimensions we p•�� Class 235 (DR18) 4"-12" Class 305 (DR14) 4"-12" Includes Coupling, O -rings, Splines, and Lubricant. At the time of printing, UL ratings were (I) In -line with the previous version of AVM C900 (DR18s150pst. DRIi=7Opsi) and 0) being updated for harmonization with 0.900.07, which Is the basis for the pressure ratings shown throughout this brochure. T Min L1 4b _ Laying Length 20' OD2 Pipe Dimensions 001 O-ring Spline Groove - Spline Insertion Hole 1w! Nylon H - Spline 6' 6.90 .383 .493 .646 .793 8' 8.05 .503 10' 11.10 .617 Approx. Weight with D1 Coupling (Ibs/!t) P L3 01 L1 0D2 Mln. Max. DRIB DR14 .313 3.000 .375 8.250 5.964 .125 .135 2.6 3.2 .313 3.000 .375 8.250 8.366 .125 .135 5.4 6.7 .656 3.183 .500 10.500 10.947 .130 .140 9.3 11.5 .656 3.500 .500 11125 13.361 .200 .215 14.2 17.8 12' 13.20 .733 .043 .656 3.500 .500 12.000 15.836 .200 .215 20.4 24.7 All dimensions are In inches and are subject to normal manufacturing tolerances. CertainTeed C900/RJ Couplings ate boxed and shipped with O•rings factory Installed in coupling. O-ring Dimensions Spline Dimensions Sizes O-ring Din. 4' .313 6' .313 Sizes W x H 4' 1/4 1/4 18 6' 1/4 1/4 24 8' .400 8' 5/16 5/16 10' .438 12' .438 10' 3/8 3/8 39 12' 3/8 3/8 46 APPENDIX III (Stuffer Envelope) 1984 Historic Drainage Plan by Nelson Engineers Existing Conditions and Demolition Plan (for historic conditions and historic drainage data) Drainage Plan Erosion/ Sediment Control and Water Quality Plan Drainage, Erosion Control and Water Quality Details N \ l ..�. 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