FINAL DRAINAGE REPORT CORNERSTONE RIVER VALLEY VILLAGE FILING NO. 1 CITY OF THORNTON, COUNTY OF ADAMS, STATE OF COLORADO

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1 FINAL DRAINAGE REPORT CORNERSTONE RIVER VALLEY VILLAGE FILING NO. 1 CITY OF THORNTON, COUNTY OF ADAMS, STATE OF COLORADO PREPARED FOR: Thornton Cornerstone LLC 558 Castle Pines Parkway Suite B4-321 Castle Pines, CO Ph: Attn: Joseph H. Quinn PREPARED BY: Contact: David R. Addor, P.E. ORIGINAL DATE PREPARED: April 26, 2016 REVISED:

2 TABLE OF CONTENTS Page No. 1. General Location and Description Drainage Basins & Sub-Basins Drainage Design Criteria Drainage Facility Design Conclusions List of References... 6 Appendix: 7 Basin and Runoff Calculations Storm Sewer Calculations Backup Information (Firmette, Soils Information) 9 (19 sheets) 29 (13 sheets) 43 (6 sheets)

3 Thornton Cornerstone LLC herby certifies that the drainage facilities for Cornerstone River Valley Village Filing No. 1 will be constructed according to the design presented in this report. I understand that the City of Thornton does not and shall not assume liability for the drainage facilities designed and/or certified by my engineer. I understand that the City of Thornton reviews drainage plans but cannot, on behalf of Thornton Cornerstone LLC, guarantee that final drainage design review will absolve Thornton Cornerstone LLC and/or their successors and/or assigns of future liability for improper design. I further understand that approval of the Plat and/o Development Permit does not imply approval of my engineer s drainage design. Attest: Name of Responsible Party Notary Public Authorized Signature I hereby certify that this report (plan) for the final drainage design of Cornerstone River Valley Village Filing No. 1 was prepared by me (or under my direct supervision) in accordance with the provisions of the City of Thornton Standards and Specifications for the Design and Construction of Public and Private Improvements for the Responsible Parties thereof. I understand that the City of Thornton does not and shall not assume liability for drainage facilities designed by others. Registered Professional Engineer State of Colorado No. Cornerstone River Valley Village Engineering Service Company

4 1. General Location and Description a. Location This property is located in the SW ¼ of Section 18, T. 2 S., R. 67 W. of the 6 th P.M. It is located on the northeast corner of Colorado Boulevard and Thornton Parkway to the west of Clermont Street. The Colorado Agricultural Ditch runs along the western edge of the property. This site is bounded on the west by The Reserve at Thornton on the west side of Colorado Boulevard and Cherrylane Subdivision to the south on the south side of Thornton Parkway. To the north and east are undeveloped portions of River Valley Village Subdivision. b. Description of Property This first filing for Cornerstone River Valley Village will subdivide the south acres of the western portion of the River Valley Village Subdivision. Tract D containing acres will be subject to future platting for additional residential development. The property is sparsely covered with native grasses. Grades are generally to the south and east at slopes between 1 and 3 percent. Thornton Parkway is elevated from 2 to 10 feet above this site along the south boundary. Soils are generally Ulm Loams which is a hydrologic group C soil. Other soils within this western portion of River Valley Village Subdivision are Samsil Shingle Complex located generally on the northwest quadrant of acres. This is a hydrologic group D soil. The proposal for this first phase is to subdivide this portion of the property into 79 single family residential lots. 2. Drainage Basins and Sub-basins a. Major Basin Description This site lies outside of the100-year floodplain. It appears on two FIRMs as provided by FEMA, Map Number 08001C0602H and 08001C0606H, both dated March 5, Cornerstone River Valley Village Engineering Service Company

5 This site falls within the Basin 4100 and Direct Flow Area 0056 Outfall System Planning Study prepared for the City of Thornton and Adams County by Kiowa Engineering, March Reach lies along the alignment for Thornton Parkway. It is not the existing flow path for any existing runoff. Local storm sewer is identified to control drainage. b. Sub-Basin Description This site is part of the River Valley Village Subdivision Amendment No. 1. That plat was the subject of a Final Drainage Report prepared by Manhard Consulting as approved by the City of Thornton on May 23, It has since been the subject of a Preliminary Drainage Report prepared by VLC, LLC that revised the original Manhard report to change the uses on the acres that lie within Cornerstone River Valley Village Filing No. 1. This report rationalizes the basins in the southern acres to align with the proposal street and storm sewer layout. 3. Drainage Design Criteria a. Regulations The key variation from the City of Thornton Standards is the use of the Rational Method for runoff calculations. This was done due to the relatively small sizes of the various subbasins created by the storm sewer system. b. Development Criteria Reference and Constraints As stated above, this property was the subject of a previous final drainage report by Manhard Consulting. That report set in place the existing detention facility for the overall River Valley Village complex. The discharge from this site will be to the existing storm sewer system that directs the flows to this pond. c. Hydrological Criteria The design rainfall is taken from the City of Thornton Standards and Specifications. The five year one-hour rainfall is 1.38 inches and the 100-year one-hour rainfall is 2.69 inches. Cornerstone River Valley Village Engineering Service Company

6 Runoff calculations were done using the Rational Method. The rainfall intensities were generated using the UDFCD formula applying the one-hour rainfall for the 5-year and 100- year storms. d. Hydraulic Criteria Water surface profiles were calculated for the storm sewer system using the UDFCD NeoUDSewer program. Streets and inlets will be evaluated using UDFCD UD-Inlet. 4. Drainage Facility Design a. General Concept The drainage pattern for this site will be the simple collection of runoff in the proposed street system and directed to the storm sewer system for delivery to the existing detention pond. There is little offsite drainage that impacts this first filing. Minor flows may collect along the northern boundary and will be directed to the existing storm system in Clermont Street. The project site has been divided into thirteen (13) sub-basins with one off-site basin. See the Drainage Plan. All of the basins are similar and were developed to show discharge to the proposed storm sewer system. The outfall will be into the existing 36 RCP storm sewer at the intersection of Thornton Parkway and Clermont Street. b. Specific Details There were no specific drainage problems encountered. The off-site basin is the existing Basin identified as CPA:1 on the VLC plan or 14C on the Manhard Plan. This basin consists of the right-of-way for Colorado Boulevard and Thornton Parkway adjacent to this site. No new calculations are included for this basin as it does not impact the proposed subdivision. Detention will be provided in the existing pond located at the northwest corner of Thornton Parkway and Riverdale Road. Cornerstone River Valley Village Engineering Service Company

7 Inlet calculations are included for key locations. Design Point 1 has the maximum flow and the calculations show that it requires a 10 foot Type R inlet. Design Point 6 has the high median flow and was calculated as the maximum for a 5 foot Type R inlet. All inlets that receive more flow are sized as 10 foot. 5. Conclusions a. Compliance with Standards The drainage for this site complies with all City of Thornton Standards and Specifications and with the Urban Drainage Flood Control District Criteria Manual. b. Drainage Concept The drainage design will control the runoff as anticipated in the previous reports and direct it to the existing detention facility. F. LIST OF REFERENCES #1) Standards and Specifications for the Design and Construction of Public and Private Improvements, City of Thornton, Colorado. October #2) Urban Storm Drainage Criteria Manual - Volumes 1,2, and 3, Urban Drainage and Flood Control District, Denver, Colorado. Published June 2001, latest edition. #3) Phase III Drainage Study for River Valley Village Subdivision, prepared by Manhard Consulting, Ltd., May, #4) Phase I Drainage Report for Cornerstone River Valley Ranch, prepared by Vision Land Connection, LLC, August, #5) Soil Map Arapahoe County, Colorado, United States Department of Agriculture, Natural Resources Conservation Service, Web Soil Survey 2.2. Cornerstone River Valley Village Engineering Service Company

8 APPENDIX Cornerstone River Valley Village Engineering Service Company

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10 BASIN & RUNOFF CALCULATIONS Cornerstone River Valley Village Engineering Service Company

11 Site Data: Cornerstone River Valley Village Total Basin: 662,027 Sq. Ft Acres #REF! Composite Coefficient of Runoff: (Developed Area) Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 51, % Asphalt Pavement 141, % Roof 190, % Landscaping 279, % Figures are from Table 1, City of Aurora Storm Drainage Design & Technical Criteria Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC Results: C 2 : C 5 : C 10 : C 100 : Developed Basin Imperviousness: I= 55.0% Cornerstone RVV 4/28/2016

12 Sub-Basin Calculations: Basin Designation: C2 Design Point: 1 Basin Area: 127,392 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 11, % Asphalt Pavement 17, % Roof 41, % Landscaping 57, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.43 C 5 : 0.47 C 10 : 0.49 C 100 : 0.61 Developed Basin Imperviousness: I= Basin Designation: C3 Design Point: 2 Basin Area: 31,249 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 2, % Asphalt Pavement 9, % Roof 7, % Landscaping 12, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.50 C 5 : 0.53 C 10 : 0.53 C 100 : 0.64 Developed Basin Imperviousness: I= Cornerstone RVV 4/28/2016

13 Sub-Basin Calculations: Basin Designation: C4 Design Point: 2 Basin Area: 66,904 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 6, % Asphalt Pavement 8, % Roof 22, % Landscaping 29, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.43 C 5 : 0.47 C 10 : 0.49 C 100 : 0.62 Developed Basin Imperviousness: I= Basin Designation: C5 Design Point: 3 Basin Area: 35,897 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 1, % Asphalt Pavement 14, % Roof 7, % Landscaping 12, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.54 C 5 : 0.57 C 10 : 0.55 C 100 : 0.66 Developed Basin Imperviousness: I= Cornerstone RVV 4/28/2016

14 Sub-Basin Calculations: Basin Designation: C6 Design Point: 4 Basin Area: 41,959 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 3, % Asphalt Pavement 6, % Roof 13, % Landscaping 18, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.45 C 5 : 0.48 C 10 : 0.50 C 100 : 0.62 Developed Basin Imperviousness: I= Basin Designation: C7 Design Point: 5 Basin Area: 7,779 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks % Asphalt Pavement 4, % Roof % Landscaping 2, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.55 C 5 : 0.58 C 10 : 0.53 C 100 : 0.64 Developed Basin Imperviousness: I= Cornerstone RVV 4/28/2016

15 Sub-Basin Calculations: Basin Designation: C8 Design Point: 6 Basin Area: 57,208 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 5, % Asphalt Pavement 8, % Roof 18, % Landscaping 25, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.44 C 5 : 0.48 C 10 : 0.50 C 100 : 0.62 Developed Basin Imperviousness: I= Basin Designation: C9 Design Point: 7 Basin Area: 24,917 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 1, % Asphalt Pavement 8, % Roof 5, % Landscaping 9, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.52 C 5 : 0.55 C 10 : 0.54 C 100 : 0.65 Developed Basin Imperviousness: I= Cornerstone RVV 4/28/2016

16 Sub-Basin Calculations: Basin Designation: C10 Design Point: 9 Basin Area: 70,351 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 5, % Asphalt Pavement 18, % Roof 18, % Landscaping 27, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.49 C 5 : 0.52 C 10 : 0.52 C 100 : 0.64 Developed Basin Imperviousness: I= Basin Designation: C11 Design Point: 10 Basin Area: 54,256 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 4, % Asphalt Pavement 10, % Roof 16, % Landscaping 22, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.46 C 5 : 0.50 C 10 : 0.51 C 100 : 0.63 Developed Basin Imperviousness: I= Cornerstone RVV 4/28/2016

17 Sub-Basin Calculations: Basin Designation: C12 Design Point: 10 Basin Area: 54,309 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 4, % Asphalt Pavement 13, % Roof 14, % Landscaping 21, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.48 C 5 : 0.52 C 10 : 0.52 C 100 : 0.64 Developed Basin Imperviousness: I= Basin Designation: C13 Design Point: 11 Basin Area: 40,671 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 2, % Asphalt Pavement 10, % Roof 10, % Landscaping 16, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.48 C 5 : 0.51 C 10 : 0.52 C 100 : 0.63 Developed Basin Imperviousness: I= Cornerstone RVV 4/28/2016

18 Sub-Basin Calculations: Basin Designation: C14 Design Point: Basin Area: 49,135 Sq. Ft Acres Composite Coefficient of Runoff: Surface Area % of Site C 2 value C 5 value C 10 value C 100 value Imp. Drives & Walks 2, % Asphalt Pavement 12, % Roof 12, % Landscaping 21, % Figures are from Table RO-3 and Figures RO-3 thru RO-5, Urban Drainage and Flood Control District Criteria Manual Formula: (% of Site)(C Value)+(% of SIte)(C Value)+(% of Site)(C Value) = CC C 2 : 0.46 C 5 : 0.49 C 10 : 0.50 C 100 : 0.62 Developed Basin Imperviousness: I= Cornerstone RVV 4/28/2016

19 STANDARD FORM SF - 1 TIME OF CONCENTRATION Project: Cornerstone River Valley Village CALCULATED BY: DRA DATE: 04/06/16 tc = ti + tt SUB - BASIN INITIAL / OVERLAND TRAVEL TIME t c CHECK FINAL REMARKS DATA TIME (t i ) (t t ) (URBANIZED BASINS) t c DESIGN AREA C5 LENGTH SLOPE ti LENGTH SLOPE VEL. tt COMP. TOTAL LEGNTH tc=(l/180)+10 POINT Ac Ft % Min Ft % FPS Min tc (Ft) Min Min (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) C C C C C C C C C C C C STORM DRAINAGE DESIGN AND TECHNICAL MANUAL

20 CALCULATED BY: DRA STANDARD FORM SF - 2 JOB NO: DATE: 4/6/2016 STORM DRAINAGE SYSTEM DESIGN PROJECT: Cornerstone River Valley Village CHECKED BY: DRA (RATIONAL METHOD PROCEDURE) DESIGN STORM: 5 YR STREET DESIGN POINT AREA DESIGN AREA (AC) 1 Hour Rainfall: 1.38 DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIME RUNOFF COEFF tc (MIN) C. A (AC) I IN / HR Q (CFS) tc (MIN) SUM C. A (AC) I IN / HR (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) 1 1 C C C C3 + C4 4 3 C C2 TO C5 5 4 C C C6 + C7 7 6 C C C 6 TO C9 Q (CFS) SLOPE (%) STREET FLOW(CFS) DESIGN FLOW(CFS) SLOPE (%) PIPE SIZE LENGTH (FT) VELOCITY (FPS) t t (MIN) REMARKS STORM DRAINAGE DESIGN AND TECHNICAL MANUAL C2 TO C9

21 CALCULATED BY: DRA STANDARD FORM SF - 2 JOB NO: DATE: 4/6/2016 STORM DRAINAGE SYSTEM DESIGN PROJECT: Cornerstone River Valley Village CHECKED BY: DRA (RATIONAL METHOD PROCEDURE) DESIGN STORM: 5 YR STREET DESIGN POINT AREA DESIGN AREA (AC) 1 Hour Rainfall: 1.38 DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIME RUNOFF COEFF tc (MIN) C. A (AC) I IN / HR Q (CFS) tc (MIN) SUM C. A (AC) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) 1 8 C C2 TO C C C2 TO C C I IN / HR Q (CFS) SLOPE (%) STREET FLOW(CFS) DESIGN FLOW(CFS) SLOPE (%) PIPE SIZE LENGTH (FT) VELOCITY (FPS) tt (MIN) REMARKS 4 10 C C12 TO C C C13 TO C STORM DRAINAGE DESIGN AND TECHNICAL MANUAL

22 CALCULATED BY: DRA STANDARD FORM SF - 2 JOB NO: DATE: 4/6/2016 STORM DRAINAGE SYSTEM DESIGN PROJECT: Cornerstone River Valley Village CHECKED BY: DRA (RATIONAL METHOD PROCEDURE) DESIGN STORM: 100 YR STREET DESIGN POINT AREA DESIGN AREA (AC) 1 Hour Rainfall: 2.69 DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIME RUNOFF COEFF tc (MIN) C. A (AC) I IN / HR Q (CFS) tc (MIN) SUM C. A (AC) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) 1 1 C C C C3 + C4 4 3 C C2 TO C5 5 4 C C C6 + C7 7 6 C C C 6 TO C9 I IN / HR Q (CFS) SLOPE (%) STREET FLOW(CFS) DESIGN FLOW(CFS) SLOPE (%) PIPE SIZE LENGTH (FT) VELOCITY (FPS) tt (MIN) REMARKS STORM DRAINAGE DESIGN AND TECHNICAL MANUAL C2 TO C9

23 CALCULATED BY: DRA STANDARD FORM SF - 2 JOB NO: DATE: 4/6/2016 STORM DRAINAGE SYSTEM DESIGN PROJECT: Cornerstone River Valley Village CHECKED BY: DRA (RATIONAL METHOD PROCEDURE) DESIGN STORM: 100 YR STREET DESIGN POINT AREA DESIGN AREA (AC) 1 Hour Rainfall: 2.69 DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIME RUNOFF COEFF tc (MIN) C. A (AC) I IN / HR Q (CFS) tc (MIN) SUM C. A (AC) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) 1 8 C C2 TO C C C2 TO C C I IN / HR Q (CFS) SLOPE (%) STREET FLOW(CFS) DESIGN FLOW(CFS) SLOPE (%) PIPE SIZE LENGTH (FT) VELOCITY (FPS) tt (MIN) REMARKS 4 10 C C12 TO C C C13 TO C STORM DRAINAGE DESIGN AND TECHNICAL MANUAL

24 DESIGN PEAK FLOW FOR ONE-HALF OF STREET OR GRASS-LINED CHANNEL BY THE RATIONAL METHOD Worksheet Protected Project: Inlet ID: Cornerstone RVV DP 1 Show Details Design Flow: ONLY if already determined through other methods: Minor Storm Major Storm (local peak flow for 1/2 of street OR grass-lined channel): *Q Known = cfs * If you enter values in Row 14, skip the rest of this sheet and proceed to sheet Q-Allow or Area Inlet. Geographic Information: (Enter data in the blue cells): Site Type: Site is Urban Site is Non-Urban Flows Developed For: Street Inlets Area Inlets in a Median Subcatchment Area = Acres Percent Imperviousness = % NRCS Soil Type = A, B, C, or D Overland Flow = Channel Flow = Slope (ft/ft) Length (ft) <--- FILL IN THIS SECTION OR FILL IN THE SECTIONS BELOW. <--- Rainfall Information: Intensity I (inch/hr) = C 1 * P 1 / ( C 2 + T c ) ^ C 3 Minor Storm Major Storm Design Storm Return Period, T r = Return Period One-Hour Precipitation, P 1 = C 1 = C 2 = C 3 = User-Defined Storm Runoff Coefficient (leave this blank to accept a calculated value), C = User-Defined 5-yr. Runoff Coefficient (leave this blank to accept a calculated value), C 5 = Bypass (Carry-Over) Flow from upstream Subcatchments, Q b = cfs years inches Total Design Peak Flow, Q = cfs Cornerstone DP 1 UD-Inlet_v3.14.xlsm, Q-Peak 4/28/2016, 9:48 AM

25 Project: Inlet ID: ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Cornerstone RVV DP 1 Gutter Geometry (Enter data in the blue cells) Maximum Allowable Width for Spread Behind Curb T BACK = 12.4 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb) S BACK = ft/ft Manning's Roughness Behind Curb (typically between and 0.020) n BACK = Height of Curb at Gutter Flow Line H CURB = 6.00 inches Distance from Curb Face to Street Crown T CROWN = 17.0 ft Gutter Width W = 2.00 ft Street Transverse Slope S X = ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or ft/ft) S W = ft/ft Street Longitudinal Slope - Enter 0 for sump condition S O = ft/ft Manning's Roughness for Street Section (typically between and 0.020) n STREET = Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm T MAX = ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm d MAX = inches Allow Flow Depth at Street Crown (leave blank for no) check = yes MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Depth Criterion Q allow = SUMP SUMP cfs Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak' Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak' Cornerstone DP 1 UD-Inlet_v3.14.xlsm, Q-Allow 4/28/2016, 9:48 AM

26 INLET IN A SUMP OR SAG LOCATION Project = Inlet ID = Cornerstone RVV DP 1 H-Curb W W P H-Vert Lo (C) Wo Lo (G) Design Information (Input) MINOR MAJOR Type of Inlet Inlet Type = CDOT Type R Curb Opening Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') a local = inches Number of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Ponding Depth = inches Grate Information MINOR MAJOR Override Depths Length of a Unit Grate L o (G) = N/A N/A feet Width of a Unit Grate W o = N/A N/A feet Area Opening Ratio for a Grate (typical values ) A ratio = N/A N/A Clogging Factor for a Single Grate (typical value ) C f (G) = N/A N/A Grate Weir Coefficient (typical value ) C w (G) = N/A N/A Grate Orifice Coefficient (typical value ) C o (G) = N/A N/A Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening L o (C) = feet Height of Vertical Curb Opening in Inches H vert = inches Height of Curb Orifice Throat in Inches H throat = inches Angle of Throat (see USDCM Figure ST-5) Theta = degrees Side Width for Depression Pan (typically the gutter width of 2 feet) W p = feet Clogging Factor for a Single Curb Opening (typical value 0.10) C f (C) = Curb Opening Weir Coefficient (typical value ) C w (C) = Curb Opening Orifice Coefficient (typical value ) C o (C) = MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Q a = cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED = cfs Cornerstone DP 1 UD-Inlet_v3.14.xlsm, Inlet In Sump 4/28/2016, 9:48 AM

27 DESIGN PEAK FLOW FOR ONE-HALF OF STREET OR GRASS-LINED CHANNEL BY THE RATIONAL METHOD Worksheet Protected Project: Inlet ID: Cornerstone RVV DP 6 Show Details Design Flow: ONLY if already determined through other methods: Minor Storm Major Storm (local peak flow for 1/2 of street OR grass-lined channel): *Q Known = cfs * If you enter values in Row 14, skip the rest of this sheet and proceed to sheet Q-Allow or Area Inlet. Geographic Information: (Enter data in the blue cells): Site Type: Site is Urban Site is Non-Urban Flows Developed For: Street Inlets Area Inlets in a Median Subcatchment Area = Acres Percent Imperviousness = % NRCS Soil Type = A, B, C, or D Overland Flow = Channel Flow = Slope (ft/ft) Length (ft) <--- FILL IN THIS SECTION OR FILL IN THE SECTIONS BELOW. <--- Rainfall Information: Intensity I (inch/hr) = C 1 * P 1 / ( C 2 + T c ) ^ C 3 Minor Storm Major Storm Design Storm Return Period, T r = Return Period One-Hour Precipitation, P 1 = C 1 = C 2 = C 3 = User-Defined Storm Runoff Coefficient (leave this blank to accept a calculated value), C = User-Defined 5-yr. Runoff Coefficient (leave this blank to accept a calculated value), C 5 = Bypass (Carry-Over) Flow from upstream Subcatchments, Q b = cfs years inches Total Design Peak Flow, Q = cfs Cornerstone DP 6 UD-Inlet_v3.14.xlsm, Q-Peak 4/28/2016, 9:46 AM

28 Project: Inlet ID: ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Cornerstone RVV DP 6 Gutter Geometry (Enter data in the blue cells) Maximum Allowable Width for Spread Behind Curb T BACK = 12.4 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb) S BACK = ft/ft Manning's Roughness Behind Curb (typically between and 0.020) n BACK = Height of Curb at Gutter Flow Line H CURB = 6.00 inches Distance from Curb Face to Street Crown T CROWN = 17.0 ft Gutter Width W = 2.00 ft Street Transverse Slope S X = ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or ft/ft) S W = ft/ft Street Longitudinal Slope - Enter 0 for sump condition S O = ft/ft Manning's Roughness for Street Section (typically between and 0.020) n STREET = Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm T MAX = ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm d MAX = inches Allow Flow Depth at Street Crown (leave blank for no) check = yes MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Depth Criterion Q allow = SUMP SUMP cfs Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak' Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak' Cornerstone DP 6 UD-Inlet_v3.14.xlsm, Q-Allow 4/28/2016, 9:46 AM

29 INLET IN A SUMP OR SAG LOCATION Project = Inlet ID = Cornerstone RVV DP 6 H-Curb W W P H-Vert Lo (C) Wo Lo (G) Design Information (Input) MINOR MAJOR Type of Inlet Inlet Type = CDOT Type R Curb Opening Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') a local = inches Number of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Ponding Depth = inches Grate Information MINOR MAJOR Override Depths Length of a Unit Grate L o (G) = N/A N/A feet Width of a Unit Grate W o = N/A N/A feet Area Opening Ratio for a Grate (typical values ) A ratio = N/A N/A Clogging Factor for a Single Grate (typical value ) C f (G) = N/A N/A Grate Weir Coefficient (typical value ) C w (G) = N/A N/A Grate Orifice Coefficient (typical value ) C o (G) = N/A N/A Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening L o (C) = feet Height of Vertical Curb Opening in Inches H vert = inches Height of Curb Orifice Throat in Inches H throat = inches Angle of Throat (see USDCM Figure ST-5) Theta = degrees Side Width for Depression Pan (typically the gutter width of 2 feet) W p = feet Clogging Factor for a Single Curb Opening (typical value 0.10) C f (C) = Curb Opening Weir Coefficient (typical value ) C w (C) = Curb Opening Orifice Coefficient (typical value ) C o (C) = MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Q a = cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED = cfs Cornerstone DP 6 UD-Inlet_v3.14.xlsm, Inlet In Sump 4/28/2016, 9:46 AM

30 STORM SEWER HYDRAULIC CALCULATIONS Cornerstone River Valley Village Engineering Service Company

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44 BACKUP INFORMATION FIRMETTE SOILS MAP Cornerstone River Valley Village Engineering Service Company

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47 104 56' 28'' W Hydrologic Soil Group Adams County Area, Parts of Adams and Denver Counties, Colorado (River Valley Village (Thornton, CO)) ' 48'' W ' 30'' N 39 52' 30'' N 39 52' 10'' N ' 10'' N ' 28'' W N Map Scale: 1:4,290 if printed on A landscape (11" x 8.5") sheet. Meters Feet Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS ' 48'' W Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/19/2016 Page 1 of 4

48 Hydrologic Soil Group Adams County Area, Parts of Adams and Denver Counties, Colorado (River Valley Village (Thornton, CO)) MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:20,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Adams County Area, Parts of Adams and Denver Counties, Colorado Survey Area Data: Version 12, Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: 18, 2014 Aug 30, 2014 Sep The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/19/2016 Page 2 of 4

49 Hydrologic Soil Group Adams County Area, Parts of Adams and Denver Counties, Colorado River Valley Village (Thornton, CO) Hydrologic Soil Group Hydrologic Soil Group Summary by Map Unit Adams County Area, Parts of Adams and Denver Counties, Colorado (CO001) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI NuA Nunn clay loam, 0 to 1 percent slopes NuB Nunn clay loam, 1 to 3 percent slopes C % C % ShF UlC UlD Samsil-Shingle complex, 3 to 35 percent slopes Ulm loam, 3 to 5 percent slopes Ulm loam, 5 to 9 percent slopes D % C % C % Totals for Area of Interest % Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/19/2016 Page 3 of 4

50 Hydrologic Soil Group Adams County Area, Parts of Adams and Denver Counties, Colorado River Valley Village (Thornton, CO) Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/19/2016 Page 4 of 4