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Home My WebLink AboutDrainage Reports - 05/11/1995I I . I I I F1NAL DRAINAGE REPORT FOR THE I WILLOW SPRINGS P.U.D. PHASE ONE I I I PREPARED FOR: I City of Fort Collins Stormwater Utility 235 Mathews I Fort Collins , CO 80524 I PREPARED BY: I Lidstone & Anderson, Inc. I 736 Whalers Way, F-200 Fort Collins , CO 80525 (LA Project No. COTST20.4) I I I May 3 , 1995 I I I I I I I I I I I I I I I I I I I I I LIDSTONE & ANDERSON, INC. Water Resources and Environmental Consultants May 3, 1995 Mr. Basil Hamdan City of Fort Collins Stonnwater Utility 235 Mathews Street Fort Collins, CO 80524 736 Whalers Way, Suite F-200 Fort Collins, Colorado 80525 (970) 226-0120 Re: Final Drainage Report for the Willow Springs P.U.D. First Filing (LA Project No. COTST20.4) Dear Basil, Lidstone & Anderson, Inc. (LA) is pleased to submit the revised Final Drainage Report for the First Filing of the Willow Springs P.U.D. The drainage plan has been modified in response to a discrepancy found in the regional SWMM model submitted in conjunction with the Stetson Creek P.U.D. The design of the drainage facilities confonns to the Preliminary Drainage Report for the Willow Springs P.U.D. [LA, 1994] which serves as an overall drainage plan for the development. The hydraulic and hydrologic evaluation of the site, documented herein, was performed in accordance with the specifications set forth in the City of Fort Collins SDDC Manual. If you have any questions regarding the procedures and results given in this report, please feel free to call us. LP J. Koch, P.E. CLD/GJK/tlt Attachment Branch Office: Box 27, Savery, Wyoming 82332 I ·I I I I I I I I I I I I I I I I I I TABLE OF CONTENTS I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Purpose and Scope of Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 II. EXISTING DRAINAGE CONDmONS . . . . . . . . . . . . . . . . . . . . . . . . . . 4 ill. FINAL DRAINAGE PLAN FOR TIIE WILLOW SPRINGS P.U.D., PHASE ONE ........................ 5 3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 Proposed Drainage Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.3 Design of Drainage Improvements . . . . . . .. . . . . . . . . . . . . . . . . . 11 3.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.3.2 Rational Method Hydrologic Analysis . . . . . . . . . . . . . . . . . . 11 3.3.3 Allowable Street Capacities . . . . . . . . . . . . . . . . . . . . . . . . 12 3.3.4 Curb Inlet Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3.5 Storm Sewer Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3.6 Drainage Swale Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3. 7 Riprap Protection Design . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.4 Detention Pond Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4.1 Hydrologic Analysis for Detention Pond Design . . . . . . . . . . . . 17 3.4.2 Final Design of Proposed On-Site Detention Ponds . . . . . . . . . . 17 3.5 Final Design of Regional Conveyance Facilities . . . . . . . . . . . . . . . . 22 3.5.1 Design of the Regional Channel . . . . . . . . . . . . . . . . . . . . . 22 3.5.2 Design of the Major Off-Site Swale (North) . . . . . . . . . . . . . . 24 3.6 Statement of Maintenance Responsibility . . . . . . . . . . . . . . . . . . . . . 24 IV. EROSION CONTROL PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 V. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 1 I I I I TABLE OF CONTENTS (CONTINUED) FIGURES/TABLES/ APPENDICES/SHEETS FIGURES I Figure 1.1. Vicinity Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 I I I I I I I I I I I I I I Table 3.1. Table 3.2 Table 3.3. Table 3.4. Table 4.1. Table 4.2. Appendix A: Appendix B: Appendix C: Appendix D: Appendix E: Appendix F: Appendix G: Appendix H: Appendix I: Appendix J: Appendix K: Appendix L: Appendix M: Sheet 1: Sheet 2: TABLES Summary of Design Flows at All Design Points for Fully Developed Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . 13 Summary of SWMM Subbasin Parameters . . . . . . . . . . . . . . . . . . . 18 Summary of Preliminary Detention Pond Facilities Design. . . . . . . . . . 21 Summary of Detention Pond Operation Parameters. . . . . . . . . . . . . . 21 Construction Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Erosion Control Cost Estimate. . . . . . . . . . . . . . . . . . . . . . . . . . . 27 APPENDICES Rational Method Calculations Street Capacity Analysis HEC-2 Analysis for Street Capacity Calculations Inlet Design Storm Sewer Design Swale Design Riprap Design On-Site SWMM Analysis Detention Pond 310 EXTRAN Analysis Regional SWMM Analysis Design of Regional Conveyance Facilities Major Off-Site Swale Design Erosion Control Calculations SHEETS Final Grading and Drainage Plan Details for Proposed Drainage Facilities 11 I I I I I I I I I I I I I I I I I I I I. INTRODUCTION 1.1 Background The Willow Springs P. U.D. is a proposed residential development located in the SE quarter of Section 6 and the NE quarter of Section 7, Township 6 North, Range 68 West, in the City of Fort Collins, Colorado. The proposed development would consist of both single-and multi-family dwellings and would be developed in several phases. The total area of the development site is 123.9 acres; the total drainage area associated with the site, including all tributary off-site fringe areas, is 130.5 acres. Phase One of the Willow Springs P.U.D. consists of 129 single-family homes and two multi-family dwelling sites . The entire development site will be rough graded in conjunction with this development phase . The development site is bounded on the west by the Union Pacific Railroad, on the south by the Mail Creek Ditch, on the east by Timberline Road and on the north by the proposed extension of Keenland Road and Battle Creek Drive. This area is part of the McClellands Basin and, consequently, is subject to the conditions specified in the McClellands Basin Master Drainage Plan [Greenhorne & O'Mara, 1986]. The McClellands regional channel flows generally west to east through the northern portion of the development site. Figure 1.1 is a vicinity map of the project site. Based on information contained in the Master Plan, on-site detention would be required to reduce the peak discharge from the site to 0.5 cfs/acre for the 100-year event and 0.2 cfs/acre for the 10-year event. A total of five detention ponds will be constructed within the development to meet the Master Plan discharge requirements . In addition, the regional channel will be realigned and enlarged in order to convey the 100-year developed condition discharge through the site. 1.2 Purpose and Scope of Study This study defines the proposed drainage plan for the Willow Springs P.U.D. in the context of Master Plan conditions and requirements. The plan provides consideration for all on site and tributary off-site runoff, as well as the design of the regional channel through the development site. Included in this plan is the final design of all major drainage conveyance and detention facilities. Specifically, detention pond grading and outlet structure configurations are designed for each of the five detention ponds in order to meet allowable release rate requirements. In addition, the regional channel with its two proposed culvert crossings are designed to provide adequate conveyance for the 100-year developed condition discharge with 1 I I I I I I I I I I I I I I I I I I I . ,9 , .. ------=-------. -·-··· ,-/ :: Figure 1.1. Vicinity Map for the Willow Springs Development. 2 I I I I I I I I I I I I I I I I I I I I a minimum of 1 foot of freeboard. Storm sewer inlets and pipes are designed to convey runoff to the detention ponds without violating street capacity criteria. All drainage facilities within Phase One have been designed to accommodate runoff from future development phases. The hydraulic and hydrologic evaluation of the site, documented herein, was performed in accordance with the specifications set forth in the City of Fort Collins SDDC Manual. 3 I I I I I I I I I I I I I I I I II. EXISTING DRAINAGE CONDIDONS Since the McClellands Basin Master Drainage Plan has set the required release rates for this basin, all hydrologic calculations for this study were conducted for developed conditions. However, this chapter is provided as an overview of the existing drainage patterns within the Willow Springs development area. For reference, the existing condition contours are provided on Sheet 1. The site currently consists primarily of irrigated grassland which slopes toward the existing "regional channel" at an average slope of approximately 1.5 percent. In the vicinity of the Willow Springs development site, the Union Pacific Railroad, the Mail Creek Ditch and Timberline Road all serve as drainage divides which isolate the site from off-site runoff. South of the existing regional channel, runoff is directed north to the channel by way of shallow overland flow. North of the existing channel, runoff from the entire northeast quarter of Section 6 flows overland to the channel at Timberline Road. It is currently proposed by others that in the future, runoff from the northeast quarter of Section 6 will be collected by the drainage facilities associated with the Harmony Crossing development. Discharge from the Harmony Crossing drainage facilities would be conveyed south to the regional channel by way of a roadside swale along the west side of Timberline Road. Off-site flow from the west is conveyed to the McClellands regional channel through a 6-foot RCP under the Union Pacific Railroad. The culvert serves as the outlet structure for the OakRidge regional detention pond on the west side of the railroad embankment. The existing channel through the Willow Springs site is a relatively shallow, narrow grass-lined channel with an average slope of approximately 0.4 percent. The existing culvert under Timberline Road is a 24-inch CMP. It is currently proposed that this culvert be replaced with two 4 'H x 8 'W RCBs in conjunction with other developments adjacent to Timberline Road south of Harmony Road. 4 I I I I I I I I I I I I I I I I I I I ID. FINAL DRAINAGE PLAN FOR THE WILWW SPRINGS P.U.D., PHASE ONE 3.1 General The final drainage plan for Phase One of the Willow Springs P. U. D . has been developed to provide a drainage system that meets the requirements set forth in the McClellands Basin Master Drainage Plan. This has been accomplished by designing a series of inlets, storm sewers and detention ponds which would serve to collect, convey and detain the runoff to allowable release levels given in the Master Plan. Sheet 1 shows the grading and drainage plan for the Willow Springs development . Included on the sheet are the proposed locations of the five detention ponds, the regional channel and the two associated culvert crossings; also shown on the sheet are the locations of the minor storm drainage facilities which include curb inlets, storm sewer pipes and minor drainage swales. Section 3 .2 presents a specific description of the proposed drainage plan for the Willow Springs development: The evaluation of street capacities and the design of all inlets, storm sewers and swales was performed based on the methodologies given in the SDDC Manual. Hydrologic calculations for the design of the local drainage facilities were performed using the Rational Method. A detailed description of the design of the local drainage facilities is provided in Section 3.3. For the purposes of detention pond design, the recently revised version of the Urban Storm Drainage and Flood Control District's Stormwater Management Model (MODSWMM) was used to determine both 10-and 100-year flows for the subbasins indicated on Sheet 1. The resulting runoff hydrographs were routed through conveyance elements and detention ponds to obtain the total peak discharge to the regional channel at Timberline Road. The detention ponds were designed to meet allowable release rate requirements. It is noted that since the McClellands Basin Master Plan has set the detention requirements for this development site, the hydrologic analysis was conducted for developed conditions only. Details of the detention pond volume and outlet structure design and other drainage improvements are provided in Section 3.4. The design of the regional channel was based on recommendations given in the Master Plan and was further modified to compliment the channel design in the Stetson Creek development downstream of the site. Analysis of the channel design was accomplished using the HEC-2 Water Surface Profiles computer model. The design of the culverts for the channel was conducted using the special culvert routine within HEC -2. In addition, the roadside swale and associated culvert parallel to Timberline Road were also designed using HEC-2 to provide a no-adverse-impact condition compared to the original design performed in conjunction with the Harmony Crossing development. Details of the channel and culvert design and all other regional drainage improvements are provided in Section 3.5. 5 I I I I I I I I I I I I I I I I I I I 3.2 Proposed Drainage Plan A qualitative summary of the flow conditions within each basin and at each design point is provided in the following paragraphs. Discussion of the detailed design of drainage facilities, which are introduced in this section, is included in Sections 3.3 and 3.4. It is noted that several subbasins will be rough graded and remain undeveloped in conjunction with Phase One. The discussion for these subbasins will be limited to their impact on drainage facilities designed in conjunction with the first phase. In general, the eastern half of the Willow Springs P. U .D. will be developed as part of Phase One. However, all detention and major drainage facilities for the · entire development site will be constructed in conjunction with Phase One. Reference is made to Sheet 1 which depicts the flow conditions and facilities described below. Detention Pond 310 would collect and detain runoff from Subbasins 1 through 10 as described in the following paragraphs. The lower portion of the pond would serve as an irrigation pond for the development; the maximum normal water surface elevation in the pond is proposed to be 4940.0 feet. A 36-inch RCP will be placed between the upper and lower portions of the pond in order to maintain a hydraulic connection. The main storm sewer system which delivers flow to Detention Pond 310 serves Subbasins 1 through 5 and 7. It is designed to convey the 2-year discharge directly to the lower portion of the pond. Within the greenbelt area south of the pond, a series of bubbler manholes will be placed to allow discharge greater than the 2-year event to exit the storm sewer system. All diversion flow will be conveyed to the upper portion of the detention pond in grass lined swales. For the first phase, Subbasin 1 will be rough graded and remain undeveloped. The 100- year runoff will be conveyed as overland flow to a low point at Design Point 1. The total 100-year discharge will be collected in a 24 -inch ADS pipe and conveyed to Design Point 2A. Runoff from the southern portion of Willow Springs Drive and the western portion of Weeping Way within Subbasins 2A and 2B, respectively, will be conveyed within rough graded street sections to the low point at Design Point 2A. (fhe 100-year developed condition flow would be collected by a 15-foot curb inlet.) In either case, flow will be joined by that from Subbasin 1 and conveyed under Willow Springs Drive in a 24-inch RCP to Design Point 2B. In both the rough-graded and future conditions, the 100-year runoff from the northern portion of Willow Springs Drive within Subbasin 2C will be conveyed within the street section to the low point at Design Point 2B and collected in a 5-foot curb inlet. All flow from Subbasins 1 and 2 will be conveyed by a 24-inch ADS pipe to MH-lC. In the future developed condition, runoff from Subbasin 5 would be collected along Arroyo Court and be conveyed to a curb inlet at Design Point 5 located at the eastern end of the cul-de-sac. The 100-year flow would be collected by the inlet and conveyed 6 I I I I I I I I I I I I I I I I in a future storm sewer to MH-lB. The flow from Subbasins 1, 2 and 5 would then be conveyed in an 18-inch ADS pipe to MH-lA. For the interim rough graded condition, runoff generated within Subbasin 5 will be conveyed to Detention Pond 310 by overland flow. Runoff from Sub basin 4 will be collected along the northern extension of Weeping Way and be conveyed to a 10-foot curb inlet at Design Point 4 located at the northern end of the cul-de-sac. The 100-year discharge will be collected by the inlet and conveyed in a 15-inch ADS pipe storm sewer to MH-lA. Runoff collected within Subbasin 3A (in the greenbelt between Weeping Way and Red Willow Court) will be conveyed to an area inlet at Design Point 3A by way of overland flow. The 100-year discharge will be collected by the inlet and conveyed to Design Point 3B by way of a 15-inch RCP. Runoff from the western portion of Red Willow Court, the eastern portion of Weeping Way and the southern portion of Willow Springs Drive (Subbasins 3B and 3C) will be conveyed by street flow to a 10-foot curb inlet at Design Point 3B. The total 100-year flow from Subbasins 3A, 3B and 3C will be transported under Willow Springs Way to Design Point 3C by way of a 21-inch RCP. Runoff collected within Subbasin 3D (northern portion of Willow Springs Way) will be collected by a 5-foot curb inlet at Design Point 3C. The 100-year flow from Subbasin 3 will be conveyed in a 24-inch ADS pipe to MH-2E. Runoff from Sub basin 7 A will be collected along Canopy Court and conveyed to a 10- foot curb inlet at Design Point 7 A, located at the western end of the cul-de-sac. The 100-year flow will be conveyed in a 15-inch ADS pipe to MH-2E. The flow will be joined with the storm sewer flow from Subbasin 3 and conveyed to MH-2D in a 24-inch ADS pipe. Runoff from Subbasin 7B will be collected along Catkins Court and conveyed to a 10-foot curb inlet at Design Point 7B, located at the western end of the cul-de-sac. The 100-year flow will be conveyed in a 15-inch ADS pipe to MH-2D. The total storm sewer flow from Subbasins 3 and 7 will be conveyed to MH-2B in a 24-inch ADS pipe and will continue to MH-lA in an 18-inch ADS pipe. The storm sewers upstream of MH-lC and MH-2E are sized to convey the 100-year flow from Subbasins 1 and 2 and Subbasin 3, respectively. Both of these manholes as well as four of the downstream manholes (MH's IA, lB, 2B and 2D) will be constructed with grated covers which are designed to divert flow out of the storm sewer to two grass-lined swales located in the central greenbelt area of the development. It is noted that MH-2C is designed not to overflow during the 100-year event. However, the manhole will be fitted with a slotted cover as a precautionary measure. For the First Filing, Subbasin 6 will be rough graded and remain undeveloped. The 100-year runoff will be conveyed as overland flow to the lower portion of Detention Pond 310. In the developed condition, runoff would be collected by inlets at Design Points 6 and 6A and be conveyed to the lower portion of Detention Pond 310 in future storm sewers. 7 I I I I I I I I I I I I I I I I I I I Runoff from Subbasin SA will be collected along the south side of Mackenzie Court and conveyed to a 10-foot inlet at Design Point 8A. Runoff from Subbasin SB will be collected along the north side of Mackenzie Court and be conveyed to a 5-foot inlet at Design Point 8B. Flow collected by the inlets will be conveyed to MH-4B by 15-inch RCPs. Flow will be conveyed to MH-4A in a 21-inch RCP and then to the lower portion of Detention Pond 310 in an 18-inch RCP. Subbasins 9 and 10 encompass the upper and lower portions of Detention Pond 310, respectively, as well as greenbelts and backs of lots surrounding the pond. Runoff from these subbasins will be conveyed to Detention Pond 310 by way of direct rainfall or overland flow. As noted above, the detention pond collects runoff from Sub basins 1 through 10. A 36-inch RCP will be placed between the upper and lower portions of the pond in order to maintain a hydraulic connection. Outflow from the lower portion of the detention pond will be conveyed directly to the regional channel in a 15-inch RCP. The pond discharge will be controlled by a 13.5-inch diameter orifice plate at the entrance to the outlet pipe. Runoff from Subbasin 15 will consist primarily of flow from the backs of lots along the west side of Black Willow Drive and the eastern portion of the Union Pacific Railroad easement. Flow will be conveyed in a swale to Detention Pond 315. Outflow from the detention pond will be conveyed to Design Point 16 in a 15-inch ADS pipe. The pond discharge will be controlled by a 4-inch square orifice plate opening at the entrance to the outlet pipe. Runoff from Subbasin 16 will be generated along the eastern portion of the Union Pacific Railroad easement and the backs of lots from the western portion of Black Bark Court. The 100-year flow will be joined with the releases from Detention Pond 315 at Design Point 16 and continue directly to the regional channel in an 18-inch ADS. Runoff collected along the southern portion of Pacific Court and the western portion of White Willow Court (within Subbasin 21A) will be conveyed by street flow to a 15-foot curb inlet at Design Point 21A. The 2-year runoff and a portion of the 100-year runoff will be conveyed to Design Point 20 in a 27-inch RCP. Runoff collected along the northern portion of Pacific Court and the western portion of White Willow Drive (within Subbasins 21B and 21C, respectively) will be conveyed as street flow to a 15-foot curb inlet at Design Point 20. Runoff from Subbasin 20 will be collected along the southern portion of Willow Springs Drive and conveyed within the street to the curb inlet at Design Point 20. Flow from the 2-year event will be collected by the inlet and conveyed to Design Point 20 in a 24- inch RCP. These flows will join the runoff from Sub basin 21 and be conveyed to Design Point 23A by way of a 29"H x 45"W HERCP. During the 100-year event, up to 6. 8 cfs will overtop the crown of the street and flow north on White Willow Drive and east on Willow Springs Drive. The portion of runoff generated along the northern portion of Willow Springs Drive and the western portion of White Willow Drive (within Subbasin 23A) will be collected by 8 I I I I I I I I I I I I I I I I I I a 10-foot curb inlet at Design Point 23A. All flow collected in the inlets at Design points 20, 21A and 23A will be conveyed under White Willow Drive in a 29"H x 45"W HERCP to Design Point 23B. The runoff from the eastern portion of White Willow Drive (within Subbasin 23B) will be collected by a 5-foot inlet at Design Point 23B. All flow will be conveyed to Detention Pond 324 by way of a 36-inch RCP. Runoff generated within Subbasin 22A (as well as overflow of 5 cfs from Design Points 20 and 21A) will be collected along the eastern portion of White Willow Drive and conveyed to Design Point 22C. Runoff from Subbasin 22B will be conveyed along Timberline Road to Design Point 22C. Prior to the final construction of Timberline Road, which will occur with the development of Willow Springs Phase 2, flow from Subbasin 22B will be conveyed in the existing roadside ditch to an 18-inch ADS pipe. The Pipe will connect to the inlet at Design Point 22C and will be abandoned with the final construction of Timberline Road. Local runoff generated within Subbasin 22C will be conveyed overland to Design Point 22C. The total 2-year flow will be collected by a 15-foot curb inlet and conveyed under Willow Springs Drive to Design Point 22D in a 24-inch RCP. Runoff from the 2-year event collected along the northern portion of Willow Springs Drive, east of White Willow Way, within Subbasin 22D will be intercepted by a 10-foot curb inlet at Design Point 22D. The flow collected by the inlets at Design Points 22C and 22D will be conveyed to Detention Pond 324 by a 30-inch RCP. For the 100-year event, up to 1.3 cfs will overtop the northern curb at Design Point 22D and flow directly to the detention pond. The 100-year runoff generated along the western portion of Timberline Road within Subbasin 24A will be collected by a 5-foot curb inlet at Design Point 24A and be conveyed to Detention Pond 324 by a 15-inch RCP. Subbasin 24B will remain undeveloped for the First Filing; in the future, it is planned that the site will serve as a neighborhood recreation area. Flow will be conveyed to Detention Pond 324 by a 4-foot sidewalk culvert at the northern end of the pond. For the interim condition, flow will be conveyed to the pond as overland flow. Flow from Sub basin 24C will be conveyed directly into the pond as overland flow. Outflow from the detention pond will discharge to Detention Pond 326 in a 24-inch ADS pipe. The release from this pond will be controlled by a 16.5-inch diameter orifice plate opening at the entrance to the outlet pipe. The 100-year runoff from Topanga Court and the western portion of White Willow Drive (within Subbasin 25A) will be conveyed by street flow to a 10-foot curb inlet at Design Point 25A, and then transported to Design Point 25B in a 21-inch RCP. Runoff from the eastern portion of White Willow Drive (within Subbasin 25B) will be conveyed by street flow to a 10-foot curb inlet at Design Point 25B. The total 100-year runoff from Subbasin 25 will be conveyed to Detention Pond 326 in a 24-inch ADS pipe. Runoff from Subbasins 26A and 26B will be conveyed to Detention Pond 326 by a swale flowing north, parallel to Timberline Road. The northern portion (Subbasin 26A) will be undeveloped for the First Filing. It is anticipated that the site will be used as a neighborhood recreation area. Subbasin 26C encompasses Detention Pond 326; all portions of the subbasin not included in the pond will overland flow into the pond. The 9 I I I I I I I I I I I I I I I I I I I pond will collect all runoff from Subbasins 20 through 26. Outflow from the pond will discharge to the regional channel by way of an 18-inch RCP. The pond discharge will be controlled by a 16-inch diameter orifice plate opening at the entrance to the outlet pipe. , The area between the regional channel and Battle Creek Drive is proposed to consist of multi-family residential dwellings. For Phase One, the eastern portion of this area will be developed. All runoff from the multi-family sites will be conveyed to Detention Pond 330 in a storm sewer. The pond is planned to meet the detention requirements for the multi-family site as well as a portion of a future residential development north of Battle Creek Drive. It is noted that the multi-family development shown in the eastern portion of Subbasin 30 has not been submitted with the utility plans for the first phase. However, the drainage plan submitted for that portion of the development has been prepared assuming a developed condition. The drainage facilities designed shall be constructed in conjunctio_n with the first phase. It is noted that prior to development of the multi-family site, a comparison must be made between the assumed and actual development pattern to ensure that the drainage facilities are adequate as designed. Runoff from Subbasin 30A will be collected along the southern half of Battle Creek Drive and conveyed as street flow to Design Point 30A. In the future, the site is slated to consist of multi-family units; flow would be collected by inlets and conveyed to Design Point 30A in a storm sewer. For Phase One, the subbasin will be rough graded and remain undeveloped. Runoff collected along Peachleaf Place (within Subbasin 30B) will be conveyed as street flow to Design Point 30A. The 100-year flow from Subbasins 30A and 30B will be collected by a 15-foot curb inlet and conveyed in a 30-inch RCP to Design Point 30E. Runoff generated along the northern portion of Battle Creek Drive (within Sub basin 30E) will be conveyed as street flow to Design Point 30E. The I 00- year flow will be collected by a 10-foot curb inlet. The total 100-year flow from Subbasins 30A, 30B and 30E will be conveyed to MH-13A in a 36-inch RCP. Runoff from Subbasins 30C and 30D will be conveyed as street flow to Design Point 300. The 100-year flow at Design Point 300 will be collected by a 15-foot curb inlet and conveyed to MH-13A in a 21-inch RCP. From MH-13A, the 100-year flow from Subbasins 30A through 30E will be conveyed to Design Point 30F in a 36-inch RCP. The 100-year flow from Subbasin 30F will be collected by a 5-foot curb inlet. The 100- year discharge from Subbasins 30A through 30F will then be conveyed to Detention Pond 330 in a 36-inch RCP. Subbasin 30G encompasses Detention Pond 330; all portions of the subbasin not included in the pond will overland flow into the pond. Outflow from Detention Pond 330 will discharge to the regional channel via a 18 -inch RCP. The pond discharge will be controlled by an 13-inch diameter orifice plate opening. 10 I I I I I I I I I I I I I I I I I I I Subbasin 40 accounts for all runoff generated within the regional channel and the back of lots adjacent to the channel upstream of the White Willow Drive culvert crossing. No detention or additional drainage facilities are planned for this subbasin. The 100-year runoff from Subbasin 40 is 12.2 cfs. Subbasin 42 accounts for all runoff generated along Timberline and Battle Creek Drive north of the Battle Creek Drive centerline. The 100-year runoff of 7.4 cfs will be collected by a 10-foot curb inlet and conveyed to the roadside swale parallel to Timberline Road by a 15-inch ADS pipe. Subbasin 41 includes runoff generated within the regional channel and along portions of Battle Creek Drive and Timberline Road which could not be directed toward any of the detention facilities. The 100-year runoff of 14. 7 cfs along Timberline Road (from Subbasins 41A and 41C) will be collected by two 5-foot curb inlets at Design Point 41 (designed in conjunction with the Timberline Road expansion). Flows intercepted by this inlet will be directed into the regional channel upstream of Timberline Road. 3.3 Design of Drainage Improvements 3.3.1 General The proposed drainage plan for Phase One consists of a combination of street flow, curb inlets, storm sewers, swales, cross pans and detention ponds. Final lot grading details will ensure that each lot is graded and landscaped to provide positive drainage around and away from building foundations. Within the first phase, drainage easements have been provided where necessary to ensure that overland flows can be collected and conveyed through well-defined drainage swales or storm sewers. 3.3.2 Rational Method Hydrologic Analysis The Rational Method was selected as the method for estimating the runoff from the site for the design of local drainage facilities. The Rational Method utilizes the SDDC Manual equation: Q = CtCIA (1) where Q is the flow in cfs , A is the total area of the basin in acres, Cr is the storm frequency adjustment factor, C is the runoff coefficient, and I is the rainfall intensity in inches per hour. 11 I I I I I I I I I I I I I I I I I I I The runoff coefficient was calculated for each subbasin using the following values: (a) 0.95 for all streets and impervious areas; (b) 0.60 for all multi-family lots; (c) 0.45 for all single-family lots; (d) 0 .20 for all open spaces and greenbelts; and (e) 0. 70 was assumed for the future neighborhood recreation area. The frequency adjustment factor, Cf, is 1.0 for the initial (2-year) storm and 1.25 for the major (100-year) storm. The appropriate rainfall intensity information was developed based on the rainfall intensity duration curves in the SDDC Manual (SDDC Figure 3-1 which is included in Appendix A of this report). To obtain the rainfall intensity, the time of concentration must be determined. The following equation was utilized to determine the time of concentration: (2) where t is the time of concentration in minutes, t f is the initial or overland flow time in C 0 minutes, and t t is the travel time in the ditch, channel, or gutter in minutes. The initial, or overland, flow time was calculated with the SDDC Manual equation: (3) where L is the length of overland flow in feet (limited to a maximum of 500 feet), S is the average basin slope in percent, and C and Cf are as previously defined. This procedure for computing time of concentration allows for overland flow as well as travel time for runoff collected in streets, gutters, channels, pipes, or ditches. A summary of the results of the hydrologic analysis are provided in Table 3.1; this table is also included on Sheet 1. All Rational Method calculations and associated information are contained in Appendix A. 3.3.3 Allowable Street Capacities The majority of streets within Phase One are considered local streets. Battle Creek Drive and Keenland Drive are both considered collector streets and Timberline Road is classified as an arterial. The local streets incorporate a roadway width (flowline to flowline) of 36 feet and are characterized by a 2 percent cross slope and a Fort Collins standard 4. 75-inch rollover curb. The collector and arterial streets are proposed to have 6-inch vertical curbs. The collector streets will incorporate a roadway width of 50 feet, Timberline Road will have a width of 70 feet. Allowable gutter flows and maximum street encroachments for both the initial and major storms were estimated and evaluated based on the specifications set forth in the SDDC Manual. 12 I I I I I I I I I I I I I I I I I I I Table 3.1. Summary of Design Flows at All Design Points for Fully Developed Conditions. 1 1 8.41 0.42 1.8 5.5 6.4 24.3 2A 1, 2A, 2B 11.46 0.47 1.8 5.5 9.7 37.0 2B 1, 2 13.05 0.49 1.8 5.5 11.5 44.0 SB 1, 2, 5 16.18 0.52 1.7 5.0 14.3 52.6 3A 3A 2.72 0.33 2.2 6.8 2.0 7.6 3B 3A, 3B, 3C 5.02 0.45 2.2 6.8 5.0 19.2 3C 3 5.73 0.47 2.2 6.8 5.9 22.9 7A 7A 1.70 0.64 2.6 7.0 2.8 9.5 7C 3, 7A 7.43 0.51 2.1 6.0 8.0 28.4 7B 7B 1.55 0.63 2.6 7.0 2.5 8.5 7D 3, 7 8.98 0.53 2.0 5.8 9.5 34.5 4 4 1.61 0.72 3.8 7.0 4.4 10.1 9 1-5, 7 26.77 0.53 1.7 5.0 24.1 88.7 9 1-5, 7, 9 45.11 0.46 1.3 4.0 27.0 103.8 6 6 11.60 0.59 1.7 5.0 11.6 42.8 8A 8A 1.37 0.66 2.8 7.0 2.5 7.9 8B 8 2.25 0.65 2.7 7.0 3.9 12.8 10 1-10 67.45 0.47 1.3 4.0 41.2 158.5 15 15 7.12 0.27 1.9 5.4 3.7 13.0 16 16 1.80 0.24 1.6 4.6 0.7 2.5 21A 21A 6.22 0.47 1.9 5.6 5.6 20.5 20 20, 21 13.10 0.48 1.7 5.0 10.7 39.3 23A 20, 21, 23A 14.33 0.49 1.7 5.0 11.9 43.9 23B 20, 21, 23 15.33 0.50 1.7 5.0 13.0 47.9 22C 22A, 22B, 22C 6.67 0.52 2.0 6.0 6.9 26.0 22D 22 7.16 0.52 2.0 6.0 7.4 27.9 24A 24A 1.04 0.74 2.7 7.0 2.1 6.7 24C 20-24 25.89 0.50 1.7 5.0 22.0 80.9 25A 25A 2.51 0.65 2.6 7.0 4.2 14.3 25B 25A, 25B 4.01 0.63 2.5 7.0 6.3 22.1 26B 26A, 26B 2.12 0.45 2.0 5.9 1.9 7.0 26C 25, 26 6.91 0.53 2.0 5.9 7.3 27.0 30A 30A, 30B 5.02 0.65 2.0 6.2 6.5 25.3 30D 30A-D 7.96 0.65 1.8 5.7 9.3 36.9 30E 30E 1.41 0.95 2.3 6.7 3.1 9.4 30F 30A-F 9.80 0.70 1.8 5.7 12.3 48.9 30G 30A-G 11.77 0.64 1.8 5.7 13.6 53.7 40 40 6.09 0.37 1.5 4.3 3.4 12.2 41A 41A, 41C 2.32 0.72 2.6 7.0 4.1 14.7 42 42 1.05 0.81 2.6 7.0 2.2 7.4 41 40, 41.42 10.60 0.47 1.5 4.3 7.5 26.8 13 11 I I I I I I I I I I I I I I I I I I During the initial storm, runoff is not allowed to overtop the curb for either of the street configurations. Initial storm flows are allowed to spread to the crown of the local streets and must leave one lane free for collector streets. Initial storm flows on Timberline Road must be limited to ensure at least one half of the road width is free of water (17.5 feet on either side of the crown). Per the SDDC Manual, the maximum street runoff criteria during the major storm event limits the depth of water over the crown to less than or equal to 6 inches for both local and arterial streets. A normal depth analysis of the allowable street capacities was performed using HEC-2 [U.S. Army Corps of Engineers, 1991]. The normal depth option with a single cross section was used to find the flow rate associated with the allowable depth. For the local streets, a nomograph was prepared to relate street slope to the allowable street flow (both with and without reduction factors). The calculations associated with the street capacity analysis are included in Appendix B. The results of the street capacity analysis are summarized in Table B-1. Street capacities would not be exceeded the First Filing. The associated HEC -2 output for the normal depth analyses and for the preparation of the street capacity nomographs are presented in Appendix C. 3.3.4 Curb Inlet Desiw As indicated in the previous section, it was determined that street capacities would not be exceeded at any location within the First Filing. As a result, all inlets within the development will be in a sump condition. Curb inlets will be placed (as described in the Section 3.4.2) at all low points within the development site. In addition, local sump conditions were created at street intersections at Design Points 20, 21A and 30B in order to meet street capacity requirements. Per SDDC Manual guidelines, the theoretical capacities of the curb inlets were reduced by 10 to 20 percent depending on the length of each inlet. The calculations associated with the curb inlet design are provided in Appendix D. A summary of the inlet design is provided in Table D. l (page Dl/32 in the Appendix). 3.3.5 Storm Sewer Desiw In general, the storm sewer pipes were designed to convey the 100-year flow to the detention ponds. The storm sewers which convey flow from Design Points 20, 21A and 30 were sized to convey the theoretical capacity of the inlets during the 100-year event since the associated inlets are not designed to intercept the full 100-year runoff. However, excess flow 14 I I .1 I I I I I I I I I I I I I I I I not conveyed by these storm sewer segments will be collected by downstream inlets. As noted in Section 3.2, the storm sewers upstream of MH-lC and MH-2E are sized to convey the 100- year flow from Subbasins 1 and 2 and Sub basin 3, respectively. Both of these manholes as well as four of the downstream manholes (MH's lA, lB, 2B and 2D) will be constructed with grated covers which are designed to divert flow out of the storm sewer to two grass lined swales located in the central greenbelt area of the development during low frequency (high flow) events. It is noted that MH-2C is designed not to overflow during the 100-year event. However, the manhole will be fitted with a slotted cover as a precautionary measure. The storm sewer system (which serves Subbasins 1 through 5 and 7) is designed to convey the 2-year discharge without any diversions to the swales . The initial design of all storm sewer pipes was accomplished using Manning's equation and assuming full pipe flow conditions. All storm sewers under streets were designed as reinforced concrete pipes (RCPs). Most of the pipes in the greenbelt areas are ADS pipes. The minimum invert slope for all pipes within the first phase is 0.5 percent. A detailed hydraulic analysis and hydraulic grade line determination of the final pipe design was performed using the UDSewer pipe hydraulic analysis model, developed by the Urban Drainage and Flood Control District. Final designs for the storm sewers connecting: (a) Subbasins 1 through 5 and 7 to Detention Pond 310, (b) Subbasin 8 to Detention Pond 310, (c) Subbasins 20, 21 and 23 to Detention Pond 324, (d) Subbasin 22 to Detention Pond 324, (e) Subbasin 24A to Detention Pond 324 , (f) Subbasin 25 to Detention Pond 326, and (g) Subbasin 30 to Detention Pond 330, were all conducted using the UDSewer model and considering the maximum tailwater in the detention ponds. For the design of the storm sewer system for Sub basins 1 through 5 and 7, an iterative process was used to determine the actual storm sewer flow and diversions expected during the 100-year event. The UDSewer program was used to determine the hydraulic gradeline at each of the manholes while the diversion discharge was calculated using the orifice equation. A continuity check was performed at each junction to ensure that the grated opening for each manhole would be sufficient to convey the diversion flow. Each of the six storm sewer manholes in the open space area south of Detention Pond 310 would have a grated opening with an open area of five square feet. Detention Pond 330 has been designed with excess capacity which is intended to be used for future development to the north of Battle Creek Drive. Therefore, the analysis of the storm sewer was based on the maximum future expected ponded water surface elevation of 4940.0 feet thereby providing 1-foot of freeboard). In addition, the hydraulic grade lines computed by this analysis are shown on the Utility Plans. All storm sewer design calculations are provided in Appendix E. 15 I I I I I I I I I I I I I I I I I I I 3.3.6 Draina~e Swale Desiw Five drainage swales have been planned in conjunction with the First Phase. Two of the swales drain the interior open space areas within Subbasin 9. The third swale drains the interior open space within Subbasin 3A, the fourth swale runs parallel to Timberline Road and would convey flow from Subbasin 26 to Detention Pond 326, and the fifth swale runs parallel to and along the north side of Battle Creek Drive to provide adequate conveyance for off-site flows. To account for freeboard requirements, all five swales were designed to convey 1.33 times the 100-year flow. A typical cross section for these five swales can be found on Sheet 2. Each of the swales was designed assuming normal flow conditions using Manning's equation. The hydraulic analysis indicated that the 100-year flow velocities in the swales, for the major storm event, would range from 1.6 to 3.3 fps which are less than the maximum velocity of 5 fps allowed for a bluegrass-lined channel (from SDDC Manual). Results of the normal depth analysis for the swales may be found in Appendix F. In addition, emergency overflow swales have been designed at nine locations in the first phase to provide conveyance for flows in the event inlets or storm sewers become substantially obstructed . Each of the swales would be placed in a drainage easement between house lots and would flow directly to one of the detention ponds. 3.3. 7 Riprap Protection Desiw At all storm sewer outlets, riprap outlet protection will be provided to minimize the potential for erosion. The riprap was sized based on procedures given in the SDDC Manual. Each of the storm sewer outlets into the detention ponds (Outlets 1, 4, 5, 6, 7, 8, 9 and 13) require a riprap installation using Class 6 riprap . Each of the storm sewer outlets to the regional channel are designed using Class 12 riprap. Details and specifications for all storm sewer outlet protection installations are given on Sheet 2. All riprap design calculations are given in Appendix G. In addition, riprap protection is required for the overland flow/swale entrances for Detention Ponds 315 and 326. This protection would be required because of concentrated flows cascading down the pond side slope (25 % slope). At both of these locations, Class 12 riprap has been specified to dissipate energy and to minimize erosion potential. Details and specifications for this installation are provided on Sheet 2. 16 I I I I I I I I I I I I I I I I I I I 3.4 Detention Pond Design 3.4.1 Hydrolo~ic Analysis for Detention Pond Desi~n SWMM was used to model the basin response to both the 10-and 100-year rainfall events. The rainfall hyetographs, surface runoff resistance factors, surface storage values and infiltration parameters were taken from the McClellands Basin Master Drainage Plan. The remaining subcatchment parameters (area, width, slope and percentage of imperviousness) and conveyance parameters (diameter, length and slope) were taken from the proposed grading and drainage plan for the Willow Springs development. The percentage of imperviousness was calculated for each subbasin using the following values: (a) 100 percent impervious for all streets; (b) 60 percent impervious for all multi-family lots; (c) 45 percent impervious for all single-family lots; and (d) 5 percent impervious for all open spaces and greenbelts; and (e) 70 percent impervious for the future neighborhood recreation center. It is noted that the overall percentage of imperviousness would be 44 .2 percent which appears to be conservatively high for a development of this density considering the amount of open space and greenbelts within the drainage basin. A summary of the SWMM subbasin parameters is provided in Table 3.2. Results of the hydrologic analyses are presented in conjunction with the final design of the detention ponds in Section 3.4.2. Documentation of the SWMM model parameters is provided in Appendix H. The output files for the SWMM analysis are also provided in Appendix H. 3.4.2 Final Desim of Proposed On-Site Detention Ponds As described in Section 3.2, five detention ponds would be required within the Willow Springs development to reduce the peak discharge from the site to the allowable levels mandated in the McClellands Basin Master Drainage Plan. The allowable release rates for the site are 0.5 cfs/acre for the 100-year event and 0.2 cfs/acre for the IO-year event. The total tributary drainage area for the Willow Springs development is 130.5 acres; this corresponds to an allowable peak discharge of 65 cfs for the 100-year event and 26 cfs for the IO-year event. The design of each of the ponds was performed to maximize detention storage while providing adequate freeboard, to meet the overall site release requirement. Detention Pond 310 provides excess detention to account for on-site areas which could not be detained in the remaining ponds , and to reduce the storage requirements for the on-site detention ponds adjacent to Timberline Road. The detention volume for Detention Ponds 324 and 326 were maximized based on the adjacent grading and site plans; the outlet structures for these ponds were designed 17 I I I I I I I I I I I I I I I I I I I 1 2 3 4 5 6 7 8 9 10 15 16 20 21 22 23 24 25 26 30 40 41 1,200 8.4 1,350 4.6 800 5.7 300 1.6 800 3.1 2,500 11.6 750 3.3 450 2.3 3,000 18.3 1,400 8.5 1,300 7.1 200 1.8 600 4.1 1,400 9.0 1,800 7.2 1,000 2.2 500 3.4 900 4.0 1,000 2.9 1,700 11.8 1,300 6.1 800 3.5 Table 3.2 Summary of SWMM Subbasin Parameters. 38 0.020 0.020 0.25 0.1 0.3 64 0.020 0.020 0.25 0.1 0.3 44 0.020 0.020 0.25 0.1 0.3 74 0.020 0.020 0.25 0.1 0.3 64 0.020 0.020 0.25 · 0.1 0.3 60 0.020 0.020 0.25 0.1 0.3 57 0.020 0.020 0.25 0.1 0.3 67 0.020 0.020 0.25 0.1 0.3 29 0.020 0.020 0.25 0.1 0.3 25 0.020 0.020 0.25 0.1 0.3 17 0.015 0.020 0.25 0.1 0.3 12 0.020 0.020 0.25 0 .. 1 0.3 46 0.020 0.020 0.25 0.1 0.3 46 0.020 0.020 0.25 0.1 0.3 51 0.020 0.020 0.25 0.1 0.3 61 0.020 0.020 0.25 0.1 0.3 42 0.020 0.020 0.25 0.1 0.3 65 0.020 0.020 0.25 0.1 0.3 31 0.020 0.020 0.25 0.1 0.3 60 0.020 0.020 0.25 0.1 0.3 29 0.020 0.020 0.25 0.1 0.3 50 0.020 0.020 0.25 0.1 0.3 18 0.51 0.50 · 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 0.51 0.50 0.0018 I I I I I ~- I I I I I I I I I I I I I 11 to maximize the active storage volume within the given detention ponds. Detention Ponds 315 and 330 were designed to release slightly less than the allowable 0.5 cfs/acre. In a cooperative effort with the adjacent landowner to the north, Detention Pond 330 was identified to provide detention storage for future residential development. Preliminary development plans for the adjacent site indicate that approximately 12 acres would be directed toward Detention Pond 330. Preliminary design calculations performed (but not included in this report) indicate that the pond would have adequate storage volume for an additional 12 acres and that the outlet pipe would have sufficient capacity to convey an additional 6 cfs (0.5 cfs/acre) if the proposed orifice plate is removed in the future. A stage-storage-discharge rating curve was developed for each of the detention ponds, using an iterative procedure, in order to meet the allowable discharge requirements for the site. First, a stage-storage rating curve was developed for each of the ponds using the methodologies given in the SDDC Manual. For each of the detention ponds, an orifice plate is required to limit the discharge from the pond. For Ponds 315, 324, 326 and 330, the stage-discharge curve for these ponds was calculated using the orifice equation: Q = CA (2gH) 112 (1) where Q is the discharge through the orifice in cfs; C is the orifice coefficient (0.62); A is the open area of the orifice opening; g is the acceleration due to gravity (32.2 ft/sec 2); and His the difference in elevation between the ponded water surface and the hydraulic gradeline in the outlet pipe immediately downstream of the orifice opening (or the centroid of the orifice opening, whichever is greater). For Pond 315 the hydraulic gradeline was calculated assuming normal flow conditions using Manning's equation. The hydraulic gradeline downstream of the outlets for Ponds 324 and 326 was calculated using UDSewer. In the case of Pond 330, the downstream hydraulic gradeline was taken to be the water surface elevation in the regional channel upstream of the proposed Timberline Road culvert crossing. The stage-storage and stage-discharge rating curves for Ponds 315, 324, 326 and 330 were combined to form storage discharge curves required for the SWMM simulation. Documentation of the development of the stage-storage-discharge rating curves is presented in Appendix H. The storage-discharge rating curve for Pond 310 used in the overall SWMM model was developed assuming that the upper and lower portions of the pond maintain a hydraulic connection. The stage-storage curve for the pond is a combination of the upper and lower portions of the pond . The stage-discharge rating curve was taken from a detailed hydraulic analysis of the pond performed using the EXTRAN model which is detailed in the following paragraph. 19 I I -I I I I I I ' I , I I I I I I I I I I I "I ' -----· --------------------------------------------- A detailed hydraulic evaluation of Detention Pond 310 was performed using the Extended Transport Block 'of the EPA's Storm Water Management Model (EXTRAN). EXTRAN is a hydraulic routing model based on the Saint-Venant equations for gradually-varied unsteady flow. The detention storage for both the upper and lower portions of the pond were input as a stage .storage rating curve. Physical parameters for the pond outlet pipe and orifice plate, as well as the pipe between the two portions of the pond, were input into the model. An equivalent Manning's n was calculated for both pipes to account for entrance and exit losses. A separate SWMM model was developed to provide inflow hydrographs to each portion of the pond. The lower portion of the pond would receive runoff from the 2-year event from Subbasins 1 through 5 and 7 as well as the 100-year flow from Subbasins 6, 8 and 10. The upper portion of the pond would receive incremental flows above the 2-year event from Subbasins 1 through 5 and 7 and the entire 100-year flow from Subbasin 9. In addition, a constant inflow of 1 cfs was added to account for possible irrigation inflow. In modeling the inflow hydrographs to Detention Pond 310, the simplifying assumption was made that the swales and pipes will not significantly attenuate storm runoff. Consequently, swale and ·pipe conveyance elements were not used in the model. This assumption will result in conservatively high peak flows to the pond. Two diversion rating curves were used in the SWMM model to simulate the overall operation of the bubbler manholes. As a result, the model is a simplified representation of the physical system and does not model each of the individual bubbler manholes. The results of the EXTRAN analysis indicated that a 36-inch RCP would be necessary to maintain an adequate hydraulic connection between the upper and lower portions of the pond. The backup calculations and final results from the EXTRAN analysis are included in Appendix I. , Results of the SWMM analysis indicate that the overall 100-year discharge from the site is 63.9 cfi which corresponds to a unit release of less than 0.5 cfs/acre; thereby meeting the Master Plan release requirement for the 100-year event. The 10-year discharge is 33 cfs which exceeds the mandate.cl release rate of 26 cfs. It is noted that direct rainfall on the regional channel and the west half of Timberline Road (which cannot be directed to any of the proposed detention ponds) results in a 10-year runoff rate of 22 cfs. Therefore, a variance is requested to allow a JO-year discharge of 33 cfs in the regional channel at Timberline Road; this qorresponds to a unit runoff of 0.25 cfs/acre, as compared to the prescribed 0.2 cfs/acre. Table 3.3 presents a summary of the design of the detention pond outlet facilities. A summary of the discharge, active storage volume, maximum ponded water surface elevation and minimum freeboard for each of the detention ponds is provided in Table 3.4. It is noted that each of the ponds would maintain at least 1.2 feet of freeboard during the 100-year event. Complete results of the SWMM analyses are given in Appendix H. 20 I I I I I I I I I I I I I I I I I I :I Table 3.3 Summary of Preliminary Detention Pond Facilities Design. 310 67.4 15-Inch 13.5" Round 4940.0 4935.9 4940.0 4947.0 RCP Orifice Plate 315 7.1 15-Inch 4.0" Square 4948.0 4945.0 4946.2 4956.0 ADS Orifice Plate 324 25.9 24-Inch 16.5" Round 4946.0 4939.0 4942.3 4954.0 ADS Orifice Plate 326 32.8 18-Inch 16" Round 4936.5 ·4933.0 4937.6 4944.0 RCP Orifice Plate 330 11.8 18-Inch 13" Round 4935.oa 4934.0 4937.6 4941.0 RCP Orifice Plate • Pond volume below elevation 4937.6 is assumed to be ineffective due to tailwater conditions in the regional channel. Table 3.4 Summary of Detention Pond Operation Parameters. 310 6.6 9.0-11.3 4945.8· 1.2 315 0.4 0.9 4951.9 1.1 1.0 4954.4 1.6 324 11.9 1.6 4949.9 16.0 3.4 4952.2 1.8 326 12.0 1.0 4941.3 15.0 1.4 4942.3 1.7 330 3.7 0.9 4938.4 5.0 1.8 4939.0b 2.0 • Pond 310 discharge and water surface elevations were calculated using the EXTRAN model. b The volume between elevations 4939.0 and 4940.0 has been reserved for future residential development north of Battle Creek Drive. 21 I I I I I I I I I I I I I I I I I I I 3.5 Fmal Design of Regional Conveyance Facilities 3.5.1 Desi2n of the Regional Channel As noted in Section 3 .1, the preliminary design of the McClellands Channel was based on recommendations given in the Master Plan and was further modified to compliment the channel design in the Stetson Creek Development downstream of the site. The channel would be grass-lined with a minimum 15-foot bottom width and with maximum side slopes of 4H: 1 V. A four-foot wide, one-foot deep trickle channel would meander within the channel bottom . The meander amplitude would be six feet; the meander wavelength will be approximately 200 feet. In accordance with requests from the Storrnwater Utility, the bottom width and side slopes will vary randomly along the channel to provide diversity in the riparian system and to increase the aesthetics of the channel. The channel has been designed to provide a minimum of one foot of freeboard for the 100-year event. The typical channel cross -section is shown on Sheet 2. The hydrology for the design of the McClellands Channel is based on the regional SWMM model developed for the Stetson Creek P. U. D. The regional SWMM model was revised as part of this analysis to correct a routing error and to account for required on-site detention between the UPRR and Timberline Road. Two SWMM nodes (50 and 51) were added upstream of Conveyance Element 17 (regional channel within the Oalaidge P. U. D.) in order to route eleven conveyance elements to Element 17 (the maximum number of tributary elements is ten). F.ach of the three undeveloped subbasins between the UPRR and Timberline Road (301, 303 and 304) were modified to reflect future developed conditions. The percentage of imperviousness was increased to 45 percent and the subbasin width was increased to correspond to an overland flow length of 300 feet. Subbasins 301, 303 and 304 were then routed into conceptual detention ponds (301, 303 and 304, respectively) with a release rate corresponding to the allowable 0.5 cfs/acre. According to the revised regional SWMM model, the 100-year peak discharge would be 357 cfs at the Union Pacific Railroad and 453 cfs at Timberline Road. The input and output files for the revised regional SWMM analysis are included in Appendix J. The design discharge profile for the regional channel was specified: (1) using the 100- year discharge (at the Union Pacific Railroad) as given in the regional SWMM model; and (2) adding the 100-year release rates along the reach from the Willow Springs site, based on the hydrologic modeling for this study. Local inflows from the detention ponds and direct rainfall on the channel were added to give a discharge profile through the development site. As currently graded, the tributary area north of the channel, upstream of Battle Creek Drive, is 4.9 acres. Since it is uncertain where the future drainage divide will be located on the property as it develops, an additional 10 acres of land were assumed to be added to the channel west of 22 I I I I I I I I I I I I I I I I I I I Battle Creek Drive. Local inflows from the undeveloped site to the north of the regional channel, were assumed to have a peak release rate of 0.5 cfs/acre. Therefore, in order to meet the channel design discharges defined for this study, future development north of the Willow Springs P. U.D. must limit the total runoff to the regional channel upstream of Battle Creek Drive to 7.5 cfs (14.9 acres x 0.5 cfslacre). Analysis of the channel design was accomplished using the HEC-2 Water Surface Profiles computer model. The six downstream cross sections of the HEC-2 model were taken from the model developed by Northern Engineering for the design of the Timberline Road crossing. The first cross section is located 118 feet downstream of Timberline Road. The downstream water surface was determined by the slope-area (normal depth) option. The Manning's n value used for the regional channel through the current study reach (upstream of Timberline Road) is 0.035. The proposed culvert crossings at Timberline Road (double 4'H x 8'W RCB), White Willow Drive (triple 60-inch RCP) and Battle Creek Drive (triple 60-inch RCP) were analyzed using the special culvert routine within HEC-2. The results of the analysis indicate that, in general, the 100-year flow depth in the channel would be approximately 4.0 feet. On the upstream side of the culvert crossings, the flow depth would be controlled by the culvert capacity. The largest flow depth within the development site would be 5 .3 feet and would occur upstream of the White Willow Drive culvert crossing; this is a local condition caused by the culvert and is not indicative of the general channel behavior. The average velocity in the non-back:watered sections of the channel would be 4. 7 fps. Upstream of each the culvert crossings, velocities during the 100-year event would be approximately 2. 8 fps. The velocity in the trickle channel would be 2.3 fps at a full depth of one foot; the trickle channel would be subjected a worst case velocity of 5.0 fps during the 100-year event. Each of these velocities are less than the maximum erosive velocities allowed for a grass-lined channel. The results of the HEC-2 water surface profile analysis and associated calculations for the design of the regional channel are included in Appendix K. 3.5.2 Desi29 of the Major Off-Site Swale (North) Off-site flows along Timberline Road, north of Battle Creek Drive, would be conveyed by pipe under Battle Creek Drive and then in an open swale to the regional channel. For the fully developed condition, the 100-year discharge would be 61 cfs which corresponds to 0.5 cfs/acre from the upstream contributing drainage basin. The existing condition discharge, including the Harmony Crossing developing, would be 66 cfs . The culvert and swale were designed, using the HEC-2 program, to convey 66 cfs (the larger of the existing and developed condition 100-year discharges). 23 I I I I I I I I The existing roadside swale was designed in conjunction with the Harmony Crossing development to be a trapezoidal grass-lined swale with 4H: 1 V side slopes. A concrete pan was designed to span the 4-foot bottom width. A backwater analysis of the existing channel was performed using the HEC-2 model. It was determined that for the existing condition, the 100- year water surface elevation at the northern end of the proposed Battle Creek Drive Crossing is 4937.63 ft, msl. The proposed configuration of the swale was designed to convey the 100-year discharge with a water surface elevation of 4937.63 ft, msl at the upstream end of the Battle Creek Drive Crossing (no-adverse-impact compared with existing conditions). The grass-lined swale from the regional channel to Battle Creek Drive would be expanded to incorporate a ten-foot bottom width with a four -foot wide concrete trickle pan. The culvert installation under Battle Creek Drive is designed to be four parallel 48-inch RCP's. The off-site hydrologic calculations and the results of the HEC-2 water surface profile analysis for both the existing and proposed conditions are included in Appendix L. I 3.6 Statement of Maintenance Responsibility I I I I I I I I I I The regional channel is expected to be seeded with a combination native dryland grasses and bluegrass and would be dedicated to the City after certification and acceptance of the facility. However , the channel is to be maintained by the Willow Springs Homeowners Association. Furthermore, any drainage facilities within city rights-of-way would be maintained by the City. All other drainage facilities would be maintained by the Willow Springs Homeowners Association. 24 I I I I I I I I I I I I I I I I I I I IV. EROSION CONTROL PLAN The Erosion Control Plan for this site was designed in accordance with the criteria set forth in the SDDC manual. Transportation of sediment to the irrigation pond (lower Portion of Detention Pond 310) and the regional channel would be controlled by the implementation of a silt fence. Inlet filters would be installed shortly after construction on all proposed inlets to trap any sediment which may be transported prior to seeding. It is also noted that the site would be reseeded and mulched immediately following final grading of the swale. Straw bale barriers would be placed within each of the major swales and the regional channel, as well as at the outlets of each of the detention ponds to further inhibit the motion of sediment to the regional channel. Erosion control effectiveness calculations were performed for the entire Willow Springs development site. The site was split into seven sub-areas for the erosion control effectiveness calculations: (1) Subbasins 1 through 5, 7 and 9 (tributary ·to the upper portion of Detention Pond 310); (2) Subbasins 6, 8, and 10 (tributary to the lower portion of Detention Pond 310); (3) Subbasins 15 and 16 (western fringe of the development, tributary to the regional channel); (4) Subbasins 20 through 24 (tributary to Detention Pond 324); (5) Subbasins 25 and 26 (tributary to Detention Pond 326); (6) Subbasin 30 (tributary to Detention Pond 330); and, (7) Subbasins 40 and 41 (tributary to the regional channel). The erosion control effectiveness was calculated for each of the sub-areas based on the methodologies given in the SDDC Manual. An overall basin effectiveness was then calculated based on a weighted average of the each of the sub -areas. It is noted that the erosion control effectiveness calculations are greater than the performance standard for the overall development. Calculations for the performance standard and the erosion control effectiveness are given in Appendix M. Table 4.1 outlines the construction sequence for the Erosion Control Plan; this table is also included on Sheet 1. The erosion control cost estimate for the single-family development is provided in Table 4.2. The cost estimate results indicate that a total security of $108,225 would be required for Phase One. 25 I I I I I I I I I I I I I I I I I I I Table 4.1. Construction Sequence. Project: Willow Sprin&s P.U.D. Sequence for 192.5. Only Completed By: CLD Standard Form C Date: 5/3/95 Indicate by use of a bar line or symbols when erosion control measures will be installed. Major modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. Year 95 Month May Jun Jul Aug Sep Oct Nov Dec Demolition Overlot Grading Wind Frosion Control: Soil Roughing Perimeter Barrier Additional Barriers Vegetative Methods Soil Sealant Other Rainfall Erosion Control Structural: Sediment Trap/Basin Inlet Filters Straw Barriers Silt Fence Barriers Sand Bags Bare Soil Preparation Contour Furrows Terracing Asphalt/Concrete Paving Other Vegetative: Permanent Seed Planting Mulching/Sealant Temporary Seed Planting Sod Installation Nettings/Mats/Blankets Other Structures: Installed by --=C--=O=NTRA..a..=.=.=...:..C=-T=-O=R-------Maintained by __ --=O"""WNE""""""'"=R'---- Vegetation/Mulching Contractor To Be Decided by Bid Date Submitted: 5/3/95 Approved by City of Fort Collins on ____ _ 26 96 Jan I I I I I I I I I I I I I I I I I I I ----~--------------------------------------- V. 1. 2. 3. 4. 5. REFERENCES City of Fort Collins, May, 1984. "Storm Drainage Design Criteria and Construction Standards". Greenhorne & O'Mara, Inc., June 20, 1986. "McClellands Basin Master Drainage Plan". Prepared for the City of Fort Collins. RBD, Inc., January 28, 1994. "Final Drainage and Erosion Control Study for Harmony Crossing P.U.D." Prepared for Richland Homes. RBD, Inc., April 29, 1994. "Final Drainage and Erosion Control Study for Stetson Creek P.U.D., First Filing" Prepared for Geneva Corporation. Roesner, L.A ., Aldrich, J.A., and R.L. Dickinson, Storm Water Management Model User's Manual, Version 4: Addendum I, EXTRAN, EPA/600/3 -88/00lb (NTIS PB88- 236658/AS), Environmental protection Agency, Athens, GA, 1988. 28 1. -------·---------- I I I I I I I APPENDIX A RATIONAL METHOD CALCULATIONS I I I I I I I I I I I I I De , , 111 Vi , , 1 1 ~ ': ) 1 ) 1 : l b c : 1 ~ 1 (I 1 0 N. . , 1 1 1 1 : J t r &i ~ , n ~u ~ e r { S w Q ( ~ - - - .{ ~ ( 1 1 1 1 / l ) _ i ( M { h , ) ,4 1) , j c W ; i r , { ( c h ) ~ § : z c i Lo r : (f , , So i = - L f · t o F {t 1 1 1 1 ' 1 ) L , '5 T V f r ( q 3- - ~ ~ -9 C, r J- - y r /( ) 0 - , r J- y , /0 ( ) - y ' (a c i t ' J ) J. ~ y r / W - y r c: , a -v i i( ~ 5 0 0 ~ (° l o ) )- v " " /0 0 - y r J~ ~ r IO J -- v (f t ) ( 0/o ) (F , n ) (~ 1 1 1 ) 2? ~ ~ \ ) 0 !1 I 1 I ri o ·J D, 4 J /, o ,. ~ s 11 , 1 ci . . s wo o b. C t /, 1 8, 8 /q , q ,s .J /, B 5, 5 8, L / 1 IP , 4 J~ . J ~ ~ ~ ~ ~ :i A r? , / l 55 [) . 0, 1 , , 5 /, D /, # 5 s. J 3, , J ~ Jo o I 1, _ i J ,1 . 0 q. 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(),tgO Lo~= 85ft Lr= t./50f./.. 1...0,-=-:: ao r+ lr=O 1 Lor:-::. hOff Lr=-o' So~.:: l.0/o Sr =0,B%, SoF ::.J 0/o :)T :: 0.5°b I OWNER-PROJECT Willow s rir1 s-nr-s+ n n<A I rEATURE Rei~oMI Md{10d 'SobkC\'Slrl "Par~rne-ter ;sA ·1,(D d, • 5 / OtC (I'; -f c)fc...l ":>f-t ( e-f-5 x.b,<i5 hOl.r>e /oh x. 0,4'5 DATE PROJECT HO. tL 7-3-/qq4 CDT-STJo,/ CHECKED BY DATE LoF" ~oft Lr = 55off SHEET or It-II I~ So,:." J 0/o Sr= / ,8°/t> · / ,}.t 6,J.D op e0'5peice xO,JD ~ o.ws ____ _ S0b ba':]1(1 J5 B f, SD o.crt':)+oJ-c;./ 6. 47 ,+ruls "' lJ, Cf 5 /, 03 hov?t lob x 0, Ll5 --;, 6,(g f Svbba~(() '15 (Compo~,+~) L/ .CJ I QC((' +ofct! '3u.bbti5,fl _ J.w A o, 7 O_ ac..rt~ -f-ok l I OO"'lu Nt11 h bor hoocl recrto:hon (J./a,. (o.?Sume lom,1it1c1«-I dem,fy) ry (), 70 Suhb1:1s,(l 8-_&B /Ad.I a·:re~ M~I -- -6~ (nq h~e {of~ X () 1'15 ,Q ,13 opm'5('Ace x o ,B.o -3 b,JJ. 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L ) lJ J a: a. ,-- - - - - - - - - - - - - - - - - - 7 6 5 4 Fi g u r e 3- 1 C I T Y OF F O R T CO L L I N S , CO L O R A D O RA I N F A L L IN T E N S I T Y DU R A T I O N CU R V E N O V E M B E R , 19 7 5 I I I ¥ I \ I \ I F\ I I I 1. 1 I I I I l + t - 1 I I I I H - H B A S E D ON D A T A A N D P R O C E D U R E S F R O M N O A A AT L A S 2 - P R E C I P I T A T I O N · F R E Q U E N C Y A T L A S O F T H E W E S T E R N U N I T E D S T A T E S i V O L U M E i l l - C O L O R A D O \F l ) -~ - . . . . . . . - ~ - t . + + + 1 - H - + + 1 - 1· 1- H - I I I I 11 \ l - - 1 - H I I I I 1 + 1 - i -+ + ·1 ~ - •- •- -• - H - - f - f - I I I I I I H - + H - H - H - H I I I 1\ 1 I \ I I 1\ 1 I r, . 1 I " I I I I I I I I I I I H - ~ I\ . I I I [ T T \ • - ~ I - - ~ · - . I -~·- - _ .. ++ ' I I I I I \ ' I \ ' ' .. .. - .. . . . . . . . . -L- H - .. . I . . ' I ' \ · - - . : • . I " " - ~ ~ - t - ~ ~ .. . . I - - I - - - - -I - ~ - . I I .. ' .. . . . . . . .. . I I I I I ,_ , _ \ \ ~ I' \ . · I , - - - - - . - - 1- 1- t - 1 - - 1 - f - - · 1- ; - - - - - · - · , · . · . . I\ . ' - - t - t - - .. _ ·- _ , _ .. _. _ __ I I - I 3 \ I\ . I ' , ' I I C ~ - .. . . . L L - . _ L - - .L - . • . ~ :, - - ,- - - - : - 1- 1 - - 1- f. - 1 - c - · . - ·· - - - - I t - t 11 1 1 1 1 1 1 1 1 1 l l . . .. . .. _ _ _ , I I I I I \ r\ . ! \ ' - . - - ' I ~ I . I - 1- f - I I I I I I I ' ,_ ' , ' ' ~ .. . . . . I\ ' • r- ; - - . . . _. _ .. - H- L L . L J . I ' - ' , I .f - : I T T - . . . . . . . . . . . . . . . . . . . . ,. 'I ' \ . "' ,. . , ~ "' : M l I I I I l ·H + + + H - l -l + I I 1 , 11 1 1 1 1 1 1 1 1 1 1 1 1 H- H - - I - H - 1 - 1 - - 1 - 1- + + + - ~ . : I - , _ i . - . - - . - r . - r - , , - 11 + - • - < l • l - i ~ I ' I I I I I I • - ', I 2 "' ,. i l r, , r- I, , , - - ~ - - ~ - ~ ~ - - - ,_ ~ ~ ~~ ~ - - ~~ -- - H~ ~ ~ ~ ~ ~ ~ ~ ~~ ~H 4 + 4 _ _ _ _ :: , , . , ~ . , " _ _ _ _ _ ' : - , , - ) ) _- - ' ~ . :: : , . . ._ - - ~ = · - 1- •- - t -- + - - .. . . . . . -1 - . . - ~ . .. . . . .. . . . . . . . . . . .. . . - 1 - - ~ - .= . :: : : "~ i , . ; , ; - - - - - t - - ~ I - .. . - : : - .. . . . . - - i. -: - .. .: I .. ~~ . " :. J . :: : , .. . - := -- - . 1 - : : - >- - : : 11 _ IJ : W ;: · -- - - - - - · ~ .. . . - -- - .. . :: : : : : ~ ~ l 6 . J , ,_,, . [ I _ __ .. . . . . . . .. . . ·, - - 1 - ~ ,- ~ - - - - - - - ,- - - - -1 - - - - - ~ .. . . . - 1 - - - - - · - · · - ~ .. . . . , - - - - - ~ f ,_ _ r- , . . . : - - - - - - ~ - - ,_ L _ .. _ t - t - - - - ~I - - - ~ -- - - - 1- - - 1- 1- - . - - - - ,- - - I- - ~ . - - - - · - .. . . . - - ., - . t; , ' " ' " " - r - ~ - ,. _ . - - >- - -- - I. . - - - - • ,- >- - · I - - , - ,_ - • t-· t·· t - t t t t t I 0. . . " - .. . _ • ~ • .. . .. . . - .. . .. . . . - ,_ >- .. . 1- .. . 1- + - f - - - + I - - - ~ - - - - - - - - · - ·- ~ - . \ . .. "- t - . . . _ __ - I r- 1 - - . i. : t : : ' . _ _ ~ 1 - 1 · • - - .. .. - ~ - ~ : "' : : . - - • .: . . . - I - r- - - . . : . . - - - . ·4 - l- - t -11 - - ~ t- - 1 - 1 - 1 - -1-1 - 1 -4 - - H - -I- • - - ~ I Il l I 111 1 1 1 1 - + H + I 1- - 1 - - 1 - - - l -i - C l=- l j j ~ l - - 1 - 1 - - f - 4 - - 1 . .. . . . . . . . ·1-1 - - - 1 - - 1 - 4 - 1-1- 1 --< -•- I: : + + 4 1 - - l - i - . J t l t t t t m . t t t - H + + .. . . J -- - 1-- 1 - - 1 - 1- - - - l - l - 1 -I • 1- 1- 1 - 1- 1-- - 1 - 1-- - I .. . . . . .. . - t t 1 U - I - U l l - l - - l - - l - l -- - t - - - H - - I - H - - - 1 - H + H + -t - t - H -l -l - l- l - - l - l+ - I - H + H + I- - - - H ta t t l I II I I I IWt B t = J B J ~ l E 8 ~ t l = t t t t l i t t t = L t t t t f 1 t = } ! f i l t t } j ± t t J I I I I I I lf f E+ F t t t t r t t - ' I I I I I I i 11 , .. . . . -1- + - - - 1 · ~ .. ~ 1-- - ™-l-l ~ H -++ - I -- - H f t l : j = f t t l i t t l t t t U t . . t t : t l : t 1 = t t t i - 1 -1-.w + - w . . . . w . . . . w - 1 - w . . . . w . 11111 1 1 111-++ + ++ ++ + --H + t + t -~ t - < . ~ '" ' \ ~ -;; : : : . ~ ~, .: s - \ C- 0 , , , . ~ ,. } \ .: : : . . . -- 0 0 3 0 6 0 9 0 T I M E IN MI N U T E S 12 0 15 0 18 0 ~ ~ ~ ~ - , , -3: : > -< ~ ID ~ Cf I \ ) 0 m en G) 2 0 :n ~ m :n )> -r r => 0 ; I : rr · w Q. rn w : I : (. . . ) z z Q J ct J -Q . (. ) w 0: : Q . -- - - - - - - - - - - - -- - - - - - - 7 i i .. . " . " " . 00 - . . . - Fi g u r e 3· 1 C I T Y OF F O R T C O L L I N S , CO L O R A D O s rf f i f i f f i H - RA I N F A L L IN T E N S I T Y DU R A T I O N CU R V E N O V E M B E R , 1 9 7 5 B A S E D ON DA T A A N D P R O C E D U R E S FR O M N O A A A T L A S 2 - PR E C I P I T A T I O N · F R E Q U E N C Y A T L A S O F T H E W E S T E R N U N I T E D S T A T E S lt t t t ' J f # t i 11 1 .1 1 1 1 1 - r - ~ 5 V O L U M E i l l · C O L O R A D O 1 I I ~· INI II ' , I ~I I I 11 I I I 11 l+ t + t - H 4 - i - H I II 1\ 1 1 1 1 H I t + H i + t + l + H + I - - H - H 1 4 - 4 me -'* • fl f f l f l ± ~ ' • ' ' • " 11 \1 1 I\ N 1- \ - f +H + t J - - t l l-M Mt t 1 1 I I I I I I H - H - 4 + + -H - H ~1 1 lf 1 1 IN 1 1- - \ 1 J l } J J ~ I+ r- + - ~ . J L U . L -+ -1- + H - - · · _ T - n . n ~ + - N l l f i S : ·:=-·: ~~ : ::= '= f '~ " ~·. : : " ' ~ ' ' tt i ± H = f ± ! ± + ~ t t t t J 11 I 11 I 11 I ~ "H " • " " ' " ,' 1 ! . ) 1 1 " 1 11 1 " 1 ' , .; - - - - , ' T . ·· ' 3 I , , , ' • • , n , , , , , , , , , , , , , • " ' " ' " ' " " " " ' " , - - ' . - " - - ~ ~ r ' - ~ · " " , " " ,n , ·- . . . . - . . - .. . ~ I I I I . " IT , _ ·- -' - , _ , _ + . r: : : f + I T T T · _, f f i ' t i i = i + h hi rt i fi : f f i t i ± t l ± ! = l t ~ t t t l t t J ~ ti =E ~I H + : - - - ! Mi t t l t d t l t l I I \ t- - t -1 - - - - • - L _ ~ _ L _ ~ ' _._ . -· l NJ I l ~ t t • - -~ ~ :r f - t 1 : h t - t l l ~ - n ~ . ~ - . ~ : '. '. : - - . - ·- -- . - t- + - 1- t - . I 1 - - + - ~ ·- l H H H - + \ f k ~ - I \ I . - I I I I I 1 11 I I I I I I I I I I I I 11 D I I I n, i 11 1 I IL L N J _ j _ j l r i . _ L J 11 1 tk l : 11 ft 4 d j LN : . 1 f i l . :: r: : r ~ c r r r r :: i = r-m 1 11 1 = m I I I I I I I I : . I 1 - - t - f - t - + - +- ~ I I II II IN I II ~ I + I I N. . ! I I I- H " ' ? d i - t- t - ; J q ( . :. :. . . . ,: : - . . . . _ L . _ L J . . . . L . J 2 I IC ; ,; ; ; : - - ~- . . - - ,- ~ ~ -~ -- . - - ~ - - ; i- - - - ' - - - - - ' . ~ _ _ _ _ :: , . , r : - , - ~. . - - - r- - . . . _ ·- ~ ,- . . _ ,_ ._ __ I ,- ~ ' - - t - 1- , - · - • - - ' - - - - 1- - "' "- ,- ,- - - ~ k - •- ,- - - "" ~ ! · I J .. . . . . . - _ .. . . _ - -+ 1 - t - - 1- l - t - r - 1- · · • - r- . - -~ · - -- - .. . . . . . . . - -- - ~~ , . - • . - ·- t - , , _ .. . . . - · - · - - - - · - ~ - - . - - - - I., - , - , _ _ -- ,- - l " K , - 1 - - 1 - - ' " = ~ - · ~ t, , - -· - - ~~ ) _ ~ , - t- . · · - - -: : : , - . - -1- - - ~ - - ,- ~ - - r , - - - - ,- - , - - : - i. : : :. _ , _ _ : _ , _ H - - ,- -,- 1- - 1- r- , . .. . . • I - ,. . , .. . . ·- - -· - ~ ( - - - ·- - ,, . k - - ,_ ~ . - _ , _ - - . . I - ' - ' l - -1- ~- t - - •- t -I I- ~ .. _ -t H -lf - - i H --t lrl - 1- < - -· ~ ~ .. - . . 1- - - .. -- __ ,. . _ k . - • - · •- ': : : . - 1- -1- , - I ' ~ - - 1-1 . -1-· - ,- I - - -- - ·- .. . . . - - - - ,. . . . . . _ : - - : - .; , ~ _: : , - - · · - - 1, ,- · ·- - ~ t - _ r .. . . . ~t - , . . _1 _ _ _ -· - . · - 1-r - ~ ~ , . . ; . L I r; : , - . . - __ - - ·- t - . - .. . _ r, , . - - - - • - r - "' - : T ,- I I I ~ - I • - _ ._ . . _ · t, , , .. . . : . . : I I , - --+ -·-·- - - ,_ _ ,- 1 - 1 1 - tl - l H H - - - f - l t t - it I I I I II IU + l l - l + t + 1 - ~ =~ l t t - l t t - l = I ~ = 1-1 - - - L - •-> - - . - + 1 - t - t . . - -l- + - I - I -I-H- - l t+-HI T T f - t 1 .: & M O O t f ] } ~ :tt t i r t t t & t- + - t - + - 1 - - ,_ -1- - f - - t - - ,_ I I I I II II I + t t H - t i ; - I I I I I A II II 1 I I H - H + H l ·t- -- m t t t I 0 0 I 3 0 6 0 9 0 12 0 15 0 18 0 ~ T I M E IN MI N U T E S - -. . . . . . . . v , ~ .. . . . . . . . -- - - - , I I I I I I I I I I I I I _, DRAINAGE CRITERIA MANUAL RUNOFF /ti~ 50 I I I ) ' I 30 .... 20 z w (.) a: w Q. 10 z w Q. 0 5 ..J C/J w en 3 a: :::> 0 (.) 2 a: w .... < ~ 1 I I I , I j J ~ I I I ' I I 6/ Qo / • I I~~ $ I t .. I Vil ,::, ~ I ::,.'ff' ~ ~ ~ ~ ~' 1:' J $' 'ff' 0 I ::, I c., ~~-, ::: J ...., ' ff ~ § ,-~'ff' ~I "' 0 .... ~ j I 'ff' ~ -er ,._"' "' .::, ...., i' ~'ff' ~ I R J .:::' I,.,, " ~ c:, I ~ q_'ff' ~"' ~ i'/ "' ::,-t-. r-· ~ ~¢ / ~ I " "' " "-J ~ ~'ff' ~ ~ ,... ~ I ---c:, ~ C, "' ~I,._ ~ !I $/ (to .... ~r1-f J fl J -·,; ~· "-/ "-; I ~1 ~ , / // f f ' J I I I I , J .5 I .1 .2 FIGURE 3-2 . 5-1-84 f f ' I I ' I I I I ' I ' .3 .5 1 2 3 5 10 VELOCITY IN FEET PER SECOND ESTIMATE OF AVERAGE FLOW VELOCITY FOR USE WITH THE RATIONAL FORMULA. • MOST FREQUENTLY OCCURRING "UNDEVELOPED" LAND SURFACES IN THE DENVER REGION. 20 REFERENCE: "Urban Hydrology For Small Watersheds" Technical Release No. 55 , USDA , SCS Jan . 1975 . URBAN DRAINAGE & FLOOD CONTROL DISTRICT I I 1· I I APPENDIX B I STREET CAPACITY ANALYSIS I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I )>.::'t? 1::t1::: :-:J+/ ·.:) .. { ... · :;}: :::;:;;:,:::: ........ 3B 30 4 7A 7B SA SB 20 21A 21B 21C 22A 21C, 22A 22C 22B 22D 23A 23B 25A 25B 30A 30C 30D 30E 30F 41A 41C Table B-1. Summary of Street Capacity Analysis. f;'[?Q k]f \IJ~·' ii{:' )i'!iff!t'~ \ .... 1 . . . ... . iN 1l:1iJ~~i}~,tlJ!ii'; . :,:.. . :/1 ,r-,n ,n·. . :··· :::,: <· > ·"' .:: ;:::::;:;::;:,:::::r ·-::::· •,·, •. .·,; .. •,• ··.·.· ·.·,• Red Willow Ct., West Half L/H Willow Spgs. Dr., North Half L/H Weping Way L/F Canopy Ct. L/F Catkins Ct. L/F Mackenzie Ct., South Half East of D.P. SA L/H West of D.P. SA L/H Mackenzie Ct., North Half L/H Willow Spgs. Dr., South Half L/H Pacific Ct., South Half L/H Pacific Ct., North Half L/H White Willow Dr., West Half L/H White Willow Dr., East Half L/H White Willow Dr. L/F Willow Spgs. Dr., South Half L/H Timberline Rd., West Half A/H Willow Spgs. Dr., North Half L/H White Willow Dr., West Half L/H White Willow Dr., East Half L/H White Willow Dr., West Half L/H White Willow Dr., East Half L/H Battle Cr. Dr., South Half C/H Battle Cr. Dr., South Half C/H White Willow Dr., West Half L/H Battle Cr. Dr., North Half C/H White Willow Dr., East Half L/H Timberline Rd., N. of D.P. 41A A/H Timberline Rd., S. of D.P. 41A A/H ::)Q:~Yi!BP.aj::JJ§#.~f i91.i:' JflAi16W:~~1e:s&eeEt :f ::/I\!?:f~R:¥*¥~:::tsfilC\) J . : :Ji;:gig)r,i r~~~) ;\ •:::::: ::1:::::~til :.:::111:::::i,~im:::::: ;i•ttl!i:::::; ::::~~x:i \: 1.6 5.6 5.8 77 1.1 3.5 4.6 4.4 10.1 14.4 2.8 9.5 9.4 122 2.5 8.5 4.6 61 1.3 4.0 2.3 30 1.2 3.9 8.4 1.5 4.9 2.3 30 3.6 13.9 6.0 78 4.8 17.4 5.0 65 1.7 6.5 5.0 65 2.7 4.0 3.0 4.0 22.6 100 3.5 18.1 6.0 78 3.6 13.5 7.3 36.8 0.8 2.5 6.0 1.7 11.2 4.0 50 1.7 5.4 4.7 61 4.2 14 .3 7.3 85 2.3 8.0 7.3 85 2.3 8.2 3.8 44 1.9 7.0 3.8 44 2.7 10.1 5.3 70 3.1 9.4 3.8 44 0.9 2.7 5.3 3.3 12.7 3.7 18.5 2.2 8.2 10.2 51.2 a L -Local; C -Collector; A -Arterial; F -Full Street Section; H -Half Street Section I • ; • • ......................... -.. ... c ........... OWNER-ROJECT !J,f bw 5 r,,1 -hr-,+ Frnei. Ana l j1s &\~,n 38 -red lJillow Cour+ 1 We:* Hctlf !/~ Loc<AI 'S+rt e.f I Slop~=-1/o io Qa.~ /,&cfs 6,oo:: 5,(ocf5 BY CL]) CHECKED BY G,..J--il.. Q, C",u = 5,e,c.fi ·. > l,liic(; DAT OJECT NO. 7-8-/c,ql-{ (![)T5TJO, I DATE SHEET or £5 l~z. /q ,i.. S I /0 G,oo ~ll) :: ~~ct:>/ J.) = 7 7 ct"J > 5,fo ch , ', 'S+ree+Capcic; ·ly I') me.f. , &~,r1 3D -\Jdlow 5pr in;r Urive I Bd~te,i Wetp1n1 Wy. j Red lc/1/1()1,.) e+ I Norfh ~ttlC'. YiP. loco..\ 5treer I M1t1trl'lvll'\ Slope :; O,&"lo Ga.;:; I, I cf5 Q 10U :: 3 I 5cf.s f?of'r) 5freet&ipcic,tyYtnaly~,,~ Qa~IQ = L/,t.,d1 >3,Sc-b )/,le~ (-p.CJ/10) ~,fl 7ft -(},0ir.opy Covrf . Fvll Loc4/ 'Stru+ I slope ::. 6,w'S "lo Do.= J, BcJ~ Q,oo -:; q,s er~ Frorn 5freef Cci~c,fy A-n~J~5 ,,: C-rr-. 9 / 11:> i ,e, ,,., ') B~~,r1 7B --G+k,115 Cbv,-t Fu/ I loca ( Sfree+ 1 5 lope= {J,4 °/0 aa.;:; c1 ,5 cf, (),oo-:; 8 ,Sc(s : . S+,u~ {!_c/pa.crfj ,~ me+ . ', 51-red-Cc.pqc,h' 1'5 fr'let- fro()1 5free+ CC(pcwfy Anti.ly,6:> ~ G2 l ... 1I) = ~.8 cti}x<J = 4,~cf~ > J,'Sc.f":> . :, 5fru-f. ~P4cdy1~ (-p?-9/r<> ~ 10/,oJ Q,oo~IJ)= ro/e:h > 8,Sc./5 Mel·, I --------· ---------- -I . . : . . . ...................... ., ........ c .......... OWNER-PROJECT BY Willow 5 r,"n .s -Fir~+ n110.f f"EATURE CHECKED BY 'Stred h nt1(y-5is "Boi':)1r1 SA -Mc'.\c..ker1i.1e t+, 'Soufh Half Eo.s./-o-f T11lef Bil VJ.Loco.I 'S+ae+ I M1 r11rriurt1 'Sfop~: 0,4°/o QJ.::.J.:5cfs "(0 • 1 Q(:({.!)/,,~1acrt~)"" l ,3cf5 ~,oa= 7P1c.h X (0 ·7,Ji,~7)-; '-1 ,0cJ, DAE PROJ CT NO. 7-8-Jqq~ (;o;')TJD, I DATE SHEET Of" BJ 10 Ga. (4n) : J. 3 c.f s '? 1, 2d~ Q,oo {;,.11 ).. ~/cf, /ri :: 30 cf~ > Lj,O c(~ ,', Sfltet~ptae d y I '.:> rnt+. &,,11 BA -Mo.cker1 i.,c C·t. 1 Sbu-rh ~~/.P , We,+-of rn fe} BA VJ LoCC41 Sfrte..f , 'Slope ::. d, 1610 QJ.= J ,S~f.., (6 ·(o 1/,,31)::: /,ad~ G 100 ::: 7 ,q cT 5 C o,l#1/1. '!,1) ~ 3, Cf cF.s {?J Co.11) = B,t.Jcf5 >3,qc.r~ :?/ . .1c+~ ,·. Sfru.f~,7 IS mef ~~11) SB -M0ie-ker1 "t.1e Cour+, North H"-IF. Vo. Loce\l s+rtc+, M1r1 1r1h;m':,lope ~ O,~tJ/o Qg,= /,5cfo 0100::: t.//fcJs From Streef Ca~c,+y ttvia ly~ 15: QJ. l'A il) ~ J. 3 cb "? /,5cJ5 ( p-p. i/1 Z> f 10 / lo ) Q,oo(~II): (glc,.{~ / ~:: ZOd, > 4,1cf5 ,'. 5-fr~et Capac,+y IS Mt.J.. r><A51fl ,l. 0 -w,1/ow Spri(!j, °Dflv~ I 6o.rfh f-la/f I be1wRen Red W,llo~ Ct o.nd LJh,Jt ~,lfo.J L);, Yi9. locC\I s+,t e-f I S /ope~ / ,o q c;l) Q8.=-3,(ucf5 Q,oo-=-/5,q cf'.5 rrom s+reef Cqpei cify !fna lrs,s : 0~{4/f):: Ge{, "7 3,~cf.5 f-f .9 /10) Q,oo(cd/)= 151ch/J ~ 78c.:f~ '? /3,qcf~ I . ; . . . w., ............................. c ........ . OWNER-PROJECT l~,llow 5 r-,n -s -Fir-sf hno. I FEATURE s+rt1ef ~ ac ,+ AnG:1/ I~ 'Ea~r(l ~I A -"Pcic1 he Cour + , Soofh 5,de Vs. LoC'1 1 'S+ad I Slop~= 0,75 °/o Qa, ::: 5,'-cf5 it (5,J'ioc,(~ / ~.J.Oo.crt,) ., 4 ,Bcls Q,oo~ J0,'5cfs t (5.o.qocrt~{ft,,J~acrt5)-: /7,~c-b y C,CiJ CHECKED BY DA P OJ CT NO. 7-B,fC/14 &>T5TBo, I DATE SHEET OF 133 ID F=,orn 5/ue+ <A()Clc1ff /t(10.{y'5t, ~ Q.g ~11) ~ 5,0cfs ;,, 4,8 cfs (rt .4/1l>1 10 /1c,) Q1oo(~II)= 130cf5/J.:: {oSct,7/7,'kfr,', 'Strtef {;c,.p o.G tfi/ l":,mti. Bas,0 &IB -Poc,fic. C!o0r+, Norfh 'S1Jl VB Loc~l 5trte+ I s1~p~ : t.J, 15 °/o Ga.~ f ,1 cf's O,oo ~ ~1 5G.fs F,ot11 5rru.f C:tpctci+y ~n~ ly51~ ~ Q8 (.~ib = 5,D c.t~ > /, 7 ch (rf .ci{,o \ 10/10) Q,o'l.411.)= (30c-A /B = (95'-6 > ,,Sch /, '5tru+ Ca.po.c, & 15meJ, Bas,a ci ( C -Wh I h~-Will ow 'Dflvt I We':>+ 5,de I Sovrh o+ Wif/oiµ ~pr,np b(l11e. v~ weed 'S+ree-1-I Sl~pe; Q,S'l 0/o 1he1~k ~if l)P itA wtl( bl"'Jited +-oa,He,+ +hl etihr',t P-yrJ,Jw~ ardvpfo /IP,J.c.6 d1111~-fht /00-f!even.if@m &iw1~/A. 1he. B·t· s+retff fo.,1 +o TJ., P ale, 1-sfrom 5vbtia5,,,~ c11B and ~ /CotHy, Th<-[001r everrf ,45 d15t<.>1scJ R,r . _ 5vb ~5,11 J.al\ M~~<. QB~ tcf 6 A ;; ~0 ,5~)(1)(1,q,,,/1r)(J,18:"c1t-:,) = J,.1 ct5 . : Prom '5trut{1pac,fy /rnC1l1s15: Oa.Lct ll] ~ 4,od~ ,~.7cf"J (-p . .., /1 1>) " . ,', 5free+ CapCK1ly t5 mt+- OWNER-PROJECT BY DATE PROJECT NO. Willow 'S r,(l C:L/ 7-!D--fqq/ t;,OT5fJO , I rEATURE CHECKED BY DATE SHEET or Sf reef Ca ora Hria. { -s, ~ B ID Doi51(l 82 A -Whde IJilkJw Dr, vt I ~ct±'5rde I 5oufh Of W,llow5p,, ~' Dr,v(. YJ. loeci.f 'Jtietf-1 'Slope:; 6, 51 °/o 0&.:. ?;. Vcf5 [}. 100 =-f l,l cJs (&s r,1 J~A-) -r J7,(p c.fs C&,,,,j JI A,Bj t)-/&,Jc{~ (In/erd.+-l).P,B,f ft)• J1,b cf5 ,', 2f1(e-/ ~pac i~; I S mt-+_ -TAe JOD·•yca.rflo~ a/0(13 iJhrfe U((ow'[;vive {Jl,4 els we1f'S1d~ 1 11,3' cfs eci5f-·Hde) ~,f/tve, kt; -fhe C(Oi,J(I of +he (0~, rt l"j ao/.Jumed +~t?d afl even .({o,...) 5 p I,+ v-Jd f ex.cc.Jr bf'/,..Jtt/1 ff~ ea:sf and We':)-f 11de5, There -{;,t, .Porfht /aJ-j(a.r ti/en+ a net +ran5te, of (), f c-G hJt II occur . -fro(() 'S:1bh a?_I/J 41c t~ "5vhbtt~/t1 J.B.~. . -J:+,j nuted i fhcif +he J'nfef 4./-T:>, p, JO cannor Cor1vty !he eii~f t (ro-yr F{oi-J, 3., 4 ch ,~cl,,trftJ bac.k .Jo 5obtJ:;is,f1 J~C, q5cro.J11 ovtr .P/o,v ..Pr()(YI D, P, Bo. 0ee p~e D /~) ~?(11 8.J.t -k/1({(),) 45pr, ~? Drive, 'SC>Jfh s,de I 6o(J/-o+ /,/h,Je, l,J,tlow 'l>r11/ ~- 0 Loe~/ 'Sfrtc./, , 'Slope=-/ 1oq °lo D!j(hqtJ,t.from 5J~.b~-, ,r1, J~ ft A,,J ;J.C . ./ D,11er'51ori -Fr,m 1), P, ~ ()3 = C.Cf t ,4 = (6 ,5'j )(t)(J. I 111/hr) (3 ,-/.']aats) ~ ),?,· ch I(.. 0100:CC.fif+ :: (0 153)(1,,-s)(~.~in/hr)('3,l9ci,r(5);. t,, / cl":J fS,O !cJ.s~ /B,/ cb F=ro(() Sfrtd Ca.paofy llr1a fr;1 7 : Q; (4ft) = h cf5 , 35;cb ( t?· ~ / ~ ? rc.J,o) Q,vo~(D ~ !'51 r.Js /i :: 7 Bets '7 f B, f cfs. ,', 5frtt/..Cap<tc tty IJ (1d . .t:aSftJ '1~ B llr'Ylbell,rie F?oCA.d , We5f ~oil( 1 SoJ1h o+ ~J, Uow ~,,n~"'J Dr,.1e ~.it Artt(,a I 5+raf , 5 lope~ CJ, (p t 0/o QJ. ~ 3.G" ~fs a ,oo = t,. '5 cf, / eeJ()C&x, ~ rc.dor Frc)'n ~t (J 'St1ee+ C4pct::th( 4r,,.!ys1 j -Fill :WS-Aff-J -'} Q,z{c;//):: (q. fc(s)(o,B): J,8c:f5 7 3,~cb Ftfr :"'1 5-ftRr-c ~ 0ioo(c..l0-=(4~ch) (o,B)::: 3/o,Bd.5 7 /1,5c{s C10-.1" +vil d,scw,cfor YI. ~+ra t J ,', .Strtt+ &fl).c,L 15 Me f s~fion l""1'it'f\/"-11'11 , co ... .,,d(11111 1f .,.ff"'"'~l:#·d,p,lh I ".) t,''~bo,tCfo.Jn, I OWNER-PROJECT DA E P OJECT NO. 0dfow 'S r, Li) 7-/0-(Cf14 (OT5TJO, I F"EATURE CHECKED BY DATE Stre e+ Cci Ja e, Ba':Jt() <i~D W1HowSf¥i~?5 Dove, No1fh 'Side 1 61:=Jof i..fht+( J../ilbw D11ve. ~ L.oc£AI 'Sfttt.f.. , 5:: /,OCf 0~ Gi~ (J, 8d~ Q,oo;; )., Se,fr, fu11r1 ~3ft IA/h,ft hJdlo..Jb(ite J k/e?t' '5,de I No,fh tJ..W,t/oi.J)p,if175D(li1t. ij J.Dcql Jf-rtet , '5;; 0, 54~/o (m,n,nwm) 0&.= /,1cf 5 ~D,iJtr5to11fr°"' D,D.3o O,oo:: ~,act,, -1-~o ch :: !l,J cf~ SHEET or 55 /0 Fro/YI 'Sfttt.f (},pac, fy lt-Y14/y-51-5: QJ. (~II)::: 4,o c..f-5 7/, 7cfs (~ <r{1e>~ 10/10') Q,cv&./0;;; JOOcf-;\J ~ 50d-s 7/l,1 ch : , 'Sfrte.f ~c,fy l:Jf"nt!. b::\'51(1 J. 513 WM,(~ 1.../dlow D,,vt, E4-:,fS,de I North'* 'l,.1', ~3.B v~ LJJCA I Strt d-, 'S ::: 6,fo(g 0 /l! Or-/, 1cF5 Q100::.5,4d5 Prom s+raf ~ctc,fy ,4~ly51:, ~ Q:J (411) = 4, 1 cf, '.> l, 7ch, <'A"· 4/10 i 10/10) a.~~ll): /JJ,c:f,\J.: !lilc-f~) 5,t/cfs &?1(1 c2'5A -w h,fc ~,(,//c,.-1 'Or1i1e 1 ~~e~+sde I 'Sovfh o+-7),p, asf't VJ Loccd 5trt ct" I 5 ::: /, S3 6/o Cr11 tr1 1t11vl?\J Qi;; L{,Jc.fs G,oo :: / ~, 3c.f 5 rrcJrn Sfruf &pac,+r /Jn/41~, j ~ Q3 (e:.11) '.: 7, 3c/.:., '7 'i ,; tl.> (rt . '9 /10 ~ 10/1~ G,oo ~11): I 10c.b 1~ = B 5 ,..rs '7 /4, ~c.f.., . I. 'Sfrtd Cci.pt:1c1fy ,~ 1r1tf I OWNER-PROJECT BY DA 1,J, llow r, -Firjf F,f1 C 7-10 tf)T5TJo. I f"EATURE CHECKED BY DATE SHEET or ~-frtt+ g&, {D Basu1 JSB -i.../b ,Je lJi/lo..J 'Drrve I f cr')+ ~,de S,Jth of 1) P, JSB v~ Loa. I Sf-raf s:; I , 53°/0 GJ'" J,3cf5 G,oo ; 8,rJ cf 5 r::-rorn 5+rtd ~c,lyft~ly~,,: CtJi:ilf); 7/3cf5 )J,3d5 C19. 9(10 i 10/10 ') Q,oo~I/)-: IC/Dl·h /J.; es~:l1 'g,Oe,{5 ; , '5..f.ru_f ~C!C,?y 1~m e+ . . /tt.J.;cnon ~ ,;.c.for- /'t:11~~1, -nle IA5·fr~r-J. 7 lla,{4/1}:(/(p,8 C 5 ~ 13,tJch >B.4ds ).2,lc.f5 . ,', 'SfrttJ ~pac,fy ,~ M~+ &ts1t1 JO tJ -~*leCreek Dr,Jt I Sov-fh Ha. If , Wt')+o.f t-fh,h W, 1/o.J 1),, J/J Cvffedor st-ru.f , 5 = OA°/o m,n 1rnJ,n -Jn f~e .fvfvrt a larqe. p>rfion Of S>b~1it1 '1J ft IJd I bl col~dtd In lA '5 f or,rJ'5(L11fr, 1/Mt(r, f/i,s l7fl1tJ 17,p~pD'x'd fobe /{Pt vndevel{)ptd for -Hu -hr"J.f fiJ,r1,. 1hert.Port 1 ec.lc.<>k.te -ftie Cvrren-f '',N,Jliproj(d'' d,scha~t~ -Aret:1" 1MOacttj (3,J5opttl'5~ct/ 01 651mptfo//~11,); C= 0,31 ; Cf;;:{J!J I <!,ptx,-·;;{,i5 -J--y(ar: tor;: /&,~ (}1/(1 1 i-t; 7,!Jr11,n ~ ic. =-.Jt/,~m1(1 ·"""? i;.: /,1,n/J,r _ Q~; CC.fl ff" {o,g/ )(1,0) ( /,7,n/J..r) (4A ·~crb) ~ J,3 cf5 . -J[XJ-ytar: toF :: /€,O tl'Jlll I ti = 7 1 8fl11t'I -) ic.. <= ~j.!3 m,11 -4 l,ov : L/,B In /hr QI{)()-: CCfi A:: (0,81 )(l,Js)(4,8,n/hr) {4,1(1,m~)" B,B-cfs f?'" e,J,;,:fio,, r:-... dr;,- Frorn HfC,J 5tred~ao fy !r~fysrs· nk·WS·Col·J -=J Q~(a/1) = (7 ,5cfs)(o,s) :: 3,Bc6 '7J,3c+J Pd<. WS-COL·C 7 Q,oo(o.11): Coo ds) (o,S) :: 14c ~ ? 8,c1 ,c.h /, 5frtt.f Car:ac,~ 15 rne+ 11 , IA»MM ..... NWIIMN 1111 .............................. c......... &~1fl 30C. -6a~le &u.k. Dri,t · , 5ovfh Hctlf . ~ Co/lee f-or s+ra+ I 'Slop, = ··o~-J./ 0/o - y C,LJ) CHECKED BY ·-·····----Qi.;_ ,,cfc.r:, -· ·-·· ----· -·-·-----· --·-- o,co= ~ 1,0d~ (a.;11(11 $~-;~1S) DA 7-f f-Jq q L( c.DT5Ti , I DATE SHEET Of' 57 ID Fro,n ll£CI~ 5f-ra+Ctr~~fy hnc.¥~,,-Pd!dJs-eoi.:;-:> &J{o.10:(J,Scb)(o,s);),Bc.fs .> ,_,ere& . . _ __ _ _ __ _ ._ Fil~i W~:C'oL-.C ~ CJ.OCJ(a11)_=_(88cfs)(o,?J= 4L/c~_.>/i4c~ 1,0 _ . ... .. :. S+ree.f (k{iqc, ty,~rnef __ _ . Bc;5; (l '30 D -~/ h 1+t · k/dlow Dr, vt ··0, hie~+ Hg I .P , -Sovfh ~.r kten fanl .. ___ .. --·-__ ·· ---~·-vi loC41 'S+re~f ,: st~pe ·;-b,-e3°/o-···-··. -~----· . · .... ----·-·-··---_---. ~---_ ----. &s. = ~-. ~-7~6 (t-ev,,tJ s-1-qs) . . -. . ·-(9,oo~ ~ /p,fc;k _ . --· -·· -fyOfll s+riei (A~~ ,fff,i~li"~, ti.f;J,~ ,. ·5,3cf, > J:zcr, --,,,.·; · ---·· · ----------·-- . .. _(rf>-"1/c t ir:,{,e.) ___ --. &100 latO= .l~Oe,~/~: _ 70c.h ';, :18aP1 :. 51-,(et ~-;,1y·,;;;,r "E,qs,11 .30 £ -:.. &nfft ~aek brt11e , Norfh H;;f { Qa :_ 11 /C cf~ O,oo: q,~1 cfs .. fr~HtC·J5lreet~,ly&J,~;·c5e~B'4Sl~Ji);Q~"{~10;-.,,ac1j ··;-.3x c:6 -.---·-·-=-··=-----·- . Q,oo(4k):: 44 ,{, > 'f,4 c F, _ -~:. Sf-reef ~poc,.ry' . _ __ _ ~ rnef . _ - 30 F -vJh,h lJ,l(ow Dt1vt , 64~f .Hcll=, SJvH,of Kut1fc.nJ. -· __ v~ l«:41 Sf-ttt+ , 51opc; O,B31o o,q QG.::. ~.:ch _ Q,ov:.Ji:Pe,(5 'J,(f cl~ &ev,-,ed.tJ,(-'f'i)1 __ s_:::_l~l_'tt_5J _ _ _ ... ---··-·-· -· . ···-·· _-·_ - 3,1 ):(Jc(s ft'orn 5+-rte,.f ~qctfy lh,afy.r,1~ -Q,J,.11) = 5,~c.h ,~-.><>, 'b (;f, _· -= . .,~. 5.f-rufJ(Ntty Cr>-ct. f,e. ') _ _ . _ _. ~ ·?c-~ ::, q,er 5-:f-s. . _ ,~_me+. I L ,cb tone & Anderson Inc . k1(11r")ld 12·.7·1~ OWNER-PROJECT DAT OJECT NO . Cl-D 7-f/-fqq4 OFJTJD, I f'EATURE CHECKED BY DATE SHEET Of' s-+rccf C~ c,ty ~~/ ~'-' B8 fD . 'Bls,f\ L/ 1;Kc. Timber-l,f1e Road, Socifh o.f-MeC/tllavid, C~arinel VB. ~r+e(10.( 5tra+ Slope::. /,/9 °/o(m1t1trt1uN1) ,64 -, c -:, =-J.Jct'> 'il J,84a.c : = g,~ cl~ ~tdvGhO"I r<_ ~,+()r ,i.)e,{,s rrort1 HtC·J Sf-1uf &ipa.,,l-y ftn4\ijl', F,le; W5-tfRT-J "' QJ. C«l1) ~ UJ,8 c.~) (o,Bo) = IO,J. cf:> , .Ji c-b 'r/5-Aef·C-:> QllJo{c.11)-= (&~cf~)(O,Bq) = S/,.2c-h 7 ~ 8 ,J c.(5 ,', 5+rt~j CQpac~f'f_!6J me./. B~-s111 ~ 11+ Timber l,t1e Rcx:td , Nor-rh of. ~l Clellancb· Cltc.rmtl VJ. Ar+tn o./ 'Strtef Slop~::. 0 , 4 °/0 ~ 5vbb~rn, ~IAi:i~4J = 3.~cfj a-6'4 c.c. -:; I J, 7 c.J, 3,3c.fs rrof/1 #te·J 5+ru.f. ~curfy A-nc.l1s,, fit,; WY~~T-J ~ ~ (411):-(7,'-lc:K)(o,5) ~ 3, 7c-h ) ~cf5 W<:r~er-c ~,oa Ce..~) ~(37c-k.) Co, s) = IB, Sd1) ~ fj,1e,{j Fu{/ L.ota( Jtre tf OJ: 4A c($ G,oo-=-/{J, I cfs . , tJo1fh of "1, 1/oa..> '5pn ri,, LY tv( 5/ope-= /, 5(7/o :, Strut CctpC1c1ry 1-smcf fro,(} 5-frttl C4p1tc1fy fln1tfys1s; Q,.~/1):(7 ,Jch,)ic?. = /4,4cf~ > t/,t./c.-F~ ') [o./J~ {pp o,/ro J 117/,o J :. '5+ru.f Captt,ry ,,;,.,d I I I I I I I I I I I I I I I I I 18 1 6 14 12 ";' 1 0 -u '-" (I) 0) I.. 0 ...c: g,,.i{ u Vl 0 8 7,3 I J Minor Storm Allowable Street Flow 1 /2 Local Street --36' Width Colculotio t,s Were F erformed n bXc;~~~~~ e & Anderson io 1;rd~~ 1994, i k:e With S~ec if ico i n the C it of Fort Co lli ns / " torm D oinoge 0, sign and riter io M bnuol''. [7 / V Curt Full C ischaq e~ / ' V/0 Re ductior F_acto ~ ,_ \"UI, UVt:f I., l'f U Ufl ~ UU ll t: ) y V V / V / / Ir <!urb FL II Oi se With Re ::Juction I / CRo l love Curb I/ I I I --I ~ I / V ~ V / I ~ I I I I/ I I / V / V harge j Facto ~s and G!Jtter) ~ 2 3 4 5 6 Gutter Slope (%) Bq /r o I I I I I -1 I I I I I I I I I I I I I 500 450 400 350 ~ 300 -u (I) CJ) I.. 0 ..c u vi 250 0 200 110 1'57 1's~ Jqo /?JO ,~ II :z 100 fo I 50 O I j I I Major Storm Allowable Street Flow Full Local Street --36' Wi dth Colculo l io ,s Were F ertormed bXc;~~~};~ e & Anderson , Inc ., Jul 1994 , in ce Wi th S~ec i fico tons Cited in t he C i C of Fort Coll ins .. torm 0 o inoge O, sign ond riterio ~ Jnuor·. No t e : Flo, , Conveyo ice Seton j t he Top of Curb / Wo Neglecte j For h i: Analys is / V / J " Abo, e Cro~ n Disc harge -~ / W/< Redu t ion Fe ,ctors Roi love r Curb and G utter) / 'V / / / ,V / 'I' I v-5" Above Crown Disch I w th Red .Jct ion t,actors (R cl/over Curb nd Gu V ~ ~ ~ I / ............._ I / -........ ~ ./ ~ V / I / I I I I I I 2 3 4 5 Gutter Slope (%) Btol (ID / ,rge ter) ~ 6 1. I I I I I I I I I I I I I I I I I I APPENDIX C HEC-2 ANALYSIS FOR STREET CAPACITY CALCULATIONS I I I I I I I I I I I I I I I I I I I DEVELOPMENT OF LOCAL STREET CAPACITY RATING CURVES I IAWMAl#WIIGl91+11MIIM ~ .............................. ~. BY C-LD CHECKED BY DATE SHEET Of Q,::J¥._ 0 /.----z-/Cj + 3B GJ-lft.,.--~dvC~Oll M,tror 'S.fvrn1 -I.Jalf 5-fm+5tdi0ti Maj()(' '5-rorm • ,=:.;If ~tm-4 Sedw11 '5/ape ,:::4dor Cvd1 F.;11 D•".ll h41tit Cd5) u" A kv11e C((),-)11 D•sthGli t kf-;) (perc.tr1t> (rtu"1 (.if, 5DPl W,fi.it,v+ LJ,H, w,Hiov+ k/,-H, r:,CJ ,;re .i.J ·J) t::!llvc:h0t1 ,:=qdor ~Jvdl!>~ ~acfpr f<ed.vcho11 r t lC ~I f<1Joct101 FacftY" oA 0 ,50 4.~· J ,'!x) tJ r 00.5 I 0 ,5 0,{g5 5.; 3,38 { 3£o 88.t.f I I O,~ 0,60 5,7 4 ,5'7 /48 //8,'-J 6,B 0,60 (p,5 5 ,{),O /7J I 3 7 ,(o /,0 0,8o 7,3 ~if3~ /C,J 153, '=1 /,~5 0,80 8,J &,'5& JIS I 1J.D / ,50 o,Bo ~10 7,J.o --J35 !88,D /,15 o.Bo q,7 7, 7& JS'-/ J,0'3 ,() J.O o,eo /0 ,~ 8 ,3J J1J J.11. fo ~,5 0, 7fo /I, (o 9,Bt7 3o~ )3/,0 3 ,0 {J, 7J l~,7 q,14 333 J39,B 4,0 0 ,00 /~,1 B,~ 3B5 :)5/,0 5,0 0,4q /lo, 4 8,o~ t/?P cR 10, 1 (o,0 0,40 IB ,O 7,J_i) t./ 7' 168, 4 I I I I I I I I I I I I I I I I I I I MAY 1984 1.0 .9 .8 0-7~ z a .5 i== o.'fj u ::, 0 ~ .4 .3 .2 .I .0 I ( i-s:06°/. F: 0 8 \ I\ I I ' \ I I \ S: 0 . f 0/o / VF: 0 . 5 I I I " I I I I I I I I BEL( ~'N I\IIINIIIIIUM ~ -1:..LC WABLE I S7R, ET GRADE I I I I i I I I I I l) I I I I I I i \ I\ 1, "' "I I ~ I I r"-r-- I 0 2 I J,5 3 4 5 6 8 10 12 SLOPE OF GUTTER (%) Figure 4·2 REDUCTION FACTOR FOR ALLOWABLE GUTTER CAPACITY -- 14 Apply reduction factor for applicable s lope to the theoretical gutter capacity to obtain allowable gutter capacity. (From: U.S. Dept. of Commerce , Bureau of Pub li c Roads, 1965) 4.4 DES IGN CRITERIA