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HomeMy WebLinkAboutCASTLE RIDGE AT MIRAMONT PUD - PRELIMINARY & FINAL - 54-87J - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTDRAINAGE AND EROSION CONTROL STUDY FOR CASTLE RIDGE AT MIRAMONT FIRST FILING FORT COLLINS, COLORADO DRAINAGE AND EROSION CONTROL STUDY FOR CASTLE RIDGE AT MIRAMONT FIRST FILING FORT COLLINS, COLORADO June 3, 1993 Prepared for: Miramont Associates 309 West Harmony Road Fort Collins, Colorado 80526 Prepared by: RBD, Inc. Engineering Consultants 209 S. Meldrum Fort Collins, Colorado 80521 (303) 482-5922 RBD Job No. 504-004 Vj w w ■ A ■ ■ ■ Engineering Consultants 209 S. Meldrum Fort Collins, Colorado 80521 303/482-5922 FAX: 303/482-6368 June 3, 1993 Ms. Kate Malers City of Fort Collins Utility Services Stormwater 235 Mathews Fort Collins, Colorado 80522 RE: Drainage and Erosion Control Study for Castle Ridge at Miramont First Filing Dear Kate: We are pleased to submit to you, for your review and approval, this Drainage and Erosion Control Study for Castle Ridge at Miramont First Filing. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, RBD Inc. Engineering Consultants Tim J. Bailey Design Engineer ■ Other Offices: Denver 303/458-5526 • Vail 303/476-6340 TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION 1 A. LOCATION 1 B. DESCRIPTION OF PROPERTY 1 II. DRAINAGE BASINS 1 A. MAJOR BASIN DESCRIPTION 1 B. SUB -BASIN DESCRIPTION 1 III. DRAINAGE DESIGN CRITERIA 2 A. REGULATIONS 2 B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 2 C. HYDROLOGICAL CRITERIA 2 D. HYDRAULIC CRITERIA 2 E. VARIANCES FROM CRITERIA 2 IV. DRAINAGE FACILITY DESIGN 3 A. GENERAL CONCEPT 3 B. SPECIFIC DETAILS 3 V. EROSION CONTROL 4 A. GENERAL CONCEPT 4 B. SPECIFIC DETAILS 5 VI. CONCLUSIONS 5 A. COMPLIANCE WITH STANDARDS 5 B. DRAINAGE CONCEPT 5 C. EROSION CONTROL CONCEPT 5 REFERENCES 6 APPENDIX VICINITY MAP 1 HYDROLOGY 2 DESIGN OF CURB INLETS, CHANNELS, AND STORM SEWERS 7 EROSION CONTROL 18 CHARTS, FIGURES AND TABLES 25 DRAINAGE AND EROSION CONTROL STUDY FOR CASTLE RIDGE AT MIRAMONT P.U.D. FIRST FILING FORT COLLINS, COLORADO 1. GENERAL LOCATION AND DESCRIPTION A. Location The Castle Ridge at Miramont First Filing development is located in the southeast part of Fort Collins, south of Harmony Road, and west of Lemay Avenue. The First Filing will be just to the south of The Upper Meadow at Miramont Second Filing and just to the north of Werner Elementary School. A vicinity map of the proposed site is included in the appendix. More particularly, the site is situated in the east half of Section 1, Township 6 North, Range 69 West, of the 6th P.M., City of Fort Collins, Larimer County, Colorado. B. Description of Property The Castle Ridge at Miramont First Filing contains 14.0 acres more or less. The area is currently undeveloped and is being proposed for single family residential construction with 18 lots. The site currently consists of cultivated farmland. The Mail Creek irrigation ditch runs in a northwest to southeast direction immediately north of the site. Topography for the site is generally sloping from the north to the south at approximately 4%. II. DRAINAGE BASINS A. Major Basin Description The Castle Ridge at Miramont First Filing lies within the Mail Creek Basin per the vicinity map in the appendix. No major drainageway exists within the site. ■ B. Sub -Basin Description 1 Historic drainage patterns of the subject site are southwesterly across the site to an existing roadside ditch along the east side of Mail Creek Lane ■ which directs storm water runoff south to Mail Creek. III. DRAINAGE DESIGN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. B. Deveiopment Criteria Reference and Constraints The Castle Ridge at Miramont First Filing historically drains southerly along Mail Creek Lane. The Mail Creek Basin Master Drainage Plan criteria and constraints recommends the northern portion of the site to drain down Castleridge Drive into Mail Creek. According to the Mail Creek Overall Drainage Plan there is to be a future water feature to the east of Highcastle approximately 300' south of the site. In the interim flow is to be routed to the site of this future water feature, which is to be usect for a sediment control basin. The remainder of the site is to flow to the west into an existing roadside ditch along the east of Mail Creek Lane. C. Hydrological Criteria The Rational method is being used to determine runoff peak flows from the site and surrounding off -site tributary areas. The 2 and 100 year rainfall criteria, which was obtained from the City of Fort Collins, is the criteria which was utilized. The criteria is included in the appendix. D. Hydraulic Criteria All calculations within this study have been prepared in accordance with the City of Fort Collins Drainage Criteria. E. Variances from Criteria No variances are being sought for this project. is IV. DRAINAGE FACILITY DESIGN A. General Concept The Castle Ridge Meadow at Miramont First Filing is planned as a single family residential housing development. The First Filing will consist of 18 lots. Storm water flows for the northern portion of the site and for Highcastle Drive will be routed to a sediment control basin approximately 300' south of the site. Overflow from the basin will follow natural drainage patterns south into Mail Creek. Flows from this portion of the site will ultimately run down Highcastle Drive into Mail Creek. The location for this basin was determined from the Overall Drainage Plan for Mail Creek Basin. The southern portion of the site will generally follow historic drainage patterns. It will be directed to the southeast corner of the property into an existing roadside ditch along Mail Creek Lane, which flows southerly into Mail Creek. Included in the back pocket of this report is the drainage plan for the First Filing. B. Specific Details Mail Creek irrigation ditch flows along the northern property line. Highcastle Drive will be crossing over the ditch. The existing ditch geometry is a 10' bottom width with 2:1 side slopes. Proposed for the crossing is an 8'x4' reinforced concrete box culvert with 45 degree wing walls. Included in the appendix is the HEC-2 runs showing the crossing. Basin 1 includes portions of lots 1 through 5 which will drain to the rear of the lots and be intercepted by a grass lined swale which will direct the flow onto Highcastle Drive. Basin 2 includes the front portion of lots 1 through 5 and 11 through 13 as well as a major portion of roadway. The flows through the basin will be directed to the east onto Highcastle Drive. Basin 7 includes the western half of Highcastle Drive as well as a minor portion of lots 17 and 18. It receives the flows from basins 1 and 2 and directs the flow along the gutter into a grass lined swale which curves along the outside of the temporary turnaround. The swale joins with another swale - which contains flows from basin 8. Basin 8 includes the eastern half of Highcastle Drive as well as off -site drainage which flows into the street. The swale then flows south approximately 300' into the sediment control basin. 3 Basin 9 is off -site flow which goes into the sediment control basin. The overflow weir from the basin is sized for the 100 year storm flow, which is to follow natural drainage patterns into Mail Creek. Basin 3 includes portions of lots 10 through 15 and all of the cul-de-sac. A swale is to be created along the drainage easement to the rear of lots 11 and 12. Flow is directed to the southern end of the cul-de-sac to a low point, where the 100 year flow is intercepted by a curb inlet. It is then to be piped to the grass lined swale along the rear of the lots. Basin 4 includes the "hammerhead" cul-de-sac, lot 7, and a portion of lot 6. Flow is directed to the south to a low point at the end of cul-de-sac. A concrete sidewalk culvert is to intercept a major portion of the flow with the remainder overtopping the sidewalk and flowing into a grass lined swale. The sidewalk culvert is to outlet into the swale which flows to the south into the open space area in the southwest corner of the site. Basin 6 includes the southern portion of the site. It receives flows from basins 3 and 4 and routes them to the southwest corner of the site. The flow then outlets into an existing roadside ditch along the east edge of Mail Creek Lane. The Ditch then routes the flow to the south into Mail Creek. Basin 5 includes lot 8 and portions of lots 5 and 6. The flow follows existing drainage patterns into the roadside ditch to the east of Mail Creek Lane where it joins the flow from basin 6. aV. EROSION CONTROL ® A. General Concept © The Castle Ridge at Miramont First Filing lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort Collins zone maps. The potential exists for erosion problems during construction, and after construction until the disturbed ground is again vegetated. It is anticipated that the First Filing construction will begin in the Fall of 1993, and be completed in the Spring of 1993. Per the City of Fort Collins Erosion Control Reference Manual for Construction Sites and related calculations in the appendix, the erosion control performance standard for this site is 82.8%. From the calculations in the appendix, the effectiveness of the proposed erosion control plan is 86.8% during the construction portion of this development. Therefore the erosion control plan as specifically detailed below, will meet the City of Fort f 0 Collins requirements. B. Specific Details Before overlot grading, the sediment control basin shall be constructed. After the overlot grading has been completed, all disturbed areas, not in a roadway, shall have a temporary vegetation seed applied per the City of Fort Collins specification. After seeding, a hay or straw mulch shall be applied over the seed at a rate of 2 tons/acre, minimum, and the mulch shall be adequately anchored, tacked or crimped into the soil per the methods shown on the Drainage and Erosion Control plan. After the utilities have been installed, the roadway surfaces should receive the pavement structure. After installation of the curb inlets, the inlets shall be filtered with a combination of concrete blocks, 1 /2 inch wire screen, and 3/4 inch course gravel. The straw bale barriers should be installed in conjunction with the overlot grading process. VI. CONCLUSIONS A. Compliance with Standards All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. B. Drainage Concept The proposed drainage concepts adequately provide for the transmission of developed on -site runoff to sediment control basin and on to natural drainage patterns into Mail Creek. They are also in compliance with the Overall Drainage Plan for the Mail Creek Basin. I C. Erosion Control Concept 'The proposed erosion control concepts adequately provide for the control _ of wind and rainfall erosion from the Castle Ridge at Miramont First Filing. Through the construction of the proposed erosion control concepts, the City of Fort Collins performance standards will be met. The proposed erosion control concepts presented in this report and shown on the erosion control plan are in compliance with the City of Fort Collins erosion control criteria. 5 REFERENCES 1. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984, Revised January 1992. 2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991. 3. Overall Drainage Study for Oak/Cottonwood Farm in Fort Collins, Colorado by RBD, Inc., May 1992. IA 400 � APPENDIX �3 Z VICINITY MAP SCALE: 1 "=20000