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HomeMy WebLinkAboutOFFICE AND LIGHT INDUSTRIAL ON TECHNOLOGY PARKWAY - FDP220007 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT Final Drainage and Erosion Control Report for 5041 Technology Parkway Fort Collins, Colorado April 27, 2022 April 27, 2022 Mr. Wes Lamarque City of Fort Collins Water Utilities--Storm water 700 Wood Street Fort Collins, Colorado 80521 RE: Final Drainage and Erosion Control Report for the 5041 Technology Parkway Dear Wes: We are pleased to submit to you, for your review and approval, this Final Drainage and Erosion Control Report for 5041 Technology Parkway. 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, Aspen Engineering John Gooch, P.E. Principal TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION 5 A. LOCATION 5 B. DESCRIPTION OF PROPERTY 5 II. DRAINAGE BASINS 6 A. MAJOR BASIN DESCRIPTION 6 B. EXISTING SUB-BASIN DESCRIPTION 6 III. DRAINAGE DESIGN CRITERIA 7 A. REGULATIONS 7 B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 8 C. HYDROLOGIC CRITERIA 8 D. HYDRAULIC CRITERIA 8 E. VARIANCE 9 IV. DRAINAGE FACILITY DESIGN 9 A. GENERAL CONCEPT 9 B. SPECIFIC DETAILS 9 C. DETENTION POND 15 D. STREET CAPACITIES 16 V. STORM WATER QUALITY 17 A. GENERAL CONCEPT & SPECIFIC DETAILS 17 VI. EROSION CONTROL 18 A. GENERAL CONCEPT 18 VII. CONCLUSIONS 18 A. COMPLIANCE WITH STANDARDS 18 B. DRAINAGE CONCEPT 19 C. STORM WATER QUALITY 19 D. EROSION CONTROL CONCEPT 20 E. EROSION CONTROL ESCROW ESTIMATE 20 REFERENCES 21 APPENDIX PAGE VICINITY MAP, SOILS MAP A RATIONAL METHOD HYDROLOGY B STORM SEWER PIPE SIZING, INLET SIZING C POND CAPACITY CALCULATIONS & RATING CURVES, OUTLET STRUCTURE CALCULATIONS, LID CALCULATIONS, ORIFICE SIZING & OVERFLOW WEIR SIZING D CURB CUT, CONCRETE SIDEWALK CULVERT, & RIPRAP SIZING, & EROSION CONTROL CALCULATIONS, & EROSION ESCROW CALCULATIONS E PROPOSED DRAINAGE BASIN EXHIBIT, EROSION CONTROL PLAN, & EROSION CONTROL NOTES AND DETAILS SHEET F 5 FINAL DRAINAGE AND EROSION CONTROL REPORT FOR 5041 TECHNOLOGY PARKWAY FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location The 5041 Technology Parkway site is bounded to the north by Precision Drive, to the east by Technology Parkway, to the south by Rock Creek Drive, and to the west by the Eye Center of Northern Colorado and the Windsong Memory Care Facility. The project site can also be described as situated in the northwest quarter of Section 4, Township 6 North, Range 68 West of the 6th P.M., of the City of Fort Collins, Larimer County, Colorado. Please refer to the vicinity map in Appendix A for the site location. B. Description of Property The 5041 Technology Parkway project is comprised of an approximate 52,000 +/- square foot building footprint along with associated parking lot, entry plazas and outdoor site areas, and utility improvements, and a regional pond (Pond 501), all of which is situated over approximately 6.72 acres and is contained within Lot 1 and Tract A, of the proposed development area. An additional 4.70 acres, situated west and north of Pond 501, will be subdivided into two lots (Lots 2 & 3) for future development. The total area of the 5041 Technology Parkway project will account for approximately 11.04 acres (Basins 1- 17) being conveyed to the proposed Pond 501, located north of Rock Creek Drive and south of Precision Drive. Offsite street runoff from Precision Drive (basins OS9, OS12, and OS13) will also be ultimately piped to detention pond 501, once development occurs, as applicable. Currently, the 5041 Technology Parkway site consists of fallow agricultural land, with an 18” storm sewer pipe, running along the south portion of the site, that serves as an outfall from the Windsong development. An existing sanitary sewer line and associated easement also exists along the western boundary of Lot 2, and provides sewer service to the Windsong development. 6 The majority of existing topography of the HTP 5041 site (and future development area) generally slopes from the northwest to southeast at approximately 0.50% to 0.80%. II. DRAINAGE BASINS A. Major Basin Description The site lies within the McClellands Basin. The site drainage has been previously accounted for in the Harmony Technology Park Site Master Plan (HTPSMP) and associated storm drainage improvements shown in the Mainstreet Health and Wellness project, dated February 18, 2015. The project drainage will be in conformance with these two studies, in which Masterplan information can be found in the East Harmony Portion of the McClellands Creek Master Drainage Plan (August 1999). Please refer to the Final Drainage Report for the Mainstreet Health and Wellness Suites, dated by February 18, 2015, and the Final HTP Infrastructure Improvement drainage report, dated November 4, 2015, for additional information, and as may be applicable to the 5041 Technology Parkway project. B. Existing Sub-Basin Description The existing project site is within SWMM basin 801 of the HTP Masterplan report. Existing basin 801 contains approximately 16.5 acres and was modeled with the entire 16.5 acres having an imperviousness of 0.80, with an allowable 100-year release rate of 7.5 cfs, for the basin area. This provides for an allowable release rate of 0.45 cfs/acre for subbasins within SWMM basin 801. The 5041 Harmony Technology Park site being developed is comprised of 11.04 acres for the 5041 Technology Parkway site (Lot 1), regional detention pond 501 (Tract A), and the two future, residual lots (Lots 2 and 3), which are located west of pond 501. An additional 1.29 acres of offsite basins OS9, OS12, and OS13, shown in the Mainstreet Health and Wellness Suites drainage report, are also accounted for in this drainage study, thus providing for 12.33 acres of total basin areas being conveyed to proposed regional pond 501. The allowable 100-year release rate for the 12.33 acres is 5.55 cfs, per the SWMM Model, for attributing basins. The runoff from the existing 11.04 site area flows primarily from northwest to southeast across the existing agricultural field, with the majority of runoff infiltrating into the existing field, with any surface flow ponding up in the southeast corner of the site and possibly entering the existing area inlet, located in the southeast corner of the site. Offsite runoff from Precision Drive is captured in Type R inlets in sumps. Flow from these inlets is piped to two-cobble stone dry wells at the south side of 7 Precision Drive to enhance infiltration into the field. With development of the 5041 site, the cobble pit at design point OS9 will remain in-place, while the cobble pit at design point OS13 will be removed. It's important to note that the Windsong Memory Care Facility and Eye Center of Northern Colorado sites were developed and provide their own onsite water quality and detention, prior to releasing into storm drain piping systems in Precision Drive and along the north side of Rock Creek Drive. Both of these developments were required to adhere to the HTP Masterplan report and SWMM model, which allows for up to 0.45 cfs/acre for the 100-year release rates from these sites. The 5041 Technology Parkway existing site basin areas will be conveyed to the original SWMM Pond 501, but the required detention volume will be reduced from the approved SWMM model to only account for the attributing site basin areas from the 5041 Technology Parkway development (Lots 1-3 and Tract A), and offsite basins OS9, OS12, and OS13 from Precision Drive. Please refer to the HTPMSP report for masterplan details, as well as the Mainstreet Health and Wellness Suites Final Drainage Report. Please see the rational calculations (Appendix B) and the drainage exhibit (Appendix F) of this report for the proposed drainage basins for the subject site. III. DRAINAGE DESIGN CRITERIA A. Regulations The 5041 Technology Parkway project is being constructed in accordance with the HTP Masterplan report and SWMM modeling for the overall HTP site. It’s important to note that proposed Pond 501 is designed to detain and provide water quality for the 5041 Technology Parkway site (basins 1-16), two future lots west of Pond 501 (basin 17), and the offsite basins in Precision Drive (OS9, OS12, and OS13). Pond 501 will serve as a regional water quality and detention pond and has been sized to provide water quality and detention for 12.33 acres (as required by the HTP Masterplan). Future development of the two residual lots will be required to adhere to the McClellands Creek Master Drainage Plan and the Harmony Technology Park Site Master Plan (HTPSMP), as well as HTP Masterplan SWMM Model, which allows for a combined impervious ratio of 80% for the developed and associated, adjacent roadway portions for the attributing parcels. LID improvements are required for the developed portion of site. The two future lots to the west of detention Pond 501 will be responsible for their own LID improvements, when the lots are developed. It’s important to note that with future development of Lot 2, the developer of Lot 2 will be required to remove the interim 8 cobble pit at design point OS9, and pipe the storm flow from basin OS9 through the Lot 2 site and into proposed Pond 501. B. Development Criteria Reference and Constraints The criteria and constraints from the City of Fort Collins will be met. Water quality and detention requirements for the site are being provided for via proposed Pond 501. LID requirements are being met with the use of raingardens, which treat approximately 75% of new, applicable LID impervious area within Lot 1, thus meeting the 75% treatment area requirement, per City criteria. Future development of Lots 2 and 3 will require additional BMP’s and LID measures be provided by those developments, as may be applicable at that time. C. Hydrologic Criteria The Rational Method for determining surface runoff was utilized for the 5041 Technology Parkway improvements. The Rational Method data for offsite basins OS9, OS12, and OS13 (in Precision Drive) from the Mainstreet Health and Wellness Suites Final Drainage Report was utilized as input into the rational method calculations for the 5041 Technology Parkway project. The 2-year and 100-year storm event intensities have been calculated and was utilized to calculate runoff to size drainage structures, storm pipes, curb cuts, chases, riprap, and erosion control fabric. Routed runoff flow was calculated with this final design. The City of Fort Collins intensity duration frequency curves were used to obtain rainfall data for each storm specified. It’s important to note that the future development of adjacent lots will be required to meet the 80% impervious ratio for the developed condition of the lots, rather than match the rational ‘c’ values shown in the rational calculations in Appendix B of this report. D. Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the City of Fort Collins Drainage Criteria and are also included in the Appendix. 9 Final sizing of storm sewer pipes was analyzed using UD Sewer (MHFCD). Storm inlet sizing was completed using UD Inlet (MHCD). Both UD sewer and UD Inlet calculations are provided in Appendix C. Design of culverts, curb cuts, and metal sidewalk culverts were completed using AutoDesk Civil3D design software and provided in Appendix E. Riprap sizing was completed using spreadsheets. Erosion control fabric was sized using Erosion Control Materials Design Software (ECMDS) from North American Green. The sizing for riprap and erosion control calculations are provided in Appendix E. Water quality control volume, detention pond volumes, LID volumes and stage storage calculations are provided in the Appendix D of this report. E. Variance No variances are being requested for the project. IV. DRAINAGE FACILITY DESIGN A. General Concept Seventeen proposed drainage basins (basins 1-17) will provide conveyance (or future conveyance, as applicable) of runoff to the proposed LID Basins, then into the proposed water quality and detention Pond 501, located north of Rock Creek Drive and south of Precision Drive. Pond 501 will provide water quality and detention for basins 1-17, and offsite basins OS9, OS12 and OS13, with an overall impervious ratio of 67% for all the basins combined. A water quality and orifice-controlled outlet structure within Pond 501 will provide the required water quality for Lots 1-3, Tract A, and offsite attributing areas, while also providing a controlled release of 5.55 cfs to the existing storm sewer that runs west-east along the southern property boundary (north of Rock Creek Drive). The 5.55 cfs release from Pond 501 will discharge to the existing 18” RCP near the southeast corner of the Lot 1. Pond 501 provides approximately 2.72 acre-feet of combined water quality and detention volume for the contributing 12.33 acres. The available pond volume up to the overflow spillway elevation of 4917.72, provides approximately 4.0 acre-feet. Pond 501 has been sized to detain up to the 100-year event, while receiving the 100- year flow from the 12.33 acre masterplan area (at a combined 67% impervious ratio). Upon development of basins 1-17 (proposed and future lots), runoff from these basins will be routed to Pond 501 via proposed storm sewer inlets, curb cuts, and piping (from roof drain connections and LID basins). 10 Please refer to the proposed drainage basin exhibit in Appendix F, and the rational calculations in Appendices B for the proposed site improvements, and future development areas. B. Specific Details Basins 1: Runoff from the paved parking lot areas, drive aisles, landscaped areas, and sidewalk areas will be conveyed to three Type R inlets in Basin 1, at design points 1a, 1b and 1c, located along the east curb and gutter. Flow will be intercepted at the 5’ Type R inlets, in sump conditions, and enter the underground storm sewer C. Piped runoff will flow north, west, then south and discharge into detention Pond 501. Riprap protection will be constructed at the outfall into detention Pond 501. Runoff from approximately 3,000 SF of basin 1, at design point 1d, will be intercepted by a curb cut and concrete chase to divert runoff away from the entry driveway and will discharge to the west flowline of Technology Parkway. Approximately 300 SF of the entry drive, not intercepted by the curb cut and chase, will flow east into the west flowline of Technology Parkway, and will be intercepted by an existing Type R storm inlet at design point 502. The entire basin area for basin 1 has been utilized for water quality and detention pond volume sizing. Basins 2 & 3: Basin 2 is comprised primarily of landscape area, and one concrete sidewalk connection. Runoff from basin 2 will sheet flow over the walk and grass parkway and enter the west curb and gutter of Technology Parkway, then flow south to an existing Type R inlet. Basin 3 runoff from paved drive aisle, landscaped areas, and sidewalk areas will be conveyed east to Technology Parkway. The landscaped area will sheet flow over the walk and grass parkway, to enter the curb and gutter in the public street. Runoff from the paved drive aisle will be conveyed southeast into the south curb and gutter in the drive aisle, and discharge to the west curb and gutter of Technology Parkway. Runoff from approximately 590 SF of area from basin 3, will drain east, into the existing curb and gutter along the west flowline in Technology Parkway. Runoff from basin 2 and basin 3 will flow south to an existing Type R inlet at design point 502, in Technology Parkway. Flow will ultimately discharge to the existing detention pond 110 of the HTP Masterplan, near the northwest corner of Lady Moon Drive and Rock Creek Drive. Runoff is treated for water quality in detention pond 110. It should be noted that the entire basin area for basins 2 and 3 has been utilized for water quality and detention pond volume sizing. 11 Basin 4: Runoff from landscaped and sidewalk areas will be conveyed north toward a swale and raingarden. Flow on the east side of the basin will concentrate in a grass swale, flow west through a 2’ sidewalk chase, with metal plate, and enter the north end of the grass-lined raingarden. The majority of basin 4 area sheet flows north and into the raingarden while a small portion in the east region of basin 4 is conveyed west in shallow swale and into the rain garden. In larger storm events, the excess runoff that surcharges the raingarden, will overflow into a grated manhole inlet with a Neenah R-2586-O grate, at design point 4. Flow will be piped west, then south and into Pond 501. Riprap protection will be constructed at the pipe outfall in Pond 501. Basin 5: Runoff from paved parking lot areas, landscape areas, and drive aisle areas will concentrate in the west curb and gutter, pass through a curb cut in the west flowline, and enter a grated manhole inlet with a Neenah R-2586-O grate, at design point 5. Flow will be piped west, and then south and into detention Pond 501. Approximately 350 SF of the drive aisle, not intercepted by the inlet, will flow north to the south flowline in Precision Drive and will be intercepted by an existing storm inlet at design point OS13. All runoff from basin 5, excluding the 350 SF of area mentioned above, will be detained and treated for water quality in Pond 501. However, the entire basin area has been utilized for water quality and detention pond volume sizing. Basins 6 & 7: Runoff from paved parking lot areas, drive aisles, landscaped areas, and sidewalk areas will be conveyed to two locations in Basin 6, being a Type R inlet, located along the east curb and gutter, and a curb cut with concrete chase in the entry drive. The majority of the runoff from basin 6 will be intercepted by the 5’ Type R inlet, in a sump condition at design point 6b. Runoff will enter an underground storm sewer, flow southwest, west, then northwest, and discharge to Pond 501. Runoff from approximately 3,000 SF of basin 6, comprised of paved and landscape area, will be intercepted by a 2 ft. curb cut and 2’ concrete chase at design point 6a, to divert runoff away from the entry driveway and discharge runoff to the west flowline of Technology Parkway. Approximately 400 SF of the entry drive, not intercepted by the curb cut and chase, will flow east into the west flowline of Technology Parkway. Runoff from both areas will be intercepted by an existing Type R storm inlet at design point 502. Basin 7 is comprised primarily of landscape area, with small areas of concrete sidewalk. Runoff from basin 7 will sheet flow over the walk and grass parkway to enter the west curb and gutter of Technology Parkway, then flows south to an existing Type R inlet at design point 502. 12 It should be noted that the entire basin area for basins 6 and 7 has been utilized for water quality and detention pond volume sizing. Basins 8 & 9: Runoff from paved parking lot areas, drive aisles, landscaped areas, and sidewalk areas will concentrate at two sump locations in Basin 8, on the south curb and gutter. Flow will pass through 2’ wide curb cuts at design points 8a and 8b, to enter a grass- lined raingarden in basin 8. In larger storm events, the excess runoff that surcharges the raingarden, will overflow into a storm manhole inlet with a Neenah R-2586-O grate at design point 9, and will be piped west, then northwest and into Pond 501. Permanent erosion control fabric protection will be constructed in the raingarden at the 2’ curb cut outfall points. Basin 9 is comprised primarily of landscape and raingarden area, with a shallow swale that will convey runoff into the LID basin. Basin 10: Runoff from the paved parking lot areas and drive aisle areas will be conveyed south and into the curb and gutter, with the majority of runoff passing through a 2’curb cut at design point 10. Flow will then be conveyed east in a shallow swale to the raingarden in basin 9. Runoff from approximately 400 SF of area from basin 10 will drain south and flow over the sidewalk and into the existing curb and gutter along the north flowline in Rock Creek Drive. Runoff will flow east to existing combination inlets, in Rock Creek Drive, that discharge to the existing detention pond 110 of the HTP Masterplan, near the northwest corner of Lady Moon Drive and Rock Creek Drive. Basin 11: Runoff from the entire roof of the building will be piped to an external, underground 12” HDPE storm sewer pipe that discharges to a raingarden along the toe of slope in Pond 501. In larger storm events, the raingarden will crest the bank of the raingarden and will overflow into Pond 501. There are 5 anticipated points of connection to the roof drain system, along the west side of the building. The roof drains will connect to the underground storm sewer near design point 11. Basins 12, 13 & 14: Runoff from paved parking lot areas, drive aisles, and sidewalk areas will concentrate at sump locations within each basin. Basins 12 will drain to a 5’ Type R inlet constructed at the sump location at design point 12. Basin 13 will drain to a 10’ Type R inlet at design point 13. Flow is piped west and discharges to a raingarden at the toe of slope within Pond 501. In larger storm events, the raingarden will 13 overflow into Pond 501. Riprap protection will be constructed from the storm pipe outfall, through the raingarden at the outfall points. Basin 14 runoff will pass through a 3’ wide curb cut with 3’ wide concrete sidewalk chase with metal culvert, to enter a grass-lined raingarden in basin 15. In larger storm events, runoff will overflow the west berm of the raingarden and drain into Pond 501. Riprap protection will be constructed from the sidewalk chase through the raingarden at the outfall point. Basin 15: Runoff from landscaped area and sidewalk area will runoff as sheet flow to the west. Portions of the basin adjacent to raingardens will drain to the raingardens within basins 15 and 16. Basin areas, beyond the limits of the raingardens, will drain to the adjacent parking lot and ultimately drain to Pond 501. Basin 16: Basin 16 includes the grass-lined area of detention pond 501. Runoff from the site will be conveyed to Pond 501 via curb cuts, storm drain piping, and raingarden underdrains and overflow conditions. As discussed in Basin 11, a raingarden will be constructed at the pipe outfall for treatment of the roof runoff before entering pond 501. Similarly, Basins 4, 8, 9, 10, 12, 13, 14, 15 will all be treated by raingardens prior to discharging to basin 16. The runoff discharging from basin 16, at design point 16, will be treated for water quality by implementing extended detention utilizing a water quality outlet structure, with orifice restrictions. Basin 17: Runoff from the undeveloped basin 17 (future developed Lots 2 and 3) will sheet flow overland to the southeast and into Pond 501. Runoff from basin 17 provides for an allowable 80% impervious ratio. Upon development of future lots 2 and 3, runoff shall be directed to Pond 501. Offsite Drainage Basin OS9: Runoff from offsite basin OS9 is conveyed east along the south half of Precision Drive, enters an existing 10’ Type R inlet, and is piped to a cobble infiltration pit. With the 5041 Technology Parkway development, the cobble pit will remain in- place. However, with the future development of Lot 2, the cobble pit will be removed, and the Lot 2 developer shall pipe the flow from offsite basin OS9 to detention Pond 501, where runoff will be treated for water quality and detained. Basins OS12 & OS13: Runoff from offsite basins OS12 and OS13 is conveyed east in curb and gutter along the north and south sides of Precision Drive, with flow entering 5’ Type R inlets at 14 design points OS12 and OS13. The combined flow from basins OS12 and OS13 is piped to the south side of Precision Drive and enters a cobble infiltration basin. With the 5041 Technology Parkway development, the existing cobble pit will be removed. Runoff from design points 1a, 1b, 1c, 4, and 5, will combine with the runoff from design points OS12 and OS13 at design point 18. The combined runoff will be piped to Pond 501, where runoff will be treated for water quality and detained. Basin 502: Runoff from offsite basin 502 is conveyed north and south in the west flowline of Technology Parkway, enters an existing 5’ Type R inlet, and is piped east and into the existing detention pond 110 (of the HTP Masterplan), located near the northwest corner of Lady Moon Drive and Rock Creek Drive, and south of the Custom Blending site. Runoff from offsite basin 502 is treated for water quality and detained in existing pond 110. Landscape area runoff from on-site basins 2 and 7 will enter basin 502. In addition, portions of basins 1, 3, and 6 will enter basin 502. The onsite areas are accounted for in Pond 501 for water quality and detention and the contributing runoff to basin 502 is minimal. Overflow Conditions: Basins 1 & 6: Should the curb cuts, inlets or pipes in basins 1 and 6 become clogged, runoff from basins 1 and 6, will spill east over the sidewalk and enter the west flowline of Technology Parkway (basin 502). Flow will drain to the existing 5’ Type R Inlet and will discharge to the existing detention pond 110 (of the HTP Masterplan), located near the northwest of the intersection of Lady Moon Drive and Rock Creek Drive, and south of the Custom Blending site. Basins 4-5: Should the inlet or pipes in basin 4 become clogged, runoff will spill north over the sidewalk and enter the south flowline of Precision Drive. Flow will drain in the curb and gutter to the existing 5’ Type R Inlet at design point OS13, which will convey flow to Pond 501. If the inlet or pipe in basin 5 were to plug, runoff will drain north through the drive and enter the south flowline of Precision Drive. Basins 8, 9 & 10: Should the curb cuts in basin 8 plug, runoff will overtop the curb and enter the raingarden in basin 9. Should the inlet or pipes in basin 9 become clogged, runoff from basins 8, 9 and 10, will spill south over the sidewalk and enter the north flowline of Rock Creek Drive. Flow will drain in the curb and gutter to the existing combination inlets in Rock Creek Drive, which will discharge to the existing 15 detention pond 110 (of the HTP Masterplan), located near the northwest of the intersection of Lady Moon Drive and Rock Creek Drive, and south of the Custom Blending site. Basin 11-14: Should the roof drains plug in basin 11, overflow from the roof will flow overland to the west through basin 13, enter the 10’ Type R inlet, and discharge to Pond 501. Should the curb cuts or inlets in basins 12-14 plug, runoff will overtop the curb and enter the raingardens in basins 15 and 16. Upon the raingardens being surcharged, runoff will overflow west and into Pond 501. Basin 16: Should the outlet structure in Pond 501 plug, overflow from Pond 501 will spill east over the proposed sidewalk and into the parking lot. Flow will crest the high points in the parking lot and flow north to Precision Drive and south to Rock Creek Drive. Overflow will eventually enter the existing inlets, that discharge runoff to the existing detention pond 110 of the HTP Masterplan. Basin 17: Basin 17 is vacant land and flow will enter pond 501. Please refer to basin 16 for overflow path. C. Detention Pond Pond 501 has been sized to provide water quality and detention for the proposed 12.33 acres of the 5041 Technology Parkway development, which includes the 2 lots for future development (4.70-acres), and the runoff from offsite basins in Precision Drive (1.29 acres), as shown on the Drainage Exhibit. Pond 501 will provide 2.72 acre-feet of combined water quality and detention volume (0.27 acre-feet of water quality volume). Please refer to the Pond 501 rating curve in Appendix D for the pond sizing and elevation information. Pond 501 will allow for water quality and detention up to the 100-year event (for 12.33 acres of developed area) and will contain a single outlet control structure. The structure will be a water quality control outlet structure and will have a water quality plate designed to provide up to 0.27 acre-feet of water quality volume (for 12.33 acres) at an elevation of approximately 4913.39. The 100-year WSEL for the 12.33 acre development will be approximately 4916.90, providing 2.72 acre-feet of volume. The release rate will be restricted to 5.55 cfs at the 100-year storm event. The structure will be constructed with an orifice control plate at the back of the structure over the entrance of the outlet pipe. The orifice plate will have a circular opening of 6.54” and will be bolted to the wall of the outlet, in front of the 18” diameter outlet pipe. The allowable release rate of 5.55 cfs will discharge to a proposed 18” RCP storm sewer system, that will connect to the existing storm sewer 16 system, located along the south side of the property and north of Rock Creek Drive, as allowed by the HTP Masterplan, and as constructed with the Windsong development. It’s important to note that the 100-year WSEL for Pond 501 for the ultimate build-out of the 12.33 acre area (for both onsite and offsite attributing basins) is approximately 4916.90. Pond 501 and the orifice control plate are being constructed for the ultimate build-out condition of the 12.33 acres at a combined impervious ratio of 67%. The allowable impervious ratio for the two future lots (Lots 2 and 3) is 80%. The emergency spillway for the pond will be along the east sidewalk, adjacent to Pond 501. The proposed spillway top-of-weir elevation will be approximately 4917.72, thus allowing overtopping flow to pass over the sidewalk and enter the parking lot. The depth of flow over the sidewalk weir is calculated to be approximately 0.19 feet. Overtopping flow will pond up until it rises to the high point in the curb and gutter, at the north and south ends of the parking lot. A portion of the flow will crest the high point at 4918.13 and drain north into the flowline of Precision Drive. The south side will crest a curb cut at 4918.0 and enter the south raingarden, then overflow into the flowline of Rock Creek Drive. In the future development of Lot 3, a shared access to Lot 1 is anticipated to be constructed. At that time the overflow path may be established across the future drive and walk to Rock Creek Drive. Overflow would be intercepted by the combination inlets west of the Lady Moon Drive intersection and conveyed to the existing detention pond 110, located northwest of the Lady Moon Drive/ Rock Creek Drive intersection and south of Custom Blending. D. Street Capacities Street capacity calculations are not required for the project as there are no public street improvements. 17 V. STORM WATER QUALITY A. General Concept & Specific Details The water quality aspect of stormwater runoff must be addressed on all final utility plans. Therefore, the proposed water quality/ detention pond (Pond 501) will have adequate capacity, in accordance with the HTP SWMM Model, and will provide all the required water quality and detention up to the 100-year event for the developed condition of the subject site and offsite adjacent areas (up to a combined impervious ratio of 67% for onsite parcel areas and associated, adjacent roadways) (total of 12.33 acres), prior to releasing flows downstream. It’s important to note that the two residual future lots (Lots 2 and 3) are allowed up to 80% imperviousness for the specific lot areas, and have been modeled as such in this report. Best Management Practices (BMP’s) for the treatment of stormwater will be provided in the 5041 Technology Parkway site through the utilization of raingardens constructed around the north, south and west sides of the lot to treat the first flush runoff from impervious paved area and building roof area. Upon the raingardens filling up, overflow in the north and south raingardens, will be captured by area inlets placed at the 1’ depth mark on the sides of the raingardens to convey overflow to Pond 501. The raingarden within basins 15 and 16 will overflow the west berm and discharge directly into Pond 501. Flow from the raingardens and other areas of the site will be conveyed to a grass- lined detention pond (Pond 501). Pond 501 will be equipped with a 40-hour extended detention structure with a water quality control orifice plate, and a single stage orifice on the outlet structure, which will restrict the release rate from the site to 5.55 cfs. These water quality features/structures will provide a mechanism for pollutants to settle out of the stormwater runoff before flows are directed downstream to the McClelland’s Drainage Basin. Best Management Practices (BMP's) for the treatment of stormwater runoff shall also be provided with development of Lots 2 and 3 in the future, which may include grass/ sod-lined swales with soft pans, riprap pads at culvert discharge points, and permanent erosion control fabric at curb cuts and swale entrances into Pond 501. Please refer to the Erosion Control Plan for onsite BMP’s and LID’s for the 5041 Technology Parkway project, and future plans by others for other BMP’s and LID’s attributable to future, development of the two west lots (Lots 2 and 3). 18 VI. EROSION CONTROL A. General Concept The subject site soils are classified as Hydrologic Group C with an erosion K factor ranging from 0.28 to 0.30. The Wind Erodibility Group is rated 6 according to the USDA Soil Properties. The potential exists for erosion problems during construction but should be minimal after completion of proposed Pond 501. Silt fence will be installed along the entire boundary of the grading area, as shown in the erosion control plan, to prevent sediment from leaving the project area. Gravel tracking pads will also be placed at three entrances/exits to the 5041 Technology Parkway site. Gravel inlet filters will be placed at area inlets and Type R inlets on the site and at the offsite inlets on Precision Drive, immediately west of the site entrance, and on Technology Parkway east of the site. Rock sock filters will be installed at each of the curb cuts to minimize sediment entering chases, raingardens, and Pond 501. Riprap will be installed at concentration points (curb cuts and pipe outlets) discharging to Pond 501 or the raingardens in Pond 501 to minimize erosion and increase soil stabilization. VII. 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. The City of Fort Collins Storm Water Utility will not maintain the private on-site storm drainage facilities within the subject site. The owners of the subject site will maintain their on-site storm drainage facilities on a regular basis. The following shall be implemented for the private stormwater improvements’ operations/ maintenance procedures for the project on an annual or bi-annual basis: 1) Storm Sewer Inlets, pipes and flared-end-sections, curb cuts and concrete sidewalk culverts/chases, structures, manholes, and the water quality/ outlet control structures, as may be applicable, shall be cleaned through the removal of debris and sediment from the associated items to allow for adequate drainage through the site to the interim facilities. 2) Pond sedimentation/ silting shall be removed to allow for adequate drainage along the bottom of the ponds and raingardens. Grass scrubbing of the ponds may be required to remove sediment and promote grass growth. 3) Re-vegetation through the use of Natural Seeding/ Sod shall be provided for disturbed areas and other permanent erosion controls shall be provided for 19 areas where erosion has taken place and requires remediation back to the proposed condition shown in the plans. The Stormwater Operating/ Maintenance Procedures listed above are guidelines to the minimum procedures that shall be implemented for the 5041 Technology Parkway project, with these and additional measures being utilized on an as-needed basis. B. Drainage Concept The proposed drainage concepts presented in this study and shown on the utility plans, adequately provide for the transmission of developed runoff from the proposed site, future lots to the west, and from offsite attributing basins to detention pond 501. The proposed storm sewers and surface conveyances will provide for the 100-year developed flows from the onsite and offsite basins to reach the proposed raingardens and water quality/detention pond, prior to being released to the existing storm sewer at the release rate of 5.55 cfs, established by the HTP drainage Masterplan. If groundwater is encountered at the time of construction, a Colorado Department of Health Construction Dewatering Permit will be required. C. Storm Water Quality The final design for the 5041 Harmony Technology Park project has addressed the water quality aspect of stormwater runoff. The proposed grass-lined rain gardens and detention pond with extended detention and water quality, will provide an opportunity for stormwater pollutants to filter out of the stormwater runoff before flows are directed downstream to Fossil Creek Reservoir Inlet Ditch. Furthermore, the proposed grass-sod-lined swales, riprap pads at curb cuts and storm pipe outlets, permanent erosion control fabric at curb cuts, and other erosion control measures which may be used for slope stabilization, will provide additional mechanisms for pollutants to settle out of the stormwater runoff before flows are directed south and ultimately to Fossil Creek Reservoir Inlet Ditch. It’s important to note that in the interim condition the two undeveloped lots (Lots 2 and 3), west of Pond 501, will convey their flow across the vacant grass field/vegetated area, as historically occurs. It is anticipated that infiltration of runoff into the soil will occur during minor storm events, with larger storm events possibly providing for runoff from these two lots directly into Pond 501. Infiltration into the existing field during the minor events, as well as the water quality provided for in Pond 501 for these two lots, will promote and maintain water quality for these two lots and the development. 20 D. Erosion Control Concept Proposed erosion control concepts have been provided for and adequately provide for the control of wind and rainfall erosion from the 5041 Harmony Technology Park development. Through the construction of the proposed erosion control concepts, the City of Fort Collins 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. Please refer to Appendix F for the Erosion Control Plan and Erosion Control Notes and Details Sheets. E. Erosion Control Escrow Estimate The Erosion Control Escrow Estimate for the 5041 Harmony Technology Park project is $27,984. The details for the calculated amount can be found in Appendix E. 21 REFERENCES 1. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984, Revised January 1997, & Associated UDFCD Updates and New City of Fort Collins Stormwater Criteria manual, adopted January 2012. 2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991, Revised January 1997, & Associated UDFCD Updates and New City of Fort Collins Stormwater Criteria manual, adopted January 2012. 3. Urban Storm Drainage Criteria Manual Volume 1; Urban Drainage and Flood Control District, Denver, Colorado, June 2001. 4. Urban Storm Drainage Criteria Manual Volume 2; Urban Drainage and Flood Control District, Denver, Colorado, June 2001. 5. Urban Storm Drainage Criteria Manual Volume 3, Best Management Practices; Urban Drainage and Flood Control District, Denver, Colorado, August 2011. 6. East Harmony Portion of McClellands Basin 100-Year Master Plan, by Icon Inc., Fort Collins, Colorado, August 1999. 7. Final Drainage and Erosion Control Report, Harmony Technology Site Master Plan, by Stantec Consulting, May 19, 2008. 8. Final Drainage and Erosion Control Study for Harmony Technology Park Third Filing, by Stantec Consulting, May 19, 2008. 9. Final Drainage and Erosion Control Report for Mainstreet Health & Wellness Suites, by Aspen Engineering, dated February 18, 2015. 22 APPENDIX 23 APPENDIX A 24 VICINITY MAP, SOILS MAP Hydrologic Soil Group—Larimer County Area, Colorado (HTP 5041) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/21/2020 Page 1 of 4448501044850504485090448513044851704485210448525044852904485330448501044850504485090448513044851704485210448525044852904485330498440498480498520498560498600498640498680 498440 498480 498520 498560 498600 498640 498680 40° 31' 8'' N 105° 1' 7'' W40° 31' 8'' N105° 0' 55'' W40° 30' 56'' N 105° 1' 7'' W40° 30' 56'' N 105° 0' 55'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 25 50 100 150 Meters Map Scale: 1:1,770 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado (HTP 5041) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/21/2020 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 73 Nunn clay loam, 0 to 1 percent slopes C 6.2 56.2% 74 Nunn clay loam, 1 to 3 percent slopes C 4.8 43.8% Totals for Area of Interest 11.0 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Hydrologic Soil Group—Larimer County Area, Colorado HTP 5041 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/21/2020 Page 3 of 4 Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado HTP 5041 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/21/2020 Page 4 of 4 K Factor, Rock Free—Larimer County Area, Colorado (HTP 5041 ) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/2/2020 Page 1 of 3448501044850504485090448513044851704485210448525044852904485330448501044850504485090448513044851704485210448525044852904485330498440498480498520498560498600498640498680 498440 498480 498520 498560 498600 498640 498680 40° 31' 7'' N 105° 1' 6'' W40° 31' 7'' N105° 0' 55'' W40° 30' 56'' N 105° 1' 6'' W40° 30' 56'' N 105° 0' 55'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 25 50 100 150 Meters Map Scale: 1:1,730 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. Wind Erodibility Group—Larimer County Area, Colorado (HTP 5041 ) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/2/2020 Page 1 of 3448501044850504485090448513044851704485210448525044852904485330448501044850504485090448513044851704485210448525044852904485330498440498480498520498560498600498640498680 498440 498480 498520 498560 498600 498640 498680 40° 31' 7'' N 105° 1' 6'' W40° 31' 7'' N105° 0' 55'' W40° 30' 56'' N 105° 1' 6'' W40° 30' 56'' N 105° 0' 55'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 25 50 100 150 Meters Map Scale: 1:1,730 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons 1 2 3 4 4L 5 6 7 8 Not rated or not available Soil Rating Lines 1 2 3 4 4L 5 6 7 8 Not rated or not available Soil Rating Points 1 2 3 4 4L 5 6 7 8 Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Wind Erodibility Group—Larimer County Area, Colorado (HTP 5041 ) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/2/2020 Page 2 of 3 Wind Erodibility Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 73 Nunn clay loam, 0 to 1 percent slopes 6 6.3 57.6% 74 Nunn clay loam, 1 to 3 percent slopes 6 4.6 42.4% Totals for Area of Interest 10.9 100.0% Description A wind erodibility group (WEG) consists of soils that have similar properties affecting their susceptibility to wind erosion in cultivated areas. The soils assigned to group 1 are the most susceptible to wind erosion, and those assigned to group 8 are the least susceptible. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Lower Wind Erodibility Group—Larimer County Area, Colorado HTP 5041 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/2/2020 Page 3 of 3 MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons .02 .05 .10 .15 .17 .20 .24 .28 .32 .37 .43 .49 .55 .64 Not rated or not available Soil Rating Lines .02 .05 .10 .15 .17 .20 .24 .28 .32 .37 .43 .49 .55 .64 Not rated or not available Soil Rating Points .02 .05 .10 .15 .17 .20 .24 .28 .32 .37 .43 .49 .55 .64 Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. K Factor, Rock Free—Larimer County Area, Colorado (HTP 5041 ) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/2/2020 Page 2 of 3 K Factor, Rock Free Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 73 Nunn clay loam, 0 to 1 percent slopes .32 6.3 57.6% 74 Nunn clay loam, 1 to 3 percent slopes .28 4.6 42.4% Totals for Area of Interest 10.9 100.0% Description Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by water. Factor K is one of six factors used in the Universal Soil Loss Equation (USLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the average annual rate of soil loss by sheet and rill erosion in tons per acre per year. The estimates are based primarily on percentage of silt, sand, and organic matter and on soil structure and saturated hydraulic conductivity (Ksat). Values of K range from 0.02 to 0.69. Other factors being equal, the higher the value, the more susceptible the soil is to sheet and rill erosion by water. "Erosion factor Kf (rock free)" indicates the erodibility of the fine-earth fraction, or the material less than 2 millimeters in size. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Layer Options (Horizon Aggregation Method): Surface Layer (Not applicable) K Factor, Rock Free—Larimer County Area, Colorado HTP 5041 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/2/2020 Page 3 of 3 25 APPENDIX B 26 RATIONAL METHOD HYDROLOGY 27 APPENDIX C 28 STORM SEWER PIPE SIZING & INLET SIZING 29 APPENDIX D 30 POND CAPACITY CALCULATIONS & RATING CURVES, OUTLET STRUCTURE CALCULATIONS, LID CALCULATIONS, ORIFICE SIZING, & OVERFLOW WEIR SIZING 31 APPENDIX E 32 CURB CUT, CONCRETE SIDEWALK CULVERT & RIPRAP SIZING, & EROSION CONTROL CALCULATIONS, & EROSION ESCROW CALCULATIONS 33 APPENDIX F 34 PROPOSED DRAINAGE BASIN EXHIBIT, EROSION CONTROL PLAN, & EROSION CONTROL NOTES AND DETAILS SHEET TTTECHNOLOGY PARKWAY (85' ROW)PRECISION DRIVE(66' ROW)ROCK CREEK DRIVE(ROW VARIES)PROPERTY BOUNDARYUTILITY EASEMENT(REC. NO 20080041258)PROPERTY BOUNDARYPROPERTY BOUNDARYPROPERTYBOUNDARYPROPOSED BUILDING427 LF SILT FENCEALONG NORTHCURB OF ROCK CREEK DRIVE610 LF SILT FENCE ALONG NORTHCURB OF ROCK CREEK DRIVE ANDEAST CURB OF TECHNOLOGY PKWY643 LF SILT FENCE ALONG SOUTHCURB OF PRECISION DRIVE ANDEAST CURB OF TECHNOLOGY PKWY1,634 LF SILT FENCE ALONG SOUTH CURBOF PRECISION DRIVE AND AROUNDOUTER WEST EDGE OF PROPOSED PONDDRAINAGE & UTILITY EASEMENT(REC. NO 20080041257)DRAINAGE & UTILITY EASEMENT(REC. NO 20080071164)INSTALL OUTLET GRAVEL FILTER(SEE DETAIL, SHEET C-007)LOT 1LOT 2LOT 3TRACT A15 12 13 14 16 17 18 152014161718191718 1919 1919 20 20 20 18 19 1716161717 18161718 1716171818 1920181920 18 1 9 18 192020 201011 12 1320181918 1819 1515 13 1616 1717 1814 1920 1918 20 19 18 1820 18 19 1718151416171818 18 17 18172018 18 15 14 14 15 1415 15 17 1 7 17 16 16 16 17 2 0 20IPIPIPIPVTCVTCRSRSIPRSRSVTCRSRSRSRRRRRRGFGFGFGRADING & UTILITY EASEMENT(REC. NO. 20150029090)SANITARY SEWER EASEMENT(REC. NO. 20160048879)9' UTILITY EASEMENT(REC. NO. 2001085362)16' DRAINAGE EASEMENT(REC. NO. 20160049345)IPIPIPIPIPIPIPRR5' WIDE24' LONG2' DEEP5' x 20'5' x 23'5' x 5'5' x 5'GF6' WIDE20' LONG2' DEEP5' WIDE20' LONG2' DEEPRR2.5' WIDE4' LONG2' DEEPRR2.5' WIDE4' LONG2' DEEP25' WIDE18' LONG2' DEEP20' WIDE50' LONG20' WIDE50' LONGIPIPRSRSASPEN0'SCALE: 1" = 30'30'60'SHEET No:PROJECT/ LOCATION: DRAWING:OFCHECKED BY:DESIGNED BY:DRAWN BY:DESCRIPTION OF REVISION:DATE:REVISED BY:APPROVED BY:REV. # 1 2 3 4 5 6 7 P R E L IM INARYNOT FOR CON S TRU CT IONproject no:date: FIFTY FORTY ONE TECHNOLOGY PARKWAY FORT COLLINS, COLORADO EROSION CONTROL PLANC-005518APRIL 27, 2022100-004JRGJRGJRGNOTES: .1.PERIMETER SILT FENCE SHALL BE INSTALLED ALONGPROPERTY BOUNDARY, AND IS SHOWN OFFSET FROMPROPERTY BOUNDARY ON THIS PLAN FOR CLARITY.·PERIMETER SILT FENCE AROUND SITE = 2,888 LF2.ALL DISTURBED AREAS ARE TO BE SEEDED AND MULCHED.3.STOCK PILES SHALL NOT TO EXCEED 10' IN HEIGHT.4.ALL OFFSITE AREAS DISTURBED DURING CONSTRUCTION ARETO BE RE-VEGETATED AND RETURNED TO HISTORICCONDITION. STRAW WATTLES OR GRAVEL INLET FILTERS MAYBE INSTALLED (IF NECESSARY AND AS REQUIRED) ONEXISTING, OFFSITE/DOWNSTREAM INLETS.5.VEHICLE TRACKING PAD(S) LOCATIONS SHALL BE DETERMINEDBY THE CONTRACTOR, PRIOR TO CONSTRUCTION, AND SHALLBE INSTALLED ACCORDINGLY.6.SEE SHEET C-006 & C-007 FOR EROSION CONTROL NOTES ANDDETAILS.7.NORTH AMERICAN GREEN C350 FABRIC WILL BE UTILIZED ATMINOR OUTFALL LOCATIONS SHOWN, WITH RIPRAP UTILIZEDWHERE LARGER STORM FLOWS WILL DISCHARGE TO THEPROPOSED DETENTION POND.8.PERMANENT STORMWATER CONTROL MEASURES SUCH ASRAINGARDENS, BIOSWALES OR BIORETENTION PONDS, SHALLBE CONSTRUCTED IN THE LAST PHASE OF CONSTRUCTION ONTHE SITE TO MINIMIZE THE POTENTIAL FOR SEDIMENTATION.9.NO DEBRIS OR MUD SHALL BE TRACKED ONTO ADJACENTSTREETS AND ANY TRACKING THAT DOES OCCUR, WILL BECLEANED IMMEDIATELY BY THE CONTRACTOR.LEGEND .INSTALL VEHICLE TRACKING PADINSTALL SILT FENCEINSTALL CONCRETE WASHOUTHAY OR STRAW DRY MULCH (1-5%)INSTALL 12" STRAW WATTLE CHECK DAMLIMITS OF DISTURBANCEINSTALL CURB INLET GRAVEL FILTERINSTALL AREA INLET GRAVEL FILTERPROPOSED DIRECTION OF SURFACE FLOWINSTALL ROCK SOCK FILTERINSTALL GRAVEL CURB CHECK BAGINSTALL NORTH AMERICAN GREEN C350PROPOSED MAJOR CONTOUR - 5 FT INTERVALPROPOSED MINOR CONTOUR - 1 FT INTERVALEXISTING MAJOR CONTOUR - 5 FT INTERVALEXISTING MINOR CONTOUR - 1 FT INTERVALVTCSFWIPIPGBMUCWORSGFEXISTING DIRECTION OF SURFACE FLOWINSTALL RIPRAP PROTECTION (TYPE M D =12")RR502526FOR THE MARKING OF UNDERGROUNDBEFORE YOU DIG, GRADE, OR EXCAVATECALL 2 BUSINESS DAYS IN ADVANCECENTER OF COLORADOCALL UTILITY NOTIFICATION1-800-922-1987MEMBER UTILITIES. www.herefordnrcd.com/Straw_Wattles.pdf) AND PER DETAILSAND INSTALLATION INSTRUCTIONS CALLED FOR ON THIS SHEET.2. IF GRAVEL INLET FILTERS ARE USED, REFER TO "CURB INLET GRAVEL FILTER" DETAIL, THIS SHEET.STRAWWATTLE/ROCKSOCK CHECKDAMwww.herefordnrcd.com/Straw_Wattles.pdfWOODENSTAKE(TYP)STRAWWATTLEWOODENSTAKE(TYP)EMBEDWATTLE/ROCKSOCK FILTERS3" TO 5" INTOSOILEMBEDWATTLE/ROCKSOCK 3" TO 5"INTO SOILSHEET No:PROJECT/ LOCATION: DRAWING:OFCHECKED BY:DESIGNED BY:DRAWN BY:DESCRIPTION OF REVISION:DATE:REVISED BY:APPROVED BY:REV. # 1 2 3 4 5 6 7 P R E L IM INARYNOT FO R CON S T RU C T IONproject no:date: FIFTY FORTY ONE TECHNOLOGY PARKWAY FORT COLLINS, COLORADO EROSION CONTROL NOTES & DETAILSC-006618APRIL 27, 2022100-004JRGJRGJRGFOR THE MARKING OF UNDERGROUNDBEFORE YOU DIG, GRADE, OR EXCAVATECALL 2 BUSINESS DAYS IN ADVANCECENTER OF COLORADOCALL UTILITY NOTIFICATION1-800-922-1987MEMBER UTILITIES. SLOPEINSTALLATIONDETAILDrawing Not To Scale1.Prepare soil before installing rollederosion control products (RECPs),including any necessaryapplication of lime, fertilizer, andseed.2.Begin at the top of the slope byanchoring the RECPs in a6"(15cm) deep X 6"(15cm) widetrench with approximately 12"(30cm) of RECPs extended beyondthe up-slope portion of the trench.Anchor the RECPs with a row ofstaples/stakes approximately 12"(30cm) apart in the bottom of thetrench. Backfill and compact thetrench after stapling. Apply seed tothe compacted soil and fold theremaining 12"(30cm) portion ofRECPs back over the seed andcompacted soil. Secure RECPsover compacted soil with a rowof staples/stakes spacedapproximately 12"(30cm) apartacross the width of the RECPs.3.Roll the RECPs (A) down or (B)horizontally across the slope.RECPs will unroll with appropriateside against the soil surface. AllRECPs must be securely fastenedto soil surface by placingstaples/stakes in appropriatelocations as shown in the staplepattern guide.4.The edges of parallel RECPs mustbe stapled with approximately 2" -5" (5-12.5cm) overlap dependingon the RECPs type.5.Consecutive RECPs spliced downthe slope must be end over end(Shingle style) with an approximate3"(7.5cm) overlap. Staple throughoverlapped area, approximately12"(30cm) apart across entireRECPs width.Drawn on: 5-4-17Disclaimer:The information presented herein is general design information only. For specific applications,consult an independent professional for further design guidance.2"-5"(5-12.5cm)3B42513A12"(30cm)6"(15cm)6"(15cm) *NOTE:In loose soil conditions, the use ofstaple or stake lengths greater than6"(15cm) may be necessary toproperly secure the RECP's.3"(7.5cm)5401 St. Wendel - Cynthiana Rd.Poseyville, IN 47633PH: 800-772-2040www.nagreen.comCHANNELINSTALLATIONDETAILDrawing Not To Scale1.Prepare soil before installing rollederosion control products (RECPs),including any necessary application oflime, fertilizer, and seed.2.Begin at the top of the channel byanchoring the RECPs in a 6"(15cm)deep X 6"(15cm) wide trench withapproximately 12"(30cm) of RECPsextended beyond the up-slope portionof the trench. Use ShoreMax mat at thechannel/culvert outlet as supplementalscour protection as needed. Anchor theRECPs with a row of staples/stakesapproximately 12"(30cm) apart in thebottom of the trench. Backfill andcompact the trench after stapling. Applyseed to the compacted soil and fold theremaining 12"(30cm) portion of RECPsback over the seed and compacted soil.Secure RECPs over compacted soilwith a row of staples/stakes spacedapproximately 12" apart across thewidth of the RECPs.3.Roll center RECPs in direction of waterflow in bottom of channel. RECPs willunroll with appropriate side against thesoil surface. All RECPs must besecurely fastened to soil surface byplacing staples/stakes in appropriatelocations as shown in the staple patternguide.4.Place consecutive RECPs end-over-end(Shingle style) with a 4"-6" overlap. Usea double row of staples staggered 4"apart and 4" on center to secureRECPs.5.Full length edge of RECPs at top of sideslopes must be anchored with a row ofstaples/stakes approximately 12"(30cm)apart in a 6"(15cm) deep X 6"(15cm)wide trench. Backfill and compact thetrench after stapling.6.Adjacent RECPs must be overlappedapproximately 2"-5" (5-12.5cm)(Depending on RECPs type) andstapled.7.In high flow channel applications astaple check slot is recommended at 30to 40 foot (9 -12m) intervals. Use adouble row of staples staggered4"(10cm) apart and 4"(10cm) on centerover entire width of the channel.8.The terminal end of the RECPs must beanchored with a row of staples/stakesapproximately 12" (30cm) apart in a6"(15cm) deep X 6"(15cm) wide trench.Backfill and compact the trench afterstapling.Drawn on: 5-4-17Disclaimer:The information presented herein is general design information only. For specific applications,consult an independent professional for further design guidance.2"-5"(5-12.5cm)62412"(30cm)6"(15cm)6"(15cm)4"-6"(10-15cm)86"(15cm)574"(10cm)31ABCABC NOTES:*Horizontal staple spacing should bealtered if necessary to allow staples tosecure the critical points along the channelsurface.**In loose soil conditions, the use of stapleor stake lengths greater than 6"(15cm) maybe necessary to properly secure theRECP's. CRITICAL POINTSA. Overlaps and SeamsB. Projected Water LineC. Channel Bottom/Side Slope Vertices4"(10cm)6"(15cm)5401 St. Wendel - Cynthiana Rd.Poseyville, IN 47633PH: 800-722-2040www.nagreen.comOUTLET PIPEENDS OF GRAVEL FILTER TO BEKEYED INTO FILL SLOPE.TOE OF FILLFLOWGRAVEL FILTER(3/4"Ø ± GRAVEL,WRAPPED IN CHICKENWIRE)MAINTENANCE NOTES:1. FORM CHICKEN WIRE WRAP ALONG FRONT OF OUTLET STRUCTURE AND EXTENDING INTO EMBANKMENT OF POND.2. PACK WITH 3/4" GRAVEL AND ROLL & TWIST CHICKEN WIRE WRAP AT TOP TO HOLD TOGETHER (WIRE TIE, IF NECESSARY).GRAVEL FILTER SHALL BE 18" TALL x 18" WIDE AND SLOPE TOWARDS OUTLET STRUCTURE OR LAID UP AGAINST OUTLETSTRUCTURE FOR STABILITY.3. SEDIMENT BASIN FILTER SHALL BE INSPECTED PERIODICALLY AND AFTER EACH RAIN EVENT, AND REPAIRED WHENNECESSARY. ACCUMULATED SEDIMENT SHALL BE REMOVED.4. SEDIMENT BASIN FILTER SHALL BE REMOVED AFTER IT HAS SERVED ITS PURPOSE.OUTLET PIPEFILTEREDWATERRUNOFF18" TALL GRAVEL FILTER.18"18"OUTLET STRUCTUREOUTLET STRUCTURESHEET No:PROJECT/ LOCATION: DRAWING:OFCHECKED BY:DESIGNED BY:DRAWN BY:DESCRIPTION OF REVISION:DATE:REVISED BY:APPROVED BY:REV. # 1 2 3 4 5 6 7 P R E L IM INARYNOT FO R CON S T RU C T IONproject no:date: FIFTY FORTY ONE TECHNOLOGY PARKWAY FORT COLLINS, COLORADO EROSION CONTROL DETAILSC-007718APRIL 27, 2022100-004JRGJRGJRG TECHNOLOGY PARKWAY (85' ROW)PRECISION DRIVE(66' ROW)PROPERTY BOUNDARYROCK CREEK DRIVE(ROW VARIES)9' UTILITY EASEMENT(REC. NO. 2001085362)16' DRAINAGE EASEMENT(REC. NO. 20160049345)UTILITY EASEMENT(REC. NO 20080041258)SANITARY SEWER EASEMENT(REC. NO. 20160048879)LOT 1WINDSONG AT ROCK CREEK(RECEPTION NO. 2016050565)LOT 1EYE CENTER OF NORTHERNCOLORADO SUBDIVISION(RECEPTION NO. 20160032638)UNPLATTED(HARMONY TECHNOLOGY PARK LLC)LOT 1MAINSTREET HEALTH & WELLNESS SUITES(RECEPTION NO. 20150031289)LOT 1 HARMONY TECHNOLOGY PARK 3RD FILING FIRST REPLAT (RECEPTION NO. 20120001483) LOT 1 HARMONY TECHNOLOGY PARK 5TH FILING (RECEPTION NO. 20170034697)UNPLATTED(POUDRE R-1 SCHOOL DISTRICT)PROPERTY BOUNDARYPROPERTY BOUNDARYPROPERTY BOUNDARYDRAINAGE & UTILITY EASEMENT(REC. NO 20080041257)TGG(2')(2')PROPOSED BUILDINGPOND 501OS9OS7OS12OS13OS14OS15LOT 1LOT 2LOT 3TRACT A5020.64AC50215 12 13 14 16 17 18 152014161718191718 1919 1919 20 20 20 18 19 1716161717 18161718 1716171818 1920181920 18 1 9 18 192020 201011 12 1320181918 1819 151513 1616 1717 1814 192019 18 20 19 18 1820 18 19 1718151416171818 18 17 18172018 18 15 14 14 15 1415 15 17 1 7 17 16 16 16 17 2 0 201213148a8b6b1c1b171016921d6a415537174.700.80161.260.25111.200.9040.480.3860.520.74100.050.85140.250.80130.710.92120.200.84OS140.070.66OS150.070.66OS120.480.72OS130.490.73OS90.320.8390.210.3280.310.7720.060.2930.070.4850.100.8810.430.74150.350.4170.140.261aDRAINAGE & UTILITY EASEMENT(REC. NO 20080071164)18OVERFLOW WEIROVERFLOW WEIROVERFLOW WEIR1011ASPEN0'SCALE: 1" = 40'40'80'LEGENDEXISTING CONTOURSNEW INTERMEDIATE CONTOURS1920NEW INDEX CONTOURSPROPOSED FLOWLINEEX RIGHT-OF-WAY/ PROPERTY BOUNDARYPROPOSED DRAINAGE BASIN BOUNDARYLINESPROPOSED STORM PIPEEXISTING STORM PIPE & MANHOLERDPROPOSED ROOF DRAIN AND STORM PIPE1.PROPOSED ELEVATIONS SHOWN ARE RELATIVE TO A DATUM OF 4900 FEET, AND ARE BASED ON THEBENCHMARKS DESCRIBED ON SHEET C-001.2.THE DRAINAGE BASINS SHOWN ON THIS EXHIBIT WILL BE CONVEYED TO DETENTION POND 501, LOCATEDBETWEEN THE DEVELOPED AND UNDEVELOPED AREAS OF THE SITE. THE DEVELOPED SITE RUNOFF ANDOFFITE BASIN RUNOFF IS CONVEYED TO THE PROPOSED DETENTION AND WATER QUALITY POND VIAOVERLAND FLOW, PIPE AND INLET SYSTEMS, AND PROPOSED SWALES. DRAINAGE DESIGN FOR THEPROPOSED SITE IS IN ACCORDANCE WITH THE HARMONY TECHNOLOGY PARK SITE MASTER PLAN (HTPSMP)AND ASSOCIATED DRAINAGE CONDITIONS IN THE MAINSTREET HEALTH AND WELLNESS PROJECT. WATERQUALITY AND DETENTION IS BEING PROVIDED IN PROPOSED POND 501. THE HTPSMP SPECIFIED ANALLOWABLE IMPERVIOUS RATIO OF UP TO 80% FOR SWMM BASIN 801. THE CALCULATED IMPERVIOUS RATIOIS 67% FOR THE 5041 HARMONY TECHNOLOGY PARK SITE AND OFFSITE ATTRIBUTING BASINS, ANDTHEREFORE, IS IN COMPLIANCE WITH THE PREVIOUSLY APPROVED MASTER PLAN STUDY FOR THIS AREA.3.PLEASE REFER TO THE RATIONAL METHOD CALCULATIONS FOR FINAL BASIN FLOW CALCULATIONS, AS WELLAS. ROUTED FLOWS.4.12" OF CDOT CLASS 'A' BEDDING MATERIAL SHALL BE PLACED UNDER ALL RIPRAP SHOWN.5.ROOF DRAINS FROM THE PROPOSED BUILDING WILL CONNECT TO AN UNDERGROUND STORM SEWER ANDWILL DISCHARGE TO A LID BASIN FOR WATER QUALITY TREATMENT IN MINOR EVENTS. EXCESS RUNOFFENTERING THE LID BASIN, WILL OVERFLOW INTO DETENTION POND 501.6.RUNOFF FROM THE SITE WILL DRAIN TO LOW POINTS AND PASS THROUGH CURB CUTS, SIDEWALK CHASES,AND SWALES BEFORE ENTERING STORM PIPES AND RAINGARDENS, WHICH ULTIMATELY DISCHARGE TO THEPROPOSED DETENTION POND 501. PERMANENT GEOTEXTILE FABRIC AND GRASS LINED DRAINAGE CHANNELSWILL ENHANCE EROSION CONTROL WITHIN THE SITE LIMITS. SITE BMP'S WILL BE IMPLEMENTED TO REDUCESEDIMENT TRANSPORT OFFSITE, AS SHOWN IN THE FINAL EROSION CONTROL PLAN, AND AS PRESENTED INTHE STORMWATER MANAGEMENT PLAN PREPARED FOR THIS PROJECT.7.ALL PROPOSED STORM DRAINAGE PIPES AND STRUCTURES (OUTSIDE OF PLATTED ROW) WILL BE PRIVATELYOWNED AND MAINTAINED. THE EXISTING SOUTH STORM SEWER SYSTEM, PASSING THROUGH THE SITE, WILLBE OWNED AND MAINTAINED BY MAVD. ALL EXISTING STORM SEWER WITHIN PUBLIC ROW, WILL BE OWNEDAND MAINTAINED BY THE CITY OF FORT COLLINS.8.OFFSITE BASIN 502 IS SHOWN FOR REFERENCE PURPOSES ONLY. RUNOFF FROM BASIN 502 IS CONVEYED TOEXISTING SWMM POND 110, LOCATED SOUTH OF THE CUSTOM BLENDING SITE.NOTES:PROPOSED DRAINAGE BASIN SUMMARY TABLE:PROPOSED DRAINAGE BASIN IDACRES / 'C' VALUEPROPOSED DRAINAGE DESIGN POINTDRAINAGE FLOW DIRECTIONDRAINAGE SWALE0.740.431PROPOSED LID SUMMARY TABLE:SHEET No:PROJECT/ LOCATION: DRAWING:OFCHECKED BY:DESIGNED BY:DRAWN BY:DESCRIPTION OF REVISION:DATE:REVISED BY:APPROVED BY:REV. # 1 2 3 4 5 6 7 P R E L IM INARYNOT FO R CON S T RU C T IONproject no:date: FIFTY FORTY ONE TECHNOLOGY PARKWAY FORT COLLINS, COLORADO DRAINAGE EXHIBITC-0101018APRIL 27, 2022100-004JRGJRGJRGPROPOSED POND SUMMARY TABLE:PONDDESC100-YRWSEL.(FT)*VOLUMEPROVIDED(AC-FT)4916.902.72DETENTION POND2.68501**VOLUMEREQUIRED(AC-FT)WQCVWSEL(FT)4913.390.27WQCV(AC-FT)*VOLUME PROVIDED OF 2.72 AC-FT IS THE INTERPOLATED VOLUME AT THE 100-YR WSEL IN POND 501. CONSIDERINGPOND 501 DOES NOT SPILL UNTIL APPROXIMATELY 4917.72, THE VOLUME PROVIDED UP UNTIL OVERFLOW FROMPOND 501 IS APPROXIMATELY 4.0 AC-FT. PLEASE REFER TO POND 501 RATING CURVE FOR DETAILS.**POND 501 IS SIZED TO PROVIDE DETENTION AND WATER QUALITY FOR 12.33 ACRES OF ATTRIBUTABLE AREA(BASINS1-17) FOR THE HARMONY TECHNOLOGY PARK 5041 DEVELOPED AREA AND INCLUDES A TOTAL OF 1.29ACRES (BASINS OS9, OS12 & OS13) OF OFFSITE AREA.