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Reports - Drainage - 10/29/2025
Page 1 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 Switchgrass Crossing Final Drainage Report Prepared for: Doug Snyder Volunteers of America 2660 Larimer St Denver, CO 80205 Prepared by: Ted Swan, PE Shopworks 301 W. 45th Ave Denver, CO 80216 __________________________________ Ted Swan, PE 43903 Page 2 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 Cover Letter-Certification I hereby attest that this report for the final drainage design for the Switchgrass Crossing Project was prepared by me or under my direct supervision, in accordance with the provisions of the Fort Collins Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others. _________________________________ ________________________ Theodore Swan, PE 43903 Date Page 3 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 Table of Contents A. Introduction pg. 4 B. Historic Drainage pg. 5 C. Design Criteria pg. 5 D. Drainage Plan pg. 6 E. Conclusions and Compliance Statement pg. 11 F. List of References pg. 11 G. Appendix pg. 12 Page 4 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 A. Introduction 1. Location a. The 1.40 ac (as platted) VOA Switchgrass site (Site) at 3800 S Mason St is bounded by Mason Street on the west, commercial property on the east and south, and Mason Place residential property on the north. The property has been platted as Creger Plaza Third Replat Lot 2 Subdivision Filing No. 1, Lot 1, Blk 1. Please see vicinity map below: Scale 1” = 300’ b. There are no major drainageways or stormwater facilities. 2. Proposed Development a. The current phase of development proposes (1) four story multifamily residential building with 45 units, private driveways and surrounding amenity areas on 1.40 acres. It is anticipated that the composite percent of impervious area will be 77%. Page 5 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 3. MDR and Master Drainage Basins a. The site falls within the Mail Creek Master Drainage Basin however, a Master Drainage Report specifically governing the Site drainage and surrounding areas has not been located. b. No conditional approval comments existed on an approved MDR. 4. Variances 1. No Variances are requested with this project. B. Historic Drainage 1. Overall Basin Description a. The existing 1.40 acre site (as platted) is currently developed with an asphalt parking lot covering the entire site. The site slopes generally to the west at 1-2% to two existing inlets that convey storm water downstream to the storm main within Mason St. Geotechnical analysis has been performed and the soil is anticipated to be mostly comprised of type C and D clayey soils as supported by the NRCS soil data. Groundwater was found at depths of 8+ ft in all borings initially, but had risen after a few days to a depth of roughly 3’. This depth is less than 2’ below the proposed storm infrastructure and detention vault and therefore the vault will be lined with an impervious membrane. The NRCS soil map has been included in Appendix A. As shown on FEMA FIRM Panel 08069C0987G in Appendix A, the site is not located in a FEMA floodplain. b. The Site is tributary to the larger Mail Creek master planned drainage basin. As noted previously, it flows directly west to two on site inlets that drain to the storm main within Mason St. c. No irrigation facilities are located near or are impacting the site. d. A portion of the residential Mason Place property, the commercial properties to the east and south and the half section of Mason St adjacent to and north of the site drain onto the site and are routed through the onsite parking lot detention pond along with the rest of the Site drainage. C. Design Criteria 1. Hydrologic Criteria a. The design frequencies used for analysis were as prescribed in the Fort Collins Stormwater Criteria Manual (The Manual): 2yr for the minor storm event and 100 yr for the major storm event. These storm events were used for determining site runoff and pipe capacities. b. The Manual was referenced for anticipated 1- hour rainfall depth in all storm events. The 2 yr 1-hour rainfall depth is 0.82 in and the 100 yr 1-hour depth is 2.86in. c. Given the site area, the rational method was used for determining site runoff flow rate (Q). Per this method, Q is determined using the basin runoff coefficient (C), site acreage (A) and storm intensity (I). Storm intensity is calculated using the Time of Concentration (Tc) for each basin. Page 6 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 d. A portion of the 100 year detention with a modified release rate was provided for the Site and tributary areas within a stormwater vault in accordance with discussions with the City of Fort Collins Stormwater department. The modified 100 year release rate was based on the existing site release. This rate was calculated as the sum of the undetained undeveloped release 2.31cfs for the northern half of the site and adjacent property (designated EXA on the existing drainage map) and the detained release 1.8cfs of the southern half of the site, adjacent property and Mason St (designated EXB on the existing drainage map). The detained release for this area was calculated by analyzing the total allowable depth of ponding and running an orifice equation for the discharge rate. The total modified release rate was 4.11cfs. The Modified FAA method was used to quantify the 100 year detention volume with this modified rate. In addition the onsite stormtech system with isolator rows was utilized to provide water quality treatment for the Site and tributary areas. The WQCV was incorporated within the detention volume. This is not a standard practice and is requested by the project due to the initial direction from the City that detention would not be required and the development of the site plan/proforma around that direction. Due to the fact that the historic developed site provided no WQCV and undersized detention the City allowed the incorporation of the WQCV within the detention volume. e. Other design criteria was not utilized for hydrologic calculations. Autodesk Hydraflow was used to calculate storm pipe capacity. 2. Hydraulic Criteria a. Private Storm infrastructure was sized to convey runoff from both the 2 year minor storm event and the 100 year major storm event. No public storm infrastructure was required for the project. Hydraulic capacity calculations are shown in Appendix C. b. As noted above, FEMA FIRM Panel 08069C0987G was referenced (and included in Appendix A) and the site does not fall within a jurisdictional floodplain. No LOMR or LOMC is required. c. All storm infrastructure on the plan is privately owned and will be maintained by the property owner d. As part of the storm water management plan to be utilized during construction, a temporary sediment trap will be used to treat construction stormwater flows prior to discharge to Mason St flowline. D. Drainage Plan 1. General Concept a. The entirety of the Site, tributary adjacent areas and a portion of Mason St comprise one larger basin A that discharges to the onsite stormtech vault with isolator rows (STV-A) for LID, water quality treatment and a portion of the 100 year detention volume as described above. The northern portion of the site drains via driveway gutter, storm inlets and storm sewer to STV-A. This 100 year flow is not captured within the storm sewer and is bypassed through the site to the next inlet. The building roof drainage is directed to downspouts that lead to storm sewer draining Page 7 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 to STV-A. The eastern and southeastern portion of the site sheet flows and drains via driveway gutter and concrete pans to STV-A. The western portion of the site as well as Mason St sheet flow to the Mason St curb and gutter which drains south through a curb chase at the southwest corner of the site. The curb chase drains into the site to an inlet and storm sewer that flows to STV-A. STV-A drains back south to the existing onsite storm sewer. As mentioned previously, a small portion of the residential property to the north and the commercial properties to the east and south of the Site (totaling 0.09 acres) will drain onto the site and will be routed through STV-A as described. There are existing pipes draining through the site from the northern and eastern neighboring properties. These pipes will continue to drain through the site in existing storm infrastructure and will discharge to the Mason St storm main. 2. Specific Details a. As noted above, all onsite basins, adjacent tributary areas and a portion of Mason St drain to the stormtech vault for LID, water quality treatment and 100 year detention before being released to storm sewer that drains to the existing storm main within Mason St. Basin A has been further divided into 5 subbasins denoted A1, RA1, RA2, A2 and OSA to allow for the analysis of storm infrastructure serving each subbasin. The subbasins are more particularly described below followed by a runoff summary table showing the local and accumulated flows at each design point: Subbasin RA1 is comprised of the northern section of the building. It is 0.08 ac and is completely impervious rooftop with an impervious percentage of 95%. Major and Minor Storm Runoff from RA1 is directed to a 2 roof drain locations which have been designated design point R1. The flows from the multiple roof drains have been combined and the downstream storm has been conservatively sized to accommodate the entire basin flow throughout the entirety of its length. The roof drain piping has been sized to convey the 100 year storm event and flows to the northern storm sewer at design point 1 where it is routed to eventually outfall at STV-A. Subbasin A1 is comprised of the northernmost portion of the drive lane, parking lot, and associated landscape. A1 is 0.17 ac and is mostly impervious paving with some pervious landscape and an impervious percentage of 80%. Major and Minor Storm Runoff from A1 is directed to a sump inlet at design point 1 and then is routed to storm sewer to outfall into STV-A. The sump inlet was analyzed for capacity using MHFD criteria found in Appendix C. In the event that the inlet is clogged, overflow will drain east through the site where it will be routed back to STV-A. Subbasin RA2 is comprised of the southernmost section of the building. It is 0.20 ac and is completely impervious rooftop with an impervious percentage of 95%. Major and Minor Storm Runoff from RA2 is directed to 2 roof drain locations which have been designated design point R2. The flows from the multiple roof drains have been Page 8 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 combined and the downstream storm has been conservatively sized to accommodate the entire basin flow throughout the entirety of its length. The roof drain piping has been sized to convey the 100 year storm event and flows to the eastern storm sewer at design point 3 where it is routed to eventually outfall at STV- A. Subbasin A2 is comprised of the courtyard, southeastern portion of the drive lane, parking lot, and associated landscape. It is 0.73 ac and is split between impervious paving and pervious landscape areas with an impervious percentage of 61%. Major and Minor Storm Runoff from A2 drains overland to a concrete pan on the eastern side of the parking lot and then south to an inlet that discharges into STV-A at design point 2. Subbasin A3 is comprised of the southwestern portion of the drive lane, parking lot, and associated landscape. It is 0.23 ac and is split between impervious paving and pervious landscape areas with an impervious percentage of 74%. Major and Minor Storm Runoff from A2 drains overland to a concrete pan on the southern side of the parking lot and then south to an area inlet that discharges into STV-A at design point 3. Basin OS1 is comprised of the westernmost landscaped portion of the Site as well as a small portion of the entry to the building on the south side. It is 0.07 ac and is mostly pervious landscape with an impervious percentage of 37%. Major and Minor Storm Runoff from OS1 is directed to the Mason St curb and gutter that drain south to a curb chase leading into the Site. The curb chase discharges into a small depressed area of the site served by an area inlet at design point 3 that drains to STV-A. Basin OS2 is comprised of Mason St adjacent to the site extending north to Creger Dr as well as a small portion of landscape within the Mason St ROW. It is 0.70 ac and is mostly impervious paving with an impervious percentage of 89%. Major and Minor Storm Runoff from OS2 is directed to the Mason St curb and gutter that drain south to a curb chase leading into the Site. The curb chase discharges into a small depressed area of the site served by an area inlet at design point 3 that drains to STV-A. Page 9 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 b. See below Runoff Summary Table. Runoff Summary Table Basin ID Design Point Area (AC) Impervious Percentage Minor Storm (C Value) Major Storm (C Value) Minor Storm Local Flow (cfs) Minor Storm Accum Flow (cfs) Major Storm Local Flow (cfs) Major Storm Accum Flow (cfs) Notes RA1 R1 0.08 95% 0.95 1.00 0.23 0.80 0.80 Roof Basin RA1 A1 1 0.17 80% 0.80 1.00 0.39 1.37 1.37 Basin A1 CF1 0.62 2.16 Roof Basin RA1 + Basin A1 RA2 R2 0.20 95% 0.95 1.00 0.53 1.86 1.86 Roof Basin RA2 A2 2 0.73 61% 0.61 0.77 1.28 2.43 4.46 8.48 CF1 + Roof Basin RA2 + Basin A2 OS1 0.07 37% 0.37 0.47 0.08 0.27 Offsite flows to onsite Design Point 3 OS2 0.70 89% 0.89 1.00 1.77 6.19 Offsite flows to onsite Design Point 3 A3 3 0.23 74% 0.74 0.92 0.49 1.85 1.71 6.46 Basin A3 + Basin OS1 + Basin OS2 c. As discussed after the BDR review, the project is required to provide LID, water quality treatment, and partial 100 yr detention for the Site, tributary adjacent areas and a portion of the Mason St right of way as shown on the proposed drainage map. The Project is proposing a stormtech vault denoted STV-A. STV-A has an upstream tributary area of 2.19 acres with an impervious percentage of 75%. The 100 year release from STV-A was determined by calculating the current release from the site. As described previously, the southern portion of the site is currently detained at a parking lot detention outlet structure. The existing onsite detention holds 2057 cu ft and releases approximately 1.8cfs based on an orifice analysis of the existing outlet structure with a 7” orifice and 1.2’ maximum ponding. The orifice calculation has been included in Appendix C. The northern portion of the site is released undetained at 2.31cfs in an undeveloped state based on the rational method calc for the basin. The basin is shown on the existing drainage map and the flow calculation is included in Appendix B. Therefore the total release rate from STV-A was held at 4.11 cfs. As mentioned previously, the water quality volume has been incorporated into the 100 year detention volume. The modified FAA method was used to calculate the detention volume utilizing the release rate defined above. STV-A will use a restrictor plate to control the outflow to the total release rate. Page 10 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 A summary table of volumes, depths, water surface elevations and discharge is shown below: Water Quality Volume Table WQCV (cu ft) WQ Depth (ft) 100 yr Vol (cu ft) 100 yr Depth (ft) 100 yr Outflow (cfs) 2430.45 0.62 9625.18 2.30 4.11 *WQCV incorporated in 100 yr Volume d. The Four Step Process for receiving water protection has been followed by the project. Below is a discussion of each step and the way the project has adhered to each. i. Employ Runoff Reduction Practices: STV-A meets the City standard for low impact development (LID) and minimized directly connected impervious areas (MDCIA) for the site by providing a permeable surface at the base of the vault and manhole that can infiltrate into the surrounding rock and underdrain. Another LID/MDCIA component is the courtyard which will drain impervious surfaces across landscape and will infiltrate along the eastern edge where an underdrain has been provided to convey excess flows downstream to STV-A. The underdrain will have a filter media over the top as well to reduce sediment and contaminant transport downstream. The dog park on the eastern side of the site has been designed to be a pervious pea gravel (as shown on the landscape plan) that will help to infiltrate stormwater runoff and pet waste prior to being conveyed downstream to STV-A. Finally, the Mason St drainage has been directed to a shallow landscaped swale at the SW corner of the site. It is anticipated that a portion of minor storm flows will infiltrate into the landscape area before being transmitted downstream to STV-A. ii. Implement BMPs that Provide a WQCV with slow release: STV-A contains isolator rows to filter storm water and is providing a reduced runoff rate compared to the existing site conditions. Although not allowing for a 40 hour release time, STV-A is improving the current storm water condition. iii. Stabilize Streams: The project is not immediately adjacent to a natural stream and downstream stabilization has not been identified for this project. However, it is anticipated that due to the project runoff reduction practices and site WQCV BMP, this project will improve the site’s impact on natural streams. iv. Implement Site Specific and Other Source Control BMPs: The project is planning to locate the construction staging area and permanent trash collection at the north end of the site so that material storage and waste facilities will be out of the main drainage path and away from the detention vault. Additionally, the community gardens are located in the courtyard upstream of the underdrain and filter media so that spilled chemicals and sediment will receive tertiary treatment by infiltrating into the underdrain. The dog park is located on the south side of the site, but is upstream of an underdrain with filter media to provide tertiary treatment for runoff. Page 11 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 These components of LID and MDCIA along with site BMPS and the aforementioned isolator row water quality treatment meet the City four step process to ensure that the impact of storms of all sizes are treated and downstream effects are minimized to the greatest extent possible. e. The emergency overflow path for STV-A is located within Mason St. In an emergency condition, the detention vault will back up through the chase at the SW corner of the site and then overflow at the high point directly south in Mason St. The overflow has been sized to provide at least 1’ of freeboard to the building FFE. Additionally this route will serve as the emergency overflow path direction for the adjacent parking lot detention in the site to the east. It is expected that the emergency overflow will route through the site and eventually through the chase as well. f. An emergency overflow path and flow cross section has been provided for STV-A. The location is shown on the Drainage Plan and the calculations for the cross section have been provided in Appendix C. g. One 4’ drainage pan (Pan-A) and one 4’ chase (Chase-A) has been provided on site to direct storm runoff downstream to STV-A. See below table of the design elements of both. Calculations for the pan and chase are included in Appendix C. Open Channel Design Element Table Name Long. Slope Minor Q Major Q Velocity Depth Freeboard Pan-A O.50% 2.43 cfs 8.48cfs 2.00ft/s 0.27ft 1.93ft h. The permanent SCM that is proposed with the development is the stormtech vault STV-A as discussed previously. Volume calculations are shown in Appendix C. E. Conclusion and Compliance Statement This drainage report and plan have been prepared in accordance with the FCSCM and follows the Mail Creek Master Drainage Plan and existing regional drainage studies to the highest extent possible. The drainage plan will effectively control damage from storm runoff and not result in an adverse impact to adjacent properties, nor will it deviate from the Master Drainage plan. F. List of References 1. Fort Collins Stormwater Criteria Manual, Fort Collins, CO, December 2018. 2. Urban Storm Drainage Criteria Manual, volumes 1, 2, and 3, Urban Drainage and Flood Control District, August 2018, September 2017, and January 2021 (respectively). Page 12 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 Appendix A Geotechnical Report Excerpts USGS Soil Survey FEMA FIRM Map FCSCM Rainfall Data Existing Drainage Report Excerpts CTL|Thompson, Inc. Denver, Fort Collins, Colorado Springs, Glenwood Springs, Pueblo, Summit County – Colorado Cheyenne, Wyoming and Bozeman, Montana VOA MASON PLACE II 3800 SOUTH MASON STREET FORT COLLINS, COLORADO Prepared for: VOLUNTEERS OF AMERICA 1660 Duke Street Alexandria, Virginia Attention: Doug Snyder Scott Dueker Project No. FC11376.000-120-R1R October 21, 2024 Revised July 31, 2025 GEOTECHNICAL INVESTIGATION NOT FOR REVIEW IN DRAINAGE REPORT VOLUNTEERS OF AMERICA 1 VOA MASON PLACE II CTLT PROJECT NO. FC11376.000-120-R1R SCOPE This revised report presents the results of our Geotechnical Investigation for the VOA Mason Place II project in Fort Collins, Colorado (Figure 1). The purpose of the investigation was to evaluate the subsurface conditions and provide geotechnical design and construction criteria for the project. This revision includes our design guidance and recommendations for the pro- posed post-tensioned (PT) slab. The scope was described in our Service Agreement (CTL|T Proposal No. FC-24-0301 Revision 3) dated August 23, 2024. Evaluation of the property for the presence of potentially hazardous materials was not included in our work scope. The report was prepared from data developed during field exploration, laboratory testing, engineering analysis, and experience with similar conditions. The report includes a description of subsurface conditions found in the exploratory borings and discussions of site development as influenced by geotechnical considerations. Our opinions and recommendations regarding de- sign criteria and construction details for foundations, floor systems, slabs-on-grade, PT slabs, lateral earth loads, pavements, and drainage are provided. The report was prepared for the ex- clusive use of Volunteers of America and your team in design and construction of the proposed improvements. If the proposed construction differs from descriptions herein, we should be re- quested to review our recommendations. Our conclusions are summarized in the following para- graphs. SUMMARY OF CONCLUSIONS 1. Strata encountered in the first set of borings consisted of up to 12 feet of native sandy clay or clayey to clean or gravelly sand underlain by sandstone bedrock to maximum explored depths of 24 feet. The new exploratory borings consisted of up to 13 feet of sandy clay and clean sand underlain by sandstone bedrock to maximum explored depths of 15 feet below existing grade. The first set of bor- ings and the three new borings were overlain by approximately 6 inches of as- phalt and 6 inches of roadbase. In the new borings, the sandy clay was encoun- tered directly beneath the pavement section. The clean sand was encountered in 1 to 3 foot thick lenses at depths of 3 to 4 feet. 2. Groundwater was encountered at approximate depths of 8 to 9.5 feet during drill- ing of the first borings. When the three new borings were drilled, groundwater was encountered at 7 feet below grade.When the borings were checked after drilling on July 4, 2025, groundwater ranged from 1.5 to 4 feet below grade. We NOT FOR REVIEW IN DRAINAGE REPORT VOLUNTEERS OF AMERICA 2 VOA MASON PLACE II CTLT PROJECT NO. FC11376.000-120-R1R recommend a minimum 3-foot, ideally 5-foot, separation between foundation ele- ments and groundwater. Grades may be raised to maintain separation. Ground- water levels may fluctuate seasonally and rise in response to precipitation, irriga- tion, and changes in land-use. 3. We judge there is low risk of heave on this site upon post-construction wetting. The presence of expansive soils and bedrock constitutes a geologic hazard. There is risk that slabs-on-grade and foundations will experience heave or settle- ment and be damaged. We believe the recommendations presented in this report will help to control risk of damage; they will not eliminate that risk. Slabs-on- grade and, in some instances, foundations may be damaged. 4. We judge footing foundations or post-tensioned slab-on-ground (PTS) founda- tions are suitable provided they are placed on natural, undisturbed soil and/or properly compacted fill. Design and construction criteria for foundations are pre- sented in the report. 5. Slab-on-grade floors have low risk of movements of about 1 inch or less, and will likely experience movements and cracking. Structurally supported floors should be used if movement is not tolerable. PTS floors have the advantage that the floor system is incorporated into the foundations, which typically results in better performance than a conventional slab floor. 6. Surface drainage should be designed, constructed, and maintained to provide rapid removal of surface runoff away from the proposed structure. Conservative irrigation practices should be followed to avoid excessive wetting. 7. Samples of the subgrade soils generally classified as AASHTO A-1-a, A-6, or A- 7-6 soils, with a group index of 6 for A-6 soils and 13 for A-7-6 (clay) soils. For the parking lot, we recommend 4 inches of asphaltic concrete over 6 inches of aggregate base course or a full depth asphaltic concrete pavement with a thick- ness of 6 inches. Thicker sections are recommended for areas with heavier traf- fic. SITE CONDITIONS The site is located at 3800 South Mason Street in Fort Collins, Colorado (Figure 1). The lot is currently a paved parking lot, with the existing VOA Mason Place to the north. The New Mercer Canal is 500 feet west of the site. The existing parking lot is of unknown age and is in fair condition. There is little to no evidence of maintenance. NOT FOR REVIEW IN DRAINAGE REPORT VOLUNTEERS OF AMERICA 20 VOA MASON PLACE II CTLT PROJECT NO. FC11376.000-120-R1R CONCRETE DESIGN REQUIREMENTS FOR SULFATE EXPOSURE PER ACI 318-19 Exposure Class Maximum Water/ Cement Ratio Minimum Compressive Strength (psi) Cementitious Material Types A Calcium Chloride Ad- mixtures ASTM C150/C150M ASTM C595/C595M ASTM C1157/C1157M S0 N/A 2500 No Type Restrictions No Type Restrictions No Type Restrictions No Restrictions S1 0.50 4000 IIB Type with (MS) Designation MS No Restrictions S2 0.45 4500 V B Type with (HS) Designation HS Not Permitted S3 Option 1 0.45 4500 V + Pozzolan or Slag Cement C Type with (HS) Designation plus Pozzolan or Slag Cement C HS + Pozzolan or Slag Cement C Not Permitted S3 Option 2 0.4 5000 V D Type with (HS) Designation HS Not Permitted A) Alternate combinations of cementitious materials shall be permitted when tested for sulfate resistance meeting the cri- teria in section 26.4.2.2(c). B) Other available types of cement such as Type III or Type I are permitted in Exposure Classes S1 or S2 if the C3A contents are less than 8 or 5 percent, respectively. C) The amount of the specific source of pozzolan or slag to be used shall not be less than the amount that has been determined by service record to improve sulfate resistance when used in concrete containing Type V cement. Alterna- tively, the amount of the specific source of the pozzolan or slab to be used shall not be less than the amount tested in accordance with ASTM C1012 and meeting the criteria in section 26.4.2.2(c) of ACI 318. D) If Type V cement is used as the sole cementitious material, the optional sulfate resistance requirement of 0.040 percent maximum expansion in ASTM C150 shall be specified. Superficial damage may occur to the exposed surfaces of highly permeable concrete, even though sulfate levels are relatively low. To control this risk and to resist freeze-thaw deteri- oration, the water-to-cementitious materials ratio should not exceed 0.50 for concrete in contact with soils that are likely to stay moist due to surface drainage or high-water tables. Concrete should have a total air content of 6 percent ± 1.5 percent. We advocate damp-proofing of all foundation walls and grade beams in contact with the subsoils. SURFACE DRAINAGE Performance of foundations, flatwork, and pavements is influenced by changes in sub- grade moisture conditions. Carefully planned and maintained surface grading can reduce the risk of wetting of the foundation soils and pavement subgrade. We recommend a minimum slope of 5 percent in the first 10 feet outside foundations in landscaped areas. Backfill around foundations should be moisture treated and compacted as described in Fill Placement. Roof drains should be directed away from buildings. Downspout extensions and splash blocks should NOT FOR REVIEW IN DRAINAGE REPORT VOLUNTEERS OF AMERICA 21 VOA MASON PLACE II CTLT PROJECT NO. FC11376.000-120-R1R be provided at discharge points, or roof drains should be connected to solid pipe discharge sys- tems. We do not recommend directing roof drains under buildings. CONSTRUCTION OBSERVATIONS / ADDITIONAL SERVICES This project will involve many activities that should be monitored during the construction phase by a geotechnical engineering firm. To provide continuity between design and construc- tion, CTL|Thompson, Inc. should provide these services. Other observations are recommended to review general conformance with design plans. If another firm is selected to provide these services, they must accept responsibility to evaluate whether conditions exposed during con- struction are consistent with findings in this report and whether design recommendations remain appropriate. When construction schedules and quantities are defined, we can develop an appro- priate scope of services and budget for construction observation and materials testing. GEOTECHNICAL RISK The concept of risk is an important aspect with any geotechnical evaluation, primarily be- cause the methods used to develop geotechnical recommendations do not comprise an exact science. We never have complete knowledge of subsurface conditions. Our analysis must be tempered with engineering judgment and experience. Therefore, the recommendations pre- sented in any geotechnical evaluation should not be considered risk-free. Our recommendations represent our judgment of those measures that are necessary to increase the chances that the structures and improvements will perform satisfactorily. It is critical that all recommendations in this report are followed during construction. Owners or property managers must assume re- sponsibility for maintaining the structures and use appropriate practices regarding drainage and landscaping. Improvements after construction, such as construction of additions, retaining walls, landscaping, and exterior flatwork, should be completed in accordance with recommendations provided in this report and may require additional soil investigation and consultation. LIMITATIONS This report has been prepared for the exclusive use of Volunteers of America and the design team for the project, to provide geotechnical design and construction criteria for the pro- posed project. The information, conclusions, and recommendations presented herein are based NOT FOR REVIEW IN DRAINAGE REPORT TH-1A TH-2A TH-3A TH-1TH-2 TH-3 TH-5 TH-4 S C O L L E G E A V E S M A S O N S T W HORSETOOTH RD BO A R D W A L K D R JO H N F K E N N E D Y P K W Y MA N H A T T A N A V E SITE LEGEND: INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING INDICATES APPROXIMATE LOCATION OF REDRILLED EXPLORATORY BORING TH-1 TH-1A VOA MASON PLACE II VOLUNTEERS OF AMERICA CTL I T PROJECT NO. FC11,367.000-120-R1R FIGURE 1 Locations of Exploratory Borings VICINITY MAP (FORT COLLINS, COLORADO) NOT TO SCALE 50'25' APPROXIMATE SCALE: 1" = 50' 0' NOT FOR REVIEW IN DRAINAGE REPORT VOLUNTEERS OF AMERICA VOA MASON PLACE II CTLT PROJECT NO. FC11376.000-120-R1R APPENDIX A SUMMARY LOGS OF EXPLORATORY BORINGS NOT FOR REVIEW IN DRAINAGE REPORT 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 27/12 7/12 50/4 50/2 50/2 WC=20.1DD=112SW=0.0 WC=20.1DD=112SW=0.0 TH-1 9/12 8/12 50/3 50/2 WC=18.1DD=115SW=0.3SS=0.01 WC=21.0DD=109SW=0.2 WC=18.1DD=115SW=0.3SS=0.01 WC=21.0DD=109SW=0.2 TH-2 24/12 7/12 50/4 50/2 50/1 WC=5.0-200=7 WC=23.6DD=106SW=0.5 WC=5.0-200=7 WC=23.6DD=106SW=0.5 TH-3 24/12 8/12 13/12 WC=5.7-200=12 WC=17.7DD=104SW=1.2SS=0.70 WC=5.7-200=12 WC=17.7DD=104SW=1.2SS=0.70 TH-4 14/12 9/12 7/12 WC=13.8DD=112SW=0.3SS=<0.01 WC=23.4DD=102LL=43 PI=28-200=59 WC=13.8DD=112SW=0.3SS=<0.01 WC=23.4DD=102LL=43 PI=28-200=59 TH-5 LEGEND: CLAY, SANDY, MOIST, MEDIUM STIFF TO STIFF, GREY, BROWN (CL) SAND, CLAYEY, MOIST, VERY DENSE, GREY, BROWN (SC) SAND, GRAVELLY, MOIST, MEDIUM DENSE, GREY, BROWN (SP) SANDSTONE, MOIST, VERY HARD, BROWN, TAN PRACTICAL DRILL REFUSAL. DRIVE SAMPLE. THE SYMBOL 27/12 INDICATES 27 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES. ASPHALT 1. NOTES: 3. GRAVEL, SANDY, CLAYEY, MOIST, MEDIUM DENSE, BROWN, GREY (GP) DE P T H - F E E T WATER LEVEL MEASURED AT TIME OF DRILLING. Summary Logs of First Exploratory Borings THE BORINGS WERE DRILLED ON OCTOBER 3, 2024 USING 4-INCH DIAMETER CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG. FIGURE A- 1 WC DD SW -200 LL PI SS - - - - - - - THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. ROADBASE INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES LIQUID LIMIT. INDICATES PLASTICITY INDEX. INDICATES SOLUBLE SULFATE CONTENT (%). 2. DE P T H - F E E T VOLUNTEERS OF AMERICA VOA MASON PLACE II CTL | T PROJECT NO. FC11,376.000-120 -R1R NOT FOR REVIEW IN DRAINAGE REPORT 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 8/12 31/12 19/12 50/2 WC=21.1DD=59LL=34 PI=21-200=50 WC=21.1DD=59LL=34 PI=21-200=50 TH-1A 7/12 31/12 9/12 50/3 WC=20.6DD=102LL=34 PI=20-200=49 WC=4.5-200=8 WC=20.6DD=102LL=34 PI=20-200=49 WC=4.5-200=8 TH-2A 13/12 17/12 11/12 50/3 WC=12.5DD=111-200=33 WC=6.2-200=7 WC=22.3DD=105SW=0.5 WC=12.5DD=111-200=33 WC=6.2-200=7 WC=22.3DD=105SW=0.5 TH-3A 2. DRIVE SAMPLE. THE SYMBOL 8/12 INDICATES 8 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES. DE P T H - F E E T WATER LEVEL MEASURED AT TIME OF DRILLING. FIGURE A - 2 NOTES: Summary Logs of Second Exploratory Borings ASPHALT DE P T H - F E E T THE BORINGS WERE DRILLED ON JULY 3, 2025 USING 4-INCH DIAMETER CONTINUOUS-FLIGHT, SOLID-STEM AUGERS AND A TRUCK-MOUNTED DRILL RIG. LEGEND: CLAY, SANDY, MEDIUM STIFF TO VERY STIFF, MOIST, BROWN, TAN, GRAY (CL). SAND, CLEAN, GRAVELLY LENSES, MEDIUM DENSE TO DENSE, SLIGHTLY MOIST, BROWN, PINK, GRAY, TAN (SP). BEDROCK SANDSTONE, VERY HARD, SLIGHTLY MOIST, TAN, BROWN, LIGHT BROWN, RUST. 1. 3. THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. WATER LEVEL MEASURED SEVERAL DAYS AFTER DRILLING. ROADBASE WC DD SW COMP -200 LL PI UC SS pF INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%). INDICATES COMPRESSION WHEN WETTED UNDER OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES LIQUID LIMIT. INDICATES PLASTICITY INDEX. INDICATES UNCONFINED COMPRESSIVE STRENGTH (PSF). INDICATES SOLUBLE SULFATE CONTENT (%). INDICATES SOIL SUCTION (pF). - - - - - - - - - - VOLUNTEERS OF AMERICA VOA MASON PLACE II CTL | T PROJECT NO. FC11,376.000-120-R1R NOT FOR REVIEW IN DRAINAGE REPORT Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/26/2025 Page 1 of 4 44 8 7 0 5 0 44 8 7 0 6 0 44 8 7 0 7 0 44 8 7 0 8 0 44 8 7 0 9 0 44 8 7 1 0 0 44 8 7 1 1 0 44 8 7 1 2 0 44 8 7 1 3 0 44 8 7 1 4 0 44 8 7 1 5 0 44 8 7 1 6 0 44 8 7 1 7 0 44 8 7 0 5 0 44 8 7 0 6 0 44 8 7 0 7 0 44 8 7 0 8 0 44 8 7 0 9 0 44 8 7 1 0 0 44 8 7 1 1 0 44 8 7 1 2 0 44 8 7 1 3 0 44 8 7 1 4 0 44 8 7 1 5 0 44 8 7 1 6 0 44 8 7 1 7 0 493260 493270 493280 493290 493300 493310 493320 493330 493340 493350 493260 493270 493280 493290 493300 493310 493320 493330 493340 493350 40° 32' 7'' N 10 5 ° 4 ' 4 6 ' ' W 40° 32' 7'' N 10 5 ° 4 ' 4 2 ' ' W 40° 32' 2'' N 10 5 ° 4 ' 4 6 ' ' W 40° 32' 2'' N 10 5 ° 4 ' 4 2 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 30 60 120 180 Feet 0 5 10 20 30 Meters Map Scale: 1:619 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 19, Aug 29, 2024 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 2, 2021—Aug 25, 2021 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 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/26/2025 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 76 Nunn clay loam, wet, 1 to 3 percent slopes C 0.5 27.7% 90 Renohill clay loam, 3 to 9 percent slopes D 0.1 7.2% 136 Water 1.2 65.1% Totals for Area of Interest 1.9 100.0% 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. Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/26/2025 Page 3 of 4 Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/26/2025 Page 4 of 4 SITE May 15, 2018 Wes Lamarque, P.E. City of Fort Collins Utilities – Stormwater Engineering 700 Wood Street Fort Collins, CO 80521 RE: Mason Place, 3750 South Mason Street – Preliminary Drainage Letter JVA Job No. 2873c Dear Wes: This letter has been prepared to summarize the drainage concept, solutions and changes in impervious area associated with the site improvements for the Mason Place redevelopment project located at 3750 South Mason Street in the City of Fort Collins. Existing Drainage Patterns The existing site, platted as Lot 5A and adjoining Lot 6 (same owner), is predominantly paved asphalt and consists of the existing Midtown Arts Center building, drive aisles, and parking areas. The existing ground surface is relatively flat, generally sloping either northwest or southwest at grades ranging from 0.5% to 2.0%. The majority of stormwater runoff is conveyed via surface flow either to the northwest into an existing curb inlet in the north parking area (into a private storm system that serves the northern portion of the site and its eastern neighbors), or to the southwest across the Lot 6 parking lot, through a curb cut and over public sidewalk and into the public storm drainage system in South Mason Street via a curb inlet. See Figure 1: Historic Drainage Map. The site is located outside FEMA and City of Fort Collins mapped 100-year and 500-year floodplains, per FEMA Flood Risk Map Panel number 08069C0987G, effective date 05/02/2012. Proposed Drainage Patterns Proposed drainage patterns are to remain generally the same as the current, but will utilize landscaped areas, concrete pans, sidewalk chases, and inlets to capture and treat the majority of runoff before discharging into the public storm system without flowing over driveway approaches or sidewalks and into the street. In general, the proposed redevelopment of the site consists of reusing the existing building, reconfiguring the north parking area, relocating the access driveway on Mason Street further to the south, and constructing a courtyard and greenspaces on the west side of the existing building along within new storm infrastructure to improve the drainage characteristics of the site. The site has been divided into four hydrologic basins for analysis. Basins A and B represent the majority of roof drainage from the existing building and runoff from the north parking area and the west courtyard. These areas will both utilize grassed swales to collect and slow runoff before discharging into area inlets and then into the existing public storm system. Basin A roof drainage and runoff in the parking area will be collected by curb inlets and routed through a Contech CDS storm filtration unit to treat for stormwater quality. Basin C represents the runoff from the remainder of the redeveloped site, draining to the south past the new Mason curb cut via a concrete pan and into a proposed curb inlet in the Lot 6 parking area. Basin OS1 represents a Mason Place Preliminary Drainage Letter May 15, 2018 2 of 2 strip of sidewalk and landscaping along the east edge of the building that drains east into the neighboring curb & gutter, and is then captured into the same private storm system that runs through the north side of the Mason Place property and discharges into the Mason Street public storm system. All four basins eventually convey stormwater to Fossil Creek. It follows that the proposed improvements will substantially decrease the total impervious area on the site, from 84.2% to 67.9%. See Figure 2: Developed Drainage Map for the drainage basin boundaries, runoff calculations, and a summary of the existing and proposed impervious areas. Chapter 2 of the Urban Drainage and Flood Control District’s Urban Storm Drainage Criteria Manual Volume 3 (USDCM) provides guidelines for the selection of appropriate structural BMPs for a site that is to be developed or redeveloped. Mason Place is best characterized as a “conventional redevelopment” with just over 1 acre of impervious area on the project site. The BMP decision tree for such sites is provided in Figure 2-2 of the USDCM. The site and surrounding vicinity is comprised of hydrologic soil group Type C & D soils, per the NRCS soil survey. Permeable pavement (with partial or no infiltration) and/or the use of a “green roof”, rain garden, or grass swale/buffer are the recommended runoff reduction practices for this scenario. The proposed Contech CDS storm filtration unit located on the private storm system will treat storm runoff for a minimum of 75% of the modified or added impervious area on the site for water quality prior to discharge into the public storm system, satisfying the City of Fort Collins Low Impact Development (LID) requirements. The hydraulic capacity of the CDS will be designed to treat runoff from the 2-year event, specific unit selection and details will be provided at final design. See sample standard CDS detail included with this letter. The proposed grass swales along the west side of the property will also help to perform this function for runoff generated on the site by capturing and slowing runoff from Basins A & B. These features will facilitate sedimentation and filtration while limiting erosion, providing both treatment and slowed release of the water quality capture volume. The proposed redevelopment of this site will serve to reduce water quality and quantity impacts to natural drainageways by decreasing the frequency, rate, duration, and volume of runoff. Erosion and Sediment Control During construction, temporary erosion and sediment control practices will be used to limit soil erosion and sediment discharge off the site. Please feel free to contact me to discuss any questions you may have. Sincerely, JVA, INCORPORATED By: ________________________________ Karen Brigman, CFM . Senior Project Engineer Enclosures: Figure 1: Historic Drainage Map, Figure 2: Developed Drainage Map, Rational Calculations, CD1.0 Grading & Drainage Details CC: Kristin Fritz, Housing Catalyst HI S T O R I C D R A I N A G E M A P FIG 1 RE V I S I O N D E S C R I P T I O N D' W N DE S ' D DA T E NO . DESIGNED BY: DRAWN BY: CHECKED BY: JOB #: DATE: © JVA, INC. HO U S I N G C A T A L Y S T MA S O N P L A C E FO R T C O L L I N S , C O SHEET NO. 2873c APRIL 2018 CRH EJK EJK JVA, Inc.213 Linden Street, Suite 200 www.jvajva.com Fort Collins, CO 80524 970.225.9099 Boulder ● Fort Collins ● Winter Park Glenwood Springs ● Denver FI R E LA N E KE E P CL E A R FIRE LANE KEEP CLEAR PR O P O S E D D R A I N A G E M A P FIG 2 RE V I S I O N D E S C R I P T I O N D' W N DE S ' D DA T E NO . DESIGNED BY: DRAWN BY: CHECKED BY: JOB #: DATE: © JVA, INC. HO U S I N G C A T A L Y S T MA S O N P L A C E FO R T C O L L I N S , C O SHEET NO. 2873c MAY 2018 CRH EJK KRB JVA, Inc.213 Linden Street, Suite 200 www.jvajva.com Fort Collins, CO 80524 970.225.9099 Boulder ● Fort Collins ● Winter Park Glenwood Springs ● Denver DRAWING NUMBER: 419 Canyon Ave. Suite 200 Fort Collins, CO 80521 phone 970.224.5828 | fax 970.225.6657 | www.ripleydesigninc.com ■ land planning ■ landscape architecture ■ ■ urban design ■ entitlement ■ ISSUED PROJECT No.: DRAWN BY: REVIEWED BY: SEAL: PREPARED BY: No.DESCRIPTION DATE REVISIONS No.DESCRIPTION DATE Pl o t t e d B y : Ka r e n R . B r i g m a n La y o u t : CD 1 . 0 2 4 x 3 6 Pr i n t e d O n : 5/ 1 5 / 2 0 1 8 1 1 : 4 5 A M Fi l e N a m e : 28 7 3 c - 0 1 - G R P - D E T - 0 0 . d w g ORIGINAL SIZE 24X36 RIPLEY DESIGN INC. 419 Canyon Ave. Suite 200 Fort Collins, CO 80521 p. 970.224.5828 f. 970.225.6657 HOUSING CATALYST 1715 W Mountain Avenue Fort Collins, CO 80521 p. 970.416.2910 CIVIL ENGINEER ARCHITECT APPLICANT JVA, INCORPORATED 213 Linden Street, Suite 200 Fort Collins, CO 80524 p. 970.225.9099 SHOPWORKS ARCHITECTURE 2882 Wyandot Street Denver, CO 80211 p. 303.433.4094 OWNER/DEVELOPER MASON PLACE PSH MAJOR AMENDMENT FORT COLLINS, CO JVA, Incorporated 2 1 3 L i n d e n S t r e e t Suite 200 Fort Collins, CO 80524 Phone: 970.225.9099 Fax: 970.225.6963 E-mail: info@jvajva.com JVA Project #2873c CONSULTING ENGINEERS 2843c EJK/KRB BJC/CRH 1 MAJOR AMENDMENT 04.25.2018 2 MAJOR AMENDMENT 2 05.16.2018 CD1.0 GRADING & DRAINAGE DETAILS CHECKED BY: CHECKED BY: CHECKED BY: CHECKED BY: CHECKED BY: Date Date Date Date Date Date City of Fort Collins, Colorado UTILITY PLAN APPROVAL Parks and Recreation Traffic Engineer Stormwater Utility Water & Wastewater Utility City Engineer CHECKED BY: APPROVED: Date Environmental Planner JVA Incorporated Job Name: Mason Place I% C2 C5 C10 C100 213 Linden St, Suite 200 Job Number: 2873c Streets Paved 100% 0.95 0.00 0.95 1.00 Fort Collins, CO 80524 Date: 4/24/18 Concrete Drives/Walks 90% 0.95 0.00 0.95 1.00 Ph: (970) 225 9099 By: KRB Roof 90% 0.95 0.00 0.95 1.00 Gravel 40% 0.50 0.00 0.50 0.63 Landscaping (B soil) 0% 0.15 0.00 0.15 0.19 Mason Place Landscaping (C/D soil) 0% 0.25 0.00 0.25 0.31 Historic Runoff Coefficient & Time of Concentration Calculations Playground 10% 0.11 0.00 0.11 0.14 Location: Fort_Collins Artificial Turf 25% 0.20 0.00 0.20 0.25 Minor Design Storm: 2 Major Design Storm: 100 Soil Type: C/D Basin Design Data I (%) = 100% 90% 90% 40% 10% 25% 0% 0%I (%)tc Comp tc Final Basin Name Design Point Apaved streets (sf) Adrives/co nc (sf) Aroof (sf) Agravel (sf) Aplygnd (sf) Aart. turf (sf) Alscape (B soil) (sf) Alscape (C/D soil) (sf) ATotal (sf) ATotal (ac) Imp (%)C2 C5 C10 C100 Upper most Length (ft) Slope (%) ti (min) Length (ft) Slope (%)Type of Land Surface K Velocity (fps) tt (min) Time of Conc ti + tt = tc Total Length (ft) tc=(L/180)+ 10 (min.) Min tc A 1 13,497 2,299 8,810 2,832 27,438 0.63 85.6% 0.88 0.00 0.88 0.93 5 2.0%3.6 150 1.3%Paved areas & shallow paved swales 20 2.3 1.1 4.7 155 10.9 5.0 B 2 7,580 3,207 9,911 2,696 23,394 0.54 82.9% 0.87 0.00 0.87 0.92 5 2.0%3.6 190 1.8%Paved areas & shallow paved swales 20 2.7 1.2 4.8 195 11.1 5.0 OS1 3 655 156 811 0.02 72.7% 0.82 0.00 0.82 0.87 5 2.0%3.6 5 1.5%Paved areas & shallow paved swales 20 2.4 0.0 3.6 10 10.1 5.0 0 0.00 Paved areas & shallow paved swales 20 0 10.0 0 0.00 Paved areas & shallow paved swales 20 0 10.0 TOTAL SITE 21,077 6,161 18,721 0 0 0 0 5,684 51,643 1.19 84.2% 0.87 0.00 0.87 0.92 Basin Name Design Point Time of Conc (tc) C2 C5 C10 C100 2 5 10 100 ATotal (sf)ATotal (ac) Q2 Q5 Q10 Q100 A 1 5.0 0.88 0.00 0.88 0.93 2.85 0.00 4.87 9.95 27,438 0.63 1.58 0.00 2.69 5.82 B 2 5.0 0.87 0.00 0.87 0.92 2.85 0.00 4.87 9.95 23,394 0.54 1.33 0.00 2.27 4.92 OS1 3 5.0 0.82 0.00 0.82 0.87 2.85 0.00 4.87 9.95 811 0.02 0.04 0.00 0.07 0.16 0 0 0 0.00 0 0 0 0.00 TOTAL SITE 51,643 1.19 2.95 0.00 5.04 10.90 Initial Overland Time (ti)Travel Time (tt) tt=Length/(Velocity x 60) tc Urbanized Check ON Runoff Coeff's Rainfall Intensities (in/hr)Area Flow Rates (cfs) Runoff Coeff's 2873c - Rational Calculations.xlsx Historic Page 1 of 5 JVA Incorporated Job Name: Mason Place I% C2 C5 C10 C100 213 Linden St, Suite 200 Job Number: 2873c Streets Paved 100% 0.95 0.00 0.95 1.00 Fort Collins, CO 80524 Date: 4/24/18 Concrete Drives/Walks 90% 0.95 0.00 0.95 1.00 Ph: (970) 225 9099 By: KRB Roof 90% 0.95 0.00 0.95 1.00 Gravel 40% 0.50 0.00 0.50 0.63 Landscaping (B soil) 0% 0.15 0.00 0.15 0.19 Mason Place Landscaping (C/D soil) 0% 0.25 0.00 0.25 0.31 Composite Runoff Coefficient Calculations Playground 10% 0.11 0.00 0.11 0.14 Location: Fort_Collins Artificial Turf 25% 0.20 0.00 0.20 0.25 Minor Design Storm: 2 Major Design Storm: 100 Soil Type: C/D Basin Design Data I (%) = 100% 90% 90% 40% 10% 25% 0% 0%I (%) Basin Name Design Point Apaved streets (sf) Adrives/c onc (sf) Aroof (sf) Agravel (sf) Aplygnd (sf) Aart. turf (sf) Alscape (B soil) (sf) Alscape (C/D soil) (sf) ATotal (sf) ATotal (ac) Imp (%)C2 C5 C10 C100 A 1 8,620 3,537 8,810 6,993 27,960 0.64 70.6% 0.77 0.00 0.77 0.83 B 2 3,494 4,559 5,506 13,559 0.31 53.5% 0.58 0.00 0.58 0.62 C 3 2,954 5,354 1,005 9,313 0.21 80.3% 0.85 0.00 0.85 0.90 OS2 4 655 156 811 0.02 72.7% 0.77 0.00 0.77 0.81 Runoff Coeff's 2873c - Rational Calculations.xlsx Developed C Page 2 of 5 JVA Incorporated Job Name: Mason Place 213 Linden St, Suite 200 Job Number: 2873c Fort Collins, CO 80524 Date: 4/24/18 Ph: (970) 225 9099 By: KRB Mason Place Time of Concentration Calculations Location: Fort_Collins Minor Design Storm: 2 Major Design Storm: 100 Soil Type: C/D Sub-Basin Data tc Comp tc Final Basin Name Design Point ATotal (ac)C5 Upper most Length (ft) Slope (%) ti (min) Length (ft)Slope (%) Type of Land Surface Cv Velocity (fps) tt (min) Time of Conc ti + tt = tc Total Length (ft) tc=(L/180)+ 10 (min) Min tc A 1 0.64 0.00 105 2.0%16.4 50 2.0% Grassed waterway 15 2.1 0.4 16.8 155 10.9 10.9 B 2 0.31 0.00 40 2.0%10.1 80 2.0% Grassed waterway 15 2.1 0.6 10.8 120 10.7 10.7 C 3 0.21 0.00 5 2.0%3.6 20 1.5%Paved areas & shallow paved swales 20 2.4 0.1 3.7 25 10.1 5.0 OS2 4 0.02 0.00 5 2.0%3.6 5 1.5%Paved areas & shallow paved swales 20 2.4 0.0 3.6 10 10.1 5.0 Initial Overland Time (ti)Travel Time (tt) tt=Length/(Velocity x 60) tc Urbanized Check ON 2873c - Rational Calculations.xlsx Developed Tc Page 3 of 5 JVA Incorporated Job Name: Mason Place 213 Linden St, Suite 200 Job Number: 2873c Fort Collins, CO 80524 Date: 4/24/18 Ph: (970) 225 9099 By: KRB Mason Place Developed Storm Runoff Calculations Design Storm : 100 Year Point Hour Rainfall (P1) : 2.86 B a s i n N a m e D e s i g n P o i n t A r e a ( a c ) R u n o f f C o e f f t c ( m i n ) C * A ( a c ) I ( i n / h r ) Q ( c f s ) T o t a l t c ( m i n ) S C* A ( a c ) I ( i n / h r ) Q ( c f s ) I n l e t T y p e Q i n t e r c e p t e d Q c a r r y o v e r Q b y p a s s P i p e S i z e ( i n ) or e q u i v a l e n t P i p e M a t e r i a l S l o p e ( % ) P i p e F l o w (c f s ) M a x P i p e Ca p a c i t y ( c f s ) L e n g t h ( f t ) V e l o c i t y ( f p s ) t t ( m i n ) To t a l T i m e (m i n ) N o t e s A 1 0.64 0.83 10.90 0.53 7.45 3.96 10.90 0.53 7.45 3.96 B 2 0.31 0.62 10.70 0.19 7.51 1.44 10.70 0.19 7.51 1.44 C 3 0.21 0.90 5.00 0.19 9.95 1.91 5.00 0.19 9.95 1.91 OS2 4 0.02 0.81 5.00 0.02 9.95 0.15 5.00 0.02 9.95 0.15 Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time 2873c - Rational Calculations.xlsx Q100 Page 4 of 5 JVA Incorporated Job Name: Mason Place 213 Linden St, Suite 200 Job Number: 2873c Fort Collins, CO 80524 Date: 4/24/18 Ph: (970) 225 9099 By: KRB Mason Place Developed Storm Runoff Calculations Design Storm : 2 Year Point Hour Rainfall (P1) : 0.82 B a s i n N a m e D e s i g n P o i n t A r e a ( a c ) R u n o f f C o e f f t c ( m i n ) C * A ( a c ) I ( i n / h r ) Q ( c f s ) T o t a l t c ( m i n ) S C* A ( a c ) I ( i n / h r ) Q ( c f s ) I n l e t T y p e Q i n t e r c e p t e d Q c a r r y o v e r Q b y p a s s P i p e S i z e ( i n ) or e q u i v a l e n t P i p e M a t e r i a l S l o p e ( % ) P i p e F l o w (c f s ) M a x P i p e Ca p a c i t y ( c f s ) L e n g t h ( f t ) V e l o c i t y ( f p s ) t t ( m i n ) To t a l T i m e (m i n ) N o t e s A 1 0.64 0.77 10.90 0.50 2.14 1.06 10.90 0.50 2.14 1.06 B 2 0.31 0.58 10.70 0.18 2.15 0.39 10.70 0.18 2.15 0.39 C 3 0.21 0.85 5.00 0.18 2.85 0.52 5.00 0.18 2.85 0.52 OS2 4 0.02 0.77 5.00 0.01 2.85 0.04 5.00 0.01 2.85 0.04 Direct Runoff Total Runoff Inlets Pipe Pipe/Swale Travel Time 2873c - Rational Calculations.xlsx Q Minor Page 5 of 5 Page 13 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 Appendix B Hydrologic Calculations Project Name:VOA Switchgrass Project No:24046 Designed By:TLS Date:10/28/2025 Reference:Fort Collins Stormwater Criteria Manual Runoff Coefficient Calculations Jurisdiction:Fort Collins Landscape (2-7%)0.25 Heavy Meadow 2.5 Landscape (>7%)0.35 Tillage/Field 5 Roof 0.95 Short Pasture and Lawns 7 Concrete 0.95 Nearly Bare Ground 10 Asphalt 0.95 Grassed Waterway 15 Gravel 0.50 Paved Areas and Shallow Paved Swales 20 Type of Soil C/D Basin ID Landscape (2-7%)Landscape (>7%)Roof Concrete Asphalt Gravel Total Area (SF)Total Area (AC)Impervious %2 yr 5 yr 10 yr 25 yr 50 yr 100 yr RA1 3669 3669 0.08 95%0.95 0.95 0.95 1.00 1.00 1.00 A1 1572 1556 4323 7451 0.17 80%0.80 0.80 0.80 0.88 0.96 1.00 RA2 8572 8572 0.20 95%0.95 0.95 0.95 1.00 1.00 1.00 A2 10746 5417 2609 13100 31872 0.73 61%0.61 0.61 0.61 0.67 0.73 0.77 A3 1530 1794 2450 4388 10162 0.23 74%0.74 0.74 0.74 0.81 0.89 0.92 OS1 2595 393 169 3157 0.07 37%0.37 0.37 0.37 0.41 0.45 0.47 OS2 2780 27514 30294 0.70 89%0.89 0.89 0.89 0.98 1.00 1.00 Total A 16443 9991 12241 7008 49494 0 95177 2.18 77%0.77 0.77 0.77 0.84 0.92 0.96 Undeveloped EXA 30122 30122 0.69 25%0.25 0.25 0.25 0.28 0.30 0.31 EXA 4888 25234 30122 0.69 84%0.84 0.84 0.84 0.92 1.00 1.00 EXB 9322 56189 65511 1.50 85%0.85 0.85 0.85 0.94 1.00 1.00 EXC 78958 78958 1.81 95%0.95 0.95 0.95 1.00 1.00 1.00 Jurisdiction Runoff Coefficient Table (Check Jurisdiction Standards!) Areas By Coverage (SF) Runoff Coefficient (C) By Storm Frequency NRCS Conveyance Factors Project Name:VOA Switchgrass Project No:24046 Heavy Meadow 2.5 Designed By:TLS Tillage/Field 5 Date:10/28/2025 Short Pasture and Lawns 7 Reference:Fort Collins Stormwater Criteria Manual Nearly Bare Ground 10 Grassed Waterway 15 Time of Concentration Calculations Paved Areas and Shallow Paved Swales 20 Basin ID Overland Travel Length (Li) ft Slope (S0) %Imp%C5 - 5 yr Coeff ti Length of Travel (Lt) ft Slope (S) % NRCS Conveyance (K)tt Total Travel Time (ti+tt)Urban Catchment Min Time FCSCM 3.3-5 Urban-Rural Min Tc Min Tc RA1 46 2.00%95.00%0.95 1.51 0 2.00%20 0.00 1.51 10.26 5.00 5.00 A1 35 1.80%80.23%0.80 2.71 98 1.00%20 0.82 3.53 10.19 5.00 5.00 RA2 65 2.00%95.00%0.95 1.80 0 2.00%20 0.00 1.80 10.36 5.00 5.00 A2 52 1.60%61.20%0.61 5.64 175 0.50%20 2.06 7.70 10.29 5.00 5.00 A3 41 1.30%73.87%0.74 3.97 71 0.70%20 0.71 4.67 10.23 5.00 5.00 OS1 26 3.40%37.46%0.37 4.62 0 2.00%20 0.00 4.62 10.14 5.00 5.00 OS2 34 2.00%89.49%0.89 1.78 700 0.50%20 8.25 10.03 10.19 5.00 5.00 Undeveloped EXA 212 1.00%25.00%0.25 23.14 0 2.00%20 0.00 23.14 11.18 5.00 5.00 EXA 212 1.00%83.64%0.84 7.18 0 2.00%20 0.00 7.18 11.18 5.00 5.00 EXB 28 1.00%85.04%0.85 2.47 784 2.00%20 4.62 7.09 10.16 5.00 5.00 EXC 500 2.00%95.00%0.95 4.99 0 1.00%20 0.00 4.99 9.85 4.99 5.00 5.00 5.00 5.00 5.00 5.00 Overland Flow Time (ti) Channelized Flow Time (tt) Min Time of Concentration tc Calculation NRCS Conveyance Factors Project Name:VOA Switchgrass Project No:24046 Designed By:TLS Date:10/28/2025 Reference:Fort Collins Stormwater Criteria Manual Minor Storm Flow Calculations Storm Interval 2 yr *Check below C Values dependent on storm interval 1 hour Rainfall (in)0.82 Basin ID Design Point Area (ac)Tc C C x A Intensity (I) Flow Rate (Q) (cfs)Revised Tc Sum of CA Revised Intensity (I) Accumulative Flow (cfs) Pipe Flow Rate (cfs) Pipe Diameter (in) Pipe Velocity (ft/s) Pipe Length (ft) Travel Time (min) Notes RA1 R1 0.08 5.00 0.95 0.08 2.85 0.23 0.23 8.00 1.31 14.00 0.18 Roof Basin RA1 A1 1 0.17 5.00 0.80 0.14 2.85 0.39 0.39 12.00 1.00 30.00 0.50 Basin A1 CF1 5.18 0.22 2.85 0.62 0.62 8.00 3.55 256.00 1.20 Roof Basin RA1 + Basin A1 RA2 R2 0.20 5.00 0.95 0.19 2.85 0.53 0.53 8.00 3.05 191.00 1.04 Roof Basin RA2 A2 2 0.73 5.00 0.61 0.45 2.85 1.28 6.20 0.85 2.85 2.43 2.43 12.00 6.18 12.00 0.03 CF1 + Roof Basin RA2 + Basin A2 OS1 0.07 5.00 0.37 0.03 2.85 0.08 Offsite flows to onsite Design Point 3 OS2 0.70 5.00 0.89 0.62 2.85 1.77 Offsite flows to onsite Design Point 3 A3 3 0.23 5.00 0.74 0.17 2.85 0.49 5.00 0.65 2.85 1.85 1.85 8.00 10.61 9.00 0.01 Basin A3 + Basin OS1 + Basin OS2 Undeveloped EXA 0.69 5.00 0.25 0.17 0.00 EXA 0.69 5.00 0.84 0.58 2.85 1.65 EXB 1.50 5.00 0.85 1.28 2.85 3.64 EXC 1.81 4.99 0.95 1.72 2.85 4.91 Basin Flow Calcs Accumulative Pipe Flows Pipe Travel Time (min) Project Name:VOA Switchgrass Project No:24046 Designed By:TLS Date:10/28/2025 Reference:Fort Collins Stormwater Criteria Manual Major Storm Flow Calculations Storm Interval 100 yr *Check below C Values dependent on storm interval 1 hour Rainfall (in)2.86 Basin ID Design Point Area (ac)Tc C C x A Intensity (I) Flow Rate (Q) (cfs)Revised Tc Sum of CA Revised Intensity (I) Accumulative Flow (cfs) Pipe Flow Rate (cfs) Pipe Diameter (in) Pipe Velocity (ft/s) Pipe Length (ft) Travel Time (min) Notes RA1 R1 0.08 5.00 0.95 0.08 9.95 0.80 0.80 8.00 4.56 14.00 0.05 Roof Basin RA1 A1 1 0.17 5.00 0.80 0.14 9.95 1.37 1.37 12.00 3.48 30.00 0.14 Basin A1 CF1 5.05 0.22 9.95 2.16 2.16 8.00 12.39 256.00 0.34 Roof Basin RA1 + Basin A1 RA2 R2 0.20 5.00 0.95 0.19 9.95 1.86 1.86 8.00 10.66 191.00 0.30 Roof Basin RA2 A2 2 0.73 5.00 0.61 0.45 9.95 4.46 5.34 0.85 9.95 8.48 8.48 12.00 21.59 12.00 0.01 CF1 + Roof Basin RA2 + Basin A2 OS1 0.07 5.00 0.37 0.03 9.95 0.27 Offsite flows to onsite Design Point 3 OS2 0.70 5.00 0.89 0.62 9.95 6.19 Offsite flows to onsite Design Point 3 A3 3 0.23 5.00 0.74 0.17 9.95 1.71 5.00 0.65 9.95 6.46 6.46 8.00 37.03 9.00 0.00 Basin A3 + Basin OS1 + Basin OS2 Undeveloped EXA 0.69 5.00 0.31 0.22 0.00 EXA 0.69 5.00 1.00 0.69 9.95 6.88 EXB 1.50 5.00 1.00 1.50 9.95 14.96 EXC 1.81 4.99 1.00 1.81 9.95 18.04 Basin Flow Calcs Accumulative Pipe Flows Pipe Travel Time (min) Project Name:VOA Switchgrass Project No:24046 Designed By:TLS Date:10/28/2025 Reference:Fort Collins Stormwater Criteria Manual Basin ID Design Point Area (AC) Impervious Percentage Minor Storm (C Value) Major Storm (C Value) Minor Storm Local Flow (cfs) Minor Storm Accum Flow (cfs) Major Storm Local Flow (cfs) Major Storm Accum Flow (cfs) Notes RA1 R1 0.08 95%0.95 1.00 0.23 0.80 0.80 Roof Basin RA1 A1 1 0.17 80%0.80 1.00 0.39 1.37 1.37 Basin A1 CF1 0.62 2.16 Roof Basin RA1 + Basin A1 RA2 R2 0.20 95%0.95 1.00 0.53 1.86 1.86 Roof Basin RA2 A2 2 0.73 61%0.61 0.77 1.28 2.43 4.46 8.48 CF1 + Roof Basin RA2 + Basin A2 OS1 0.07 37%0.37 0.47 0.08 0.27 Offsite flows to onsite Design Point 3 OS2 0.70 89%0.89 1.00 1.77 6.19 Offsite flows to onsite Design Point 3 A3 3 0.23 74%0.74 0.92 0.49 1.85 1.71 6.46 Basin A3 + Basin OS1 + Basin OS2 Undeveloped EXA 0.69 25%0.25 0.31 0.00 0.00 Undeveloped conditions. EXA 0.69 84%0.84 1.00 1.65 6.88 Existing conditions. EXB 1.50 85%0.85 1.00 3.64 14.96 Existing conditions. EXC 1.81 95%0.95 1.00 4.91 18.04 Existing conditions. Runoff Summary Table Page 14 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 Appendix C Hydraulic Calculations Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Sunday, Oct 26 2025 <Name> Rectangular Bottom Width (ft) = 4.00 Total Depth (ft) = 0.50 Invert Elev (ft) = 5036.90 Slope (%) = 2.00 N-Value = 0.013 Calculations Compute by: Known Q Known Q (cfs) = 6.46 Highlighted Depth (ft) = 0.27 Q (cfs) = 6.460 Area (sqft) = 1.08 Velocity (ft/s) = 5.98 Wetted Perim (ft) = 4.54 Crit Depth, Yc (ft) = 0.44 Top Width (ft) = 4.00 EGL (ft) = 0.83 0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 Elev (ft) Depth (ft)Section 5036.00 -0.90 5036.50 -0.40 5037.00 0.10 5037.50 0.60 5038.00 1.10 Reach (ft) CHASE-A FLOW Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Sunday, Oct 26 2025 <Name> Gutter Cross Sl, Sx (ft/ft) = 0.040 Cross Sl, Sw (ft/ft) = 0.083 Gutter Width (ft) = 2.00 Invert Elev (ft) = 5037.19 Slope (%) = 0.70 N-Value = 0.013 Calculations Compute by: Known Q Known Q (cfs) = 8.48 Highlighted Depth (ft) = 0.49 Q (cfs) = 8.480 Area (sqft) = 2.08 Velocity (ft/s) = 4.08 Wetted Perim (ft) = 10.48 Crit Depth, Yc (ft) = 0.57 Spread Width (ft) = 9.98 EGL (ft) = 0.74 0 2 4 6 8 10 12 14 16 Elev (ft) Depth (ft)Section 5036.75 -0.44 5037.00 -0.19 5037.25 0.06 5037.50 0.31 5037.75 0.56 5038.00 0.81 Reach (ft) STV-A EMERGENCY OVERFLOW BASIN A - CONCRETE PAN FLOW ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Project:Switchgrass Inlet ID:A01 Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =15.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.032 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.013 Height of Curb at Gutter Flow Line HCURB =0.00 inches Distance from Curb Face to Street Crown TCROWN =22.0 ft Gutter Width W =4.00 ft Street Transverse Slope SX =0.027 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.000 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.013 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =20.0 20.0 ft Warning 02 Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 12.0 inches Check boxes are not applicable in SUMP conditions MINOR STORM Allowable Capacity is not applicable to Sump Condition Minor Storm Major Storm MAJOR STORM Allowable Capacity is not applicable to Sump Condition Qallow =SUMP SUMP cfs MHFD-Inlet, Version 6.00 (August 2025) 1 INLET IN A SUMP OR SAG LOCATION MHFD-Inlet, Version 6.00 (August 2025) Design Information (Input)MINOR MAJOR Type of Inlet Type = CDOT/Denver 13 Valley Grate Local Depression (additional to continuous gutter depression 'a' from above)alocal =2.00 2.00 inches Number of Unit Inlets (Grate or Curb Opening)No =2 2 Water Depth at Flowline (outside of local depression)Ponding Depth =6.0 9.2 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) =3.00 3.00 feet Width of a Unit Grate Wo =1.73 1.73 feet Open Area Ratio for a Grate (typical values 0.15-0.90)Aratio =0.43 0.43 Clogging Factor for a Single Grate (typical value 0.50 - 0.70)Cf (G) =0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60)Cw (G) =3.30 3.30 Grate Orifice Coefficient (typical value 0.60 - 0.80)Co (G) =0.60 0.60 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) =N/A N/A feet Height of Vertical Curb Opening in Inches Hvert =N/A N/A inches Height of Curb Orifice Throat in Inches Hthroat =N/A N/A inches Angle of Throat Theta =N/A N/A degrees Side Width for Depression Pan (typically the gutter width of 2 feet)Wp =N/A N/A feet Clogging Factor for a Single Curb Opening (typical value 0.10)Cf (C) =N/A N/A Curb Opening Weir Coefficient (typical value 2.3-3.7)Cw (C) =N/A N/A Curb Opening Orifice Coefficient (typical value 0.60 - 0.70)Co (C) =N/A N/A Low Head Performance Reduction (Calculated)MINOR MAJOR Depth for Grate Midwidth dGrate =0.56 0.82 ft Depth for Curb Opening Weir Equation dCurb =N/A N/A ft Grated Inlet Performance Reduction Factor for Long Inlets RFGrate =0.71 1.00 Curb Opening Performance Reduction Factor for Long Inlets RFCurb =N/A N/A Combination Inlet Performance Reduction Factor for Long Inlets RFCombination =N/A N/A MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition)Qa =4.0 10.2 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q Peak)Q PEAK REQUIRED =1.3 4.5 cfs H-VertH-Curb W Lo (C) Lo (G) Wo WP Override Depths 1 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 30" Standard Grate Inlet Capacity Chart Inlet A01.1 ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Project:Switchgrass Inlet ID:A03 Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =20.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.015 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.013 Height of Curb at Gutter Flow Line HCURB =6.00 inches Distance from Curb Face to Street Crown TCROWN =26.0 ft Gutter Width W =2.00 ft Street Transverse Slope SX =0.015 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.000 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.013 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =20.0 20.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 12.0 inches Check boxes are not applicable in SUMP conditions MINOR STORM Allowable Capacity is not applicable to Sump Condition Minor Storm Major Storm MAJOR STORM Allowable Capacity is not applicable to Sump Condition Qallow =SUMP SUMP cfs MHFD-Inlet, Version 6.00 (August 2025) 1 INLET IN A SUMP OR SAG LOCATION MHFD-Inlet, Version 6.00 (August 2025) Design Information (Input)MINOR MAJOR Type of Inlet Type = Denver No. 16 Combination Local Depression (additional to continuous gutter depression 'a' from above)alocal =2.00 2.00 inches Number of Unit Inlets (Grate or Curb Opening)No =1 1 Water Depth at Flowline (outside of local depression)Ponding Depth =5.2 5.2 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) =3.00 3.00 feet Width of a Unit Grate Wo =1.73 1.73 feet Open Area Ratio for a Grate (typical values 0.15-0.90)Aratio =0.31 0.31 Clogging Factor for a Single Grate (typical value 0.50 - 0.70)Cf (G) =0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60)Cw (G) =3.60 3.60 Grate Orifice Coefficient (typical value 0.60 - 0.80)Co (G) =0.60 0.60 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) =3.00 3.00 feet Height of Vertical Curb Opening in Inches Hvert =6.50 6.50 inches Height of Curb Orifice Throat in Inches Hthroat =5.25 5.25 inches Angle of Throat Theta =0.00 0.00 degrees Side Width for Depression Pan (typically the gutter width of 2 feet)Wp =2.00 2.00 feet Clogging Factor for a Single Curb Opening (typical value 0.10)Cf (C) =0.10 0.10 Curb Opening Weir Coefficient (typical value 2.3-3.7)Cw (C) =3.70 3.70 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70)Co (C) =0.66 0.66 Low Head Performance Reduction (Calculated)MINOR MAJOR Depth for Grate Midwidth dGrate =0.46 0.46 ft Depth for Curb Opening Weir Equation dCurb =0.27 0.27 ft Grated Inlet Performance Reduction Factor for Long Inlets RFGrate =0.82 0.82 Curb Opening Performance Reduction Factor for Long Inlets RFCurb =N/A N/A Combination Inlet Performance Reduction Factor for Long Inlets RFCombination =0.82 0.82 MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition)Qa =4.0 4.0 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q Peak)Q PEAK REQUIRED =0.4 1.4 cfs H-VertH-Curb W Lo (C) Lo (G) Wo WP Override Depths 1 Project Name:VOA Switchgrass Project No:24046 Designed By:TLS Date:10/28/2025 Reference:Fort Collins Stormwater Criteria Manual WQCV Calculation WQCV = a(0.91I-1.19I+0.78I) a=0.8 I=77% WQCV =0.31 Watershed Inches WQCV =2430.45 cu ft Time Increment (min) Intensity (in/hour) C Volume In (cu ft) Volume Out (cu ft) Volume Stored (cu ft) 0 9.95 0.96 0.00 0.00 0.00 5 9.95 0.96 6245.60 1233.00 5012.60 10 7.72 0.96 9691.66 2466.00 7225.66 15 6.52 0.96 12277.78 3699.00 8578.78 20 5.6 0.96 14060.44 4932.00 9128.44 25 4.98 0.96 15629.69 6165.00 9464.69 30 4.52 0.96 17023.18 7398.00 9625.18 35 4.08 0.96 17927.07 8631.00 9296.07 40 3.74 0.96 18780.74 9864.00 8916.74 45 3.46 0.96 19546.53 11097.00 8449.53 50 3.23 0.96 20274.66 12330.00 7944.66 55 3.03 0.96 20921.19 13563.00 7358.19 60 2.86 0.96 21542.61 14796.00 6746.61 65 2.71 0.96 22113.82 16029.00 6084.82 70 2.59 0.96 22760.35 17262.00 5498.35 75 2.48 0.96 23350.38 18495.00 4855.38 80 2.38 0.96 23902.76 19728.00 4174.76 85 2.29 0.96 24436.30 20961.00 3475.30 90 2.21 0.96 24969.84 22194.00 2775.84 95 2.13 0.96 25402.96 23427.00 1975.96 100 2.06 0.96 25861.18 24660.00 1201.18 105 2.00 0.96 26363.33 25893.00 470.33 110 1.94 0.96 26790.17 27126.00 0.00 115 1.88 0.96 27141.68 28359.00 0.00 120 1.84 0.96 27719.16 29592.00 0.00 Detention Modified FAA Table Version 1.1 Project: Chamber Model - SC-160LP Units -Imperial Number of Chambers - 451 Voids in the stone (porosity) - 40 % Base of Stone Elevation - 5034.50 ft Amount of Stone Above Chambers - 10 in Interpolation Tools Amount of Stone Below Chambers - 6 in Click to Define Top and/or Bottom of storage Click to Define Target Volume & Reference Elevation Area of system - 8446 sf Min. Area - Height of System Incremental Single Chamber Incremental Total Chamber Incremental Stone Incremental Ch & St Cumulative Chamber Elevation Depth Elevation Area Area (inches)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(cubic feet)(feet)(feet)(feet)(ft²)(acres)Toggle Printout 28 0.00 0.00 281.53 281.53 9737.52 5036.83 0.00 5034.50 3378.40 0.0776 Top of Storage Elevation 27 0.00 0.00 281.53 281.53 9455.98 5036.75 0.08 5034.58 3378.40 0.0776 Volume above Top of Storage Elevation 9737.52 26 0.00 0.00 281.53 281.53 9174.45 5036.67 0.17 5034.67 3378.40 0.0776 Volume below Top of Storage Elevation 0.00 25 0.00 0.00 281.53 281.53 8892.92 5036.58 0.25 5034.75 3378.40 0.0776 24 0.00 0.00 281.53 281.53 8611.38 5036.50 0.33 5034.83 3378.40 0.0776 Volume between Top and Bottom of Storage 23 0.00 0.00 281.53 281.53 8329.85 5036.42 0.42 5034.92 3378.40 0.0776 22 0.00 0.00 281.53 281.53 8048.32 5036.33 0.50 5035.00 3378.40 0.0776 Volume above elevation = 9737.52 Bottom of Storage Elevation 21 0.00 0.00 281.53 281.53 7766.78 5036.25 0.58 5035.08 6283.52 0.1442 Volume below elevation = 0 Volume above Bottom of Storage 9737.52 20 0.00 0.00 281.53 281.53 7485.25 5036.17 0.67 5035.17 6172.13 0.1417 Volume between elevations and = Volume below Bottom of Storage 0.00 19 0.00 0.00 281.53 281.53 7203.72 5036.08 0.75 5035.25 6057.04 0.1391 Volume above elevation = 9737.52 18 0.05 23.10 272.29 295.39 6922.18 5036.00 0.83 5035.33 5922.26 0.1360 Volume below elevation = 0 17 0.13 60.63 257.28 317.91 6626.79 5035.92 0.92 5035.42 5767.95 0.1324 Target Volume achieved at Elevation 5036.8 Toggle Printout 16 0.29 131.05 229.11 360.17 6308.88 5035.83 1.00 5035.50 5588.92 0.1283 Target Volume achieved at Elevation Target Volume 9625.18 15 0.44 199.31 201.81 401.12 5948.72 5035.75 1.08 5035.58 5379.77 0.1235 Reference Elevation 5034.50 14 0.54 243.16 184.27 427.43 5547.60 5035.67 1.17 5035.67 5129.16 0.1177 Volume below Reference Elevation 0.00 13 0.62 277.97 170.35 448.31 5120.17 5035.58 1.25 5035.75 4813.42 0.1105 Target Volume + Volume Below Reference Elevation 9625.18 12 0.68 307.02 158.73 465.74 4671.85 5035.50 1.33 5035.83 4321.99 0.0992 Target Volume achieved at Elevation 5036.80 11 0.74 331.88 148.78 480.66 4206.11 5035.42 1.42 5035.92 3814.90 0.0876 (Optional) Apply % Credit toward Target Volume 10 0.78 353.31 140.21 493.52 3725.45 5035.33 1.50 5036.00 3544.72 0.0814 % Credited toward Target Volume below Reference Elevation 100% 9 0.82 372.03 132.72 504.75 3231.92 5035.25 1.58 5036.08 3378.40 0.0776 Volume Credited below Reference Elevation 0 8 0.86 388.02 126.33 514.34 2727.17 5035.17 1.67 5036.17 3378.40 0.0776 Volume Discredited below Reference Elevation 0 7 0.89 403.49 120.14 523.63 2212.83 5035.08 1.75 5036.25 3378.40 0.0776 0 6 0.00 0.00 281.53 281.53 1689.20 5035.00 1.83 5036.33 3378.40 0.0776 % Credited toward Target Volume above Reference Elevation 50% 5 0.00 0.00 281.53 281.53 1407.67 5034.92 1.92 5036.42 3378.40 0.0776 Volume Credited above Reference Elevation 9625.18 4 0.00 0.00 281.53 281.53 1126.13 5034.83 2.00 5036.50 3378.40 0.0776 Volume Discredited above Reference Elevation 9625.18 3 0.00 0.00 281.53 281.53 844.60 5034.75 2.08 5036.58 3378.40 0.0776 19250.36 2 0.00 0.00 281.53 281.53 563.07 5034.67 2.17 5036.67 3378.40 0.0776 Target Volume achieved at Elevation 1 0.00 0.00 281.53 281.53 281.53 5034.58 2.25 5036.75 3378.40 0.0776 Remaining Volume above = -9512.84 2.33 5036.83 3378.40 0.0776 VOA - Switchgrass Crossing 6687 sf min. area NOTE: If the software program being used allows for Stage Volume data, it is recommended to use the stage volume data from this spreadsheet. Software programs typically use linear interpolation to take stage area data and estimate stage volume data. Due to rounding differences over the total number of stages provided in this spreadsheet, the accuracy of the estimated volume could be off as much as 1%. It is recommended that the user check the software estimated volume and compare it to the volume listed in this spreadsheet to ensure the accuracy is within acceptable levels. Stage Area DataStormTech SC-160LP Cumulative Storage Volumes Include Perimeter Stone in Calculations Click Here for Metric Click for Stage Area Data Click to Invert Stage Area Data Click for WWHM Stage Data WQCV (cu ft) WQ Depth (ft) 100 yr Vol (cu ft) 100 yr Depth (ft) 100 yr Outflow (cfs) 2430.45 0.62 9625.18 2.30 4.11 Orifice Discharge Calculations: Q=Cd*A*(2*g*h)^.5 with Cd=0.6 Q (CFS) A (SF) H (FT) 4.1096 0.6752 1.5979 aka 2 (5/8)" above pipe invert *Invert of pipe .1' below bottom of system aka 2.4' to 100yr WSEL Water Quality Volume Table 2-Year Layout A02.1 7 A02.6 A02.5 2-Year Hydraulic Summary A0 1 OU T F A L L A0 2 A0 2 . 2 A0 2 . 1 A0 3 STORM LINE A HYD PROFILE - 2YR OU T F A L L A0 1 A0 2 . 1 A0 2 . 2 A0 2 . 3 A0 2 . 4 A0 2 . 5 A0 2 . 6 ROOF DRAIN HYD PROFILE - 2YR OU T F A L L A0 1 . 1 STORM LINE A01.1 HYD PROFILE - 2YR 100-Year Layout A02.1 9 A02.6 A02.5 C01 Outfall A01.1 100-Year Hydraulic Summary A0 1 OU T F A L L A0 2 A0 2 . 2 A0 2 . 1 A0 3 STORM LINE A HYD PROFILE - 100YR OU T F A L L A0 1 A0 2 . 1 A0 2 . 2 A0 2 . 3 A0 2 . 4 A0 2 . 5 A0 2 . 6 ROOF DRAIN HYD PROFILE - 100YR OU T F A L L A0 1 . 1 STORM LINE A01.1 HYD PROFILE - 100YR OU T F A L L C0 1 C0 2 C0 3 STORM LINE C HYD PROFILE - 100YR OU T F A L L B0 2 EX - B 0 1 STORM LINE B HYD PROFILE - 100YR BBBBB B B B B B B B B SSSS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS E EE E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO W W W W W W W W W W W W W W W W W W W W W SANITARY MH RIM=5038.02 8" PVC INV S=5032.52 10" PVC INV N=5032.32 SANITARY MH RIM=5039.00 10" PVC INV S=5031.85 10" PVC INV N=5031.70 STORM INLET TOG=5036.90 12" PVC INV N=5035.10 12" PVC INV W=5035.10 STORM MH ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST STST ST ST STORM MH RIM=5038.87 15" RCP INV E=5035.02 18" RCP INV S=5034.17 18" RCP INV NE=5034.17 ST STORM MH RIM=5038.85 18" RCP INV S=5034.45 12" RCP INV W=5034.65 18" RCP INV N=5034.45 STORM INLET TOG=5035.93 15" RCP INV W=5034.45 ST UTILITY CABINET TRANSFORMER GENERATOR UTILITY VAULT UTILITY VAULT UTILITY VAULT ST ST ST SS SS AA 2 3 4 5 6 BB CC EE II KK DD JJ HH 1 GG A1A1 FF 4.1 LOADING FDC VAN T WWW WWW WWW SS SS ST ST ST ST ST ST ST ST STST 50 3 8 503 9 503 9 5038 5038 5039 503 9 50 4 0 504 1 503 8 50 3 9 50 3 9 50 4 0 50 3 8 50 3 9 50 4 0 50 3 9 50 3 8 50 3 9 50 4 0 50 3 7 503 7 50 3 8 50 3 9 50 4 1 50 4 0 50 3 8 50 3 9 50 4 1 50 4 2 LOT 2 MORELAND SUBDIVISION (PLAT - REC. NO. 91030712) OWNER: D AND M AUTOMOTIVE LOT 1 CREGER 3RD REPLAT (PLAT - REC. NO. 20190044858) OWNER: MASON PLACE LLLP LOT 1 PLAT OF MASON STREET PUD (PLAT - REC. NO. 520208) OWNER: RCA MASON LLC BUILDING FFE: 5039.50 BUILDING FFE: 5039.50 ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST 50 3 9 DETENTION VAULT STV-A REQUIRED WQ VOLUME: 2430 CF REQUIRED FAA VOLUME: 9625 CF PROVIDED VOLUME: 9737 CF TREATMENT AREA: 95,188 SF 4' CONCRETE PAN SS W W STORM MH W ST ST ST ST ST fi l e p a t h : C: \ U s e r s \ k a t h r y n \ D C \ A C C D o c s \ S h o p w o r k s A r c h i t e c t u r e \ 2 4 0 4 6 V O A F o r t C o l l i n s M a s o n S t - \ P r o j e c t F i l e s \ C i v i l \ S h e e t s \ C o n s t r u c t i o n D o c u m e n t s \ 2 4 0 4 6 _ L I D P l a n . d w g N 40'0 SCALE: 1" = 20' 20' NOTES 1.ALL STORM INFRASTRUCTURE SHOWN IS PRIVATE UNLESS OTHERWISE NOTED AND WILL BE MAINTAINED BY THE PROPERTY OWNER - VOLUNTEERS OF AMERICA. STORM INFRASTRUCTURE HAS BEEN DESIGNED TO ACCOMMODATE THE 100 YEAR STORM DRAINAGE PLAN LEGEND BOUNDARY LINE EXISTING CURB AND GUTTER EXISTING STORM LINE EXISTING STORM MANHOLE EXISTING STORM INLET EXISTING MINOR CONTOUR EXISTING MAJOR CONTOUR PROPOSED CURB AND GUTTER PROPOSED SIDEWALK PROPOSED STORM LINE PROPOSED STORM MANHOLE PROPOSED STORM INLET PROPOSED MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPOSED RETAINING WALL LID TREATMENT BOUNDARY 5281 5280 5281 5280 ST ST 1 PROJECT #: DRAWN: REV: SCALE: NO. SHEET TITLE: REVIEWED: DATE: FILE: 12345 A B C D A B C D 12345 TS CONSTRUCTION DOCS LID PLAN LID TS 24046 10/29/2025 SW I T C H G R A S S C R O S S I N G 38 0 0 S O U T H M A S O N ST -------- ---- -------- FO R T C O L L I N S , C O 8 0 5 2 5 24046_LID Plan REF PLAN ----2 3 MATCHLINE THIS SHEET MATCHLINE THIS SHEET Page 15 of 15 301 West 45th Avenue, Denver, CO 80216 303 433-4094 Appendix D Drainage Map SS SS SS SS SS SS SS SS SS SS SS SS SS EEEE E E E E E E E E E E E E E E E E E E E E E E E E E E EE E E E E E E E E E EE E E E E E E E E E E E FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO FO W W W W W W W W W W W W W W ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST W ST ST ST SS SS SS ST ST ST 5037 50 3 7 50 3 8 5038 50 3 8 50 3 8 50 3 9 50 3 9 50 3 9 5037 503 7 503 7 50 3 7 503 7 50 3 7 50 3 7 50 3 7 50 3 8 50 3 8 50 3 8 50 3 8 50 3 8 50 3 8 50 3 8 50 3 8 503 8 50 3 8 50 3 8 50 3 8 503850 3 8 503 9 503 9 50 3 9 50 3 9 50 3 9 5039503 9 50 3 9 50 3 9 50 3 9 5037 5038 5039 5040 5041 5037 5037503750385038 5038503850395039 503950395040504050405040504150415041 5041 504150415042 504250425042 50 3 9 50 4 0 50 4 1 503 9 50 3 9 50 3 9 50 4 0 50 4 0 50 4 0 50 4 0 50 4 1 50 4 1 50 4 1 50 4 1 50 4 2 50 4 2 5043 5042 5043 5043 5043 5043 5044 50 3 8 50 3 8 50 3 8 50 3 8 50 3 8 SS SS SS SS SS SS SS SS SS SS SS 0.69 AC EXA EXA1 0.84 1.00 1.50 AC EXB 0.85 1.00 -0.7 4 % -1.58% -0. 5 4 % -1.0 6 % -1.04% -3.28% -8.13% EXB1 1.81 AC EXC 0.95 1.00 OFFSITE STORMWATER FLOWS FROM EASTERN PARKING LOT - ASSUMED FULL FLOW FOR PIPE 1.40 CFS W W ST ST ST ST N 0 30'60' SCALE: 1" = 30' EXISTING DRAINAGE PLAN LEGEND BOUNDARY LINE EXISTING CURB AND GUTTER EXISTING STORM LINE EXISTING STORM MANHOLE EXISTING STORM INLET EXISTING MINOR CONTOUR EXISTING MAJOR CONTOUR BASIN DELINEATION FLOW ARROW BASIN LABEL DESIGN POINT LABEL 5281 5280 ST XX XX XX XX BASIN ID AREA 2 YR C-VALUE XX 100 YR C-VALUE 1 PROJECT #: DRAWN: REV: SCALE: NO. SHEET TITLE: REVIEWED: DATE: FILE: 12345 A B C D A B C D 12345 TS CONSTRUCTION DOCS EX DRAINAGE PLAN DR1 TS 24046 10/29/2025 SW I T C H G R A S S C R O S S I N G 38 0 0 S O U T H M A S O N ST -------- ---- -------- FO R T C O L L I N S , C O 8 0 5 2 5 24046_Existing Drainage Plan REF PLAN ----2 3 NOTES 1.UNDEVELOPED CONDITIONS SHOWN IN RUNOFF SUMMARY TABLE FOR REFERENCE. ALL VALUES IN EXISTING DRAINAGE PLAN ARE EXISTING CONDITIONS. MATCHLINE THIS SHEET MATCHLINE THIS SHEET BBBBB B B B B B B B B SSSS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST ST STSTST ST ST ST STST ST ST SS SS AA 2 3 4 5 6 BB CC EE II KK DD JJ HH 1 GG A1A1 FF 4.1 LOADING FDC VAN SS SS ST ST ST ST ST 50 3 8 503 9 503 9 5038 5038 5039 503 9 50 4 0 504 1 503 8 50 3 9 50 3 9 50 4 0 50 3 8 50 3 9 50 3 9 50 3 8 50 3 9 50 4 0 50 3 7 503 7 50 3 8 50 3 9 50 4 1 50 4 0 50 3 8 50 3 9 50 4 1 50 4 2 LOT 2 MORELAND SUBDIVISION (PLAT - REC. NO. 91030712) OWNER: D AND M AUTOMOTIVE LOT 1 CREGER 3RD REPLAT (PLAT - REC. NO. 20190044858) OWNER: MASON PLACE LLLP LOT 1 PLAT OF MASON STREET PUD (PLAT - REC. NO. 520208) OWNER: RCA MASON LLC BUILDING FFE: 5039.50 BUILDING FFE: 5039.50 50 3 9 EMERGENCY OVERFLOW SPILLWAY ELEV 5037.19 WSEL 5037.00 0.17 AC A1 0.08 AC RA1 1 R1 0.20 AC RA2 0.73 AC A2 0.61 0.77 0.07 AC OS1 R2 0.95 1.00 0.95 1.00 0.80 1.00 0.37 0.47 2 0.23 AC A3 0.74 0.92 3 DETENTION VAULT STV-A (DETENTION AND WATER QUALITY) 4' CONCRETE PAN OFFSITE STORMWATER FLOWS OFFSITE STORMWATER FLOWS OFFSITE STORMWATER FLOWS OFFSITE STORMWATER FLOWS OFFSITE STORMWATER FLOWS OFFSITE STORMWATER FLOWS FROM EASTERN PARKING LOT - FULL FLOW FOR PIPE 1.40 CFS PER CREGER PLAZA SOUTH PDR CF1 2' CONCRETE CHASE 100-YR FLOW PATH FROM BASIN A1 fi l e p a t h : C: \ U s e r s \ k a t h r y n \ D C \ A C C D o c s \ S h o p w o r k s A r c h i t e c t u r e \ 2 4 0 4 6 V O A F o r t C o l l i n s M a s o n S t - \ P r o j e c t F i l e s \ C i v i l \ S h e e t s \ C o n s t r u c t i o n D o c u m e n t s \ 2 4 0 4 6 _ D r a i n a g e P l a n . d w g N 40'0 SCALE: 1" = 20' 20' NOTES 1.ALL STORM INFRASTRUCTURE SHOWN IS PRIVATE UNLESS OTHERWISE NOTED AND WILL BE MAINTAINED BY THE PROPERTY OWNER - VOLUNTEERS OF AMERICA. STORM INFRASTRUCTURE HAS BEEN DESIGNED TO ACCOMMODATE THE 100 YEAR STORM 2.BENCHMARK: PROJECT DATUM: NAVD88 BENCHMARK: CITY OF FORT COLLINS BM 'VIRATA”- 2” ALUMINUM CAP STAMPED “CITY OF FORT COLLINS BENCHMARK VRATA” FOUND AT THE NORTHWEST CORNER OF COLLEGE AVE., AND HORSETOOTH ROAD ON THE BACK OF WALK AT THE EAST END OF THE PARAPET WALL OF THE BRIDGE OVER CANAL NO. 2. ELEVATION: 5034.31 PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM. SURROUNDING DEVELOPMENTS HAVE USED NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) FOR THEIR VERTICAL DATUMS. IF NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) IS REQUIRED FOR ANY PURPOSE, THE FOLLOWING EQUATION SHOULD BE USED: NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) = NAVD88 DATUM 5031.12’. DRAINAGE PLAN LEGEND BOUNDARY LINE EXISTING CURB AND GUTTER EXISTING STORM LINE EXISTING STORM MANHOLE EXISTING STORM INLET EXISTING MINOR CONTOUR EXISTING MAJOR CONTOUR PROPOSED CURB AND GUTTER PROPOSED SIDEWALK PROPOSED STORM LINE PROPOSED STORM MANHOLE PROPOSED STORM INLET PROPOSED MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPOSED RETAINING WALL BASIN DELINEATION FLOW ARROW BASIN LABEL DESIGN POINT LABEL 5281 5280 5281 5280 ST ST XX XX XX XX BASIN ID AREA 2 YR C-VALUE XX 100 YR C-VALUE 1 PROJECT #: DRAWN: REV: SCALE: NO. SHEET TITLE: REVIEWED: DATE: FILE: 12345 A B C D A B C D 12345 TS CONSTRUCTION DOCS DRAINAGE PLAN DR2 TS 24046 10/29/2025 SW I T C H G R A S S C R O S S I N G 38 0 0 S O U T H M A S O N ST -------- ---- -------- FO R T C O L L I N S , C O 8 0 5 2 5 24046_Drainage Plan REF PLAN ----2 3