The URL can be used to link to this page

Home My WebLink AboutBELLA VIRA FILING 2 - MJA/FDP - FDP140001 - REPORTS - DRAINAGE REPORT1501 Academy Ct. Ste. 203 Fort Collins, Colorado 80524 (970) 530-4044 Final Drainage Addendum Bella Vira SSSSuuuubbbbddddiiiivvvviiiissssiiiioooonnnn Filing TTTTwwwwoooo FortCollins Fort Collins, , CO Prepared for: Bella Vira Town Homes Inc. 1313 Fairway Five Drive Fort Collins, CO 80525 February 12, 2014 Drainage Addendum Bella Vira Subdivision Filing Two Fort Collins, CO 1 U13012-DrainageAddendum-Final.doc February 12, 2014 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Bella Vira Subdivision Filing Two Fort Collins, Colorado Project Number: U13012 Dear Staff: United Civil Design Group, LLC. is pleased to submit this Final Drainage Addendum for the Bella Vira Subdivision Filing Two site in Fort Collins, Colorado. In general, this summary serves to document the stormwater impacts associated with the proposed project and to verify that the project does conform to the intent and requirements set forth in the approved final drainage report prepared by Jim Sell Design (JSD) entitled “Final Drainage and Erosion Control Report for Bella Vira”, and dated December 21, 2007. Site Location and Project Description The Bella Vira Subdivision Filing Two development site (referred herein as ”the site”) is located in Fort Collins and is described as Lot 1 within Bella Vira Subdivision Filing Two located within the south half of Section 17, Township 7 North, Range 69 West of the Sixth P.M., City of Fort Collins, Larimer County, Colorado. The site has a platted area of 3.47 acres and is bounded by Overland Trail to the east, West Elizabeth Street (currently under construction) to the north, and The Ponds at Overland Trail Second Filing to the west and south. See the attached Drainage Plan for additional information. The planned development for the site will consist of the following: • The construction of six (6) single family attached buildings with twenty-five (25) units. • The construction of a private drive and parking stalls in support of the building construction. • The construction of utilities to support the proposed buildings including sanitary, water and storm drainage. Existing Conditions Hydrology The site, which is located within the Canal Importation Basin, currently exists mainly as agricultural farm land and is currently covered with grasses and weeds. Storm runoff Drainage Addendum Bella Vira Subdivision Filing Two Fort Collins, CO 2 U13012-DrainageAddendum-Final.doc from the site currently drains towards the south and west to an existing City regional detention pond located within Tract C of the Bella Vira Subdivision just west of the site. Floodplain A small portion of the southern site is located within a City-regulatory moderate risk floodway adjacent to the Pleasant Valley and Lake Canal. No improvements are being proposed within this area. Detention The City regional detention pond located within Tract C of Bella Vira Subdivision just west of the site provides both detention and water quality for the site. Developed Conditions In part, the intent of this Drainage Addendum is to verify that the Filing Two project conforms to the intent and requirements set forth in the JSD Final Drainage Report for this site. As such, the following sections of this Addendum compare the proposed design for Filing Two to the design as shown in aforementioned report. Hydrology Basin A as shown in the attached Drainage Plan collects the vast majority of the developed flows from the site and routes them via swales and storm sewer to the City regional pond west of the site. Basin A largely corresponds to Basins 20-21b, 25-27, and 29 as were shown in the approved JSD report. A summary of the results of the analysis of Basin A as compared to the JSD basins is as follows: Comparison Summary Table Basin A JSD Basins Overall Area (acres) 3.16 3.54 Impervious Area (acres) 1.75 2.08 Q2 (cfs) 5.67 6.07 Q100 (cfs) 24.21 26.87 As shown in the above table, the proposed improvements for Filing Two of Bella Vira result in lower overall and impervious areas and resulting flowrates from those shown in the approved JSD report. Therefore, the proposed Filing Two improvements appear to meet the intent and requirements set forth in the original JSD report and it is anticipated that the Filing Two improvements will not have a negative impact to the downstream improvements as designed by JSD. Drainage Addendum Bella Vira Subdivision Filing Two Fort Collins, CO 3 U13012-DrainageAddendum-Final.doc Storm Sewer Storm Sewer Line 1 is located in the center of the proposed development and collects water from Basins A1 and A4-A6. In order to eliminate as much surface water as possible through Basin A5, several downspouts within Basin A6 are being collected and piped directly into the storm drain. Due to the collection of some roof areas, the minor flows that are to be collected, and the desire to eliminate as much surface flow through Basin A1 due to erosion concerns, Storm Line 1 has been designed to convey the 100- year flows away from the site and into the downstream pond. Detention and Water Quality Requirements As previously mentioned, the site is provided with detention and water quality from the City regional pond just west of the site. With the Filing Two improvements not exceeding those assumed during the design of the regional facility, no further detention or water quality improvements are required with Filing Two. Low Impact Development (LID) Requirements In February of 2013, City Council adopted the LID policy and criteria. Filing Two of Bella Vira is required to meet the newly adopted criteria. Per the criteria, the site must: • Treat no less than 50% of any newly added impervious area using one or a combination of LID techniques. • Treat no less than 25% of any newly added pavement area using a permeable pavement. In communication with City personnel, this site, as it was originally approved prior to the LID requirements, will not be required to provide the permeable pavement if the development proposes to treat more than 50% of the newly added impervious area. For this development, Basin A contains all the impervious area associated with the project which totals 1.75 acres. In order to accommodate the above mentioned requirement, the development is proposing to treat the newly added impervious area as follows: • The upstream basins of A4-A6 (totaling 1.31 acres of impervious area) will be treated with a series of grass lined swales prior to entering the storm drain system. Once in the storm drain system, the entirety of the impervious area within said basins will be treated within Inlet 1-2 using a Snout BMP along with an associated bioskirt. Upon exiting the storm drain runoff will then be directed to a level spreader with bioretention sand media to further treat stormwater and promote groundwater infiltration. Refer to the Drainage Plan and Construction Documents for additional information. • Basin A2 (with 0.22 acres of impervious area) will be treated with a grass line swale prior to entering a bioswale with underdrain proposed at the downstream end of the basin. This bioswale (which has total length of 135- feet) will treat the entirety of the impervious area within the basin prior to directing the runoff to the downstream pond. Drainage Addendum Bella Vira Subdivision Filing Two Fort Collins, CO 4 U13012-DrainageAddendum-Final.doc In total, the development is proposing to collect and treat 1.53 acres of the newly added impervious area using a series of LID techniques. The percentage of the impervious area within the site being treated with LID techniques totals 87%. Due to the percentage of the site that is proposed to be treated, and based upon communication with City personnel, the development team is proposing to not provide any pervious pavement with Filing Two of this project. Four Step Process With the adoption of the USDCM, the City has also adopted the “Four Step Process” that is recommended in Volume 3 of the USDCM in selecting structural BMPs for the redeveloping urban areas. The following portions of this addendum describe each step and how it has been utilized for this project: Step 1 – Employ Runoff Reduction Practices The objective of this step is to reduce runoff peaks and volumes and to employ the technique of “minimizing directly connected impervious areas” (MDCIA). This project accomplishes this by: • Providing grass buffers throughout the site between impervious areas to minimize directly connected impervious areas. • Routing flows through a series of vegetated swales to increase time of concentration, promote infiltration and provide initial water quality. • Routing a portion of the site through a bioswale to promote infiltration and provide additional water quality. Step 2 – Provide Water Quality Capture Volume (WQCV) The objective of providing WQCV is to reduce the sediment load and other pollutants that exit the site. For this project WQCV is provided within the regional pond located west of the site, so no additional WQCV is required. Step 3 – Stabilize Drainageways The site is adjacent to the Pleasant Valley and Lake Canal. The project is not directly stabilizing this manmade drainageway; however, the project is indirectly maintaining the existing stability of the drainageway by directing the vast majority of onsite flows away from the canal and to the existing regional pond west of the site. Additionally, this project will pay stormwater development and stormwater utility fees which the City uses, in part, to maintain the stability of the City drainageway systems. Step 4 – Consider Need for Industrial and Commercial BMPs This step is generally considered for industrial and commercial sites. As this development is proposing single family attached dwellings only, no specialized BMPs have been considered for this project. Drainage Addendum Bella Vira Subdivision Filing Two Fort Collins, CO 5 U13012-DrainageAddendum-Final.doc Standard Operating Procedures (SOPs) In order for physical stormwater Best Management Practices (BMPs) to be effective, proper maintenance is essential. Maintenance includes both routinely scheduled activities, as well as non-routine repairs that may be required after large storms, or as a result of other unforeseen problems. Standard Operating Procedures should clearly identify BMP maintenance responsibility. BMP maintenance is typically the responsibility of the entity owning the BMP. Identifying who is responsible for maintenance of BMPs and ensuring that an adequate budget is allocated for maintenance is critical to the long-term success of BMPs. Maintenance responsibility may be assigned either publicly or privately. For this project, the privately owned BMPs shown in Appendix C of this Addendum are to be maintained by the property owner, homeowner’s association (HOA), or property manager. Conclusions In conclusion, the drainage system proposed within this Drainage Addendum provides adequate conveyance of the developed stormwater runoff from the proposed development to existing discharge locations and drainage systems. In addition, the calculations provided show that the proposed drainage system does meet the intent and requirements set forth in the original JSD Final Drainage Report. It should also be noted that with this addendum and the corresponding design, every attempt has been made to minimize any negative impacts on the downstream receiving waters. With the incorporation of the LID techniques throughout the development, the site will discharge a lower sediment load and less runoff than the design originally proposed with the Bella Vira Subdivision project. We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria contained in the Fort Collins Stormwater Criteria Manual (FCSCM). This addendum was prepared in compliance with technical criteria set forth in both the Urban Drainage and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual and the FCSCM. If you should have any questions or comments as you review this drainage summary, please feel free to contact us at your convenience. Sincerely, United Civil Design Group, LLC Kevin Brazelton, PE Engineering Manager APPENDIX A Hydrology Calculations Bella Vira Filing 2 Fort Collins, CO Runoff Summary Area Q2 Q100 (acre) (cfs) (cfs) A1 A1 0.28 27% 0.45 0.57 0.35 1.55 A2 A2 0.60 35% 0.51 0.64 0.87 3.82 A3 A3 0.46 29% 0.46 0.58 0.60 2.62 A4 A4 0.78 80% 0.86 1.00 1.90 7.73 A5 A5 0.64 69% 0.77 0.96 1.39 6.07 A6 A6 0.32 47% 0.60 0.76 0.56 2.42 OS1 OS1 0.27 2% 0.25 0.31 0.16 0.68 OS2 OS2 0.10 2% 0.25 0.31 0.06 0.27 Onsite Total 3.44 47% 0.61 0.76 5.67 24.21 19 19 0.35 78% 0.82 1.00 0.82 3.52 23 23 0.06 82% 0.84 1.00 0.15 0.63 Proposed Basins -Filing 2 Modified Phase 1 Basins C100 C2 Basin Design Point %I Calculations by: KRB Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx Bella Vira Filing 2 Fort Collins, CO Runoff Coefficients and % Impervious Roof (1) Concrete(1) Asphalt(1) Landscape(1) %I = 90% %I = 90% %I =100% %I=2% C = 0.95 C = 0.95 C = 0.95 C = 0.25 acres sf sf sf sf sf C2 C100 Proposed Basins -Filing 2 A1 A1 0.275 11993 3354 107 0 8532 27% 0.45 0.57 A2 A2 0.599 26113 9764 4 0 16345 35% 0.51 0.64 A3 A3 0.455 19839 6023 0 0 13816 29% 0.46 0.58 A4 A4 0.777 33850 12253 11276 5807 4514 80% 0.86 1.00 A5 A5 0.637 27743 8057 6773 5630 7283 69% 0.77 0.96 A6 A6 0.322 14038 7028 86 0 6924 47% 0.60 0.76 OS1 OS1 0.270 11750 0 0 0 11750 2% 0.25 0.31 OS2 OS2 0.104 4523 0 0 0 4523 2% 0.25 0.31 Onsite Total 3.440 149849 46479 18246 11437 73687 47% 0.61 0.76 Modified Phase 1 Basins 19 19 0.354 15403 0 4961 7501 2941 78% 0.82 1.00 23 23 0.064 2776 0 557 1766 453 82% 0.84 1.00 Notes: (1) Recommended % Imperviousness Values from USDCM Vol 1 - Ch 5 - Table RO-3. Increased Lawns from 0% to 2% Impervious. (2) Runoff C2 is based on UDFCD Eq RO-8 per City Amendment to Chapter 5. Runoff C100 is based upon Table RO-12 per City Amendment to Chapter 5. Composite Runoff Basin Coefficients (2) Areas Composite Imperviousness (%I) Total Total Design Pt. Calculations by: KRB Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx Bella Vira Filing 2 Fort Collins, CO Time of Concentration Area Length Slope ti (2) Length Slope Velocity (3) t t (4) Check tc? Total Length tc (5) acres ft % min ft % fps min min u = urban ft min min Proposed Basins -Filing 2 A1 A1 0.28 Roof 0.73 15 2 2.1 90 12 20 6.9 0.2 2.3 u 105 11 5 A2 A2 0.60 Roof 0.73 20 2 2.4 560 3.5 20 3.7 2.5 4.9 u 580 13 5 A3 A3 0.46 Roof 0.73 20 2 2.4 85 11.5 20 6.8 0.2 2.6 u 105 11 5 A4 A4 0.78 Walk 0.73 35 5.6 2.2 335 2.9 20 3.4 1.6 3.9 u 370 12 5 A5 A5 0.64 Roof 0.73 25 2 2.6 305 3.5 20 3.7 1.4 4.0 u 330 12 5 A6 A6 0.32 Roof 0.73 25 2 2.6 110 1.5 20 2.4 0.7 3.4 u 135 11 5 OS1 OS1 0.27 Lawn 0.09 55 4 8.5 10 2 20 2.8 0.1 8.6 u 65 10 9 OS2 OS2 0.10 Lawn 0.09 80 11 7.4 30 2.5 20 3.2 0.2 7.5 u 110 11 8 Modified Phase 1 Basins 19 19 0.35 Street 0.90 10 2 0.9 130 1.7 20 2.6 0.8 1.7 u 140 11 5 23 23 0.06 Street 0.90 35 2 1.7 60 3.5 20 3.7 0.3 2.0 u 95 11 5 Notes: (1) C5 based initial ground type and Table RO-5 (4) tt =L/(V*60 sec/min) (2) ti = [1.8(1.1-C5 )L 1/2 ]/S 1/3 , S= slope in %, L=length of overland flow (400' max) (5) tc check (for urban or developed areas only) = total length/180 + 10 (3) V=Cv S 0.5 , S=watercourse slope in ft/ft, UDFCD Equation RO-4 (6) min tc = 5 min Initial Ground Type C5 Bella Vira Filing 2 Fort Collins, CO Rational Method Peak Runoff Final tc (6) I2 I100 Q2 Q100 sf min in/hr in/hr cfs cfs Proposed Basins -Filing 2 A1 A1 11,993 5 0.45 0.57 2.85 9.95 0.355 1.548 A2 A2 26,113 5 0.51 0.64 2.85 9.95 0.875 3.816 A3 A3 19,839 5 0.46 0.58 2.85 9.95 0.600 2.620 A4 A4 33,850 5 0.86 1.00 2.85 9.95 1.897 7.732 A5 A5 27,743 5 0.77 0.96 2.85 9.95 1.391 6.070 A6 A6 14,038 5 0.60 0.76 2.85 9.95 0.555 2.424 OS1 OS1 11,750 9 0.25 0.31 2.30 8.03 0.155 0.677 OS2 OS2 4,523 8 0.25 0.31 2.40 8.38 0.062 0.272 Onsite Total 149,849 5.673 24.210 Modified Phase 1 Basins 19 19 15,403 5 0.82 1.00 2.85 9.95 0.823 3.518 23 23 2,776 5 0.84 1.00 2.85 9.95 0.152 0.634 0.975 4.153 Design Pt. Peak Discharge Area Basin Runoff Coefficients Rainfall Intensity C2 C100 Calculations by: KRB Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx APPENDIX B Hydraulic Calculations Project = Inlet ID = Design Information (Input) Length of a Unit Inlet Lu = 10.00 ft Local Depression, if any (not part of upstream Composite Gutter) alocal = 3.00 inches Height of Curb Opening in Inches H = 6.00 inches Side Width for Depression Pan Wp = 3.00 ft Clogging Factor for a Single Unit (typical value = 0.1) Co = 0.20 Angle of Throat (see USDCM Figure ST-5) Theta = 63.4 degrees Orifice Coefficient (see USDCM Table ST-7) Cd = 0.67 Weir Coefficient (see USDCM Table ST-7) Cw = 3.00 Total Number of Units in the Curb Opening Inlet No = 1 Curb Opening Inlet Capacity in a Sump As a Weir Design Discharge on the Street (from Street Hy ) Qo = 7.4 cfs Water Depth for the Design Condition Yd = 8.37 inches Total Length of Curb Opening Inlet L = 10.00 ft Capacity as a Weir without Clogging Qwi = 26.9 cfs Clogging Coefficient for Multiple Units Coef = 1.00 Clogging Factor for Multiple Units Clog = 0.20 Capacity as a Weir with Clogging Qwa = 23.4 cfs As an Orifice Capacity as an Orifice without Clogging Qoi = 18.5 cfs Capacity as an Orifice with Clogging Qoa = 14.8 cfs Capacity for Design with Clogging Qa = 14.8 cfs Capture Percentage for this Inlet = Qa / Qo = C% = 100.00 % Note: Unless additional ponding depth or spilling over the curb is acceptable, a capture percentage of less than 100% in a sump may indicate the need for additional inlet units. CURB OPENING INLET IN A SUMP Bella Vira - Filing 2 Inlet 1-2 Storm Inlet 1-1.xls, Curb-S 12/19/2013, 2:02 PM Bella Vira - Filing 2 Fort Collins, CO Area Inlet Capacity INLET ID: Inlet 1-7 (Basin A6) Governing Equations: Inlet capacity equation at low flows (weir calculation): Where: P = 2(L + W) H = depth of water above the flowline Inlet capacity equation at higher flows (orifice calculation): Where: A = open area of the inlet grate H = depth of water above the centroid of the cross-sectional area (A) Input Parameters: Grate: 15" Nyloplast (1599CGD) Wier Perimeter: 3.93 Open Area of Grate (ft 2 ): 0.80 Q2 = 0.56 cfs Flowline Elevation (ft): 5127.62 Q100 = 2.42 cfs Allowable Capacity: 50% Depth vs. Flow: Depth Above Inlet (ft) Elevation (ft) Shallow Weir Flow (cfs) Orifice Flow (cfs) Actual Flow (cfs) 0.00 5127.62 0.00 0.00 0.00 0.10 5127.72 0.19 0.68 0.19 0.21 5127.83 0.56 0.98 0.56 Q2 0.10 5127.72 0.19 0.68 0.19 0.30 5127.92 0.97 1.18 0.97 0.40 5128.02 1.49 1.36 1.36 0.50 5128.12 2.08 1.52 1.52 0.60 5128.22 2.74 1.67 1.67 0.70 5128.32 3.45 1.80 1.80 0.80 5128.42 4.22 1.93 1.93 0.90 5128.52 5.03 2.04 2.04 Q = 3 . 0 P H 1 . 5 Q = 0 . 67 A ( 2 gH ) 0 . 5 Calculations by: KRB Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Inlets\U13012-Area Inlets.xlsx Bella Vira-Filing 2 Fort Collins, CO Riprap Sizing at Pipe Outlets Circular D or Da, Pipe Diameter (ft) H or Ha, Culvert Height (ft) W, Culvert Width (ft) Yt/D Q/D1.5 Q/D2.5 Yt/H Q/WH0.5 Storm Line 1 Outlet 16.23 1.50 0.60 0.40 8.83 5.89 N/A N/A 1.80 5.89 3.25 7.04 Type L 10.00 7.50 1.5 Circular Pipe (Figure MD-21) Rectangular Pipe (Figure MD-22) Spec Min. Width of Riprap (ft) 2*d50, Depth of Riprap (ft) for L/2 Froude Parameter Q/D2.5 Max 6.0 or Q/WH1.5 Max 8.0 Riprap Type (From Figure MD-21 or MD-22) Urban Drainage pg MD-107 Culvert Parameters Box Culvert Pipe Designation Design Discharge (cfs) L= 1/(2tanq)* [At/Yt)-W] (ft) INPUT CALCULATE Channel Report Hydraflow Express Extension for AutoCAD® Civil 3D® 2013 by Autodesk, Inc. Thursday, Dec 19 2013 Swale - Upstream Basin A5 (Between Buildings 5&6) User-defined Invert Elev (ft) = 5126.64 Slope (%) = 1.75 N-Value = 0.025 Calculations Compute by: Known Q Known Q (cfs) = 1.80 (Sta, El, n)-(Sta, El, n)... ( 0.00, 5128.50)-(0.10, 5128.00, 0.013)-(7.50, 5127.96, 0.013)-(13.00, 5126.64, 0.025)-(24.00, 5128.00, 0.025)-(24.10, 5132.75, 0.013) Highlighted Depth (ft) = 0.35 Q (cfs) = 1.800 Area (sqft) = 0.75 Velocity (ft/s) = 2.40 Wetted Perim (ft) = 4.35 Crit Depth, Yc (ft) = 0.36 Top Width (ft) = 4.29 EGL (ft) = 0.44 -5 0 5 10 15 20 25 30 Elev (ft) Depth (ft) Section 5125.00 -1.64 5126.00 -0.64 5127.00 0.36 5128.00 1.36 5129.00 2.36 5130.00 3.36 5131.00 4.36 5132.00 5.36 5133.00 6.36 Sta (ft) APPENDIX C Standard Operating Procedures STANDARD OPERATING PROCEDURES (SOPs) A. Purpose In order for physical stormwater Best Management Practices (BMPs) to be effective, proper maintenance is essential. Maintenance includes both routinely scheduled activities, as well as non-routine repairs that may be required after large storms, or as a result of other unforeseen problems. Standard Operating Procedures should clearly identify BMP maintenance responsibility. BMP maintenance is typically the responsibility of the entity owning the BMP. Identifying who is responsible for maintenance of BMPs and ensuring that an adequate budget is allocated for maintenance is critical to the long-term success of BMPs. Maintenance responsibility may be assigned either publicly or privately. For this project, the privately owned BMPs shown in Section B below are to be maintained by the property owner, homeowner’s association (HOA), or property manager. B. Site-Specific SOPs The following stormwater facilities contained within Bella Vira Subdivision Filing Two are subject to SOP requirements: - Vegetated Swales - Bioswale - Snout BMP - Level Spreader with Bioretention Sand Media The location of said facilities can be found on the Utility Plans for Bella Vira Subdivision Filing Two. Inspection and maintenance procedure and frequencies, specific maintenance requirements and activities, as well as BMP-specific constraints and considerations shall follow the guidelines outlined in Volume 3 of the Urban Drainage and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual for the Vegetated Swales and Bioswale. Note that the Level Spreader shall follow the same criteria as those for Bioswales. Inspection and maintenance procedure and frequencies, specific maintenance requirements and activities for the Snout BMP shall adhere to guidelines provided by the manufacturer. SOP Maintenance Summary Table Stormwater Facility / BMP Ownership / Responsibility Maintenance Reference Vegetative Swales Private Follow applicable guidelines for Vegetative Swales within UDFCD. Bioswale Private Follow applicable guidelines for Bioretention and Vegetative Swales within UDFCD. Level Spreader w/ Bioretention Sand Media Private Follow applicable guidelines for Bioretention and Vegetative Swales within UDFCD. Snout BMP Private Follow applicable guidelines for Snout BMP provided by the manufacturer. The complete UDFCD BMP maintenance references listed above can be found in Chapter 6 of Volume 3. The complete Snout BMP maintenance references “Maintenance Considerations for SNOUT Stormwater Quality Systems”, and can be found at www.bmpinc.com. Applicable excerpts for "Routine" maintenance requirements for each BMP can be found below. Additionally, it is strongly recommended that the Guidelines for Use of Pesticides, Herbicides and Fertilizers (UDFCD Fact Sheet S-8), and the Landscape Maintenance procedures (UDFCD Fact Sheet S-9) be followed, not just within the drainage facilities themselves, but for the entire development. Vegetative Swales Routine Maintenance Table (Summary from Chapter 6 of UDFCD) Required Action Maintenance Objective Frequency of Action Lawn mowing and Lawn care Maintain irrigated grass at 2 to 4 inches tall and nonirrigated native grass at 6 to 8 inches tall. Collect cuttings and dispose of them offsite or use a mulching mower. Routine – As needed. Debris and Litter removal Keep the area clean for aesthetic reasons, which also reduces floatables being flushed downstream. Routine – As needed by inspection, but no less than two times per year. Sediment removal Remove accumulated sediment near culverts and in channels to maintain flow capacity. Replace the grass areas damaged in the process. Routine – As needed by inspection. Estimate the need to remove sediment from 3 to 10 percent of total length per year, as determined by annual inspection. Inspections Bioswale & Level Spreader Routine Maintenance Table (Summary from Chapter 6 of UDFCD) Required Action Maintenance Objective Frequency of Action Lawn mowing and vegetative care Occasional mowing of grasses and weed removal to limit unwanted vegetation. Maintain irrigated turf grass as 2 to 4 inches tall and nonirrigated native turf grasses at 4 to 6 inches. Routine – Depending on aesthetic requirements. Debris and Litter removal Remove debris and litter from bioswale area to minimize clogging of the sand media. Routine – Including just before annual storm seasons (that is, April and May), end of storm season after leaves have fallen, and following significant rainfall events. Landscaping removal and replacement The bioretention sand media and landscaping layer will clog with time. This layer will need to be removed and replaced, along with all turf and other vegetation growing on the surface, to rehabilitate infiltration rates. Every 5 to 10 years, depending on infiltration rates needed to drain the WQCV in 12-hours or less. May need to do it more frequently if exfiltration rates are too low to achieve this goal. Inspections Inspect bioswale area to determine if the sand media is allowing acceptable infiltration. Routine – Bi-annual inspection of hydraulic performance. Snout BMP Routine Maintenance Table (Summary from Manufacturer Recommendations) Required Action Maintenance Objective Frequency of Action Monitoring Monitor new installation after site has been stabilized. Measure sediment depth and note surface pollutants in the structure. Routine – Monthly for first year. Determine yearly schedule from monitoring performed. Sediment removal Remove sediment from sump. Maintenance is best completed with a vacuum truck. Routine – Optimally completed when sump is half full of sediment. Routine schedule should be determined during first year monitoring. Structures should also be cleaned if a spill or other incident causes a larger than normal accumulation of pollutants. Floatable and trash removal Remove floatables and trash from sump. Routine - Optimally completed when 6" of floating material accumulates on surface APPENDIX D Drainage Plan A1 PROPOSED BIOSWALE WITH UNDERDRAIN HABITAT BUFFER (TYP.) Basin Design Point Area %I C2 C100 Q2 Q100 (acre) (cfs) (cfs) Proposed Basins -Filing 2 A1 A1 0.28 27% 0.45 0.57 0.35 1.55 A2 A2 0.60 35% 0.51 0.64 0.87 3.82 A3 A3 0.46 29% 0.46 0.58 0.60 2.62 A4 A4 0.78 80% 0.86 1.00 1.90 7.73 A5 A5 0.64 69% 0.77 0.96 1.39 6.07 A6 A6 0.32 47% 0.60 0.76 0.56 2.42 OS1 OS1 0.27 2% 0.25 0.31 0.16 0.68 OS2 OS2 0.10 2% 0.25 0.31 0.06 0.27 Onsite Total 3.44 47% 0.61 0.76 5.67 24.21 Modified Phase 1 Basins 19 19 0.35 78% 0.82 1.00 0.82 3.52 23 23 0.06 82% 0.84 1.00 0.15 0.63 PREPARED FOR: DATE SUBMITTED: The engineer preparing these plans will not be responsible for, or liable for, unauthorized changes to or uses of these plans. All changes to the plans must be in writing and must be approved by the preparer of these plans. CAUTION BELLA VIRA TOWNHOMES INC. 02/12/2014 BELLA VIRA SUBDIVISION FILING TWO 26 U13012 PRELIMINARY PLANS NOT FOR CONSTRUCTION Civil Engineering & Consulting 1501 Academy Court, Suite 203 Fort Collins, CO 80524 (970) 530-4044 www.unitedcivil.com NONE KEVIN D:\DROPBOX\PROJECTS\U13012 BELLA VIRA\CADD\CP C6.00_DRAINAGE PLAN.DWG 2/12/2014 8:42:13 AM KRB DRAINAGE PLAN C6.00 N/A CHECKED BY: 30' CHECKED BY: CHECKED BY: CHECKED BY: CHECKED BY: APPROVED: 1. EXISTING UNDERGROUND AND OVERHEAD PUBLIC AND PRIVATE UTILITIES AS SHOWN ARE INDICATED ACCORDING TO THE BEST INFORMATION AVAILABLE TO THE ENGINEER. 2. EXISTING INFORMATION AS SHOWN ON THIS PLAN IS PER DESIGN INFORMATION PROVIDED BY JIM SELL DESIGN AS SHOWN IN THE PHASE 1 CONSTRUCTION PLANS ENTITLED "BELLA VIRA SUBDIVISION" AND DATED DECEMBER 7, 2007. AT THE TIME OF THIS SUBMITTAL, CONSTRUCTION OF THE PHASE 1 BELLA VIRA IMPROVEMENTS IS NOT YET COMPLETE. CONTRACTOR SHALL FIELD VERIFY ACTUAL CONDITIONS AT ALL INTERFACES WITH PHASE 1 IMPROVEMENTS PRIOR TO THE COMMENCEMENT OF FILING 2 CONSTRUCTION. 3. REFER TO SECTION 3.4.1 OF THE LAND USE CODE FOR ALLOWABLE USES WITHIN THE HABITAT BUFFER ZONE. 4. LANDSCAPING WITHIN THE HABITAT BUFFER ZONE SHALL CONSIST OF NATIVE MATERIALS. REFER TO THE LANDSCAPE PLANS. 6. VEGETATIVE SWALES, THE BIOSWALE, AND THE SNOUT BMP SHALL BE MAINTAINED BY THE PROPERTY OWNER OR HOA AND FOLLOW APPLICABLE STANDARD OPERATING PROCEDURES AS SHOWN IN DRAINAGE REPORT FOR BELLA VIRA SUBDIVISION FILING TWO. LEGEND NOTES D-101 BASIN DESIGNATION BASIN AREA (ACRE) 2 - YR RUNOFF COEFF. 100 - YR RUNOFF COEFF. BASIN BOUNDARY DESIGN POINT FLOW DIRECTION 0 30' 60' SCALE: 1" = 30' 15' above static water level. Routine schedule should be determined during first year monitoring. Structures should also be cleaned if a spill or other incident causes a larger than normal accumulation of pollutants. Bio-Skirt service or replacement Maintain/replace Bio-Skirt. "Maintenance" includes wringing out of the unit to remove accumulated oils and then washed in an industrial washing machine with warm water. The Bio-Skirt may then be re-deployed as long as the material maintains it's structural integrity. Routine – Optimally completed when more than 2/3 of the boom is submerged, indicating a nearly saturated state. At a minimum, annual service or replacement is required. Check the grass for uniformity of cover, sediment accumulation in the swale, and near culverts. Routine – Annual inspection is suggested. Yt, Tailwater Depth (ft) At=Q/V (ft) Expansion Factor 1/(2tanq) (From Figure MD-23 or MD-24) OUTPUT Spec Min. Length of Riprap (ft) Calculations by: KRB Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Riprap\Riprap Calcs Spreadsheet.xls (1) Cv ti+tt Final tc (6) tc Check for Urbanized Basin Initial Overland Flow Time (ti) Travel/Channelized Time of Flow (tt) Design Pt. Calculations by: KRB Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx