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HomeMy WebLinkAboutNEW BELGIUM BREWERY - IP SITE PLAN REVIEW / MINOR SUBDIVISION - 1-95 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT' REFERENCES 1 . RBD, Inc. Engineering Consultants, Final Drainage, Erosion and Storm water Quality Study East Vine Streets Facility P.U.D., Phase One Final, March 1, 1993, Revised April 26, 1993, Updated June 28, 1993. 2. City of Fort Collins, Colorado, Storm drainage Design Criteria and Construction Standards, May 1984, Revised January 1991. 3. Denver Regional Council of Governments, Urban Storm Drainage Criteria Manual, Volumes I and II, March, 1969, 6th Printing Vol I September 1978. 1 INSTALLATION SCHEDULE Construction of New Belgium Brewery is proposed to start in mid -march 1995 and continue during the winter with the floors, grading and paving completed by of May 1995. The approximate date of implementation of the erosion control measure during construction are shown on Standard Form C in Appendix I.I. As shown on Form. C the silt fence will be constructed prior to overlot grading. Paving,of the parking and walk areas is scheduled to begin in May be complete by June. Permanent vegetation will be seeded and mulched during the fall planting season beginning in August prior to the next wind erosion season. The silt fence will be left in place until landscaping is complete and establishment of the permanent grass cover. EROSION CONTROL SECURITY The erosion control security requirement for the New Belgium Brewery site was estimated based on the specification of Section 2.0 of the Manual. The cost of the erosion control measures at the site as detailed above were estimated to cost $1,000 with a security requirement of $1,500. The estimated cost to revegetate the disturbed areas with a dryland grass mix according to the city's 1993 mulch and revegetation bid was $2,600 with a security requirement of $3,900. The larger amount is required prior to construction. Both cost estimates are detailed in Appendix II. L 4 It it it I WIND EROSION ANALYSIS The surface soils at the New Belgium Brewery site are rated as low to moderately wind erodible. Construction at the site will occur during the end of the windy season of November to May and the site does not fall under any of the exclusions available in the Manual. Construction disturbance at the site as detailed above will occur across the entire site. The limited size of the construction area and the necessary access in this area will restrict the available area for placement of a wind barrier. For this reason the wind erosion features to be constructed at the site will consist primarily of natural features at the site, water erosion controls and the features to be constructed. The wind erosion control measures which will be implemented during construction will include the items listed below and are located on Figure 2. • The Coy Ditch along the southwest margin of Lot 1. • The silt fence along the entire south and east margin of Lot 1. • The proposed soil stockpile to be located on in the northeast corner of Lot 1. • The stormwater detention pond berms along the north of Lot 1. • The walls and structural fill of the building. • The paved parking and walk areas. • The proposed vertical curbing along the south and west sides of the Site. Wind erosion control measures which will be implemented after construction will consist of mulching and seeding the disturbed areas. Hay or straw mulch will be applied and crimped into the soil surface at a rate of 2 tons per acre after seeding of the site. The topsoil stockpile will be removed when the mulch is applied. The remainder of the wind erosion control features will remain intact to counter soil loss during vegetative establishment. it 1.1 Practice Factor Measures Sediment control practice measures for the New Belgium Brewery development will consist of the construction of a silt fence. The location and the silt fence is shown on Figure 2. .Practice factor measures for the site after construction will be dismantled and thus a weighted P - Factor of 1.0 was used to calculate the effectiveness. The calculations for the weighted P - Factor for areas contributing to the ponds A and B for both during and after construction cases are presented on Standard Form B in Appendix II. Cover Factor Measures Cover factor measures for the site during construction will consist of the building and the parking areas. The building and paved areas were assigned a C - Factor value of 0.01. The soil stockpile area will be located along the northeast property line for Lot 1. Cover factor measures for the site after construction is completed will consist of implementation of the landscaping plan which calls for establishment of grass cover of at least 60 percent over the disturbed, non -landscaped areas of the site. Grass will be established with the use of hay or straw mulch applied and secured at a rate of 2 tons per acre. The mulched and revegetated areas were assigned C - Factor values of 0.06 as selected from Table 5.2 and Figure 5.1. Cover factor values for the paved areas and the undisturbed grassed areas were not changed from during construction conditions. The calculations for the weighted C - Factor for areas contributing to the Pond A and B for both during and after construction are presented on Standard Form B in Appendix II. "During Construction" Effectiveness Evaluation The Net Effectiveness for the erosion control measures at the site during construction was calculated as 75.8 percent and exceeds the "During Construction" Performance Standard value of 75.5 percent. The Net Effectiveness was calculated using basin effectiveness values of 78.2 and 70.0 percent for basins A and B, respectively. Calculations of the basin effectiveness value and the Net Effectiveness for the site are presented on Standard Form B in Appendix II. "After Construction" Effectiveness Evaluation The Net Effectiveness for the erosion control measures at the site after construction t was calculated as 96.6 percent and exceeds the "After Construction" Performance Standard value of 89.3 percent. The Net Effectiveness was calculated using basin effectiveness values of 96.8 and 96.0 percent for basin A and B, respectively. Calculations of the basin effectiveness value and the Net Effectiveness for the site are presented on Standard Form B in Appendix II. IJ WIND AND RAINFALL EROSION EVALUATION Site Soils The Larimer County, Soil Conservation Service Soils Report identifies the soils as _ belonging to the Caruso Clay Loam which is described as having slight rainfall ' erodibility. The rainfall erosion season as detailed in the City of Fort Collins, Erosion Control Reference Manual (21 (the Manual) is between May 1 and October 31. The natural drainage of the site is from the northwest to southeast where runoff is ponded north of the Coy Ditch. A mixture of dryland grass cover currently provides an estimated 70 percent cover over the entire site. The Manual details the site as having low to moderate wind erodibility characteristics. The Manual states the predominant wind direction is from the west-northwest in this area. The wind erosion season as detailed in the Manual is between November 1 st and May 31 st. Construction at the Site is estimated to begin in mid -March 1995 and continue through August of 1995, with the majority of the structural and grading work completed by July of 1995. This schedule places the project within the .wind and rain erosion seasons. Performance Standard The estimated "During Construction" and "After Construction" Performance Standard for the New Belgium Brewery are 75.5 and 89.3 percent, respectively. For the purpose of estimating the site's Performance Standard the entire site was broken into two separate basin areas based on the final development contours. The basins, as shown on Figure 2 consist of: • 2.48 acre Basin A, located south and east of the buildings and draining 1 generally south to Detention Pond A, and • 1 .04 acre Basin B, located west and southwest of the buildings draining to the ' south to Detention Pond B. The Performance Standard for the site was estimated using the methods detailed in the Manual and the estimated, average slope length and slope for each basin. Flow lengths and slopes developed for calculation of the "During Construction" Performance Standard are presented on Standard Form A in Appendix II. The Performance Standard was taken from Table 5.1 of the Manual. The "After Construction" Performance 11 Standard is calculated by dividing the "During Construction" Performance Standard by 0.85. 7 L At Design Point B the flow from Point A will combine with the 2-year flows from Lots 2 and 3 and the Streets Facilities. The peak flow leaving the manhole is estimated to be approximately 5.76 cfs. This flow will be conveyed to the south in two 15", N-12, ' ADS pipes to the existing ROW west of 1 st Street. The ROW extends 20' west of the quarter section line with only 9' paved. These pipes will extend approximately 75' south of the manhole• to a point wherethey can be daylighted by minor excavation ' along :the -ROW. The pipes were mgdele.d using Mlanning's equation with n = 0.012 and a slope of 0.15 percent. With these conditions the full flow capacity of each pipe will be 3.2 cfs. I t IN 11, 11, The historic 2-year peak runoff from the site was estimated for Basins A and B to establish the allowable discharges from Detention Ponds A and B. Time of concentrations of 33 and 23 minutes were estimated for Basins A and B, respectively, using conventional methods for the City of Fort Collins and Denver Drainage Criteria [21 [3]. Based on these time of concentrations the peak flows for the 2-year storm events are 0.33 and 0.50 cubic feet'persecond (cfs), respectively,. The required capacity for Detention Ponds A and B were established based on a mass balance for each pond using the post -development runoff coefficients for Basins A and B with the 100-year storm event and the allowable release rates for each basin as detailed in the paragraph above. Tabular representations of the mass balances are presented in Appendix I. Based on these estimates the maximum storage required in Detention Pond A and Pond B is 16,700 and 5,600 cubic feet, respectively. The storage volume provided in ponds A and B is 18,300 and 6,500 cubic feet, respectively. The hydraulics of the primary spillway for Pond A was evaluated using the Hazen - Williams equation with the pond at full stage and a tailwater level in the curb inlet box at the gutter flowline. Under these conditions (anticipated during large storm events) the peak release flow will be approximately 0.69 cfs which slightly exceeds the allowable release rate of 0.65 cfs. The hydraulics of the primary spillway for Pond B was evaluated assuming the pipe entrance will act as the constriction. Under maximum head the flow through the entrance to the pipe will be approximately 0.42 cfs which slightly exceeds the allowable release rate of 0.35 cfs and will decrease with time as the head falls off. Off Site Hydrology and Hydraulics: The 10-year storm event was estimated at the 4', sump curb inlet in the north flowline of Buckingham. An area of approximately 0.5 acres with a runoff coefficient of 0.95 and a time of concentration of 10 minutes was use to estimate the peak flow of 2.16 cfs. The curb inlet will be capable of collecting approximately 4.0 cfs although the outlet pipe from the box will only handel 3.2 cfs at full flow. Combined Lots 2 and 3 plus the specified 2-year releases from the Streets Facilities were used to estimate the historic 2-year peak runoff and release rate to Design Point B. A runoff coefficient of 0.20 was used for the historic, existing conditions of the site consisting of dry -land grasses on gentle 0.5 to 1 percent slopes. An area of 4.15 acres with a time of concentration of 39 minutes was used to estimate a peak flow of 0.996 cfs. The 2-year release rate from the tributary areas of the city Streets Facilities, as detailed in Attachment A, is 1.6 cfs. This represents the 2-year release rate from 3.9 acres to the north of Parcel 5. The combined peak flow from Lot 1 and the tributary street area at Design Point A is 3.16 cfs. This flow will be conveyed east to the manhole at Design Point B through a 15", N-12, ADS pipe. The pipe was modeled using Manning's equation with n = 0.012 and a slope of 0.15 percent with a full flow capacity of 3.2 cfs. Details The two 15" N-12, ADS pipes conveying flows south from Point B to the west ROW of 1 st Street have been sized to convey the 2-year storm releases from the upstream tributary areas as explained above. Linden and Buckingham Streets: Drainage from Linden and Buckingham streets adjacent to Lots 1,2 and 3 will drain either to.the existing curb inlets located in the west flowline of Linden or the proposed-4', sump, curb inlet at the vertical, sag curve in the north flowline of Buckingham Street. This is a continuation of the existing drainage patterns for these roadways and will serve to provide rapid drainage to the Poudre River of these areas in close proximity to the river. Linden Street from the point of curvature (PC), 100' south of the joint access to Lots 1 and 2, will sheet drain across the existing and extended superelevation to the west flowline of Linden and to the two, 4', sump, curb inlets in the flowline. These curb inlets discharge to the Coy Ditch and it's spillover which flows directly to the Poudre River along the northwest side of Linden. The 4', sump, curb inlet at Design Point A will collect flows from the roadway from the high point at the intersection of 1 st and Buckingham and half the streets from the PC in Linden to the sump. The sump was designed to collect flows in excess of the 10-year storm event. Drainage from the curb inlet will be limited by the pipe capacity from the box. Drainage in excess of the 10-year storm event will spill across the crown of Buckingham and drain to the Poudre River via the historic oxbow. Coy Ditch: Construction within the Coy Ditch easement will consist of two culverts to allow access to the parking and truck dock areas. These culverts were designed to convey the maximum flows for the Coy Ditch allotment of 31.5 cfs. A single 3' and two, 2', N-12, ADS pipes will be used under the parking area and truck dock entrance, respectively. The 3' pipe will not back up headwater at the design flow and thus will not undermine the performance of the flume approximately 10' upstream of the headwall. The two, 2' pipes will back up headwater sufficient to drive the design flow through the pipes on the flat grade. Support for the following discussion will be found in the calculations in Appendix I and on the drawings furnished with this report. As stated above, the Rational Method was used for drainage estimates. Lot 1, Basins A and B: The site was divided into drainage basins A and B, for analysis purposes. The basins are detailed on Figure 2. The composite runoff coefficients for developed conditions of 0.65 and 0.56 were estimated for Basins A and B, respectively. These values were derived with runoff coefficients of 0.95 for impervious surfaces and 0.25 for pervious surfaces. The area summary table at the beginning of Appendix I provides a breakdown of the types of surface used to estimate the composite runoff coefficients. The Drainage Summary Table provides areas, runoff coefficients, times of concentration, rainfall intensities, and peak flows. DRAINAGE DESIGN Concept Drainage from Lots 1, 2 and 3 will drain to Design Points A and B as shown on Figure 2. Drainage from Lot 1 will flow to two separate detention basins, Ponds A and B. Ponds A and B will pond and detain the runoff difference between the -land 100-year. storm events. Releases from Lot 1 will flow to Design Point A, a 4', sump curb inlet at the sag vertical curve created by the street expansion along the north side of Buckingham Street. From the curb inlet the drainage will flow in a 15" N-12, ADS pipe in the north Buckingham Right -Of -Way (ROW) to the manhole at Design Point B. Flows from Lots 2 and 3, when developed, will be collected at Point B. From the manhole, flows it will turn south and drain to the existing street ROW west of 1 st Street. Flow from the manhole will be carried in two, 15", N-12, ADS pipes to a point approximately 75' south of the manhole where it will daylight to a roadside depression and flow in the historic river meander to the Poudre River. Lot 1, Basin A: Basin A, consisting of the building, truck dock and future facilities,.will drain to Pond A located along the south and east margins of the building. Pond A will be formed by a low berm along its margins and a rise in the truck dock entrance from Buckingham. The primary spillway from Pond A will consist of a 4" PVC pipe with the inlet located north of the Coy Ditch and west of the truck dock facility entrance. The pipe will traverse the west side of the truck dock entrance over the two, 24" ADS pipes conveying the Coy Ditch flows and drain into the back of the 4' curb inlet at Design Point A. The emergency spillway for Pond A will be formed by the entrance ramp and allow excess flow to drain to Buckingham Street. Drainage from the northeast portion of Basin A will be conveyed to the primary spillway via overland flows to a concrete pan in the truck ramp, then through a 6" PVC pipe under a forklift ramp extending from the south corner of the building and to the spillway in a 4' concrete pan. Drainage from the building and areas southwest of the building will drain to the primary spillway via overland and pan flows as shown on Figure 2. Lot 1, Basin B: Basin B, consisting of the south and west parking and plaza areas, will drain to Pond B located in the turnaround at the end of the parking area. Pond B will be formed by a berm and the turnaround curbing adjacent to the Coy Ditch. The primary spillway from Pond B will consist of a 4" PVC pipe with the inlet at the low point in the gutter of the turnaround and drain to a sidewalk culvert under the sidewalk to the proposed north flowline of Buckingham Street. The emergency spillway for Pond B will be formed by a low area in the berm with excess flows draining down the face of the vegetated berm to the north flow line of Buckingham. Drainage will be conveyed to Pond A by overland flow to the parking area and then in the southwest gutter to the primary spillway at the east end of the turnaround. Lots 2. 3 and Streets Facilities: Drainage from Lots 2, 3 and the city Streets Facilities when fully developed will pond and detain the difference between the 2 and 100-year storm events. The released water will be conveyed over Lots 2 and 3 to the southeast corner of Lot 3 where it can be drained to the manhole at Design Point B. IDRAINAGE BASIN IDENTIFICATION Description ■ The site is situated in the Poudre River drainage basin as identified in the Basin Master Plan. Tributary drainage to Parcel 5 consist of approximately 3.9 acres located in the East Vine Street P.U.D. (Streets Facilities). This drainage is conveyed to Parcel 5 via a road side ditch on the east side of Linden from the west access to the Street Facilities, and flows southeast to a low spot at the southeast corner of Lot 3. Drainage from Lots 1, 2 and 3 drain to the same point as shown on Figure 2. The precedent for drainage control in this area was set by the Streets Facilities drainage Plan [ 1 ]• This plan sets the detention requirement for the property at the difference between the 2-year and 100-year storm events and that the released water shall flow to the Poudre River over contiguous property. A copy of the pertinent report pages is included as Attachment A to this report. DRAINAGE DESIGN CRITERIA Regulations The City of Fort Collins Storm Drainage Design Criteria [2] is being used as the basis for this report. Develooment Criteria Constraints Neither off site detention nor downstream drainage capacity for the 100-year storm event exist for Lots 1 through 3. Therefore, these properties will have to detain stormwater on site and release at the 2-year historic discharge for the property for storm events up to the 100-year storm event in accordance with the requirements established with the Streets Facilities. Hydrologic Criteria The Rational Method was used to predict the peak and cumulative runoff from the proposed development. The 100-year and 2-year storms events were used as the basis of design of the drainage systems for New Belgium Brewery. Calculations are included in Appendix I. Calculations All calculations for this report have been made in accordance with criteria established by the City of Fort Collins. Variances No variances are requested with this project. DRAINAGE AND EROSION CONTROL REPORT FOR NEW BELGIUM BREWERY FORT COLLINS, COLORADO DEVELOPMENT LOCATION AND DESCRIPTION Location New Belgium Brewery shall be a micro -brewery consisting of a one story structure housing brewing facilities and office space. The facility will have frontage along Linden Street as shown on Figure 1. The site is located at the northeast corner of Linden and Buckingham Streets. Specifically, the site consist of Lot 1 encompassing an area of 3.76 acres which will be subdivided from an existing Parcel 5 (Lots 1,2 and 3) of 7.96 acre. A proposed street widening right-of-way exists to the south of Parcel 5 consisting of 0.49 acres. The site lies in the northeast quarter of the northwest quarter of Section 12, Township 7 North, Range 69 West, City of Fort Collins, County of Larimer, State of Colorado. Prooerty Description The property the New Belgium Brewery (the Site) will occupy is currently undeveloped. It is presently covered with dry -land grasses and slopes from the northwest to southeast at a gradient of less than 1 percent. Historic drainage from the Site was to the south, southeast to an oxbow meander, which existed around the turn of the century. The oxbow butted to the south side of what is now Buckingham Street and the west side of 1st Street. Drainage from the site was cut off by construction of Buckingham Street in the early 1900s and relocation of the Coy Ditch to the north side of the street. No positive drainage has been established for the property. WATER WASTE & LAND December 30, 1994 2629 Redwing Rd. Suite 200, Fort Collins, Colorado 80526-2879 (303)226-3535 fax (303) 226-6475 Mr.Glen D. Schlueter City of Fort Collins Utility Services Stormwater 235 Mathews Fort Collins, Colorado 80522 RE: NEW BELGIUM BREWERY- FINAL DRAINAGE AND EROSION CONTROL REPORT Dear Mr. Schlueter: Transmitted herewith is a copy of the subject report for your review and approval. All calculations for this report have been made in accordance with criteria established by the City of Fort Collins. If you have any questions or require any modifications please call me. Thank you. Sincerely, WATER, WASTE & LAND, INC. Tom Knostman Project Manager Civil Engineering Division Consulting Engineers and Scientists DRAINAGE AND EROSION CONTROL REPORT FOR NEW BELGIUM BREWERY FORT COLLINS, COLORADO Prepared for: THE NEENAN COMPANY 2290 East Prospect Fort Collins, CO 80525 Prepared by: Water, Waste & Land, Inc. 2629 Redwing Road, Suite 200 Fort Collins, Colorado 80526 December 30, 1994 DRAINAGE AND EROSION CONTROL REPORT FOR NEW BELGIUM BREWERY FORT COLLINS, COLORADO ��III WATER WASTE II\ / IIi�!