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HomeMy WebLinkAboutLONG POND WIRELESS TELECOMMUNICATIONS FACILITY - FDP - FDP180016 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTDate: October 10, 2018 City of Fort Collins – Development Review Center 281 North College Avenue Fort Collins, CO 80524 (970) 221-6750 Tower Engineering Professionals, Inc. 500 E. 84th Avenue, Suite C-10 Thornton, CO 80229 (303) 566-9914 nconstantine@tepgroup.net Subject: Drainage Report Site Applicant Designation: Atlas Tower Site Name: Long Pond Engineering Firm Designation: TEP Project Number: 67927 Site Data: 2008 Turnberry Rd. Fort Collins, CO 80524 Township 08, Range 68, Section 32 N 40° 36’ 53.67” (NAD ’83) W 105° 02’ 15.74” (NAD ’83) City of Fort Collins, Tower Engineering Professionals is pleased to submit this “Drainage Report” regarding the proposed wireless telecommunications facility. The purpose of the report is to show that the proposed development will meet the stormwater requirements of the City of Fort Collins. Based on our analysis we have determined that a stormwater Best Management Practice (BMP) will not be required to meet the requirements for the City of Fort Collins. If you have any questions or need further assistance on this project, please give us a call. Respectfully submitted by Nicholas M. Constantine, P.E. This FDP Drainage Report for the design of Long Pond – Proposed Telecommunications Facility was prepared by me (or under my direct supervision) in accordance with the provisions of Fort Collins Stormwater Criteria Manual and was designed to comply with the provisions thereof. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others. Drainage Report October 10, 2018 TEP Project Number 67927 Long Pond Page 2 TABLE OF CONTENTS 1) VICINITY MAP 2) INTRODUCTION 3) ANALYSIS CRITERIA 4) ANALYSIS PROCEDURE 4.1) Analysis Method 4.2) Analysis Results 4.3) Assumptions 5) ANALYSIS RESULTS Table 1 – Drainage Area 1 Stormwater Quantity Analysis Results 6) CONCLUSION 7) APPENDIX A DA1 Stormwater Quantity Analysis Calculations 8) APPENDIX B Stormwater Drawings 9) APPENDIX C City of Fort Collins Floodplain Review Checklist 2) INTRODUCTION LEGEND EXISTING PARENT PARCEL BOUNDARY EXISTING 50' RIGHT-OF-WAY 3 TOWER ENGINEERING PROFESSIONALS 67927 (303) 566-9914 THORNTON, CO 80229 500 E 84TH AVE, SUITE C-10 www.tepgroup.net SITE NAME: LONG POND VICINITY MAP V-1 Drainage Report October 10, 2018 TEP Project Number 67927 Long Pond Page 3 The proposed telecommunication facility is located at 2008 Turnberry Road. The 4.51acre parent parcel currently has 0.55 acres of weighted impervious surface. For a weighted impervious area value, open/landscaped areas are considered 0% impervious, gravel is considered 40% impervious, and roofs/concrete are considered 90% impervious, and asphalt is considered 100% impervious. The parcel currently consists of a residential/farming development. A concrete dich runs along the southwestern boundary and agricultural land borders the property to the east. The average slope of the site is approximately 5% and is located in the Cooper Slough/ Boxelder Basin. Additionally, the proposed site is not located in a flood plain according to FEMA panel # 08069C0981G dated June 17, 2008. The scope of the project will encompass a gravel surfaced 30’x12’ lease area within a 50’ x 50’ otherwise unsurfaced compound. A 45’ tall silo tower on a concrete foundation is also located within the compound and 266’ off the eastern property line and 58’ off the northern property line of the parcel. The compound will house concrete foundations for an equipment rack and telecommunications cabinets. The site will be accessed using a 12’ wide gravel access road. The construction will result in a weighted increase of 0.02 acres (643 SF) of impervious area or 0.29% increase in impervious area of the parcel. The project area will not require any grading or methods for drainage. Project will remain at existing grade. 3) ANALYSIS CRITERIA The stormwater quantity analysis was performed for this site using the Rational Method with the following design criteria: 1) Type of Analysis: Pre/Post Runoff Analysis 2) Storm Events: 2, 10, & 100 Year Storm Events 3) Land Covers: Lawn, Gravel, Impervious 4) ANALYSIS PROCEDURE 4.1) Analysis Method The Rational Method was used to analyze pre- and post-development runoff for the 2,10, and 100-year storm events. The analysis was completed by applying the Rational Method in conformance with the Fort Collins Stormwater Criteria Manual. The parent parcel is located on the boundary between Fort Collins Drainage Basin 24 and 28. The proposed drainage area includes a portion of the parent parcel and 50% of the Turnberry Road Right-of-Way that falls in Drainage Basin 28. This drainage area was chosen because it reflects the entirety of the effects of the parent parcel and proposed development on any properties downstream of the parent parcel and Fort Collins Drainage Basin 28. The proposed development does not affect Drainage Basin 24. 4.2) Analysis Results There is an increase in runoff for Drainage Area 1 between pre-development and post- development flow of 0.03 cfs (0.86% increase) for the 2-year storm event, an increase of 0.05 cfs (0.84% increase) for the 10-year storm event, and an increase of 0.12 cfs (0.79% increase) for the 100-year storm event for the drainage area affected by the proposed development. The Planning Commission has an assumed target impervious area of 9% for Basin 28. Basin 28 is already over the assumed impervious for the area, and this development causes a minimal increase to the runoff. There is a 0.00 cfs (0%) increase in runoff for Drainage Area 2 since there will be no proposed development within the boundaries of Drainage Area 2. Drainage Report October 10, 2018 TEP Project Number 67927 Long Pond Page 4 4.3) Assumptions 1) Existing land cover has not changed since the aerial image was taken. 2) Existing topography has not changed since the Larimer County data was gathered. 3) Time of concentration of 5 minutes is assumed for flow rate calculations. 5) ANALYSIS RESULTS Table 1 – Drainage Area 1 Stormwater Quantity Analysis Results 2 Year 10 Year 100 Year (cfs) (cfs) (cfs) Pre- Development 3.47 5.93 15.15 Post- Development 3.50 5.98 15.27 % Increase 0.86% 0.84% 0.79% 6) Conclusion The following summary describes the measures used to meet the City of Fort Collins stormwater requirements for the proposed tower site. The stormwater runoff for the site will sheet flow off the property. The minor increase in stormwater runoff shown in Table 1 is negligible and will not negatively impact the downstream properties. Along with the small amount of increased run-off, the overall imperviousness of the site increases by only 0.29%. Therefore, detention for this site is not required since the site will continue to sheet flow the stormwater runoff at close to historic values and downstream neighboring properties will not be affected. The proposed site will comply with the City of Fort Collins stormwater requirements without the implementation of a Stormwater Control Measure (SCM). Drainage Report October 10, 2018 TEP Project Number 67927 Long Pond Page 5 APPENDIX A DA1 STORMWATER QUANTITY ANALYSIS CALCULATIONS Job Name: Job Number: ATotal sqft x = acres Aimpervious sqft x = acres AGravel sqft x = acres Alawn sqft x = acres Ci = 0.95 (Runoff Coefficients taken from Table RO-11 Cg = 0.50 of the Fort Collins Stormwater Critieria Manual) Cl = 0.25 CTotal = (Per Table RA-7 of the Fort Collins Stormwater Manual) CF = Q (cfs) = *See sheet DA-1 for Land Cover 2 = 0.321 (0.295*0.95)+(0.254*0.5)+(3.243*0.25) 10 3.792 100 10 2.85 4.87 2 100 9.95 1.00 1.00 1.25 Design Storm Event (yr) Tower Engineering Professionals, Inc. 326 Tryon Road, Raleigh, North Carolina 27603 (Ph) 919.661.6351 (Fax) 919.661.6350 Pre-Development Stormwater Runoff : Drainage Area 1 JKW Checked by: JKW Long Pond Calculated by: 9/11/2018 67927 Date: Date: (1 acre/43560 sqft) (1 acre/43560 sqft) 165,173 12,846 11,075 3.792 0.295 3.243 = 0.254 (1 acre/43560 sqft) (1 acre/43560 sqft) Design Storm Event (yr) 141,252 (AI*cI) + (AG*cG)+(AL*cL) AT Rainfall Intensity at Tc of 5 min. 3.47 5.93 15.15 Q = C (unitless) * i (inches/hour) * A (acres)*Cf(unitless) Design Storm Event (yr) 2 10 100 Job Name: Job Number: ATotal sqft x = acres Aimpervious sqft x = acres AGravel sqft x = acres Alawn sqft x = acres Ci = 0.95 (Runoff Coefficients taken from Table RO-11 Cg = 0.50 of the Fort Collins Stormwater Critieria Manual) Cl = 0.25 CTotal = (Per Table RA-7 of the Fort Collins Stormwater Manual) CF = Q (cfs) = 2 = 0.313 (0.341*0.95)+(0.0*0.5)+(3.451*0.25) 10 3.792 100 10 2.85 4.87 2 100 9.95 1.00 1.00 1.25 Design Storm Event (yr) Tower Engineering Professionals, Inc. 326 Tryon Road, Raleigh, North Carolina 27603 (Ph) 919.661.6351 (Fax) 919.661.6350 SW Master Plan Stormwater Runoff : 9% Impervious (Basin 28) JKW Checked by: JKW Long Pond Calculated by: 9/11/2018 67927 Date: Date: (1 acre/43560 sqft) (1 acre/43560 sqft) 165,173 14,866 0 3.792 0.341 3.451 = 0.000 (1 acre/43560 sqft) (1 acre/43560 sqft) Design Storm Event (yr) 150,307 (AI*cI) + (AG*cG)+(AL*cL) AT Rainfall Intensity at Tc of 5 min. 3.38 5.78 14.76 Q = C (unitless) * i (inches/hour) * A (acres)*Cf(unitless) Design Storm Event (yr) 2 10 100 Job Name: Job Number: ATotal sqft x = acres Aimpervious sqft x = acres AGravel sqft x = acres Alawn sqft x = acres Ci = 0.95 (Runoff Coefficients taken from Table RO-11 Cg = 0.50 of the Fort Collins Stormwater Critieria Manual) Cl = 0.25 CTotal = (Per Table RA-7 of the Fort Collins Stormwater Manual) CF = Q (cfs) = *See sheet DA-1 for Land Cover 2.85 4.87 1.00 1.00 1.25 Design Storm Event (yr) 10 Q = C (unitless) * i (inches/hour) * A (acres)*Cf(unitless) Design Storm Event (yr) 2 10 100 139,962 (AI*cI) + (AG*cG)+(AL*cL) AT 12,111 3.50 2 100 9.95 Design Storm Event (yr) 2 10 100 5.98 15.27 Rainfall Intensity at Tc of 5 min. 3.213 = 0.278 (1 acre/43560 sqft) (1 acre/43560 sqft) = 0.324 (0.301*0.95)+(0.278*0.5)+(3.213*0.25) 3.792 (1 acre/43560 sqft) (1 acre/43560 sqft) 165,173 13,100 3.792 0.301 Tower Engineering Professionals, Inc. 326 Tryon Road, Raleigh, North Carolina 27603 (Ph) 919.661.6351 (Fax) 919.661.6350 Post-Development Stormwater Runoff : Drainage Area 1 JKW Checked by: JKW Long Pond Calculated by: 9/11/2018 67927 Date: Date: Drainage Report October 10, 2018 TEP Project Number 67927 Long Pond Page 6 APPENDIX B STORMWATER DRAWINGS D1 A1 B1 C1 A2 B2 DRAINAGE AREA 2 Tc FLOW PATH ANALYSIS POINT 2 DRAINAGE AREA 2: 1.23 ACRES DRAINAGE AREA 1 Tc FLOW PATH ANALYSIS POINT 1 DRAINAGE AREA 1: 3.79 ACRES EXISTING PARENT PARCEL BOUNDARY 5050 5050 5045 5040 5035 5030 5025 PROPOSED TOWER COMPOUND EXISTING PARENT PARCEL BOUNDARY IMPERVIOUS SURFACE GRAVEL SURFACE LAND COVER POST-DEVELOPMENT LAND COVER TABLE DA 1 AREA (FT²) DA 2 AREA (FT²) LAWN D1 A1 B1 C1 A2 B2 DRAINAGE AREA 2 Tc FLOW PATH ANALYSIS POINT 2 DRAINAGE AREA 2: 1.23 ACRES DRAINAGE AREA 1 Tc FLOW PATH ANALYSIS POINT 1 DRAINAGE AREA 1: 3.79 ACRES EXISTING PARENT PARCEL BOUNDARY 5050 5025 PROPOSED TOWER COMPOUND LAND COVER EXISTING GRAVEL DRIVEWAY BARN HOUSE GARAGE PROPOSED SILT FENCE. SEE THIS SHEET FOR DETAILS. 5050 PROPOSED TOWER COMPOUND EXISTING PARENT PARCEL BOUNDARY PROPOSED TOWER COMPOUND EXISTING PARENT PARCEL BOUNDARY ZONE "X" SECTION A-A NOTES: DRAINAGE AREA MAPS II AND GRADING & EC PLAN SW-2 3 SITE NAME: LONG POND JKW SCB TOWER ENGINEERING PROFESSIONALS OFFICE: (303) 566-9914 THORNTON, CO 80229 500 E 84TH AVE, SUITE C-10 FAX: (303) 566-9916 67927 0 10-10-16 DRAINAGE REPORT SEE COVER SHEET FOR SEAL 1 02-27-17 DRAINAGE REPORT 2 03-07-17 DRAINAGE REPORT 3 07-11-18 DRAINAGE REPORT SOIL & EROSION CONTROL PLAN QUADRANGLE MAP FEMA FLOOD MAP SILT FENCE DETAILS Drainage Report October 10, 2018 TEP Project Number 67927 Long Pond Page 7 APPENDIX C CITY OF FORT COLLINS FLOODPLAIN REVIEW CHECKLIST City of Fort Collins Floodplain Review Checklist 100% Development Review Submittals Instructions: Complete this checklist by marking all boxes that have been adequately completed. Put an “NA” next to any items that are not applicable to this particular submittal. Any boxes that are left blank and do not have an “NA” marked next to them are considered incomplete. Date of Review:_____________ Reviewer’s Name:____________________________ Plat Map  The following required items are on the plat:  100-year floodplain boundary  City  FEMA  Floodway boundary  City  FEMA  The benchmark number and elevation of benchmark  These items match the FIRM. (FEMA Basin)  These items match the Master Plan. (City Basin)  The benchmark number and elevation match with those published in the City of Fort Collins benchmark system. Site Plan The following required items are on the site plan:  100-year floodplain boundary- FEMA and City  500-year floodplain boundary (if proposed structure is a “critical facility” and a 500-year floodplain is mapped)  Floodway boundary  Erosion buffer zones  Restrictions related to use (ie. critical facility or no residential use of lower floor if floodproffed mixed use structure) Drainage and/or Grading Plan (or a separate Floodplain Sheet if it is too cluttered on Drainage and Grading Plan) The following required items are on the drainage and/or grading plan:  100-year floodplain boundary- FEMA and City  500-year floodplain boundary (if proposed structure is a “critical facility” and a 500-year floodplain is mapped)  Floodway boundary  Erosion buffer zones  Cross-section locations  BFE lines  Lowest floor elevation of structures (bottom of basement or crawl space is considered the lowest floor)  The floodplain and floodway boundaries are in the correct location and labeled properly.  The cross-section and BFE lines are in the correct location and labeled properly.  Elevations are referenced to the appropriate datum:  FEMA basins – list in both NGVD 29 and NAVD 88  City basins – list only in NGVD 29  Floodway regulations have been met.  No fill in the floodway unless a hydraulic analysis shows “no-rise”.  No manufactured homes, except in an existing park, can be placed in the floodway.  No changing a nonconforming non-residential or mixed use structure to a residential structure.  Landscaping meets requirements for no encroachment in the floodway without a hydraulic analysis to show “no-rise”.  No storage of materials or equipment.  A note is on the plans about the above floodway restrictions.  Critical facilities regulations have been met:  100 year – no life safety, emergency response or hazardous material critical facilities  500 year Poudre – no life safety or emergency response critical facilities  Any pedestrian bridges in the floodway that are not able to pass the 100-year flow are designed to be “break-away”.  Fences in the floodway will not block conveyance. Example: split-rail fence cabled together to not float, flap at bottom of privacy fence to allow water through (flap at BFE or above).  Any items in the floodway that can float (Example: picnic tables, bike racks, etc.) are noted as being anchored.  Erosion Buffer Zone requirements have been met:  Design of any allowed development minimizes disturbance to channel bed and banks.  No structures allowed.  No additions to existing structures allowed.  Any fencing is split-rail design and break-away, but cabled. Must be oriented parallel to general flow direction.  No detention or water quality ponds.  No bike or pedestrian paths or trails except as required to cross streams or waterways.  Road, bicycle and pedestrian bridges must span erosion buffer zone.  No fill.  No outdoor storage of non-residential materials or equipment.  No driveways or parking areas.  No irrigated vegetation and non-native trees, grasses, or shrubs.  No utilities except as necessary to cross streams or waterways.  No grading or excavation except as required for permitted activities in erosion buffer zone.  No construction traffic except as required for permitted activities in erosion buffer zone.  Any construction in the erosion buffer zone shows that it will not impact the channel stability.  A note is on the plans about the above erosion buffer zone restrictions.  Any necessary floodplain modeling has been submitted and approved. All modeling must follow the City’s floodplain modeling guidelines. Special Poudre River Regulations  Poudre River Floodway Regulations have been met.  No construction of new residential, non-residential or mixed-use structures.  No redevelopment of residential, non-residential or mixed-use structures.  No additions to residential, non-residential or mixed-use structures.  No fill unless hydraulic analysis shows “no-rise”.  Poudre River floodplain regulations have been met  No construction of new residential or mixed-use structures  No additions to residential structures  No additions to mixed-use structures if there is an expansion in the residential-use area of the structure.  No floatable materials on non-residential sites Information Related to Structures in the Floodplain  For structures in the floodplain, a table is shown that lists the following:  City BFE at upstream end of structure  FEMA BFE at upstream end of structure (if different than City BFE)  Regulatory flood protection elevation  Lowest floor elevation (bottom of basement or crawl space is considered lowest floor)  Floodproofing elevation for non-residential structures (if applicable)  Garage slab elevation  HVAC elevation  The BFE at upstream end of structures are correct based on interpolation between the cross-sections.  The regulatory flood protection elevation is correct.  The lowest floor and HVAC are at or above the regulatory flood protection elevation.  Elevations are referenced to the appropriate datum:  FEMA basins – list in both NGVD 29 and NAVD 88  City basins – list only in NGVD 29  A typical drawing detail is included for each foundation type proposed (slab-on- grade, basement, crawl space) showing the elevation of the HVAC and lowest floor elevation (which includes bottom of the basement or crawl space) relative to the BFE.  If garage is not elevated to the regulatory flood protection elevation, then a drawing detail is included showing vent placement, size, and number.  There is 1 square inch of venting for every 1 square foot of enclosed area.  The bottom of the venting is not higher than 1 foot above grade.  The venting is on at least two sides, preferably on upstream and downstream sides. (Does not have to be divided equally).  If a non-residential structure is to be floodproofed, one of these conditions is met:  All requirements on separate sheet titled “Floodproofing Guidelines” have been met.  If floodproofing information is not submitted as part of the plans, then a note is on the plans stating that floodproofing information will be submitted at the time of the building permit application.  For manufactured homes, all submittal requirements on separate sheet titled “Installation of a Mobile Home Located in a Floodplain: Submittal Requirements” have been met.  If the floodplain use permit is not going to be submitted until the building permit is applied for, then a note is on the plans stating that the floodplain use permit will be submitted at the time of building permit application. N/A N/A N/A N/A N/A N/A N/A  A note is on the plans stating that a FEMA elevation or floodproofing certificate will be completed and approved before the CO is issued. This is required even if property is only in a City floodplain. Drainage Report  The site is described as being in the floodplain. Floodplain name and if the floodplain is a FEMA or City-designated is described. Any floodway or erosion buffer zones on the site are described.  The FEMA FIRM panel # and date and/or the Master Plan information is cited.  A copy of the FIRM panel with the site location marked is included in the report.  If a floodplain modeling report has been submitted, that report is referenced. The reason for the floodplain modeling report is described.  If a FEMA CLOMR or LOMR has been approved for the site, the case number is referenced. The reason for the CLOMR or LOMR is described.  If a FEMA LOMR is required after construction, this is stated in the report.  The location of the structures relative to the floodplain is described. If there is both a FEMA and a City floodplain on the site, the location of the structures relative to both is described.  The use of the structures is described. This is to determine if the structure is residential, non-residential, or mixed-use. Also, structures in all 100-year and Poudre River 500-year floodplains cannot be used as a critical facility. (See Chapter 10 of City Code for definitions.)  The report describes how the development is in compliance with the applicable floodplain regulation (Chapter 10 of City Code). (Examples: elevation of lowest floor above regulatory flood protection elevation, floodproofing, floodway regulation, erosion buffer zone regulation, no-rise, etc.)  The type of foundation construction for the structures (i.e. slab-on-grade, crawl space, basement, etc.) is discussed in the report.  The type of foundation matches with the lowest floor elevations and grading plan.  If any of the garages are not going to be elevated above the regulatory flood protection elevation, the hydraulic venting requirements are discussed.  For structures in the floodplain, a table is included (same table as on the Drainage/Grading Plan) that lists the following:  City BFE at upstream end of structure  FEMA BFE at upstream end of structure (if different than City BFE)  Regulatory flood protection elevation  Lowest floor elevation (bottom of basement or crawl space is considered lowest floor)  Floodproofing elevation for non-residential structures (if applicable)  Garage slab elevation  HVAC elevation  Elevations are referenced to the appropriate datum:  FEMA basins – list in both NGVD 29 and NAVD 88  City basins – list only in NGVD 29  If the floodplain use permit is not going to be submitted until the building permit is applied for, then a note must be included in the report that states the permit will be submitted at the time of building permit application.  If floodproofing information is not submitted as part of the plans, then a note must be in the report stating that floodproofing information will be submitted at the time of the building permit application.  A note is in the report stating that a FEMA elevation or floodproofing certificate will be completed and approved before the CO is issued.  In the compliance section, Chapter 10 of City Code is listed. Floodplain Use Permit  Floodplain Use Permit has been submitted for each structure.  Permit fee has been submitted  All information on permit matches the plans  All information on permit meets floodplain regulations FEMA CLOMR Approval  FEMA has approved any necessary CLOMRs. Additional Comments: ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ N/A N/A N/A N/A N/A Terms to Note Lowest Floor Elevation – Elevation of the lowest floor of the lowest enclosed area (including bottom of basement or crawlspace). This is not the same as finished floor. The lowest floor should be distinguished from finished floor on plans and reports. Regulatory Flood Protection Elevation – For all floodplains except the Poudre River, the regulatory flood protection elevation is eighteen (18) inches above the base flood elevation. For the Poudre River floodplain, the regulatory flood protection elevation is twenty-four (24) inches above the base flood elevation. If there is both a FEMA and a City BFE, the higher BFE should be used to determine the regulatory flood protection elevation. Additional floodplain terminology is defined in Chapter 10 of City Code. NOTE: Issues specific to individual sites may arise that result in additional requirements. These will be discussed during initial meetings with the applicant. X PRE-DEVELOPMENT LAND COVER TABLE DA 1 AREA (FT²) EXISTING PARENT PARCEL BOUNDARY IMPERVIOUS SURFACE GRAVEL SURFACE LAWN DA 2 AREA (FT²) DRAINAGE AREA MAPS I SW-1 3 SITE NAME: LONG POND JKW SCB TOWER ENGINEERING PROFESSIONALS OFFICE: (303) 566-9914 THORNTON, CO 80229 500 E 84TH AVE, SUITE C-10 FAX: (303) 566-9916 67927 0 10-10-16 DRAINAGE REPORT SEE COVER SHEET FOR SEAL 1 02-27-17 DRAINAGE REPORT 2 03-07-17 DRAINAGE REPORT 3 07-11-18 DRAINAGE REPORT PRE-DEVELOPMENT LAND COVER MAP PRE-DEVELOPMENT DRAINAGE AREAS MAP POST-DEVELOPMENT DRAINAGE AREAS MAP POST-DEVELOPMENT LAND COVER MAP