HomeMy WebLinkAboutPOWERHOUSE 2 - PDP220006 - DOCUMENT MARKUPS - ROUND 4 - DRAINAGE REPORT
PRELIMINARY DRAINAGE REPORT AND EROSION CONTROL REPORT
POWERHOUSE 2
FORT COLLINS, COLORADO
AUGUST 17, 2022
NORTHERNENGINEERING.COM
970.221.4158
FORT COLLINS
GREELEY
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FORT COLLINS | GREELEY COVER LETTER
August 17, 2022
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FOR
POWERHOUSE 2
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report for your review.
This report accompanies the combined Project Development Plan (PDP) submittal for the proposed Powerhouse
2 development.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual (FCSCM) and
serves to document the stormwater impacts associated with the proposed Powerhouse 2 development. We
understand review by the City of Fort Collins is to assure general compliance with standardized criteria
contained in the FCSCM.
If you have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
CARLOS ORTIZ GARCIA AUSTIN SNOW, PE
Project Engineer Project Engineer
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FORT COLLINS | GREELEY TABLE OF CONTENTS
TABLE OF CONTENTS
GENERAL LOCATION AND DESCRIPTION .......................................................... 1
DRAIN BASINS AND SUB-BASINS ..................................................................... 5
DRAINAGE DESIGN CRITERIA .......................................................................... 6
DRAINAGE FACILITY DESIGN .......................................................................... 7
CONCLUSIONS ........................................................................................... 11
REFERENCES .............................................................................................. 11
TABLES AND FIGURES
FIGURE 1 – VICINITY MAP .................................................................................................1
FIGURE 2 – AERIAL PHOTOGRAPH ...................................................................................2
FIGURE 3 – PROPOSED SITE PLAN ...................................................................................3
FIGURE 4 – AREA FLOODPLAIN MAPPING ........................................................................3
FIGURE 5 – FOUNDATION DETAIL ....................................................................................4
APPENDICES
APPENDIX A – HYDROLOGIC COMPUTATIONS
APPENDIX B – DETENTION POND COMPUTATION
APPENDIX C – INLETS & WEIRS (WILL BE SIZED AT FINAL)
APPENDIX D – EROSION CONTROL REPORT
APPENDIX E – PRELIMINARY LID DESIGN INFORMATION
APPENDIX F – PREVIOUS STUDIES AND USDA SOILS REPORT
MAP POCKET
DR-A – EXISTING VS. PROPOSED IMPERVIOUS AREA – BASIN A
DR1 – POWER HOUSE II DRAINAGE EXHIBIT; (NORTHERN ENGINEERING)
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GENERAL LOCATION AND DESCRIPTION
A. LOCATION
Vicinity Map
The Powerhouse 2 site is located in the Southwest Quarter of Section 1, Township 7 North,
Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of
Colorado.
The project site (refer to Figure 1) is bordered to the north by the Lake Canal, to the south by
East Vine Drive to the east by Jerome Street, and to the west by N. College Avenue.
B. DESCRIPTION OF PROPERTY
The Powerhouse 2 site is comprised of roughly ±4.97 acres.
The site is currently occupied by three buildings as well as concrete sidewalks, open areas,
gravel parking areas, and ±48,482 square feet of asphalt. The existing imperviousness of the
site is 54%. An exhibit for existing versus proposed imperviousness is provided in the Map
Pocket section. The existing ground slopes with a mild to moderate grade (i.e., 0.5 – 2.0±%)
Figure 1 – Vicinity Map
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through the interior to the south across flat grades into East Vine Drive. The drainage continues
through the Poudre River Whitewater Park and on to the Cache La Poudre River.
A soils report (Project No. FC10223-125) was completed by CTL Thompson, Inc. on March 14,
2022. The report contains the results of a complete geotechnical subsurface exploration as well
as pertinent geotechnical recommendations.
There are two major drainageways close to the site. The Lake Canal is located on the north side
of the site and the Cache la Poudre River is located approximately 550 feet south of the site.
The proposed project site consists of one building. Other proposed improvements include
concrete and permeable paver drive aisle, gravel parking, walkways, a courtyard, landscape,
and open space areas. The proposed imperviousness of the site is 56%. An existing and
proposed imperviousness exhibit is provided in the Map Pocket section. Figure 3 shows the
proposed site plan.
Figure 2 – Aerial Photograph
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C. FLOODPLAIN
The Powerhouse 2 project is located within a FEMA Special Flood Hazard Area of the Cache la
Poudre River (Poudre River). Most of this area is designated as With Base Flood Elevation (BFE)
or Depth in Zone AE on FIRM Panel 08069C0997G, effective June 17, 2008. The floodplain from
the Whitewater Park Letter of Map Revision (LOMR) Case No. 20-08-0643P, effective June 25,
2021, will supersedes the current FEMA RiskMap. Most of the property falls inside the regulated
100-year floodplain. Chapter 10 of the City of Fort Collins Municipal Code regulates critical
facilities within this Flood Hazard Zone. It should be noted FEMA, as part of RiskMap, is
Figure 4 – Area Floodplain Mapping
Figure 3 – Proposed Site Plan
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currently remapping the Poudre River. Anderson Consulting Engineers (ACE) will provide the
updated Floodplain modeling, mapping, and report for the site when completed.
Anderson Consulting Engineers is in the process of preparing a variance request to the Fort
Collins Water Commission to allow construction of the Powerhouse 2 Building, which is
considered to be a critical facility, within the currently effective 1% annual chance of
occurrence (100-year) floodplain. Once constructed, the building will be elevated above, and
mapped out of, both the 100-year and 0.2% annual chance (500-year) floodplains. The as-built
condition will be documented in a LOMR to be submitted to the City and FEMA for review and
adoption. However, since the building (as a critical facility) is planned to be constructed prior
to the LOMR being approved by FEMA, a variance is required by City Code. The variance request
also seeks to allow the City to issue a Certificate of Occupancy (CO) for the building once the
City has reviewed and approved the LOMR application, but prior to final adoption by FEMA. It is
currently anticipated that this variance request will come before the Water Commission in
September 2022.
It is assumed a portion of the project site will continue to be located within the updated 100-
year floodplain. To ensure the proposed buildings have adequate flood protection, the finished
floors and all ductwork, heating, ventilation, electrical systems, etc., will be elevated 24-inches
above the effective Base Flood Elevation (BFE). This elevation is known as the Regulatory Flood
Protection Elevation (RFPE). The RFPE = BFE + 24 inches. The solar panels and the electric
vehicle charging components in the parking lot shall be installed above the RFPE or have
floodproofing as required by Chapter 10 of the City of Fort Collins Municipal Code. A minimum
of 24-inches of freeboard will be provided from base (100-year) flood elevation (BFE). This
freeboard level will be applied to either the design of finished floor elevations or the minimum
level of floodproofing measures
The vertical datum utilized for site survey work is the City of Fort Collins Benchmark # 1-00
(Elevation=4968.74); NAVD 88.
Furniture or site components not elevated above the floodplain or contained within a utility
wall shall be securely anchored with a system of 4" lag bolts epoxied into ground base concrete
or stone with straps and/or chains secured to elements to prevent flotation. Anchoring details
will be supplied at the time of the floodplain use permit.
Figure 5 – Foundation Detail
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A floodplain use permit will be required for the building structure and each site construction
element in the floodplain. The floodplain use permit for the building will be approved at the
time of the building permit application.
A floodplain use permit and no rise certification is required prior to performing any work within
the floodplain (i.e., curb cut removal, landscaping).
A post-construction elevation certificate including components like transformer, yards, EV.
charging stations, solar panel components, elevator, HVAC equipment, emergency vehicle
access gate, other electrical and mechanical systems, etc. must be approved before a
certificate of occupancy will be issued.
All elevators installed below the RFPE in the project will comply with FEMA NFIP technical
bulletin on June 4, 2019, and the 2021 IBC.
An Emergency Response and Preparedness Plan (ERPP) will be required by the City of Fort
Collins prior to a floodplain or building permit being issued.
Outdoor classrooms and informal outdoor gathering space will be used for site tours and
outdoor learning. These spaces will be constructed using large boulders and crusher-fine
surfacing.
DRAIN BASINS AND SUB-BASINS
A. MAJOR BASIN DESCRIPTION
Powerhouse 2 is located in the Cache la Poudre River Basin, a major tributary to the South
Platte River. The river is located in Larimer and Weld Counties, with a small portion of the
drainage basin extending into southern Wyoming. Passing through Fort Collins, the Poudre
River corridor provides stormwater drainage from various contributing city drainage basins.
Floodplain restrictions have limited the amount of building in the floodplain, resulting in lower
development density. This lower density, combined with sensitivities to the natural
environment, has resulted in a high concentration of parks and open spaces along the river
corridors.
B. SUB-BASIN DESCRIPTION
The subject property historically drains overland through the interior to the south across flat
grades. Runoff from the site has historically been routed to an existing pond/wetland on the
south side of Vine Drive.
The project site was a part of a previous drainage study in this area, "Drainage, Water Quality
and Erosion Control Report for the Poudre River Whitewater Park Project" by Anderson
Consulting Engineers, Inc., dated June 6, 2017. Within the drainage study, Powerhouse 2 is
associated with Basin 9, with a contributing area of 4.68 acres and an assumed fully-developed
imperviousness of 85%.
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DRAINAGE DESIGN CRITERIA
A. REGULATIONS
There are no optional provisions outside of the FCSCM proposed with the proposed project.
B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
In June 2017, Anderson Consulting Engineers, Inc. (ACE), per the direction of the City of Fort
Collins Stormwater staff, provided a Stormwater Management Model (SWMM) model for a fully-
developed condition scenario to evaluate the size of the proposed project infrastructure for the
Poudre River Whitewater Park project. The objective of this modeling was to generate a
conceptual drainage plan for future improvements. In the final modeling, Subbasins 8, 9, 10,
and 11 are related to the site. ACE considered conceptual detention ponds for the privately
owned properties located north of East Vine Drive (Subbasins 9 and 11) to detain and release
fully-developed 100-year flows at a 2-year historical rate. For the Powerhouse 2 project, the
corresponding basin is Subbasin 9 of the drainage study. An excerpt from the "Drainage, Water
Quality and Erosion Control Report for the Poudre River Whitewater Park Project" drainage
report is included in Appendix F.
In order to bring Powerhouse 2 into compliance with the current land use code and stormwater
criteria, 75% of all newly added impervious areas will be treated by Low Impact Development
(LID) techniques. The remaining water quality will be provided in the proposed detention
pond.
C. HYDROLOGICAL CRITERIA
The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure 3.4-1
of the FCSCM, serve as the source for all hydrologic computations associated with the proposed
development. Tabulated data contained in Table 3.4-1 was utilized for Rational Method runoff
calculations.
The Rational Method was employed to compute localized stormwater runoff utilizing
coefficients contained in Tables 3.2-1 and 3.2-2 of the FCSCM.
Two separate design storms were utilized to address distinct drainage scenarios. The first
event analyzed is the "Minor" or "Initial" storm, which has a two-year recurrence interval. The
second event considered is the "Major" storm, which has a 100-year recurrence interval.
No other assumptions or calculation methods were used for this development that is not
referenced by the current City of Fort Collins criteria.
D. HYDRAULIC CRITERIA
As previously noted, the subject property maintains historical drainage patterns.
All drainage facilities proposed with the project are designed in accordance with the criteria
outlined in the FCSCM and/or the Urban Drainage and Flood Control District (UDFCD) Urban
Storm Drainage Criteria Manual.
As discussed above, the subject property is located in a 100-year floodplain. The proposed
project does not propose to modify any natural drainageways.
E. MODIFICATIONS OF CRITERIA
The proposed development is not requesting any modifications to the criteria at this time.
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F. STORM MANAGEMENT STRATEGY
The overall stormwater management strategy employed with the Powerhouse 2 development
utilizes the "Four Step Process" to minimize adverse impacts of urbanization on receiving waters.
The following describes how the proposed development has incorporated each step.
Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the
stormwater impacts of this development is the site selection itself and the selection of
developable areas on the site.
The Powerhouse 2 development aims to reduce runoff peaks, volumes, and pollutant loads from
frequently occurring storm events (i.e., water quality (i.e., 80th percentile) and two-year storm
events). Site constraints limit the possible LID techniques; however, rain gardens have been
provided for this site as LID techniques for storm quality management.
Step 2 – Implement Best Management Practices (BMPs) that provide a Water Quality Capture
Volume (WQCV) with slow release. The efforts taken in Step 1 will help to minimize excess runoff
from frequently occurring storm events; however, the development still generates additional
stormwater runoff beyond historical conditions. The primary water quality treatment and volume
control will occur in the detention pond.
Step 3 – Stabilize Drainageways. As stated in Section I.A.3, the Lake Canal is located on the north
side of the site; however, no changes are proposed to Lake Canal with this project. While this step
may not seem applicable to the Powerhouse 2 development, the proposed project indirectly helps
stabilize drainageways. Once again, site selection has a positive effect on stream stabilization.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies to
industrial and commercial developments.
DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT
The main objectives of the project drainage design are to maintain existing drainage patterns
and ensure no adverse impacts to any adjacent properties.
A total combined release rate of 16.77 cubic feet per second (cfs) has been determined for the
proposed detention facility. This release rate has been grandfathered and agreed to by City
staff. The methodology accounts for existing impervious areas on the site, which will be
allowed to be released at the 100-year historical rate. There is a combined 1.32 acres of existing
impervious area within the development site, which drains to East Vine Drive. The 100-year
discharge from this impervious area is 13.11 cfs. There is a combined 3.66 acres of existing
pervious area within the development site, which also drains to East Vine Drive. A 2-year
discharge of 3.66 cfs has been calculated from this pervious area. The sum of "grandfathered"
existing impervious areas discharging into East Vine Drive combined with 2-year existing
pervious areas is 16.77 cfs, which is considered the allowable peak release rate for the site. We
have subtracted the 100-year undetained discharge computed from Basins 5, 7, 8, 10, 11, and
12 (2.73 cfs total) for an allowable release rate of 16.77-2.73=14.04 cfs. However, the detention
pond calculations are limited to a release rate of 8.5 cfs due to the capacity of the proposed 15"
outlet pipe.
The Conceptual Design from Anderson Consulting Engineers, Inc. included an 18" RCP outlet
pipe. Upon checking the conceptual design, it was discovered that the pipe did not have
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enough cover on the north flowline of Vine Drive; therefore, the pipe diameter has been
changed to a 15" pipe with a lower release rate of 8.5 cfs. We have used this value when sizing
our detention pond.
Onsite detention and water quality treatment for the Powerhouse 2 project will be provided
within the detention pond and rain gardens.
A temporary piezometer was installed approximately 25’ north of the proposed detention
pond. On July 29, 2022, the groundwater reading was at 5 feet below existing grade, which is
approximately 1’ below the proposed detention pond bottom. While it is desired to have more
separation between the pond bottom and groundwater, the pond bottom has been elevated as
much as possible and the outfall pipe is already as shallow as it can go. Undulations have been
added to the pond bottom, so most areas of the pond have more separation than the 1’
minimum.
LID treatment requirements will be met using rain gardens on the north and south sides of the
project, thereby meeting the requirement of at least 75% of all newly added impervious areas.
As mentioned above, Anderson Consulting Engineers, Inc. included East Vine Drive and the
Powerhouse 2 site in their drainage study for the Poudre River Whitewater Project. Their Site
Map can be found in Appendix F. That study dictated that flows from Vine, Jerome, and the
parcel at the northeast corner of the Jerome/Vine intersection be conveyed along Vine to an
inlet that would then convey flows south using the proposed 18 RCP and on to the downstream
detention and water quality features. Our proposed drainage design follows this approach but
uses a 15" pipe, as noted above.
B. SPECIFIC DETAILS
The detention volume required for the site is 0.34 acre-feet. This volume was calculated using
the FAA Method.
City Code requires LID treatment for all projects. This project proposes meeting the
requirement by using rain gardens as a LID technique. The rain gardens will capture the
majority of the water quality volume (WQCV) for the entire site, providing a total volume of
3,045 cubic feet. This configuration will treat at least 75% of the new impervious area. The
project is also including permeable pavers and gravel parking areas throughout the project.
While these don't count towards the official LID calculation, they achieve similar outcomes and
further enhance stormwater treatment on the site.
The Powerhouse 2 site has been broken into onsite sub-basins for design purposes. Anticipated
drainage patterns for proposed drainage basins are described below.
Basin 1
Basin 1, approximately 2.23 acres, consists of building, asphalt, sidewalk, paver, gravel, open
areas, and solar panel rooftops in the parking area. Runoff from the basin will sheet flow north
into a swale along the north property line. The swale will discharge into the rain garden and
then to Basin 6.
Basin 2
Basin 2, approximately 0.74 acres, consists of asphalt, sidewalk, gravel, open areas, and solar
panel rooftops in the parking lot. Runoff from the basin will sheet flow to a proposed curb
opening located on the southeast side of the parking area and then to Basin 6.
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Basin 3
Basin 3, approximately 0.72 acres, consists of a building, sidewalk, and open areas. Runoff from
the basin will convey flows via sheet flow and roof leaders to a rain garden located on the
south and then to Basin 6.
Basins 4
Basin 4, approximately 0.11 acres, consists of asphalt, sidewalk, and landscape areas. Runoff
from the basin will convey flows via sheet flow to a proposed Type R Inlet and then to Basin 6.
Basins 5 & 7
Basin 5, approximately 0.14 acres, and Basin 7, approximately 0.04 acres, consists of sidewalk
and landscape areas. Runoff from the basins will convey flows via sheetflow to a proposed area
inlet located on East Vine Drive, then routed to the Whitewater Park detention pond.
Basin 6
Basin 6, approximately 0.41 acres, consists of open space. This basin is the onsite detention
pond.
Basin 8 and Co1
Basin 8, approximately 0.11 acres, and Basin Co1, approximately 0.42 acres, consists of asphalt,
sidewalks, and landscape. Runoff from the basins will drain via sheet flow to the curb and
gutter along North College Avenue, then into an existing inlet in sump. The runoff will follow
existing drainage patterns.
Basin 9
Basin 9, approximately 0.14 acres, is an offsite basin and consists of open space. Runoff from
the basin will be conveyed through the north rain garden and then through Basin 6 without
being detained.
Basins 10 and 11
Basin 10, approximately 0.03 acres, and Basin 11, approximately 0.05 acres, consist of open
space. Runoff from the basins will drain via sheet flow north to Lake Canal. The areas are
outside the limits of disturbance and will continue to drain to the ditch as they currently do.
Basin 12
Basin 12, approximately 0.14 acres, consists of sidewalks and landscape. Runoff from the basin
will drain via sheet flow east to Jerome Street and follow existing drainage patterns to a
proposed area inlet located on East Vine Drive. Runoff from the basin will be routed to the
Whitewater Park detention pond.
Basins W8 & W10
Basin W8, approximately 0.63 acres, and Basin 10, approximately 1.50 acres, are part of the
"Drainage, Water Quality and Erosion Control Report for the Poudre River Whitewater Park
Project" Drainage Study. Runoff from the basins will follow the assumed fully-developed
conceptual design path from the drainage study. The runoff will be routed to a proposed area
inlet on East Vine Drive and then to the Whitewater Park detention pond.
Basin W11
Basin W11, approximately 0.89 acres, is part of the "Drainage, Water Quality and Erosion
Control Report for the Poudre River Whitewater Park Project" Drainage Study. Runoff from the
basin will follow the assumed fully-developed conceptual design path from the drainage study
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and will be routed via storm drain to Whitewater Park detention pond in the future when the
parcel is developed.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report.
C. LID SUMMARY
Powerhouse 2 is providing a rain garden to treat a portion of the north area of the site that will
see the highest runoff rate and contains portions of the building, concrete drive aisles,
sidewalk, permeable pavers, gravel parking, landscape areas, and solar panel rooftops in a
portion of the parking lot (Basin 1).
Powerhouse 2 is providing a rain garden to treat a portion of the southwest area of the site,
which contains a portion of the building, sidewalks, and open areas (Basin 3).
Powerhouse 2 On-Site LID Treatment
Project Summary
Total Impervious Area 114,856 sf
Target Treatment Percentage 75%
Minimum area to be Treated by LID measures 86,142 sf
Treated Impervious Areas by Treatment Method
Rain Garden 91,420 sf
Total Treated Impervious Areas 91,420 sf
Percent Total Project Area Treated 79.6%
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CONCLUSIONS
A. COMPLIANCE WITH STANDARDS
The drainage design proposed with the Powerhouse 2 project complies with the City of Fort
Collins Stormwater Criteria Manual.
The drainage design proposed for this project complies with the "Drainage, Water Quality and
Erosion Control Report for the Poudre River Whitewater Park Project" Drainage Study.
The drainage design proposed with this project complies with the Cache la Poudre River Basin
requirements.
REFERENCES
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted,
Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service,
United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
6. Drainage, Water Quality and Erosion Control Report for the Poudre River Whitewater Park Project
dated June 6, 2017, by Anderson Consulting Engineers, Inc.
EAST VINE DRIVENORTH COLLEGE AVENUE
LAKE CANALTVAULTF.O.VAULTF.O.F.O.CONTROLIRR CONTROLIRR
GAS/ / / / / / / // / / / / / / /GASLOT 1BRUSH MOBILEHOME P.U.D.(740 N. COLLEGE)LOT 3BRUSH MOBILEHOME P.U.D.(108 E. VINE)LOT 2BRUSH MOBILEHOME P.U.D.(704 N. COLLEGE)LOT 4(202 E. VINE)EAST VINE DRIVENORTH COLLEGE AVENUE
LAKE CANALTVAULTF.O
.VAULTF.O.F.O.CONTROLIRR CONTROLIRR
GAS/ / / / / / / // / / / / / / /GASLOT 1BRUSH MOBILEHOME P.U.D.(740 N. COLLEGE)TFTFLOT 3BRUSH MOBILEHOME P.U.D.(108 E. VINE)LOT 2BRUSH MOBILEHOME P.U.D.(704 N. COLLEGE)LOT 4(202 E. VINE)ROOFTOPCONCRETEASPHALTPAVERSSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)8,9255,04843,18809010010040TOTALS201,281109,526TOTAL=EXISTINGP:\207-030\DWG\DRNG\207-030_DRNG-IMP.DWG
POWERHOUSE 2FORT COLLINS COLORADODESCRIPTIONEXISTING VS. PROPOSEDIMPERVIOUS AREA - BASIN ADRAWN BYC. ORTIZDATEJUNE 29th, 2022PROJECT207-030DR-ADRAWINGSCALE1"=100'GRAVEL133,1454053,258LANDSCAPE10,975008,0335,04843,1880TOTAL PERCENT IMPERVIOUS = 54%PROPOSEDROOFTOPCONCRETEPAVERSGRAVELSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)TOTALS206,172114,855TOTAL=LANDSCAPEASPHALT39,028 35,93833,4146,44690%100%100%40%12,93440%5,17371,8460%035,12535,93833,4142,578TOTAL PERCENT IMPERVIOUS = 56%GRAVEL W/ SOLAR6,56740%2,627STORMWATER RATE FACTOR TABLEPremiseAddressSURFACEAREA (SF)% IMPERV.IMPER.AREA (SF)Lot 2704 N. COLLEGE37,7380 -Lot 3108 E. VINE12,88095 12,236Lot 4202 E. VINE 166,00660 99,604 216,62452 111,840