HomeMy WebLinkAboutPOWERHOUSE 2 - PDP220006 - DOCUMENT MARKUPS - ROUND 2 - DRAINAGE REPORT (2)
PRELIMINARY DRAINAGE REPORT AND EROSION CONTROL
REPORT
POWERHOUSE II
FORT COLLINS, COLORADO
APRIL 18, 2022
NORTHERNENGINEERING.COM
970.221.4158
FORT COLLINS
GREELEY
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NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY COVER LETTER
April 18, 2022
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FOR
POWERHOUSE II
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 II 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 II
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
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY TABLE OF CONTENTS
TABLE OF CONTENTS
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 1 | 10
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 2 | 10
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 3 | 10
C. FLOODPLAIN
The Powerhouse II project is located within a FEMA Special Flood Hazard Area for 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.
Therefore, 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. However, no critical facilities are proposed.
It should be noted FEMA is currently remapping the Poudre River. Anderson Consulting
Engineers (ACE) will provide the updated floodplain modeling, mapping, and report for the
site when completed. It is assumed 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 new Base Flood Elevation (BFE). This elevation is
known as the Regulatory Flood Protection Elevation (RFPE). The RFPE = BFE + 24 inches.
Figure 4 – Area Floodplain Mapping
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 4 | 10
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 5 | 10
associated with the proposed development. Tabulated data contained in Table 3.4-1 was
utilized for Rational Method runoff calculations.
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 6 | 10
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically applies
to industrial and commercial developments.
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 7 | 10
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 8 | 10
Basins W10 and W11
Basins W10 and W11 are part of the “Drainage, Water Quality and Erosion Control
Report for the Poudre River Whitewater Park Project” drainage study. These basins will
drain via overland flow to a proposed Type R Inlet on E. Vine Dr and then to the Outlet
Stom Line.
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 9 | 10
This basin will generally drain via overland flow to the property adjacent to the west ost
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: Powerhouse II
FORT COLLINS | GREELEY 10 | 10
Runoff Coefficient1
Percent
Impervious1 Project:
Location:
0.95 100%Calc. By:
0.95 90%Date:
0.50 40%
0.55 50%
0.20 2%
0.20 2%
Basin ID Basin Area
(sq.ft.)
Basin Area
(acres)
Asphalt, Concrete
(acres)Rooftop (acres) Gravel (acres)
Residential: Low
Density (acres)
Undeveloped:
Greenbelts,
Agriculture (acres)
Lawns, Clayey Soil, Flat
Slope < 2% (acres)
Percent
Impervious
C2*Cf
Cf = 1.00
C5*Cf
Cf = 1.00
C10*Cf
Cf = 1.00
C100*Cf
Cf = 1.25
Imp. Areas lot 2 & 3 30,613 0.70 0.60 0.10 0.00 0.00 0.00 0.00 99% 0.95 0.95 0.95 1.00
Perv. Areas lot 2 & 3 20,004 0.46 0.00 0.00 0.32 0.00 0.00 0.14 28% 0.41 0.41 0.41 0.51
Imp. Areas lot 4 26,797 0.62 0.51 0.11 0.00 0.00 0.00 0.00 98% 0.95 0.95 0.95 1.00
Perv. Areas lot 4 139,212 3.20 0.00 0.00 3.08 0.00 0.00 0.11 39% 0.49 0.49 0.49 0.61
H1 216,626 4.97 1.11 0.20 3.40 0.00 0.00 0.25 54% 0.60 0.60 0.60 0.76
1 (North Rain Garden) 98,905 2.27 0.92 0.41 0.20 0.00 0.00 0.75 61% 0.66 0.66 0.66 0.83
2 28,583 0.66 0.33 0.15 0.16 0.00 0.00 0.02 81%0.82 0.82 0.82 1.00
3 (South Rain Garden) 36,261 0.83 0.15 0.54 0.00 0.00 0.00 0.15 76% 0.82 0.82 0.82 1.00
4 4,971 0.11 0.11 0.00 0.00 0.00 0.00 0.01 95% 0.91 0.91 0.91 1.00
6 15,843 0.36 0.00 0.00 0.00 0.00 0.00 0.36 2% 0.20 0.20 0.20 0.25
5 4,979 0.11 0.06 0.00 0.00 0.00 0.00 0.05 54% 0.60 0.60 0.60 0.75
7 8,737 0.20 0.11 0.00 0.00 0.00 0.00 0.09 57% 0.62 0.62 0.62 0.78
8 3,134 0.07 0.03 0.00 0.00 0.00 0.00 0.04 42% 0.50 0.50 0.50 0.63
9 3,221 0.07 0.02 0.00 0.00 0.00 0.00 0.06 25% 0.38 0.38 0.38 0.47
10 1,268 0.03 0.00 0.00 0.00 0.00 0.00 0.03 2% 0.20 0.20 0.20 0.25
11 4,762 0.11 0.00 0.00 0.00 0.00 0.00 0.11 2% 0.20 0.20 0.20 0.25
12 7,413 0.17 0.08 0.00 0.00 0.00 0.00 0.09 47% 0.55 0.55 0.55 0.68
Co1 18,348 0.42 0.29 0.00 0.00 0.00 0.00 0.13 69% 0.71 0.71 0.71 0.89
W8 27,443 0.63 0.62 0.00 0.00 0.00 0.00 0.01 98% 0.93 0.93 0.93 1.00
W10 65,340 1.50 Information taken from "Drainage, Water Quality and Erosion Control Report for Poudre River Whitewater Park"90%
W11 38,768 0.89 Information taken from "Drainage, Water Quality and Erosion Control Report for Poudre River Whitewater Park"85%
1 to 12 Site 218,075 5.01 1.8005 1.0933 0.36 0.00 0.00 1.75 59% 0.65 0.65 0.65 0.82
4 and 6 to WQ1 20,813 0.48 0.11 0.00 0.00 0.00 0.00 0.37 24% 0.37 0.37 0.37 0.46
1, 2, 3, 4, 5, 6, 9 and W8 to
DETENETION 220,204 5.06 2.20 1.09 0.36 0.00 0.00 1.41 66% 0.71 0.71 0.71 0.89
Basins Not Detain
Lawns and Landscaping:
Combined Basins A,B & C
2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins
Stormwater Manual (FCSM).
Lawns, Clayey Soil, Flat Slope < 2%
USDA SOIL TYPE: C
Undeveloped: Greenbelts, Agriculture Composite Runoff Coefficient2
1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM.
Historic Basins:
Developed Basins:
DEVELOPED RUNOFF COEFFICIENT CALCULATIONS
Asphalt, Concrete
Rooftop
Gravel
Residential: Low Density
Streets, Parking Lots, Roofs, Alleys, and Drives:
Character of Surface:Powerhouse II
Fort Collins
C. Ortiz
April 18, 2022
Notes:
1) Basins 1 and 2 are draining towards Rain Gardens (LID).
2) "WQ1" consist of basins draining into detention pond that is not treated by LID.
3) Basin 10 and 11 Drain to Lake Canal.
4) Basin 12 Drain to Jerome St.
5) Basin 8 and Co1 Drain to College Ave.
Page 1 of 3
Project Title Date:
Project Number Calcs By:
City
Basins
1
WQCV = Watershed inches of Runoff (inches)66%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100)0.258 in
A =5.06 ac
V = 0.13 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Provided (LID) Rain Gardens =
Volume to be provided in the Pond =
0.06 Ac-ft
3045 cu. ft.
2643 cu. ft.
Powerhouse II April 18, 2022
207-030 C. Ortiz
Fort Collins
5688 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
1, 2, 3, 4, and 6 DETENTION POND Dp1
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
00.10.20.30.40.50.60.70.80.91WQCV (watershed inches)Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
()iii78.019.10.91aWQCV 23 +-=
()iii78.019.10.91aWQCV 23 +-=
AV*
12
WQCV
=
40 hr
SWUGEUGETUDUDUDUDTVAULTF.O.VAULTF.O.F.O.CONTROLIRRCONTROLIRRGASXXOHU OHU
NORTH RAIN GARDENREQUIRED VOLUME: 1,580 CU. FT.MINIMUM FLAT AREA: 1,207 SFPROVIDED VOLUME: 2,117 CU. FT.PROVIDED FLAT AREA: 2,246 SFTREATMENT AREA: 98.905 SFSOUTH RAIN GARDENSREQUIRED VOLUME: 737 CU. FT.MINIMUM FLAT AREA: 551 SFPROVIDED VOLUME: 928 CU. FT.PROVIDED FLAT AREA: 1,231 SFTREATMENT AREA: 36,261 SFEAST VINE DRIVENORTH COLLEGE AVENUE
JEROME STREET JEROME STREET LLC,216 E OAK ST FORTCOLLINSJEROME STREET STATIONLLC, 742 N COLLEGE AVEFORT COLLINSLMC VENTURES LLC,742 N COLLEGE AVEFORT COLLINSCITY OF FORT COLLINS405 N COLLEGE AVEFORT COLLINSMORAK KAREN LLC622 N COLLEGE AVEFORT COLLINSPOWERHOUSE IISHEET NO:P:\207-030\DWG\DRNG\207-030_LID.DWG301 N. Howes Street, Suite 100Fort Collins, Colorado 80521ENGINEERNGIEHTRON RNPHONE: 970.221.4158www.northernengineering.comDRAWING REFERENCE:LID TREATMENT EXHIBITC. Ortiz 1" = 80'APRIL 2022LID-1DRAWN BY:SCALE:ISSUED:NOTES1. FOR LID UNDERGROUND DETENTION CALCULATIONS PLEASEREFER TO THE PRELIMINARY DRAINAGE REPORT, DATED APRIL18, 2022.2. REFER TO UTILITY PLANS FOR POWERHOUSE II FOR ADDITIONALGRADING AND UTILITY INFORMATION.3. REFER TO LANDSCAPE PLANS FOR ADDITIONAL INFORMATION ONHARDSCAPES.4. REFER TO DRAINAGE EXHIBIT SHEET DR1 OF UTILITY PLANS FORSOIL AMENDMENT NOTESLEGENDPROPOSED CONTOURPROPOSED STORM SEWERPROPOSED SWALEEXISTING CONTOURPROPOSED CURB & GUTTERPROPERTY BOUNDARYPROPOSED INLETUNTREATED AREATREATMENT AREANORTH( IN FEET )01 INCH = 80 FEET8080Powerhouse 2 On-Site LID TreatmentProject SummaryProject SummaryTotal Impervious Area125,301sfTarget Treatment Percentage50% Total Paved Area 53,058sfMinimum Area to be Treated by LIDmeasures 62,650sfTarget Percentage25%Treated Impervious Areas by TreatmentMethodMinimum Area to be Pervious 13,264sfRain Garden87,444sf Pervious Area15,575sfTotal Treated Impervious Areas87,444sf Total Pervious Areas15,575sfPercent Total Project Area Treated69.8%Percent Total Project AreaTreated29.4%