HomeMy WebLinkAboutDrainage Reports - 12/04/2018 INTlRW lST c O N 5 U LTI N G GROUP
October 31,2018
Ms. Heather McDowell, P.E.
Fort Collins Utilities—Stormwater
700 Wood Street
Fort Collins, CO 80522 City of Fort Colli s Approved Plans
Approved by:
Re: Hoffman Mill Fueling Site pate:
Final Storm Drainage Letter
Dear Heather,
Please accept the following letter describing the storm drainage intent demonstrating the proposed site
improvement's ability to comply with the City's stormwater requirements.
INTRODUCTION
The Hoffman Mill Fueling Site project proposes to construct a gas and diesel fueling station on the
Hoffman Mill recycling/crushing operations site. The site is located north of Hoffman Mill Road, east of
Lemay Avenue and south of the Cache La Poudre River and is only a portion of the recycling/crushing
operations site. The fueling site is proposed to be located south of the existing building, closest to
Hoffman Mill Road.
A vicinity map is attached for reference.
EXISTING CONDITIONS
The project site is located within the Cache La Poudre drainage basin. The existing site consists of
miscellaneous material storage and is generally undeveloped. The site generally slopes from the
northwest to the southeast at approximately 1.0% grade. All existing material storage and miscellaneous
site improvements will be removed from the site to accommodate the new construction.
We are not aware of any site-specific drainage studies for this site.
The project is not located within a FEMA mapped 100-yr floodplain and is not within a defined City of
Fort Collins floodplain.
PROPOSED DEVELOPMENT
The prosed redevelopment improvements will consist of a constructing a 24 ft wide looping drive lane
and fuel storage/dispensing equipment. A detention pond and sand filter are proposed to satisfy the storm
drainage detention and Low Impact Development (LID) requirements. A long Swale is proposed to be
constructed along the north side of Hoffman Mill Road and will provide a gravity outfall for the site's
storm drainage runoff. The project is planned to be constructed in a single phase.
1218 W.ASH,STE.A, WINDSOR, COLORADO 80550
TEL.970.674.3300-FAX 970.674.3303
Hoffman Mill Fueling Site
Final Storm Drainage Letter
October 31,2018
Page 2 of 4
The proposed improvements are included in a single drainage basin with one offsite basin drainage to and
being conveyed through the proposed improvements. These basins consist of:
Basin D1 consists of the fueling site and is approximately 0.59 acres and 44.8% impervious. The
detention and water quality facilities are located within this basin and outfall to the proposed swale.
Basin OS1 consists of the are north and west of the proposed site that drains to Basin D1. The basin is
approximately 3.05 acres and is 12.4% impervious. The runoff from this basin will be routed through the
detention pond.
An outfall swale is proposed along the north side of Hoffman Mill Road and will discharge to the existing
water quality structure, similar to as is has historically. Due to grade limitations, the swale is designed
with a 0.5% slope. This slope will help sediment settle from the adjacent crushing operations areas and
provide a gravity outfall for the fuel site.
All calculations and exhibits are attached for reference.
Detention Pond
The proposed detention pond detains the developed runoff to the historic 2-yr runoff rate. The historic 2-
yr runoff rate is 0.50 cfs and combined with the offsite flows routed through the pond of 7.2 cfs,provides
a release rate of 7.70 cfs. The required 100-yr detention volume is 2,788 cu-ft with a water surface
elevation of 4946.90 ft. Majority of the site improvement's runoff surface drains to the sand filter and
spills into the detention pond when runoff rates exceed the capacity of the sand filter. The water quality
capture volume for the sand filter is 283 cu-ft. Combined with the 100-yr detention volume, the required
pond volume is 3,071 cu-ft. The water quality capture volume water surface elevation is controlled by the
spillway with an elevation of 4947.70 ft. The sand filter is intended to provide water quality enhancement
and to satisfy the Low Impact Development(LID)requirements.
All calculations and exhibits are attached for reference.
LOW IMPACT DEVELOPMENT TECHNIQUES
In reference to the code requirements for implementation of Low Impact Development(LID)techniques,
the use of sand filter is proposed to satisfy these requirements. The sand filter will slow runoff,promote a
reduction of runoff through infiltration, and will also capture sediment prior to discharging through the
perforated underdrain.
Below is a description of the 4 step process for selecting structural BMPs:
Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process for receiving
water protection that focuses on reducing runoff volumes, treating the water quality capture volume
(WQCV), stabilizing drainageways and implementing long-term source controls. The Four Step Process
applies to the management of smaller, frequently occurring events.
Step 1: Employ Runoff Reduction Practices
To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low Impact
Development(LID) strategies,including Minimizing Directly Connected Impervious Areas(MDCIA).
Hoffman Mill Fueling Site
Final Storm Drainage Letter
October 31,2018
Page 3 of 4
The sand filter will slow runoff, promote infiltration, and filter runoff prior to being released into the
adjacent storm drain system.
Step 2:Implement BMPs that Provide a Water Quality Capture Volume with Slow Release
The sand filter will provide a slow release by infiltration through the sand media.
Step 3: Stabilize Drainageways
Natural Drainageways are subject to bed and bank erosion due to increases in frequency, duration, rate
and volume of runoff during and following development. The site will ultimately drain to an existing
Swale that is well vegetated and addition bank stabilization is unnecessary with this project.
Step 4:Implement Site Specific and Other Source Control BMPs
Proactively controlling pollutants at their source by preventing pollution rather than removing
contaminants once they have entered the stormwater system or receiving waters is important when
protecting storm systems and receiving waters. This can be accomplished through site specific needs
such as construction site runoff control, post-construction runoff control and pollution prevention / good
housekeeping. It will be the responsibility of the contractor to develop a procedural best management
practice for the site.
A spill control structure is proposed with this project. Runoff from the dispensing area and fuel storage
area will drain to a modified Type R inlet. The inlet is modified to provide a baffle to capture spilt fuel.
It also has a valve to control the flow leaving the inlet during a spill event. It will the operators'
responsibility to frequently observe structure and removed any accumulated fuel and also close the outlet
valve during a spill event.
All calculations are attached for reference.
EROSION CONTROL
Erosion and sedimentation will be controlled on-site by use of sediment control logs, inlet protection, a
gravel construction entrance, seeding, mulch, and turf. The measures are designed to limit the overall
sediment yield increase due to construction as required by the City of Fort Collins. During overlot and
final grading the soil will be roughened and furrowed perpendicular to the prevailing winds.
During the performance of the work required by these specifications or any operations appurtenant
thereto, whether on right-of-way provided by the City or elsewhere, the contractor shall furnish all labor,
equipment, materials, and means required. The Contractor shall carry out proper efficient measures
wherever and as necessary to reduce dust nuisance, and to prevent dust nuisance that has originated from
his operations from damaging crops, orchards, cultivated fields, and dwellings, or causing naissance to
persons. The Contractor will be held liable for any damage resulting from dust originating from his
operations under these specifications on right-of-way or elsewhere.
It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights-of-way.
Wherever construction vehicles access routes or intersect paved public roads,previsions must be made to
minimize the transport of sediment by runoff or vehicles tracking onto the paved surface. Stabilized
Hoffman Mill Fueling Site
Final Storm Drainage Letter
October 31,2018
Page 4 of 4
construction entrances are required with base material consisting of 6" coarse aggregate. The contractor
will be responsible for clearing mud tracked onto city streets on a daily basis.
All temporary and permanent erosion and sediment control practices must be maintained and repaired as
needed to assure continued performance of their intended function. Silt fence and sediment control logs
will require periodic replacement. Maintenance is the responsibility of the contractor.
All disturbed areas must be seeded and mulched within 30 days of project start. Vegetation shall not be
considered established until a ground cover is achieved which is demonstrated to be mature enough to
control soil erosion to the satisfaction of the City Inspector and to survive severe weather condition.
Thank you in advance for you ou have any questions or comments please contact me at
(970) 347-8917. �C
Sincerely,
m;
t yi
Jason T. Claeys, P.E., LEED TONAL
Interwest Consulting Group
Attachments
MULBERRY ST (HWY 114)
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VICINITY MAP
SCALE: 1" = 1000'
PROJECT DATUM: NAVD88
CITY OF FORT COLLINS BENCHMARK#17-92
300 FEET SOUTH OF THE SOUTHWEST CORNER OF EAST DRAKE RD
AND TIMBERLINE RD, IN THE TOP OF AN IRRIGATION STRUCTURE
ELEV= 4938.70
CITY OF FORT COLLINS BENCHMARK#8-02
ON THE SOUTHEAST CORNER OF THE INTERSECTION OF LEMAY AVE AND
MULBERRY ST, IN THE CURB,ON THE SOUTHEAST SIDE OF A TRIANGULAR
ISLAND THAT CONTAINS THE TRAFFIC SIGNAL.
ELEV= 4939.27
PLEASE NOTE:THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM.
SURROUNDING DEVELOPMENTS MAY HAVE USED NGVD29 UNADJUSTED
FOR THEIR VERTICAL DATUMS
IF NGVD29 UNADJUSTED IS REQUIRED FOR ANY PURPOSE,THE FOLLOWING
EQUATIONS SHOULD BE USED:
NGVD UNADJUSTED = (NAVD88)-3.19
v — V tJ i u
LEGEND 'A
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O BASIN DESIGNATION
BASIN COEFFICIENT(100-YR)
BASIN AREA s
D01 DESIGN POINT e
DRAINAGE FLOW ARROW a
J ' \ _ ^ ' ( ;\\`\\1��� - - DRAINAGE BASIN
BOUNDARY
DRAINAGE BASIN
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HOFFMAN MILL ROAD �_ -D F 0 W
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PROJ.NO.134409500
3 1 OF 1
Hoffman Mill Fuel Site
EXISTING IMPERVIOUS AREA CALCULATION
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6, 2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001 (Revised January 2016)
BASINS:
% Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins-Storm Water Criteria Manual
Frequency
Land Use % Runoff Return Adjustment
Impervious Coefficient C Period
Factor(C)
Paved 100% 0.95 2-year to
1.00
10 ear
Roof 90% 0.95 100-year 1.25
Walks/RAP 90% 0.95
Gravel/Pavers 40% 0.50
Lawns
0% 0.25
(Heavy,2-7%Slope)
Sub-basin Atotal Atotal Apaved Aroof Awalk/RAP Apavers Alawn Weighted% COMPOSITE
Designation (sq feet) (acres) (sq feet) (sq feet) (sq feet) (sq feet) (sq feet) Impervious CZ to C10 C100
osi 133,035 3.054 0 8,330 9,935 0 114,770 12.4% 0.35 0.43
H1 25,833 0.593 0 2,480 3,038 0 20,315 19.2% 0.40 0.50
1344-095-00 Rational Calcs (FC).xlsx Page 1 of 4 Interwest Consulting Group
Hoffman Mill Fuel Site
HISTORIC TIME OF CONCENTRATION
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6,2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001(Revised January 2016)
Overland Flow Equations for City of Fort Collins-Storm Water Criteria Manual
EQUATIONS: L
t. =t +t V =C So.s -Equation 6-4 — ( )� -Equation 6-2 tc 18— 15i +60(24i+ 12),[S- -Urbanized Check Equation 6-5
_ L
L — 1.87(1.1— CXCf)V t. -CoFC Overland Flow It
6
t
CONSTRV MINTS:
300 ft-Overland flow shall not exceed for developed condition
500 ft-Overland flow shall not exceed for undeveloped condition
Final tc =minimum of ti +tt and urbanized basin check
recommended minimum t,=5 min for urbanized basins
Time of Concentration (2-yr to 10-yr)
INITIAL/OVERLAND TIME
SUB-BASIN DATA TRAVEL TIME(tt) Urban Check Final
(t;)
t�t;+t, tc
Table RO-2 min
DESIGN % AREA LENGTH SLOPE t; LENGTH SLOPE VELOCITY tr (min) OVERALL SLOPE t' (min)
POINT Sub-basin Impervious C2-ro (acres) (ft) (ft/ft) (min) (ft) (ft/ft) 7ypeofiravel � (ft/s) (min) (ft/ft) (min)
Surface
O51 OSi 12.4% 0.35 3.054 300 0.0157 21.02 234 0.0120 Paved Areas 20 2.19 1.78 22.80 0.0141 21.16 21.16
H1 I H1 19.2% 0.40 0.593 88 0.0291 8.63 154 0.0093 Paved Areas 20 1.93 1.33 9.96 0.0165 17.01 9.96
1344-095-00 Rational Calcs(FC).xlsx Page 2 of 4 Interwest Consulting Group
Hoffman Mill Fuel Site
HISTORIC TIME OF CONCENTRATION
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6,2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001(Revised January 2016)
Overland Flow Equations for City of Fort Collins-Storm Water Criteria Manual
EQUATIONS: S0.5L
-Equation 6-2 -Equation 6-4 tc 18— 15i +60(24i+12)TS -Urbanized Check Equation 6-5
_ L
1.87(1.1 —CXCf)� -COFCOverlandFlow tt 6
ti =
CONSTRAINTS:
300 ft-Overland flow shall not exceed for developed condition
500 ft-Overland flow shall not exceed for undeveloped condition
Final tc =minimum of ti +tr and urbanized basin check
recommended minimum t,=5 min for urbanized basins
Time of Concentration(100-yr)
SUB-BASIN DATA INITIAL/OVERLAND TIME TRAVEL TIME(tJ Urban Check
Final(t.)
t t;+tt t
Table RO-2 min `
DESIGN % AREA LENGTH SLOPE t; LENGTH SLOPE VELOCITY tt (min) OVERALL SLOPE tt
POINT Sub-basin Impervious C100 (acres) (ft) (ft/ft) (min) Ift) (ft/ft) Type rfTravel (ft/s) (min) (ft/ft) (min) (min)
Surface
OS1 OS1 12.4% 0.43 3.054 300 0.0157 18.61 234 0.0120 Paved Areas 20 2.19 1.78 20.39 0.0141 21.16 20.39
H1 H1 19.2% 0.50 0.593 88 0.0291 7.40 154 0.0093 Paved Areas 20 1.93 1.33 8.73 0.0165 17.01 8.73
1344-095-00 Rational Calcs(FC).xlsx Page 3 of 4 Interwest Consulting Group
Hoffman Mill Fuel Site
HISTORIC PEAK RUNOFF
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6,2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001(Revised August 2006)
EQUATIONS: I =rainfall intensity(in/hr)
Q" = n-yr peak discharge(cfs) P 1 =one-hour point rainfall depth(in)
C I"A" C" =n-yr runoff coefficient 28 5 pl tc =time of concentration(min)
Q" 1" =n-yr rainfall intensity(in/hr) I (10+t 0.786651) P 1-2yr= 0.82 in
An =Basin drainage area(ac) Pi-10yr = 1.40 in
P1-100yr = 2.86 in
BASIN SUMMARY:
2-yr Peak Runoff 10-yr Peak Runoff 100-yr Peak Runoff
Design Sub basin Area(acres) Runoff Coeff Intensity 3 Runoff Coeff. Intensity 3 Runoff Coeff. Intensity 3
Point t,(min) C(A)(acres) Q(ft/s) t,(min) C(A)(acres) Q(ft/s) tr(min) C(A)(acres) Q(ft/s)
IC,) (in/hr) (cm) (in/hr) (C-) (in/hr)
O51 o51 3.054 21.16 0.35 1.06 1.56 1.65 21.16 0.35 1.06 2.67 2.82 20.39 0.43 1.32 5.45 7.20
H1 H1 0.593 9.96 0.40 0.24 2.22 0.53 9.96 0.40 0.24 3.79 0.90 8.73 0.50 0.30 7.74 2.29
1344-095-00 Rational Calcs(FC).xlsx Page 4 of 4 Interwest Consulting Group
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/mL���1► SCL WOCV WSE-/947.70 c I tm TRENCH GRAN � )[OI
10D-YR DETENTION VOLUME-2.708 CU-FT EX A/U(CH EX >�N II ( a +['L.' E / ��V) / a' U) >m 0
100-YR WISE-4M.90 ❑ / e ` lil Q
TOTAL VOLUME REWIRED-3.071 CU-FT 1 ' - / / IL 0 r`
SITE RELEASE RATE-0.5 CFS / / - �.- U O
® 1 - ;100-YR OFFSITE RIRaOFF RATE-7.2 CPS / / --44+- W N
TOTAL RELEASE RATE-7.7 CFS �- / I EX � / pA W W
VIC �►, _ - -- SCL ORIFICE PLATE DIA-14-5/16' - Sm ? z I\
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LEGEND BASIN SUMMARY: W
2-VFhA Runoff 10- Peak Rt-ff 1 Mat INnIoR �. n'
Defer wlwaan Areal:n•.) IW�rowtaR J
P- GAI IebeYty s,Eewf«w qAI '60V lns,CRew. 'a IrV-Ad
BASIN DESIGNATION t.Iminl QR'/i 49nIEl QRI/+1 4Mn1 qRI/el O
IMPERVIOUS ARFA I035 (LI N PMNeI 10.3r1 lanaq BNEeI K,..1 Ps.eY Itn/Im)
I BASIN COEFFICIENT(100VR) TREATED BY UD \ 053 OSl 3.0>4 11.t6 p.35 1.06 1.56 1.65 21.16 0.35 1 1.06 1.67 2J] 11.16 5.45).W ]39 T.IO
1.25 0.50 (6.980 \ v LL SOFT) Dl 03 0.593 1311 0 7o 0.60 .36 1.9E a. 13.11 0.E0 03E 33T iJa 10.1E D.)9 O.N
BASIN AREA ® SEDIMENT CONTROL LOG \
DESIGN POINT O E3 CHECK DAM(PERMANENT) \ O
\\ \ NOTES 3. RE-DISTURBANCE VEGETATION SHALL BE PROTECTED AND RETAINED W
WHEREVER POSSIBLE.REMOVAL OR DISTURBANCE OF EXISTING U
DRAINAGE FLOW ARROW \ \\ \ \ Q
I CE VIG CONSTRUCTION ENTRANCE 1. CONTRACTOR TO ES PRIG AND MAINTAIN ALL NECESSARY EROSION VEGETATION SHALL R LIMITED TO THE AREA REQUIRED FOR IMMEDIATE Z
O® W/VEHICLE TRACKING CONTROL \ \ \ CONTROL MEASURES PRIOR TO AND THROUGHOUT CONSTRUCTION. PERIODCONSTRUCTIONFME OPERATIONS,AND FOR THE SHORTEST PRACTICAL Z LL
_ - DRAINAGE BASIN \ PLACE EROSION CONTROL PROTECTION AT ALL EXISTING INLETS PERIOD OF TIME. O
BOUNDARY 30 1 5 O 30 60 \ DOWNSTREAM FROM THE CONSTRUCTION AREA.EROSION CONTROL F
\ 4. ALL SOILS EXPOSED DURING LAND DISTURBING ACTIVITY(STRIPPING.SHALL
V ,^
_ DRAINAGE BASIN CWA CONCRETE WASHOIfT AREA \ \ PROTECTION SHALL REMAIN IN PLACE ND IS CONSTRUCTION IS V/
\ GRADING.UTILITY INSTALLATIONS.STOCKPILING.FILLING.ETCJ SHALL III
-� FLOW PATH SCALE:1"=3O' � J \ COMPLETE AND ALL DISTURBED GROUND IS ADEQUATELY VEGETATED BE KEPT INARWGHENEDCONDfIION BY RIPPING OR DISKING ALONG �Y
\ WTTHOWNER'S APPROVAL FOR REMOVAL
\ LAND CONTOURS UNTIL MULCH.VEGETATION.OR OTHER PERMANENT O T
\ 2. THE EXTENT OF EROSION CONTROL PROTECTION SHALL BE OBSERVED EROSION CONTROL IS INSTALLED.NO SOILS IN AREAS OUTSIDE w ` x
I \ AND ADJUSTED AS NEEDED DURING CONSTRUCTION BASED ON SR'E PROJECT STREET RIGHTS OF WAY SHALL REMAIN EXPOSED BY LAND (L
\ CONDIITONS AND THE PERFORMANCE OF THE EROSION CONTROL DISTURBING ACTTVITV FOR MORE THAN THIRTY(30)DAYS BEFORE Z W
\11)I CONTROL MEASURES SHOWN. SUPPLY SUFFICIENT EROSION REQUIRED TEMPORARY OR PERMANENT EROSION CONTROLIE.G. y
(\ CONTROL AND MINIMIZE DOWNSTREAM WATERWAY POLLUTION. SEE/MULCH.LANDSCAPING.ETC)IS INSTALLED,UNLESS OTHERWISE 4I
3. LIMIT DISTURBANCE TO AREAS WITHIN EROSION CONTROL BOUNDARIES. APPROVED By THE STORMWATER DEPARTMENT. C w
ADJUST EROSION CONTROL BOUNDARIES AS NECESSARY TO 5. THE PROPERTY MUST BE WATERED AND MAINTAINED AT ALL IAUSED �L
EX OMH J7 EX 8'PIC
_ \ \ fZ=49JS1 SHALL BE PREPARED(SEEDED BMULLCHED SURFACE ROUGHENISED WORK.ALL DISTURBED NG. EROSION.OALL LAND DISTURBINNSTRUCTION G ACTIVITIES SHALL BES SO AS TO EI IMMEDIATELY EX GRAV£L --- �� �/W7H DIN - (PROTECT N PLACE) )TO MINIMIZE EROSION POTENTIAL AND SOILMIGRATION. DISCONTINUED WHEN FUGITIVE DUST IMPACTS ADJACENT PROPERTIES,
Ld W ' / - - 4 SUBMITTED G
Z (PROTECT N PLACE) _
S -
AS DETERMINED BY THECT'EN ENGINEERINGDEPARTMENT.
---_-__-_ - ���� �rl
_ STORMWATER MANAGEMENT PLAN SHALL BE PREPARED AND SUB D
_ _r ED
---- ____ -- 93T --_ SEE LANDSCAPE PLAN FOR R(VEGETATIONNMETHODS AND DETAILS. FTER R
INCH pUNOANDEVEM AND EVERY 14 D REPAIRED OR REC AYSLM ORDER TTED AS O MEASURES
MUST
( ST BE
-(- DURING CONSTRUCTION. SOIL DISTURBED AND NOT UNDER ACTIVE CONTINUED PERFORMANCE OF THEIR INTENDED FUNCTKJN.ALL
- CONSTRUCTION SHALL BE SEEDED AND MULCHED PER LCUASS RETAINED SEDIMENTS.PARTICULARLY THOSE ON PAVED ROADWAY
= QF Iva CD 38- _�� STANDARDS. SURFACES,SHALL BE REMOVED AND DISPOSED OF IN AMANNER AND O
IIII _ / � �) _ �.« �� ' _ ��\ I 6. ANY DISTURBED LAND MUST RECEIVE SURFACE ROUGHENING, LOCATION SO AS NOT TO CAUSE THEIR RELEASE INTO ANY
e U) _--- � - � - __ mtC- ( L INCLUDING BUT NOT LIMITED TO SLOPED AREAS. DRAINAGEWAY.
7. AREAS THAT EXPERIENCE EROSION ISSUES FROM STEEP SLOPES OR 7. NO SOIL STOCKPILE SHALL EXCEED TEN(10)FEET IN HEIGHT.ALL SOIL
--- Rrx 8, � y- -- WATER EROSION RESULTING IN SEED NOT BEING ABLE TO ESTABLISH STOCKPILES SHALL BE PROTECTED FROM SEDIMENT TRANSPORT BY
- _ _20•r`. �'� EX B'PVL' _ DURING THE FIRST GROWING SEASON SHALL REQUIRE RESEEDING AND SURFACE ROUGHENING,WATERING,AND PERIMETER SILT FENCING.ANY
DA ACCESS,DRAINAGE,UTILITY -�� fZ=4937J emu?= EROSION CONTROL BLANKETS TO STABILIZE THE SOIL. SOIL STOCKPILE REMAINING AFTER 30 DAYS SHALL BE SEEDED AND
d SCL !EMERGENCY ACCESS ALIGNMENT = MULCHED. O U U
5 / \mom ROAD -" �`asr i S. THE SAND FILTER ISTO BE INSTALLED AT THE CONCLUSION OF OT 0) � l
MILL _-� - CONSTRUCTION ACTIVITIES ON THE SITE. 8. CRY ORDINANCE PROHIBITS THE TRACKING.DROPPING,OR DEPOSITING II Q
_ _ ___ (PROTECT w PLACE)
A
-�� OFFMAN .� d981' OF SOILS IC ANY INADVEATERIALONTO CITY EDMATERIAL BY ORHALL FROM \
H 9. REFERENCE SHEET 9 FOR EROSION CONTROL DEPAILS. ANY VEHICLE.ANY INADVERTENT DEPOSITED MATERIAL SHALL BE Z m m
\ A$%/ALT �y�1\l��� - EX B'PIC _ _ CLEANED IMMEDIATELY BY THE CONTRACTOR.
_ fL.49J7.J' COFC STANDARD EROSION AND SEDIMENT CONTROL NOTES: I S W Q
-_-_- �•�----- 1 �- ' PROPERTY LINE(TYP) - (PROTECT N PLACE)- - _ IX/0200' }{-1-H+++ - Z y
RR 1. THE CITY STORMWATER DEPARTMENT EROSION CONTROLINSPECTOR yj -I -I U
MUST BE NOTIFIED AT LEAST 24 HOURS PRIOR TO ANY CONSTRUCTION City of Fort Collins,Colorado I- Q < a W
ONTHISSITE. UTILITY PLAN APPROVAL o U U o u
--»s` - - - - - -- -
ALL REQUIRE BMPS MUST BE INSTALLED PRIOR TO ANY LAND
DISTURBING ACTIVITY(STOCKPILING.STRIPPING,GRADING.ETC).ALL
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Hoffman Mill Fuel Site
DEVELOPED IMPERVIOUS AREA CALCULATION
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6, 2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001 (Revised January 2016)
BASINS:
%Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins-Storm Water Criteria Manual
Frequency
Land Use % Runoff Return adjustment
Impervious Coefficient C Period
Factor(C)
E21yearPaved 100% 0.95 1.00
Roof 90% 0.95 1.25
Walks 90% 0.95
Gravel/Pavers 40% 0.50
Lawns
(Heavy,2-7%Slope) 0% 0.25
Sub-basin Atotal Atotal Apaved Aroof Awalk Agravel/pavers Alawn Weighted% COMPOSITE
Designation (sq feet) (acres) (sq feet) (sq feet) (sq feet) (sq feet) (sq feet) Impervious C2to Cio Cioo
D1 25,836 0.59 0 2,481 10,384 0 12,971 44.8% 0.60 0.75
1344-095-00 Rational Calcs (FC).xlsx Page 1 of 4 Interwest Consulting Group
Hoffman Mill Fuel Site
DEVELOPED TIME OF CONCENTRATION
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6,2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001(Revised January 2016)
Overland Flow Equations for City of Fort Collins-Storm Water Criteria Manual
EQUATIONS: L
t, =ti +t V =CAS v -Equation 6-4 t = (18— 151) + -Urbanized Check Equation 6-5
+ -Equation 6-2 � c
60(24i+12)�
L
1.87(1.1 — CxCf)y L. -CoFC Overland Flow It
_ 6
ti = 3 r
CONSTRAINTS:
300 ft-Overland flow shall not exceed for developed condition
500 ft-Overland flow shall not exceed for undeveloped condition
Final t, =minimum of ti +tt and urbanized basin check
recommended minimum t,=5 min for urbanized basins
Time of Concentration(2-yr to 10-yr)
SUB-BASIN DATA INITIAL/OVERLAND TIME TRAVEL TIME(tt) Urban Check
Final(ti)
t`t;+t< t
Table RO2 min `
DESIGN % AREA LENGTH SLOPE t; LENGTH SLOPE ae -
VELOCITY t, (min) OVERALL SLOPE t,
Sub-basin Cz-to T eof
Travel (min)
POINT Impervious (acres) (ft) (ft/ft) (min) (ft) (ft/ft) vv Surface
c� (ft/s) (min) (ft/ft) (min)
D1 D1 44.8% 1 0.60 1 0.593 1 156 1 0.0072 13.08 1 150 0.0229 Paved Areas 20 3.03 0.83 13.90 0.0149 13.11 13.11
1344-095-00 Rational Calcs(FC).xlsx Page 2 of 4 Interwest Consulting Group
Hoffman Mill Fuel Site
DEVELOPED TIME OF CONCENTRATION
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6,2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001(Revised January 2016)
Overland Flow Equations for City of Fort Collins-Storm Water Criteria Manual
EQUATIONS: L
t�. =t; +t V =C A S 0 5
-Equation 6-2 -Equation 6-4 tc = (18— 15i)+60(24i+12)V-S- -Urbanized Check Equation 6-5
ti =
1.87(1.1—CXCf)yL -COFCOverlandFlow tr _ L
6
CONSTR;I ANTS:
300 ft-Overland flow shall not exceed for developed condition
500 ft-Overland flow shall not exceed for undeveloped condition
Final t, =minimum of ti +tt and urbanized basin check
recommended minimum t,=5 min for urbanized basins
Time of Concentration (100-yr)
SUB-BASIN DATA INITIAL/OVERLAND TIME TRAVEL TIME(tt) Urban Check
Final(ti)
t,=t;+t, tc
DESIGN % AREA LENGTH SLOPE t; LENGTH SLOPE VELOCITY t, (min) OVERALL SLOPE tc
Sub-basin Ct� T Table eofTravel RO-2 (min)
POINT Impervious (acres) (ft) (ft/ft) (min) (ft) (ft/ft) vP (ft/s) (min) (ft/ft) (min)
Surface
Dl I Dl 1 44.8% 1 0.75 0.593 1 156 1 0.0072 1 9.18 1 150 0.0229 Grassed waterway 1 15 2.27 1 1.10 10.28 0.0149 13.11 10.28
1344-095-00 Rational Calcs(FC).xlsx Page 3 of 4 Interwest Consulting Group
Hoffman Mill Fuel Site
DEVELOPED PEAK RUNOFF
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: June 6,2018
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District,June 2001(Revised August 2006)
EQUATIONS: 1 =rainfall intensity(in/hr)
Q = n-yr peak discharge(cfs) P I =one-hour point rainfall depth(in)
=C ! A C =n-yr runoff coefficient 28.5 pl tr =time of concentration(min)
Q" 1 =n-yr rainfall intensity(in/hr) I — (10+t 0786651) P1-2rr = 0.82in
A =Basin drainage area(ac) P -1 I 0y„= 1.40 in
P1.100y,= 2.86 in
BASIN SUMMARY:
2-yr Peak Runoff 10-yr Peak Runoff 100-yr Peak Runoff
Design Sub-basin Area(acres) Runoff Coeff Intensity a Runoff Coeff Intensity 3 Runoff Coeff. Intensity n
Point t,(min) (Cz.1d C(A)(acres) (in/hr) Q(ft/s) tc(min) Ic-oll C(A)(acres) (in/hr) Q(ft/s) t,(min) (C—) C(A)(acres) (in/hr) Q(ft/s)
D1 D1 0.593 1 13.11 0.60 0.36 1.98 0.70 13.11 0.60 0.36 3.37 1.20 10.28 0.75 0.44 1 7.64 3.39
1344-095-00 Rational Calcs(FC).xlsx Page 4 of 4 Interwest Consulting Group
Hoffman Mill Fueling Site
Critical Pond Elevations
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: September 25,2018
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District,June 2001 (Revised April 2008)
Volume obtained utilizing 2018 AutoCAD Civil3D
Storage Summary
Sand Filter Invert Elevationi 4947.00 ft
Required Water Qualtiy Capture Volume(WQCV) 283 cu-ft
WQCV Provided 290 cu-ft
WQCV Water Surface Elevation(WSE) 4947.70 ft
Require 100-yr Detention Volume 2,788 cu-ft
Combined Required 100-yr Detention&WQCV 3,071 cu-ft
Pond Invert Elevation 4944.56 ft
Total Detention Volume Provided 3,164 cu-ft
100-yr WSE 1 4946.90 ft
1344-095-00 PondCalcs.xls-Pond Stage Storage Page 1 of 3 Interwest Consulting Group
Hoffman Mill Fuel Station
100-yr Detention Volume- FAA Method
Design Engineer: J.Claeys
Design Firm: Interwest Consulting
Project Number: 1344-095-00
Date: June 6,2018
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual,Urban Drainage and Flood Control District,June 2001(Revised April 2008)
City of Fort Collins-Storm Water Criteria Manual
Detention Volume Calculation
Runoff Coefficient(C) 0.60
Frequency Factor(C,) 1.25 Required Detention
Adjusted Runoff Coefficient(CCf) 0.75 W acre-ft
Area(A) 0.59 acres 2,788 0.064
Allowed Release Ratel 0.50 cfs
100-yr Accumulative Release Detained Detained
Time Intensity Q100 Runoff Volume Volume Volume Volume
(min) (1,in/hr) (cfs) (ft) (ft) (ft) (acre-ft)
0 0.00 0.00 0.00 0.00 0.00 0.0000
5 9.95 4.40 1,320.86 150.00 1,170.86 0.0269
10 7.72 3.42 2,049.66 300.00 1,749.66 0.0402
15 6.52 2.89 2,596.59 450.00 2,146.59 0.0493
20 5.60 2.48 2,973.60 600.00 2,373.60 0.0545
25 4.98 2.20 3,305.48 750.00 2,555.48 0.0587
30 4.52 2.00 3,600.18 900.00 2,700.18 0.0620
35 4.08 1.81 3,791.34 1,050.00 2,741.34 0.0629
40 3.74 1.65 3,971.88 1,200.00 2,771.88 0.0636
45 3.46 1.53 4,133.84 1,350.00 2,783.84 0.0639
50 3.23 1.43 4,287.83 1,500.00 2,787.83 0.0640
55 3.03 1.34 4,424.56 1,650.00 2,774.56 0.0637
60 2.86 1.27 4,555.98 1,800.00 2,755.98 0.0633
65 2.72 1.20 4,694.04 1,950.00 2,744.04 0.0630
70 2.59 1.15 4,813.52 2,100.00 2,713.52 0.0623
75 2.48 1.10 4,938.30 2,250.00 2,688.30 0.0617
80 2.38 1.05 5,055.12 2,400.00 2,655.12 0.0610
85 2.29 1.01 5,167.96 2,550.00 2,617.96 0.0601
90 2.21 0.98 5,280.80 2,700.00 2,580.80 0.0592
95 2.13 0.94 5,372.39 2,850.00 2,522.39 0.0579
100 2.06 0.91 5,469.30 3,000.00 2,469.30 0.0567
105 2.00 0.89 5,575.50 3,150.00 2,425.50 0.0557
110 1.94 0.86 5,665.77 3,300.00 2,365.77 0.0543
115 1.89 0.84 5,770.64 3,450.00 2,320.64 0.0533
120 1.84 0.81 5,862.24 3,600.00 2,262.24 0.0519
125 1.79 0.79 5,940.56 3,750.00 2,190.56 0.0503
130 1.75 0.77 6,040.13 3,900.00 2,140.13 0.0491
135 1.71 0.76 6,129.07 4,050.00 2,079.07 0.0477
140 1.67 0.74 6,207.39 4,200.00 2,007.39 0.0461
145 1.63 0.72 6,275.09 4,350.00 1,925.09 0.0442
150 1.60 0.71 6,372.00 4,500.00 1,872.00 0.0430
155 1.57 0.69 6,460.94 4,650.00 1,810.94 0.0416
160 1.54 0.68 6,541.92 4,800.00 1,741.92 0.0400
165 1.51 0.67 6,614.93 4,950.00 1,664.93 0.0382
170 1.48 0.65 6,679.98 5,100.00 1,579.98 0.0363
175 1.45 0.64 6,737.06 5,250.00 1,487.06 0.0341
180 1.42 0.63 6,786.18 5,400.00 1,386.18 0.0318
185 1.40 0.62 6,876.45 5,550.00 1,326.45 0.0305
190 1.38 0.61 6,961.41 5,700.00 1,261.41 0.0290
195 1.36 0.60 7,041.06 5,850.00 1,191.06 0.0273
200 1.34 0.59 7,115.40 6,000.00 1,115.40 0.0256
205 1.32 0.58 7,184.43 6,150.00 1,034.43 0.0237
210 1.30 0.58 7,248.15 6,300.00 948.15 0.0218
215 1.28 0.57 7,306.56 6,450.00 856.56 0.0197
220 1.26 0.56 7,359.66 6,600.00 759.66 0.0174
225 1.24 0.55 7,407.45 6,750.00 657.45 0.0151
230 1.22 0.54 7,449.93 6,900.00 549.93 0.0126
235 1.21 0.54 7,549.49 7,050.00 499.49 0.0115
240 1.20 0.53 7,646.40 7,200.00 446.40 0.0102
Design Procedure Form: Sand Filter(SF)
UD-BMP(Version 3.06,November 2016) Sheet 1 of 2
Designer: J.Claeys
Company: Interwest Consulting Group
Date: October 31,2018
Project: Hoffman Mill Fueling Site
Location:
1.Basin Storage Volume
A)Effective Imperviousness of Tributary Area,h I„= 100.0
It00%if all paved and roofed areas upstream of sand filter)
B) Tributary Area's Imperviousness Ratio(i=Id100) i= 1.000
C) Water Quality Capture Volume(WQCV)Based on 12-hour Drain Time WQCV= 0.40 watershed inches
WQCV=0.8'(0.91*i3-1.19'iz+0.78'i)
D) Contributing Watershed Area(including sand filter area) Area= 8,500 sq ft
E) Water Quality Capture Volume(WQCV)Design Volume Vwocv= 283 cu ft
Vwocv=WQCV/12'Area
F) For Watersheds Outside of the Denver Region,Depth of d6= 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VwocvOTHER= 283 cu ft
Water Quality Capture Volume(WQCV)Design Volume
H) User Input of Water Quality Capture Volume(WQCV)Design Volume VwocvusER= cu ft
(Only if a different WQCV Design Volume is desired)
2.Basin Geometry
A)WQCV Depth Dwocv= 0.75 ft
B)Sand Filter Side Slopes(Horizontal distance per unit vertical, Z= 4.00 ft/ft
4:1 or flatter preferred). Use"0"if sand filter has vertical walls.
C)Minimum Filter Area(Flat Surface Area) AM,,,= 106 sq ft
D)Actual Filter Area AAM.1= 114 sq ft
E)Volume Provided VT= 290 cu ft
Choose One
3. Filter Material (*18"CDOT Class 8 or C Filter Material
O Other(Explain):
4. Underdrain System
Choose One
A)Are underdrains provided? @)YES
ONO
B)Underdrain system orifice diameter for 12 hour drain time
i)Distance From Lowest Elevation of the Storage y= ft
Volume to the Center of the Orifice
ii)Volume to Drain in 12 Hours Vol„= N/A cu It
iii)Orifice Diameter,3/8"Minimum D,= in
UD-BMP v3.06.xisrn,SF 10/25/2018,11:20 AM
Design Procedure Form: Sand Filter(SF)
Sheet 2 of 2
Designer: J.Claeys
Company: Interwest Consulting Group
Date: October 31,2018
Project: Hoffman Mill Fueling Site
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric Choose One
Q YES QQ NO
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6-7. Inlet/Outlet Works
A) Describe the type of energy dissipation at inlet points and means of
conveying flows in excess of the WQCV through the outlet
Notes:
UD-BMP v3.06.xlsm,SF 10/25/2018,11:20 AM
Hoffman Mill Fueling Site
Emergency Overflow Spillway Calculations
Design Engineer: 1.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: September 25,2018
Broad-Crested Weir Equation-Trapezoidal Shape
(H�5 where: Q =Discharge(cfs)
CLHZ +C2 C =WeirCoeffecient
Q= y L =Weir Length(ft)
H =Average Weir Head(ft)
H:V=Side Slope
Calculations
Knowns: Side Slopes(H:V) 4.00
Desired Spillway Head 0.25 ft
Weir Coefficient 2.6
Spillway Elevation 4947.70 ft
100-yr Pond Inflow 3.39 cfs
Calculated Spillway Length 9.43 ft
Use Spillway Length 10 ft
Spillway Freeboard 0.00 ft
Total Spillway Depth 0.25 ft
Top of Berm Elevation 4947.95 ft
1344-095-00 PondCalcs.xls-Spillway Page 2 of 3 Interwest Consulting Group
Hoffman Mill Fueling Site
Circular Orifice Plate Sizing
Design Engineer: J.Claeys
Design Firm: Interwest Consulting Group
Project Number: 1344-095-00
Date: September 25,2018
Orifice Equation
Q=CA, 2gO => A,, = where: C =Orifice Discharge Coefficient
C 2 Ah A o =Orifice Area(ft)
576A� g =Gravity(32.2 ft/sz)
D„ _ Dh =Difference in Elevation Head(ft)
Do =Orifice Diameter(in)
Calculations
100-yr Orifice Sizing 100-yr Orifice Rating Table
Knowns: 100-yr Release Rate 7.7 cfs Elevation Discharge
c
100-yr WSEL 4946.90 ft 4944.56 0.00
4945.00 0.00
Pond Outlet Invert 4944.56 ft 4946.00 5.36
4946.90 7.70
Discharge Coefficient 0.65
Tailwater Elevation 4944.94 ft
Orifice Diameter 14 5/16 in
Orifice Area 1.118 ftz
Centroid Elevation 4945.16 ft
Actual Release Rate 7.70 cfs
1344-095-00 PondCalcs.xls-Outlet Orifice Plate Sizing Page 3 of 3 Interwest Consulting Group
Culvert Report
Hydraflow Express Extension for Autodesk0 AutoCADO Civil 3DO by Autodesk,Inc. Tuesday,Jun 5 2018
Hoffman Mill Fuel Station - Culvert Sizing
Invert Elev Dn (ft) = 100.00 Calculations
Pipe Length (ft) = 32.00 Qmin (cfs) = 0.00
Slope (%) = 0.50 Qmax (cfs) = 10.00
Invert Elev Up (ft) = 100.16 Tailwater Elev (ft) _ (dc+D)/2
Rise (in) = 18.0
Shape = Circular Highlighted
Span (in) = 18.0 Qtotal (cfs) = 8.00
No. Barrels = 1 Qpipe (cfs) = 8.00
n-Value = 0.012 Qovertop (cfs) = 0.00
Culvert Type = Circular Concrete Veloc Dn (ft/s) = 4.92
Culvert Entrance = Square edge w/headwall (C) Veloc Up (ft/s) = 5.79
Coeff. K,M,c,Y,k = 0.0098, 2, 0.0398, 0.67, 0.5 HGL Dn (ft) = 101.30
HGL Up (ft) = 101.25
Embankment Hw Elev (ft) = 101.98
Top Elevation (ft) = 102.50 Hw/D (ft) = 1.21
Top Width (ft) = 24.00 Flow Regime = Inlet Control
Crest Width (ft) = 20.00
Hoffman Mill fuel Station-Culvert Sizing • "' t.
tL'J
t oc
1L1 5L t*,a
101.00
100.50
100.00
99.fi0 •c
0 fi i0 15 20 25 30 35
Gnolx Culvert HOL Embank
Channel Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3130 by Autodesk,Inc. Tuesday,Jun 5 2018
Hoffman Mill Fuel Site - Ditch Capacity
Triangular Highlighted
Side Slopes (z:1) = 4.00, 4.00 Depth (ft) = 0.98
Total Depth (ft) = 2.00 Q (cfs) = 8.000
Area (sqft) = 3.84
Invert Elev (ft) = 100.00 Velocity (ft/s) = 2.08
Slope (%) = 0.50 Wetted Perim (ft) = 8.08
N-Value = 0.030 Crit Depth, Yc (ft) = 0.76
Top Width (ft) = 7.84
Calculations EGL (ft) = 1.05
Compute by: Known Q
Known Q (cfs) = 8.00
Elev (ft) Section Depth (ft)
103.00 3.00
102.50 2.50
102.00 2.00
101.50 1.50
101.00 1.00
100.50 0.50
100.00 0.00
99.50 -0.50
0 2 4 6 8 10 12 14 16 18 20
Reach (ft)