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ASPEN
ENGINEERS
Stormwater Management Calculations
for
SIGNATURE SMILES
OYLER DENTISTRY
3200 N. Leslie Way
Meridian, Idaho
Prepared for
Lance Warrick
Aspen Engineers
2422 12th Ave Rd #323
Nampa, Idaho 83686
(208)466-8181
Prepared by
Lance Warnick, P.E.
Principal Engineer
Aspen Engineers, Chartered
Date Prepared
June 21, 2012
Aspen File 12009
RT012\120090acumentskStonn Calcs\RevAV1. Stone Calculation Introduction.doc
Aspen Engineers, Chartered
2422 12th Ave Rd #323
Nampa, Idaho 83686
Phone(208)466-8181
Fax(208)442-7858
lanm@AspenEngineers.com
Stormwater Management Calculations for
Signature Smiles / Oyler Dentistry
3200 N. Leslie Way
June 21, 2012
Page 2
Table of Contents
ASPEN
ENGINEERS
Section and Description
Page
1. Project Description..............................................................................................................................
3
2. Sources of Information........................................................................................................................
3
3. Applicable Standards..........................................................................................................................
3
4. Drawing Showing Site Drainage Areas..............................................................................................
5
5. Stormwater Runoff Calculations for Drainage Area#1.......................................................................
6
6. Stormwater Runoff Calculations for Drainage Area#2.......................................................................
8
Appendices
A. Runoff Coefficient and Rainfall Intensity ........................................................
B. Infiltration Rate Information............................................................................
C. Sand / Grease Trap Cut Sheet.......................................................................
P: V2012\1200910ocumentstStorm Calcs\RevA11. Storm Calculation Introduclion.doc
...... 2 pages
...........1 page
.............. 1 page
Stormwater Management Calculations for
Signature Smiles / Oyler Dentistry
3200 N. Leslie Way
June 21, 2012
Page 3
1. Project Description
ASPEN
ENGINEERS
These calculations and attachments provide the background for the design for a new stormwater
management system associated with a new dental office located at 3200 N. Leslie Way in Meridian,
Idaho.
These calculations, together with the associated civil plans are meant to provide information on the
proposed size and location of the seepage beds that will be used to manage stormwater runoff from
the proposed building, driveway and parking area.
The proposed stormwater system will use pavement grading to direct the stormwater runoff to two
inlet catch basins and seepage beds. A 1,000 gallon sand / grease trap will be used to help remove
sediment and oil prior to entering the each of the two proposed seepage beds. The distance
between the baffles of the sand / grease trap was selected to keep the velocity of the water below
0.50 ft/sec to help provide residence time so sediment can settle in the trap.
Each seepage bed was sized to handle the anticipated runoff from the 100 -year, 1 -hour storm event
using a combination of internal storage in the drain rock and the calculated percolation volume
during the 1 -hour design storm event.
Each seepage bed will be constructed with drain rock underlain by a 6-12" layer of ASTM C-33 filter
sand. This will help provide some treatment before the stormwater infiltrates into the subsurface as
well as promote infiltration into the subsurface. Since no site specific soils report was provided, for
the purpose of these calculations an infiltration rate of 2 in/hr was used which is about ''/< of the rate
observed for filter sand.
The elevation of seasonal high groundwater was estimated to be at least 10 feet below existing
grade using information collected from nearby sites and observations from a test hole excavated by
the Contractor.
2. Sources of Information
The following sources of data were used in preparing these calculations:
A. Urban Runoff Control Handbook for Ada and Canyon Counties, Idaho Ada/Canyon Waste
Treatment Management Committee (January 1977).
B. Architectural Site Layout provided by Dale Binning, Architect, (March 2012).
3, Applicable Standards
The following standards were used in preparing these calculations:
A. Idaho Standard Public Works Construction Committee, Idaho Standards for Public Works
Construction, Current Edition.
B. City of Meridian, Ada County, Idaho. Supplementation Specification and Drawings to the
Idaho Standards for Public Works Construction. 2008.
PA2012112009t0ocuments\storm Calcs\RevA\t. Stonn Calculation Introduction.doc
Stormwater Management Calculations for
Signature Smiles / Oyler Dentistry
3200 N. Leslie Way
June 21, 2012
Page 4
ASPEN
ENGINEERS
C. Linsley, Ray, at al, 1992. Water Resources and Environmental Engineering, Fourth Edition,
McGraw-Hill, Publishers, Inc.
P52012k12009tDomments44[orm CaIm RevA\i. Storm Calculation Introduction.doc
PAGE 5
4. SITE DRAINAGE AREAS
0 15 30 60
N SCALE (FT)
J
2622 - 07�
262, �IUI
Project: Signature Smiles / Oyler Dentistry
Number:
12009
A S P E N
Subject: Stormwater Runoff Calculations
Date:
04/20/12
' ENGINEERS
By: L.Warnick
Page:
S
I Intensity
S. RUNOFF CALCULATIONS FOR DRAINAGE AREA 1
A. FIND TIME OF CONCENTRATION (tc)
Assume: The time of concentration (tc) for this area is defined as the time needed to reach
the inlets from the point that is farthest away. It is assumed the time is 10 minutes.
B. FIND PEAK DISCHARGE (Q)
Design Storm 100 -yr, 10 -min
Using the Rational Method (Q = CIA) for the 100 -yr, 10 -min storm which is the estimated
time of concentration.
Given:
C Runoff Coefficient
0.80 See Appendix A.1
I Intensity
3.1 in/hr See Appendix A.2
A Drainage Area
I
0.33 acres See Page 5
Solution:
Q Peak Discharge = C*1*A
0.82 cfs
C. FIND FLOW THROUGH DRAIN PIPE
Given:
Total Area
D Pipe Diameter
12 in
A Pipe flow area = pi * DA2 / 4 =
0.79 fit'
n Roughness coefficient =
0.009
R Hydraulic Radius = D/4
0.250 feet
s Slope =
0.40%
Solution:
q Flow= (1.49/n * A * RA2/3 * sA0.5]
q Flow = 3.26 cfs
Check:
Flow (q) > Peak Discharge (Q)? YES
D. FIND VELOCITY IN GREASE TRAP (v)
Given:
Grease Trap Size 1,000 gal See Appendix CA
wt Trap Width 4.00 ft
d Distance Between Baffles 15 in
a Flow Area = wt*d 5.00 sf
Solution:
v Velocity = Q/a 0.16 f s
Check:
Velocity (v) < 0.5 fps? YES
C:Aspen\Projects\2012\12009\Documents\Storm Calcs\RevA\3. Storm Calcs - 12009
Project: Signature Smiles ! Oyler Dentistry Number: 12009ASPEN
S 7i E TAT
Subject: Stormwater Runoff Calculations Date: 04/20/12
ENGINEERS
By: L.Warnick Page: !
E. FIND EXPECTED RUNOFF VOLUME (Vr) AND DESIGN VOLUME (Vd)
Design Storm 100 -yr, 1 -hr
Using the Rational Method (Q =CIA) for the 100 -yr, 1 -hr storm which is the estimated
Solution:
Vr Runoff Volume= Q*t 9-50-7f
Vol Allow for 15% Sedimentation = Vr*1.15 1,093 cf
F. FIND SEEPAGE BED PROPERTIES
Given:
H Height 5 ft Seepage Bed #1 = Tx 10'x 50.5'
W Width 10 ft
L Length 50.5 It
Solution:
Vb Bed (Rock) Volume = He*W*L 2,525 cf
Vs Storage Volume = Vb*0.4 1,010 cf
G. FIND VOLUME FROM INFILTRATION
Given:
As Area of bottom of infiltration window 505 sf
r Infiltration Rate 2 in/hr Use 1/4 of sand (See Appendix B.1)
t Duration 1 hr
Solution:
Vi Volume from Infiltration= As*(r/12)*t 84 cf
H. CHECK AVAILABLE STORAGE > REQUIRED STORAGE (V)
Given
Va Available Storage Volume (Vs + Vi) 1,094 of
Vd Required Volume 1,093 of
Check:
Available > Required? YES
C:\Aspen\Projects\2012\12009\Documents\Storm Calcs\RevA\3. Storm Calcs -12009
time of concentration.
Given:
C
Runoff Coefficient
0.80
See Appendix A.1
I
Intensity
1 in/hr
See Appendix A.2
A
Drainage Area
0.33 acres
See Page 5
Q
Discharge = C*I*A
0.26 c
t
Storm Duration
1 hr
Solution:
Vr Runoff Volume= Q*t 9-50-7f
Vol Allow for 15% Sedimentation = Vr*1.15 1,093 cf
F. FIND SEEPAGE BED PROPERTIES
Given:
H Height 5 ft Seepage Bed #1 = Tx 10'x 50.5'
W Width 10 ft
L Length 50.5 It
Solution:
Vb Bed (Rock) Volume = He*W*L 2,525 cf
Vs Storage Volume = Vb*0.4 1,010 cf
G. FIND VOLUME FROM INFILTRATION
Given:
As Area of bottom of infiltration window 505 sf
r Infiltration Rate 2 in/hr Use 1/4 of sand (See Appendix B.1)
t Duration 1 hr
Solution:
Vi Volume from Infiltration= As*(r/12)*t 84 cf
H. CHECK AVAILABLE STORAGE > REQUIRED STORAGE (V)
Given
Va Available Storage Volume (Vs + Vi) 1,094 of
Vd Required Volume 1,093 of
Check:
Available > Required? YES
C:\Aspen\Projects\2012\12009\Documents\Storm Calcs\RevA\3. Storm Calcs -12009
Project:
Signature Smiles / Oyler Dentistry
Subject:
Stormwater Runoff Calculations
By:
L.Warnick
Number: 12009 ,tet A S P E N
Date: 04/20/12 �E1�j ENGINEERS
Page: 8�I�1/
6. RUNOFF CALCULATIONS FOR DRAINAGE AREA 2
A. FIND TIME OF CONCENTRATION (tc)
Assume: The time of concentration (to) for this area is defined as the time needed to reach
the inlets from the point that is farthest away. It is assumed the time is 10 minutes.
B. FIND PEAK DISCHARGE (0)
Desi n Storm 100 -yr, 10 -min
Using the Rational Method (Q = CIA) for the 100 -yr, 10 -min storm which is the estimated
time of concentration.
Given:
C Runoff Coefficient 0.80 See Appendix A.1
1 Intensity 3.1 in/hr See Appendix A.2
A Drainage Area 0.28 acres See Page 5
Solution:
Q Peak Discharge = C*1*A 0.69 cfs
C. FIND FLOW THROUGH DRAIN PIPE
Given:
Total Area
D
Pipe Diameter
12 in
A
Pipe flow area = pi * DA2/4 =
0.79 ftz
n
Roughness coefficient =
0.009
R
Hydraulic Radius = D/4
0.250 feet
s
Slope =
0.40%
Solution:
q
Flow= [1.49 / n * A * RA2/3 * SAO 5]
q
Flow =
3.26 cfs
Check:
Flow (q) > Peak Discharge (Q)?
YES
D. FIND VELOCITY IN GREASE TRAP (v)
Given:
Grease Trap Size 1,000 gal See Appendix CA
wt Trap Width 4.00 ft
d Distance Between Baffles 15 in
a Flow Area = wt*d 5.00 sf
Solution:
v Velocity = Q/a 0.14 s
Check:
Velocity (v) < 0.5 fps? YES
C:Wspen\Projects\2012\12009\Documents\Storm Calcs\RevA\3. Storm Calcs -12009
Project: Signature Smiles / Oyler Dentistry Number: 12009
I A SPL' N
Subject: Stormwater Runoff Calculations Date: 04/20/12
ENGINEERS
By: L.Warnick Page: 9
E. FIND EXPECTED RUNOFF VOLUME (Vr) AND DESIGN VOLUME (Vd)
C
Design Storm 100- r, 1 -hr
Using the Rational Method (Q =CIA) for the 100 -yr, 1 -hr storm which is the estimated
Solution:
Vr Runoff Volume= Q*t 806 cf
Vd Allow for 15% Sedimentation = Vr*1.15 927 cf
F. FIND SEEPAGE BED PROPERTIES
Given:
H Height 5 ft Seepage Bed #2 = 5' x 8'x 54'
W Width 8 ft
L Length 54 ft
Solution:
Vb Bed (Rock) Volume = He*W*L —16-07-1
Vs Storage Volume = Vb*0.4 864 cf
G. FIND VOLUME FROM INFILTRATION
Given:
As Area of bottom of infiltration window 432 sf
r Infiltration Rate 2 in/hr Use 1/4 of sand (See Appendix B.1)
t Duration 1 hr
Solution:
Vi Volume from Infiltration = As*(r/12)*t 72 cf
H. CHECK AVAILABLE STORAGE > REQUIRED STORAGE (V)
Given:
Va Available Storage Volume (Vs + Vi) 936 of
Vd Required Volume 927 of
Check:
Available > Required? YES
C:\Aspen\Projects\2012\12009\Documents\Storm Calcs\RevA\3. Storm Calcs -12009
time of concentration.
Given:
C
Runoff Coefficient
0.80
See Appendix A.1
I
Intensity
1 in/hr
See Appendix A.2
A
Drainage Area
0.28 acres
See Page 5
Q
Discharge = C*I*A
0.22 cfs
t
Storm Duration
1 hr
Solution:
Vr Runoff Volume= Q*t 806 cf
Vd Allow for 15% Sedimentation = Vr*1.15 927 cf
F. FIND SEEPAGE BED PROPERTIES
Given:
H Height 5 ft Seepage Bed #2 = 5' x 8'x 54'
W Width 8 ft
L Length 54 ft
Solution:
Vb Bed (Rock) Volume = He*W*L —16-07-1
Vs Storage Volume = Vb*0.4 864 cf
G. FIND VOLUME FROM INFILTRATION
Given:
As Area of bottom of infiltration window 432 sf
r Infiltration Rate 2 in/hr Use 1/4 of sand (See Appendix B.1)
t Duration 1 hr
Solution:
Vi Volume from Infiltration = As*(r/12)*t 72 cf
H. CHECK AVAILABLE STORAGE > REQUIRED STORAGE (V)
Given:
Va Available Storage Volume (Vs + Vi) 936 of
Vd Required Volume 927 of
Check:
Available > Required? YES
C:\Aspen\Projects\2012\12009\Documents\Storm Calcs\RevA\3. Storm Calcs -12009
Stormwater Management Calculations for
Signature Smiles / Oyler Dentistry
3200 N. Leslie Way
APPENDIX A
RUNOFF COEFFICIENTS AND RAINFALL INTENSITY
R=12\12009\Documents\Stone Calcs\RevMl. Storm Cakulafion introductlon.doc
ASPEN
ENGINEERS
i
EXHIBIT "A"
Recommended "C" Coefficients
for "Rational Method Equation"
Peak Rate of Discharge
DeecrlptIon of Run -Oft Area
Runoff Coefficients "C"
Business
Downtown areas
0.95
Urban neighborhood areas
0.70
Residential
Single-family
0.50
Multi -family
0.75
Residential (rural)
0.40
Apartment dwelling areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, cemeteries
0.10
Playgrounds
0.20
Railroad yard areas
0.20
Unimproved areas
0.10
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.85
Drives and walks
0.85
Roofs
0.95
Fields: Sandy soil
Flat 2%
0.05
Average 2-7%
0.10
Steep 7%
0.15
Fields: Clay soil
Flat 2%
0.13
Average 2-7%
0.18
Steep 7%
0.25
Adapted from ASCE (1972
USE 0.80
A.1
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W
Z
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Z
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Stormwater Management Calculations for
Signature Smiles / Oyler Dentistry
3200 N. Leslie Way
APPENDIX B
INFILTRATION RATE INFORMATION
P9201211200Mocumentsl8torm CalcslRevAll, Storm Calculation Introduction.doc
ASPENGINEERS
B.1
TABLE 3 - INFILTRATION RATES
SCS Group and Type
Infiltration Rate
(Inches Per Hour)
A. Sand
g
A. Loamy Sand
2
B. Sandy Loam
1
B. Loam
0.5
C. Silt Loam
0.25'
C. Sandy Clay Loam
0.15
D. Clay Loam & Silty Clay Loam
<0.09
D. Clays
<0.05
`Minimum rate, soils with lesser rates should not be considered as
candidates for infiltration facilities.
8013.4 Sediment and Grease Traps
Properly sized standard sediment and grease traps shall be installed upstream
of infiltration facilities.
8013.5 Ground Water Elevations
Groundwater elevation shall be established in accordance with Section 8010.5.
If groundwater is encountered during construction of the facility at an elevation
higher than that shown on the plans, the facility shall be re -designed to account
for the higher elevation.
Water quality testing may be required by the District, Idaho Department of
Water Resources or Central District Health Department.
8014 PERCOLATION FACILITIES
8014.1 Design
In general percolation facilities are designed to contain the design inflow
without overtopping. The water is stored within the effective pore volume and
percolates into the ground.
Percolation facilities may be designed to contain the runoff from the design
stone for a primary system if the facility has a positive outflow to a secondary
system. If there is not a positive outflow to a secondary system, the percolation
facility must be designed to accommodate the runoff from the design storm for
Adopted: Res. 469 (7!13/94) 8000-17
Revised: 7/19/95; 2/14196; Res. 657 (8/28/02)
Stormwater Management Calculations for
Signature Smiles / Oyler Dentistry
3200 N. Leslie Way
APPENDIX C
SAND / GREASE TRAP CUT SHEETS
RX2012X120090ccurnenatStorrn Calm\RevA\1. Storm Calculation Introducton.doc
ASPEN
ENGINEERS
cl
PLAN VIEW
19-
D
D CONSTRUCTION JOINTS ` r 1--Q5)
EL IN_ INLET
OW
@ELB
OUTLET BAFFLE ALL
OUTLET �EL INLET BAFFLE WALL 4
FLOW
(see calculations and plan for
distance between bafn )
SECTION A -A
NOTES
LEGEND
AO
DESIGN LOAD: AASHTO HS -25 HIGHWAY LOADING.
OB
ALL REINFORCING STEEL SHALL BE GRADE 60.
iO
MANHOLE FRAME AND COVER PER
SD -617 (TYPICAL)
O
DETAILED DRAWING OF A PRECAST BOX OR A POURED
IN PLACE BOX DESIGN MUST BE APPROVED BY THE
2
O
. LOCATION AND FL ELEV. PER DESIGNPLANS.
ENGINEER PRIOR TO CONSTRUCTION.
TYPICAL
(TYPICAL)
OD
HEIGHT OF OUTLET BAFFLE WALL AND LENGTH OF INLET3O
H512" USE GRADE RINGS (TYPICAL)
BAFFLE WALL DETERMINED BY TANK CAPACITY AND
12"<H 24" USE 24" DIA RCP RISER
FLOW RATE.
24"<H 120" USE MANHOLE CONE &
OE
BEFORE THESE BOXES. ARE USED THE APPLICATION
48" Dl� RI§ERS
MUST BE APPROVED BY THE ENGINEER.
®
EL IN > EL B BY 1" MIN,
O
MANHOLE FRAME, COLLAR AND COVER SHALL BE
EL. OUT < EL B BY 1' MIN.
PER SO—Hifi AND SO -617
UNLESS OTHERWISE APPROVED BY
PROVIDE STEPS WHEN THE DISTANCE FROM
ACHD
TOP OF MANHOLE FRAME TO TOP OF BOX
WATERTIGHT SEAL
EXCEEDS 24".
PRECAST BOX MANUFACTURER SHALL
MARK FLOW DIRECTION AND LABEL
INLET OR OUTLET ON SIDE OF BOX
ACHD 2010 ReWsmns
IDAHO
STANDARDS
FOR PUBLIC
WORKS
STANDARD DRAWING
SAND AND GREASE TRAP
No.
CONSTRUCTION
SD -624
(ACHD suPPtlaeEAlr)