HomeMy WebLinkAboutJacksons #56 - Drainage Report (RevA)
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Aspen Engineers, Chartered
485 W. Main St, Suite B
PO Box 205
Kuna, Idaho 83634
(208) 466-8181
www.AspenEngineers.com
Drainage Report
for
JACKSONS STORE #56
PARKING EXPANSION
66 E. and 52 E. State Ave
Meridian, Idaho
Prepared for
Scott Stom
Jacksons Food Stores, Inc
3450 Commercial Ct
Meridian, Idaho
(208) 888-6061
Prepared by
Jordan Crain
Civil Designer I
Aspen Engineers, Chartered
Date Prepared
June 1, 2015
Aspen File 15034
Drainage Report for
Jacksons Store #56 Parking Expansion
66 E. and 52 E. State Ave
Meridian, Idaho
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Table of Contents
Section and Description Page
1. Project Description .............................................................................................................................. 3
2. Sources of Information ........................................................................................................................ 3
3. Applicable Standards ........................................................................................................................ 4
4. Drawing Showing Site Drainage Areas ............................................................................................... 5
5. Stormwater Runoff Calculations for Drainage Area #1 ...................................................................... 6
Appendices
A. Runoff Coefficient and Rainfall Intensity. ................................................................................. 2 pages
B. Typical Infiltration Rates for Soils ............................................................................................... 1 page
C. Sand / Grease Trap Cut Sheet ..................................................................................................... 1 page
Drainage Report for
Jacksons Store #56 Parking Expansion
66 E. and 52 E. State Ave
Meridian, Idaho
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1. Project Description
These calculations and attachments provide the background for the design for a new stormwater
management system associated with a parking lot expansion for Jackson Store #56, located at 66 E.
State Ave 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 bed that will be used to manage stormwater runoff
from the proposed parking lot.
The proposed stormwater system will use pavement grading to direct the stormwater runoff to a
seepage bed used to manage runoff from the site. A 1,000 gallon sand / grease trap will be used
to help remove sediment and oil prior to entering the seepage bed. 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 for sedimentation and in the trap.
The 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.
The seepage bed will be constructed with drain rock underlain by a 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 assumed based off of
surrounding projects.
The elevation of seasonal high groundwater was estimated to be at least 9 feet below existing
grade based on experience in the surrounding area.
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 Plan provided by Scott Stom (May 2015).
Drainage Report for
Jacksons Store #56 Parking Expansion
66 E. and 52 E. State Ave
Meridian, Idaho
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3. Applicable Standards
The following standards were used in preparing these calculations:
C. Idaho Standard Public Works Construction Committee. Idaho Standards for Public Works
Construction, Current Edition.
D. City of Meridian, Ada County, Idaho. Supplementation Specification and Drawings to the
Idaho Standards for Public Works Construction.
E. Linsley, Ray, et al, 1992. Water Resources and Environmental Engineering, Fourth Edition,
McGraw-Hill, Publishers, Inc.
Project:Jacksons Store #56 Number:15034
Subject:Stormwater Runoff Calculations Date:05/29/15
By:Jordan Crain Page:
5. 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 0.85 See Appendix A.1
I Intensity 3.1 in/hr See Appendix A.2
A Drainage Area 0.22 acres See Page 5
Solution:
Q Peak Discharge = C*I*A 0.58 cfs
C. FIND FLOW THROUGH DRAIN PIPE
Given:Total Area
D Pipe Diameter 12 in
A Pipe flow area = pi * D^2 / 4 =0.79 ft2
n Roughness coefficient =0.009
R Hydraulic Radius = D/4 0.250 feet
s Slope =0.40%
Solution:
q Flow = [1.49 / n * A * R^2/3 * s^0.5]
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 C.1
wt Trap Width 4.00 ft
d Distance Between Baffles 12 in
a Flow Area = wt*d 4.00 sf
Solution:
v Velocity = Q/a 0.14 fps
Check:
Velocity (v) < 0.5 fps?YES
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Project:Jacksons Store #56 Number:15034
Subject:Stormwater Runoff Calculations Date:05/29/15
By:Jordan Crain 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
time of concentration.
Given:
C Runoff Coefficient 0.85 See Appendix A.1
I Intensity 1 in/hr See Appendix A.2
A Drainage Area 0.22 acres See Page 5
Q Discharge = C*I*A 0.19 cfs
t Storm Duration 1 hr
Solution:
Vr Runoff Volume = Q*t 673 cf
Vd Allow for 15% Sedimentation = Vr*1.15 774 cf
F. FIND SEEPAGE BED PROPERTIES
Given:
H Height 4 ft Seepage Bed #1 = 4' x 12' x 37'
W Width 12 ft
L Length 37 ft
Solution:
Vb Bed (Rock) Volume = He*W*L 1,776 cf
Vs Storage Volume = Vb*0.4 710 cf
G. FIND VOLUME FROM INFILTRATION
Given:
As Area of bottom of infiltration window 444 sf
r Infiltration Rate 2 in/hr Assumed to be 1/4 of sand (see Appendix B.1)
t Duration 1 hr
Solution:
Vi Volume from Infiltration = As*(r/12)*t 74 cf
H. CHECK AVAILABLE STORAGE > REQUIRED STORAGE (V)
Given:
Va Available Storage Volume (Vs + Vi)784 cf
Vd Required Volume 774 cf
Check:
Available > Required?YES
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APPENDIX A
RUNOFF COEFFICIENTS AND RAINFALL INTENSITY
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APPENDIX B
SOIL INFILTRATION RATES
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APPENDIX C
SAND / GREASE TRAP CUT SHEET