HomeMy WebLinkAboutCT 08-06; HIGHLAND JAMES SUBDIVISION; HYDROLOGY AND HYDRAULIC DRAINAGE REPORT ADDENDUM; 2018-04-02.. .,
HYDROLOGY/ HYDRAULIC DRAINAGE
REPORT ADDENDUM
100-YEAR PEAK FLOW IN POST-DEVELOPMENT CONDITIONS
For
HIGHLAND JAMES SUBDIVISION
APN: 207-130-75-00 to 207-130-78-00
Prepared for:
Client: Elizabeth Temple
Prepared by:
R·E·C
Consultants, Inc.
Raab Rydeen
REC Consultants, Inc.
2442 Second Avenue
Sa n Diego, CA 92101
'
Telephone: 619-232-9200
ECEIVED
APR 3 0 2018
LAND DEVELOPMENT
ENGINEERING
Report Prepared:
April 2, 2018
RECORD COP
-~-1-vi\\OJ
lnitI,1I Date
Section 1 -EXECUTIVE SUMMARY
1 -Introduction & Objective
This document will serve as a storm drain design addendum for the connection
and conveyance of onsite runoff (from the approved Highland James Subdivision)
to the existing offsite public storm drain system on James Drive. The objective of
this addendum is to verify size, capacity and construction of two 1 O" PVC storm
drain pipes in parallel.
The Highland James Subdivision is currently under construction. It has been
discovered that a group of underground electrical conduits run along the frontage
of Lot 3 within the right-of-way of James Drive. These existing electrical conduits
prohibit the installation and connection of the proposed 18" PVC storm drain
conveyance pipe that will convey the onsite runoff to an adjacent existing public
storm drain inlet. Because of this, an alternative connection is proposed using two
1 O" PVC storm drain pipes in parallel as a replacement for the 18" PVC storm
drain pipe. The parallel pipe system will be constructed between the existing
electrical conduits and convey onsite runoff to the public storm drain system.
Post-developed runoff data from approved Hydrologic/Hydraulic Drainage Report
for the 100-year peak flow (prepared by Terramar Engineering) shall be used in
this study to verify size and capacity of the dual 1 O" parallel pipe system.
2 -Methodology
The maximum capacity flowrate (cfs) for the two 1 O" PVC storm drain pipes in
parallel has been determined using the Hydraflow Express Extension for Autodesk
AutoCAD Civil 3D (an AutoDesk 2015 product). This program utilizes the Manning
formula to calculate the channel characteristics for particular flow instances. The
Manning formula estimates the flow rate of a liquid flowing in a conduit that does
not completely enclose the liquid , i.e. open channel flow.
2
3 -Calculations
Post-Development Site Flow Rate per approved Hydrologic/Hydraulic Drainage Report:
2.99 CFS
Two 1 0" PVC Pipes in Parallel Dimensions:
0.83' = Diameter (interior length)
0.83% = Slope (0 .08'/9.60')
0.009 = "n" Value" (Manning's Roughness Coefficient for concrete)
Manning's Equation:
Q =VA= ( 1
·:
9 )AR i -Js
Q = Flow Rate (cfs) n= Manning's Roughness Coefficient
A= Area (sf) = 0.55 sf
R = Hydraulic Radius (ft) = 0.42 ft
S = Slope (ft/ft) = 0.0083
Findings / Results:
Dual 1 0" Pipes in Parallel Flow Rate = 4.64 cfs
Post-Development Site Flow Rate= 2.99 cfs
It is determined that the dual 1 0" PVC storm drain pipes in parallel flow rate capacity
is larger than the Post-Development Site Flow Rate for a 100-year peak storm.
Please refer to attached Highland James Subdivision Hydraflow Channel Report and
Exhibit for construction details.
3
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 30® by Autodesk, Inc.
Highland James Subdivision
Circular
Diameter (ft)
Invert Elev (ft)
Slope(%)
N-Value
Calculations
Compute by:
Known Q ( cfs)
Elev (ft)
129.00
127.50
127.00
0
= 0.83
= 127.58
= 0.83
= 0.009
Known Q = 2.32
Wednesday, Apr 18 2018
Highlighted
Depth (ft) = 0.57
Q (cfs) = 2.320
Area (sqft) = 0.40
Velocity (ft/s) = 5.85
Wetted Perim (ft) = 1.62
Crit Depth, Ye (ft) = 0.68
Top Width (ft) = 0.77
EGL (ft) = 1.10
Section
2
Reach (ft)
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PROJECT SITE
LOT 3
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re_
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(130.4) TG
(127.5) IE
0 (/)
00 -st-
m
m
127.58 FL OUT
PROPOSED TWO 1 O" STORM
DRAIN PIPES IN PARALLEL
SEE DETAIL BELOW FOR
DIMENSIONS
_ _J
CONTRACTOR TO
CONNEC T PIPES TO
EXISTING CURB INLET
(127.5) FL IN
-18" SD ·1{' PROFILE VIEW-NEW PVT CATCH BASIN TO EX. PU BLIC CURB INLET CONNECTION
SCALE: 1" = 5'
Sl SD MH TO REMAIN
~
~ ~
Q
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~
~
00 v
0 ~0
co v
(130.9) TG
(1 26.5) IE (1 8").
(125.4) IE (48")
INLET PER SDRSD, ~
D-29 AND 2~10" SD
RCP PER DWG. 483-6B
vi
'ic v
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00 'SI-
127.58 FL OUT
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EXISTING CURB
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CAUTION: EXISTING
ELECTRICAL CONDUIT TO
REMAIN . PROTECT IN PLACE. ~-9.6'
SCALE: 1" = 5'
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Pu&IC. 6 U R.B IN<.-Gi C-e>i,VNGCTlt';J DIMENSION DETAIL 0 •.
SCALE:NTS
SHEET 1
OF 1 SHEETS i ----
I ,;
4 -Declaration of Responsible Charge
I HEREBY DECLARE THAT I AM THE ENGINEER OF WORK FOR THIS PROJECT, THAT I HAVE
EXERCISED RESPONSIBLE CHARGE OVER THE DESIGN OF THE PROJECT AS DEFINED IN
SECTION 6703 OF THE BUSINESS AND PROFESSIONS CODE, AND THAT THE DESIGN IS
CONSISTENT WITH CURRENT STANDARDS.
I UNDERSTAND THAT THE CHECK OF PROJECT DRAWINGS AND SPECIFICATIONS BY THE
CITY OF CARLSBAD IS CONFINED TO A REVIEW ONLY AND DOES NOT RELIEVE ME, AS
ENGINEER OF WORK, OF MY RESPONSIBILITIES FOR PROJECT DESIGN.
4