HomeMy WebLinkAboutCT 05-12; Ocean Street Residences; DRAINAGE; 2013-06-18Of]
,-13
DRAINAGE REPORT FOR OCEAN STREET RESIDENCES
February 22, 2013
Revised: April 19, 2013
Revised: May 20, 2013
Revised: June 18, 2013
Prepared for:
Zephyr Partners
11750 Sorrento Valley Road, Suite 130
San Diego, CA 92121
(858) 558-3650
Contact: Jim MclVlenamin
Prepareci by:
David Wiener, P.E.
RBF CONSULTING
5050 Avenida Encinas, Suite 260
Carlsbad, CA 92008
(760) 476-9193
Table of Contents
1 Introduction and Purpose 1
1.1 Background and Project Description 1
1.2 Pre-Development Drainage Patterns 1
1.3 Post Development Drainage Patterns 1
2 Rational Hydrology 2
3 Pipe Hydraulics 3
4 Conclusions 4
Technical Appendices
Appendix A: Existing Hydrology Map
Appendix B: Proposed Private Storm Drain - Hydraulics Map and Hydraflow
Calculations
Appendix C: Proposed Public Storm Drain - Hydrology Map and Hydraflow Calculations
Ocean Street Residences
Drainage Report
1 Introduction and Purpose
1.1 Background and Project Description
In the existing condition, the project site is occupied by several apartment buildings, one
main drive aisles, and covered and uncovered parking spaces. The existing site is tiered
into two levels. The upper, larger tier is approximately three feet below Ocean Street
and is occupied by three of the five apartment buildings. The lower tier is approximately
22 feet below the upper tier and is largely occupied by the main drive aisle and hwo
apartment buildings.
In the proposed condition, the existing apartment buildings and covered parking areas
will be demolished and removed. In its place, 35 condominium units (within 13
buildings) will be constructed, along with two driveway entrances from Ocean Street,
swimming pool, and onsite & underground parking. The drive isles will be constructed
with a combination of un-grouted concrete unit pavers and grass pavers.
1.2 Pre-Development Drainage Patterns
The runoff from the site flows in a northwestern direction, through a series of pipes and
gutters within the apartment complex campus, where it then sheet-flows to the natural
area to the north. Flows then reach a poorly defined natural swale that takes the runoff
to a grassy sump area to the west. The sump area contains an 18-inch culvert that
outlets directly to Buena Vista Lagoon. The existing culvert discharges approximately
100 feet east of an existing weir structure, separating the lagoon from the Pacific Ocean
shoreline. Runoff from the project's frontage road, Ocean Street, flows to existing curb
inlets in Ocean Street, which convey flow to the undeveloped area north of the project
site. A high point exists on Ocean Street at the midpoint of the property frontage. There
is no cross-lot drainage onto the project site. Refer to the Existing Hydrology Map in
Appendix A.
1.3 Post-Development Drainage Patterns
On the southern half of the site, 14 of the condominium units (7 buildings) will be
constmcted above an underground parking stmcture. The roofs of these units will drain
to raised planter areas adjacent to the buildings. The planters will be piped through curb
outlets onto Ocean St to the south. This runoff will be captured in existing curb & gutter,
and flow into existing curb inlets on the north side of Ocean Street. These inlets
Ocean Street Residences 1
Drainage Report
discharge to the undeveloped area north ofthe site, adjacent to Buena Vista Lagoon and
the Pacific Ocean.
The remaining 19 units (within 6 buildings on the northern half of the site) will be
constmcted at grade, adjacent to landscape and hardscape areas. Roofs and hardscape
will drain to the adjacent landscaping, which contain four bioretention areas. The
majority of onsite hardscape will be comprised of permeable pavement. Along the site's
northern and western property lines, there will be a 20-foot wide permeable paver fire
lane. Inlets contained in the landscape areas, as well as underdrain piping in the
bioretention and permeable paver areas, will be conveyed to a proposed private onsite
storm drain system, which will discharge at the northwest corner of the site. Outfall at
this location will either infiltrate, flow into Buena Vista Lagoon, or flow to the Pacific
Ocean. Refer to the Proposed Hydraulics Exhibit in Appendix B.
In addition to the private storm drain improvements; there will be public storm drain
improvements along the site's eastern boundary. An existing 36" storm drain pipe, which
receives flow from an curb inlet on Ocean Street, will be replaced with an 18" RCP storm
drain pipe and new outlet structure. The existing outlet is buried. Refer to the Offsite
Storm Drain Improvements Map and calculations in Appendix C.
2 Rational Hydrology
The Rational Method hydrology study was completed using methodology described in
the San Diego County Hydrology Manual. The design storm for this study is the 100-year
events. Using the San Diego County Hydrology Manual Isopluvial Map, the 100-year Pe
was found to be 2.6 inches. The soil type was assumed to be type 'C A runoff
coefficient ("C") value of 0.54 was used for pervious area and 0.90 for impervious areas.
The time of concentration (Tc) to each node was assumed to be 5 minutes.
The intensity was found using Figure 3-2 (San Diego County Hydrology Manual). The
drainage areas and node designations used can be seen in Appendix A. The Flow (Q) at
each node was calculated using the Rational Equation Q=CIA, where:
• Q = Flow (cubic feet per second)
• C = runoff coefficient
• I = Intensity (inches per hour)
• A = Drainage Area (acres)
The proposed lateral pipes connecting to the downstream inlet within the swale are
conservatively sized to be 24" in diameter. Inlet control calculations and rip-rap sizing
information is also included in this report in Appendix F and G, respectively.
Ocean Street Residences
Drainage Report
3 Pipe Hydraulics
"Hydraflow" software was used to verify the adequacy of the proposed pipe systems.
The design software uses fiows generated from the post-development site hydrology to
calculate hydraulic grade line and fiow velocity. The software computes pipe hydraulics
using the widely accepted "Standard Step" Method, in which iterative calculations are
performed to achieve on overall system energy balance, as described in Bernoulli's
Principal. The software makes an assumption at the upstream end about hydraulic
grade elevation (HGL), and then checks for an energy balance behween the hwo points
after considering head loss due to pipe friction and junctions. The assumption process
is repeated until the assumed upstream HGL achieves an energy balance, at which time
a calculation is done to determine HGL based upon inlet control and is compared to the
previous results from energy balance. The more conservative (higher) of the hwo
elevations is added to a computed junction loss. The sum elevation becomes the control
for the next upstream segment and the process is repeated. If an energy balance
cannot be achieved the software sets the hydraulic grade line at critical depth, and
proceeds to the next line. The proposed pipes are sized to accommodate the 100-year
storm event.
For this improvement project, the proposed stonn drain system connects each of the
swale discharge points for collection and discharge at Nodes 107 and 108/109. Detailed
hydraulic calculations for each proposed pipe segment during the 100-year event are
included in Appendix C.
4 Conclusions
Drainage patterns will not change significantly as a result of the proposed improvements.
Onsite and offsite storm drain piping has been sized for the 100-year event.
The 100-year storm event that is captured in the proposed curb & gutter along Ocean
Street will be contained within the Right-of-Way, and does not flow onto the project site.
Refer to the attached Appendices for maps and calculations.
Ocean Street Residences
Drainage Report
Appendix A: Existing Hydrology IVlap
Appendix B: Proposed Private Storm Drain Hydraulics Map and Calculations
Hydraflow Plan View
Outfall'
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Ocean Street - Private No. Lines: 24 05-20-2013
Hydraflow Storm Sawere 200S
•fTifrran—••
MyCustom Page 1
Line
No.
Line
ID
Storage Invert
Dn
Drng
Area
RunofI
Coeff
F Total
CxA
Tc j
Sys
Flow
Rate
Capac
Full
Line
Size
Line
Slope
Vel
Ave
Invert
Up
Invert
Dn
HGL
Up
HGL
Dn
Gnd/RIm
El Up
n-val
Pipe
(eft) (ft) (ac) (C) (min) (in/hr) (cfe) (cfs) (in) (%) (ft/s) (ft) (ft) (ft) (ft) (ft)
1 Line 1 81,16 12.00 0.00 0.00 0.00 2.9 0.00 8,30 9,62 18 0,50 5.97 12.29 12.00 13,39 13,10 17.25 0.010
2 Une 2 99.22 12.29 0.00 0.00 0.00 2.6 0.00 8,30 9.59 18 0.49 5.12 12.59 12,29 13.81 13.68 15.41 0,010
3 Line 13 8.56 12.59 0.00 0.00 0.00 0,0 0.00 1,29 4.65 12 1.01 1.64 12.70 12.59 14,39 14.38 16.23 0,010
4 Une 3 167.71 12.59 0.00 O.OO O.OO 2.1 0.00 5,40 9.70 18 0.50 3.08 13.07 12,59 14.51 14.38 16,25 0,010
5 Line 4 122.28 13.07 0.00 0.00 0.00 1.7 0.00 5.40 9.65 18 0,50 3,34 13.44 13,07 14.62 14.56 17.00 0.010
6 Line 19 23.57 13.44 0.00 0.00 0.00 0.8 0.00 0.21 7.44 12 2.58 0.27 14.22 13,44 15.13 15.13 18,12 0,010
7 Line 20 19.90 14.22 0.00 0.00 0.00 0.5 0.00 0.21 6.56 12 2,01 1,12 15,13 14.22 15.32j 15.13 19.67 0.010
8 Line 21 7.39 15.13 0.00 0.00 0.00 0.2 0.00 0.21 8,02 12 3.00 1,65 16,82 15.13 17.01 j 15.38 21.65 0.010
9 Line 22 1.50 16,82 0.00 0.00 0.00 0.1 0.00 0.21 6.57 12 2.01 1,65 17.05 16.82 17.24] 17.07 32.00 0.010
10 Line 23 1.23 27.86 0.00 0.00 0.00 0.1 0.00 0,21 4.66 12 1.01 2,46 28.00 27.86 28.20 28.00 32.00 0.010
11 Line 24 1.23 28.00 0.00 0.00 0.00 0.0 0.00 0.21 10.83 12 5.47 1.62 28.50 28.00 28.69] 28.26 35.00 0.010
12 Line 5 64.29 13.44 0.00 O.OO 0.00 1.2 0,00 2.90 6.06 12 1.72 4.23 14.90 13.44 15.62j 14.93 18.90 0.010
13 Line 29 16.96 14.90 0.00 0.00 0.00 0.6 0.00 0.60 13.72 12 8.78 1.72 17.30 14.90 17.63] 16.18 21.30 0.010
14 Line 30 12.51 17.30 0.00 0.00 0.00 0.4 0.00 0,60 6.53 12 1.99 2.26 18.21 17.30 18.54] 17.73 22,32 0.010
15 Line 31 2.54 18.21 O.OO 0.00 0.00 0.3 0,00 0,60 6.63 12 2,05 2.26 18,40 18.21 18.73] 18,64 32,00 0.010
16 Line 32 8.21 27.14 0.00 0.00 0.00 0.0 0,00 0,60 6,54 12 2.00 3.93 28.11 27.14 28.44 27.34 31.80 0.010
17 Line 33 1.69 28.11 0.00 0.00 0,00 0.0 0,00 0.20 10,42 12 5,06 1.25 28,50 28,11 28.69] 28.56 35.00 0.010
18 Line 6 61.64 14.90 0.00 0.00 0.00 0.8 0.00 1.31 3,26 12 0,50 1.68 15.29 14.90 16.24 16.18 18.35 0.010
19 Line 7 9.01 15.29 0.00 0.00 0.00 0.7 0,00 1.31 12,74 12 7.57 2.57 16.41 15.29 16.90] 16.28 21.00 0.010
20 Line 8 19.38 16.41 0.00 0.00 0.00 0.4 0,00 0.26 7,17 12 2.40 1.25 17.68 16.41 17.90] 17.14 22.00 0,010
21 Line 9 1.40 17.68 0.00 0.00 0.00 0.4 0,00 0.26 6,50 12 1.97 1,76 17.86 17.68 18,08] 17.96 32.00 0.010
Ocean Street - Private Number of lines: 24
NOTES: Intensity = 69.87 / (Inlet time + 13.10) 0.87 - Retum period = 2 Yrs.; i Inlet control; " CriUcal depth
Date: 04-17-2013
Hydraflow Storm Sewers 2005
•-T"-8i-rni:T3n-'-'-""--
MyCustom Page 2
Une
No.
Line
ID
Storage
(eft)
Invert
Dn
(ft)
Dmg
Area
(ac)
Runoff
Coeff
(C)
Total
CxA
Tc
(min)
i
Sys
(In/hr)
Fiow
Rate
(cfe)
Capac
Full
(cfe)
Line
Size
(in)
Line
Slope
(%)
Vel
Ave
(ft/s)
invert
Up
(ft)
Invert
Dn
(ft)
HGL
Up
(ft)
HGL
Dn
(ft)
Gnd/Rim
El Up
(ft)
n-val
Pipe
22
23
24
Line 10
Line 11
Line 12
2,34
3.14
3,85
26.47
26.70
27.00
0.00
0.00
0.00
0.00
O.OO
o.co
0,00
0,00
0.00
0.2
0,1
0,0
0.00
0.00
0.00
0.26
0.26
0.26
4.67
5.81
12.44
12
12
12
1.02
1,58
7,22
2.62
1.67
1.76
26.70
27.00
28.82
26.47
26.70
27.00
26.92
27.22]
29.04]
26.63
27.01
27.28
32.04
32,00
32.82
0.010
0.010
0.010
Ocean Street - Private Number of lines: 24 Date: 04-17-2013
NOTES: Intensity = 69.87 / (inlet time + 13.10) * 0.87 - Retum period = 2 Yrs.; i Inlet control; ** Critical depth
Hydraflow Slorm Sewers 2005
r~i!Trnr?jii- "
Appendix C: Proposed Public Storm Drain Hydraulics Map and Calculations
Channel Report
Hydraflow Express by Intelisolve
MODIFIED G-14A DRIVEWAY (WEST DRIVEWAY)
Thursday, May 16 2013
User-defined
Invert Elev (ft)
Slope (%)
N-Value
Calculations
Connpute by:
Known Q (cfs)
= 9.55
= 2.25
= 0.013
Known Q
= ''5.00 >Q,^^ Cllci^s'^
Highlighted
Depth (ft) = 0.45
Q(cfs) = 15.00
Area (sqft) = 2.95
Velocity (ft/s) = 5.08
Wetted Perinn (ft) = 17.90
Crit Depth. Yc (ft) = 0.57
Top Width (ft) = 17.80
EGL (ft) = 0.85
(Sta, El, nHSta, El, n)...
(0.00, 10.00)-(4.00, 9.92, 0.013)-(7,00, 9.63, 0.013)-(7.00, 9,55, 0.013)-(8.50, 9.67, 0.013)-(28.50, 10.38, 0,013)
Elev (ft)
11.00
10.50
9.50
9,00
-5
Section
10 15 20 25
1
Oatcty\
-1" c + 6. , H
J
30
Depth (ft)
- 1.45 '
0.95
0.45
-0.05
-0.55
35
Sta (ft)
Hydraflow Plan View
Project File: 857-PUBLIC.stm
s
3
•7
3
No. Lines; 2 05-14-2013
Hydraflow Stonn Sewers 2005
MyCustom Page 1
Line
No.
Line
ID
Storage
(eft)
124.51
213.72
Invert
Dn
(ft)
17.30
19.37
Drng
Area
(ac)
0.00
0.00
Runoff
Coeff
(C)
0.00
0.00
Total
CxA
0.00
0.00
Tc
(min)
0,6
0.0
Sys
(in/hr)
0.00
0.00
Flow
Rate
(cfe)
8.95
8.95
Capac
Full
(cfe)
34.76
79,36
Line
Size
(in)
24
24
Une
Slope
(%)
2,36
12.31
Vel
Ave
(ft/s)
-5:3e-
4.0G"
Invert
Up
(ft)
19,04
32.79
0{ II^C
Invert
Dn
(ft)
17.30
19.37
HGL
Up
(ft)
20.10
33.85]
HGL
Dn
(ft)
18,36
20.70
Gnd/Rim
El Up
(ft)
27,70
38.75
R€f>. or-
n-va(
Pipe
0.013
0.013
Project File: 857-PUBLIC,stm Number of lines: 2 Date: 05-14-2013
NOTES: Intensity = 69.87 / (Inlet time + 13,10) * 0.87 ~ Retum period = 2 Yrs.; i Inlet control; ** Critical depth
Hydraflow Storm Sewers 2005
Tnnniniir
Channel Report
Hydraflow Express by Intelisolve Tuesday, Jun 18 2013
Velocity of Q100 in 24-inch RCP at 12% slope
Circular
Diameter (ft)
Invert Elev (ft)
Slope (%)
N-Value
Calculations
Compute by:
Known Q (cfs)
= 2.00
= 19.37
= 12.02
= 0.013
Known Q
= 8.95
Highlighted
Depth (ft) = 0.46
Q(Gfs) = 8.950
Area (sqft) = 0.55
Velocity (ft/s) = 16.2(
Wetted Perim (ft) =2.01
Crit Depth, Yc (ft) = 1.07
Top Width (ft) = 1.69
EGL (ft) = 4.54
20.50
20.00
19.50
19,00
18.50
Reach(ft)
Channel Report
Hydraflow Express by Intelisolve
Velocity of Q100 in 24-inch RCP at 2% slope
Tuesday, Jun 18 2013
Circular
Diameter (ft)
Invert Elev (ft)
Slope (%)
N-Value
Calculations
Compute by:
Known Q (cfs)
= 2.00
= 19.37
= 2.09
= 0.013
Known Q
= 8.95
Highlighted
Depth (ft)
Q (Cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
0.72
8.950
1.02
8.74*
2.58
1.07
1.92
1.91
20.00
19.50
19.00
18.50 0.87
Reach(ft)