02-15-1994 - City Project #SD-94127 - Charlinda & Citrus Drainage ControlCity Manager and City, Council
FROW - Harry W. Thomas
SUBJECT: CITY ]PROJECT NO. SD-94127
CHARLINDA AND CITRUS
DRAINAGE CONTROL
0, Ciry oFTVcsr Carina
Mem' orandum
AGENDA
ITEM NO. C-4b
DATE February 15, 1994
RADIARY City CouncH has previously authorized a preliminary study of
the drainage' conditions in the vicinity of Charlinda and Citrus
Street. Staff is proposing to proceed with the design of a storm
drain project, based upon the results of that preliminary study.
BACKGRO1UND
Due to significant runoff during a January 1993 rain storm and resident reports of similar
occurrences on several. occasions over the past 30 years, the City Council authorized a three part
drainage'study in the South Hills area. One part of that study involved the area of Charlinda
and Citrus. That part of the study has indicated that, utilizing the County's conservative
hydrology procedures, this area is subject to a significant quantity of runoff for a 50 year storm
frequency. Additional storm drain facilities are needed in the area to accommodate runoff from
a 50 year storm that cannot be handled by existing facilities.
The study has indicated two alternatives with various phases. The minimum estimated cost to
accommodate most of the Charlinda Street runoff is $326,000; This. phased approach still leaves
significant quantities of surface flow on Citrus Street that will only be reduced upon completion
of the hill project. The estimated cost to construct a complete underground drainage facility as
a single project is $612,000.
The County has recently approved a $200 million bond issue for. drainage improvements.
Although the Charlinda/Citrus project is not currently on the project list, we,have requested it
be added to the list along with projects for the Vine Creek and,Eddes Drain drainage areas. We,
have met. with County staff and they informally indicate that the Charlinda/Citrus project meets
their desirable project criteria and that they would like to include it depending upon the
availability of funding. If the County adds this project, they would construct a complete
underground drain. within three years. The County is more likely to fund the project if
construction cost is a - t or below $500,000. 'The'.$612,000 cost estimate for'the drain includes .
$450,000 in actual, construction, $45,000 in design engineering, $45,000 in construction
engineering and $72,000 in'contingencies. This means the City would most likely have pay for
design and construction engineering costs (approximately $90,000).
ANALYSIS
Due to the importance of this drainage facility and.the short time frame to have any possibility
of County funding, immediately proceeding with design of the'storm drain is warranted.
However, to,provide flexibility for either County funding of a complete project or City funding
for a phased project, it will be necessary to design for both alternates identified in the study.
Although there is substantial commonality between the two alternate alignments some additional
design costwill be incurred through this approach. (approximately $5,000).
Initiating the design does.not commit theCity to any specific. construction costs. Depending
upon the County response, the City Council may still need to consider further funding to reduce
the County's cost and/or enhance the project's priority. If the County fails to fund the project,
Council -will need to consider whether or not. to undertake phased construction of the drain.
in the interim,'the City has installed block "splash" walls along Charlinda Street and Cameron
Avenue to provide better drainage control in the area. These measures are temporary and should
not be considered as part of any permanent facility. The homeowners have been advised through
Mr.. Carter of the status of the City's efforts. They will receive a copy of this report.
- T-- -
FISCAL IMPACT
The estimated cost of proceeding with the design for both storm drain -alternates is ' $50,000.
The design will be done by City staff utilizing consultant services for specialty items as- needed,
such as surveying, soils testing, etc. There is no established and/or dedicated funding for storm
drains available to the City.
The Capital improvement Fund was established by the City Council in part to provide a source
of funds for projects that lack dedicated funding. In the event that funds become available for
design costs, theCapital Improvement fund would be'reimbursed for. any project costs.
RECOAEM044DATION
It is recommended that City Council take the following action:
a) Establish Project SD-94127 Charlinda Avenue/Citrus Street Storm Drain
b) Appropriate $50,000 from the Capital Improvement Fund to Project.SD-94127
4 W. Thomas
as
DirectorlCity Engineer
Public Works
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DRAINAGE STUDY
EXECUTIVE SUMMARY
Obiectives
This report presents the Charlinda - Citrus'Drainage Study (Study). The purpose of
this Study is to analyze the drainage conditions in Chadinda Street between Citrus
Street and Cameron Avenue and to recommend both an interimand ultimate solution
for drainage control.
Findings
This Study analyzed two slightly different alignments With Alternate One having four
phases and Alternate Two having three. phases. , Phase I of both alternatives is
designed to address the drainage conditions on Charlinda Street and for future
extension to connect to the South Hills Drain located in Citrus Street between Cortez
Street and Larkwood Street. The difference in cost between the alternatives is about
$87,000. Although Alternate One is more expensive overall the cost of its Phase'l is
less than Alternate Two's Phase I by 24 percent while achieving essentially the same
level of drainage control on Charlinda Street.
The estimated cost of constructing Alternate One Phase I and 11 is $326,000. The
estimated cost of *constructing Alternate One. Phase 1, 11, and III is $550,000.
Recommendation
Therefore, it is our recommendation that Alternate One be chosen and'that Phase I be
constructed as soon as possible. We are also recommending th at, Phase 11 be
designed to provide for the construction of a parallel line within the driveway of the lot
on the south side of Cameron Avenue adjoining the existing storm drain' rather than
removing and replacing this facility.
1
Charlinda-Citrus Drainage Study
STUDY
Purpose
This, Charlinda - Citrus- Drainage Study (Study) will analyze the drainage conditions in
the Chadinda - Citrus Area. The residences in the area of Charlinda Street between
Citrus Street and Cameron Avenue and those on Cameron Avenue near its
intersection with Charlinda Street have experienced significant runoff during periods of
heavy rainfall.* This Study identifies significant drainage issues and recommends the
most economical remedial measures for drainage control in this area. 'The study
provides recommendations for both an interim and ultimate drainage area plan.
Setting & History
The Study site is located between the intersections of Cortez Street and Citrus Street
and Cameron Avenue and Charlinda Street. A Location Map and Site Photos are
presented in Appendices A and C. The drainage area originates south of Cameron
Avenue within the South Hills, Count ry Club (golf course) and adjacent areas. Flows
are directed to an, inlet structure at the rear property line of. the homes south of the
intersection of Cameron Avenue And Charlinda Street. At this point any flows
exceeding the capacity of this inlet will flow between these - homes via the driveway on
the property east of the present drain. The home on this lot is built on a raised
` d the home on whose lot the drain is located has constructed a flood
foundation an
wall such that both appear pro.tected from flooding at this time.
From there, runoff flows through a combination of drainage conduits that discharge
onto the south side of Charlinda Street by way of an existing oversized parkway
culvert. Flows that exceed the capacity of the underground drainage system will -flow
.between the houses south of Cameron Avenue, cross Cameron Avenue at the
intersection of Charlinda Street and join with the flow from the underground drainage
system. This flow is then conveyed west in Charlinda Street to Citrus Street and then
north in Citrus Street to Cortez Street where it enters the existing iSouth Hills Drain.
The last four or five houses on the northern side of Charlinda Street on the western
end near Citrus Street were built at or below the top -of -curb grade. When the
carrying capacity of the street section is exceeded, runoff may drain onto the adjacent
properties., It is our understanding that runoff in excess of the drainage facility
capacities has been.reported in Charlinda Street between Cameron Avenue and
Citrus Street.'
2
Charlinda-Citrus Drainage Study
Alignment
In I this Study we analyzed'two . alignments. Alternate One extended the Citrus Street
Lateral of the existing South Hills Drain south,in Citrus Street to Charlinda Street
where it turns east. It then runs east and south in Charlinda Street and crosses
Cameron'Avenue to the existing inlet in the golf course. This alternate also has a
lateral that runs south in Citrus Street from Charlinda Street to Cameron Avenue.
Alternate Two also extends the Citrus* Street Lateral of the existing South Hills Drain
south in Citrus Street, but instead of turning east at Charlincla Street it continues
south to Cameron Avenue where it turns east. It then runs east in Cameron Avenue
to Charlindd Street and then turns south to the existing inlet in the golf course.
Hydrology
The hydrology study was performed using the Los Angeles County.Hydrology Method
and their IBM PC software. The results of this study determined that during a 50-yr.
capital storm approximately 284cfs,would be flowing through the Cameron-Charlinda.
street intersection with 261cfs tributary to, the inlet within the golf -course. The
Hydrology Calculations and Map are presented in Appendix, B of this Report.
Hydraulic
Our investigation indicates that the existing- drainage system. in the area of Cameron
Avenue and Charlinda Street is capable of carrying less than 20 cubic feet per
second (20cfs) (See Hydraulic Calculations, Appendix G). Our, investigation also
indicates that the maximum carrying capacity of Charlinda Street.is about 25cfs
before the storm flows exceeds the curb height (See Street Capacity Calculations,
Appendix IF). These flow rates are capable of being generated by a storm with a
frequency of less than a one year storm.
Due to the limited carrying capacity of this conveyance system we would expect to
have flows being conveyed on the surface between.the houses located on the south
side of Cameron Avenue, as well as beyond the street right-of-way on the west end of
Charlinda Street during most storms.*
Phase I of this system is proposed to carry enough of the storm flows,to relieve,
excess runoff in Charlinda Street. Phase 11 would control drainage between the
houses south of Cameron Avenue. With Phase I & 11 constructed at the peak flow
from the design storm, Citrus Street will be flowing beyond the street right-of-way with
3
Chadinda-Citrus Drainage Study
a maximum depth of flow in the gutter of slightly less than thirteen inches (13"). The
flow that can be retained within the curbs (8" deep) is less than a 1 -yr. frequency
storm and a storm a little above a 2.6-yr. frequency will have the flows extending past
the right-of-way. See street capacity calculations, Appendix F.
Phase III will connect Phase I I and 11 drainage facilities to the existing South Hills Drain
and in doing so increase Phase I and 11's carrying capacity to the full. capital storm as
well as reduce the flow in Citrus Street to levels satisfying the City's design criteria.
Phase IV was added to Alternate One to collect the approximately. 14.7cfs runoff that
crosses Cameron Avenue at its intersection with Citrus. Street as Phase I of Alternate
Two does. Without this lateral the maximum depth of flow in the cross gutter in the
design, storm will be about five inches (61) deep. � See street capacity calculations,
Appendix F.
PhasinQ
Phases I and 11 of both alternatives: will provide a . facili ' ty that after completion of Phase
III will be capable of conveying the L.A. Co.. Flood Control District's Design Capital
Storm. I n the interim -the Phase I conduit will outlet at Citrus Street near the
Charlinda Street intersection. In this phase the storm flows will be returned to the
street surface in Citrus Street by way of catch basins that will in the interim act as
bubblers and ultimately they will become an inlet for storm flows. The underground
system in Phas6 I of Alternate One will carry the flow generated by a 35-yr. storm.
During a 50-yr. storm 10cfs from the area upstream of the intersection of Charlinda
Street and Cameron Avenue plus about 30cfs from the local drainage will be carded
on the surface within Charlinda Street. In Alternate Two the entire 50-yr., storm will be
carried by the underground'system at this phase. Charlinda Street has.the capacity
of carrying 25.5cfs before any flows drain onto adjacent properties (See Street
Capacity Calculations, Appendix F). Therefore, with Alternate One in its interim
phase the adjacent properties may be subject to. some very minor flows through there
properties during a 50-yr. storm event.
When Phase 11 is completed all of the 50-yr. frequency storm, flows would be carded
underground between the houses located on the south side of Cameron Avenue i - n
both the interim and theultimate condition. Phase 11 in both alternatives is identical..
It proposes the construction of a conduit between the existing inlet in the golf course
and the existing manhole in Cameron Avenue. The existing 24 inch reinforced
concrete pipe (24!,RCP) has insufficient capacity to convey runoff from a 50-yr. storm.
The 24" RCP'is within a ten foot (10') drainage easement. The house appears to
4
Charlinda-Citrus Drainage Study
have been built on the edge of this easement. A block wall is on the lot line and the
home owner- has built his swimming pool equipment along with,other landscaping
improvements over the pipe (See Appendix C. Site Photos). Because of the.
restricted working area removal and reconstruction within the existing right-of-way
would appear to be more expensive than acquiring r new right-of-way from the
adjacent lot where fewer.improvements would need to be replaced and more space is
available for construction. We therefore, are Istrrongly recommending that in the final
design a parallel line within the. adjacent lot be considered. However, the cost
estimate assumes -removal and replacement within the existing easement.
The reduction of the hydraulic grade line (HGQ due to the construction of Phase III
will. bring an increase in the capacity of the system to where, Chadinda Street will
carry only local surface drainage in a 50-yr. storm event. Phase III is designed to
connect Phase I and 11 to the existing South Hills Drain and bring the depth and
velocity of �flows in Citrus Street within the City's design criteria,
Alternate One has a Phase. IV that extends a 24"RQP to the intersection of Citrus
Street and Cameron Avenue which will collect storm flows now crossing this This
intersection on the surface and allow the removal of the existing cross -gutter.
lateral is not required in Alternate Two because the main line storm drain collects. the
intersection flow as. part of. Phase 1.
Cost Estimate
ates include the
The cost estimates were based on current contract data.. The estim
cost of preliminary engineering and construction engineering but do not include the
cost for mobilization between phases or right-of-way. acquisition. A summary of the
estimates is shown below. For details of the Cost Estimates, see. Appendix E.
Phases
Alternate One
Alternate Two
Phase 1
$285,000
$353,000
Phase 11
$41,000-
$41,000
Phase 111
$2 1 24,000
$218,000,
hase IV
$112,000
Total
$662,000
M_
I
Charlinda-Citrus Drainage Study
DISCUSSION OF ALTERNATES
Both alternates when all phases are built afford the same level'of drainage protection.
Alternate One
Alternate One p . rovides drainage control for the study area at the lowest initial capital
expenditure.
The cost for Alternate One is higher than the cost for Alternate Two because of o * ur
attempt to make both alternates equivalent. Since Alternate Two collected the small
amount of flow crossing Cameron Avenue at Citrus Street we added Phase IV to
Alternate One to collect this small flow.
If the City were to decide that the small amount of flow, about 14.7cfs during a 50-yr.
storm, crossing Cameron Avenue at Citrus Street is not of any significance and Phase
IV were to be. omitted then this alternate will only cost $550,000. At present the
intersection of Cameron Avenue.and Citrus Street is controlled by a four way stop
signs. In the future if a traffic signal it constructed at Cameron Avenue and Citrus
Street, higher speed traffic would be exposed to the storm flows in the cross gutter
on the east side of Citrus Street. At present removal of the cross gutter and
construction of a separate lateral would be of marginal benefit. Deletion of Phase IV
would make Alternate One not only 24% lower in cost for Phase I but. also 11 % lower
in cost overall.
Alternate Two
Alternate Two provides drainage control forthe study area and removes runoff from .
the Cameron Avenue / Citrus Street intersection at the lowest total capital expenditure.
This alternate results in about $68,000 or a. 24% greater initial capital expenditure for
Phas . e I but a $50,000 or an 8% overall savings compared to Alternate One with
Phase IV lateral included.
CONCLUSION'.
This Study analyzed two slightly different alignments with Alternate One havin ' g four
phases and Alternate Two having three phases. Phase I of both alternatives is
designed to control storm runoff in Charlinda Street and provide for future extension
to connect to the South Hills Drain located in Citrus Street between Cortez Street and
Larkwood Street. The difference in cost between the two alternates is about $50,000
The main advantage of Alternate One is that the cost of its Phase I is less t . han
C
Charlinda-Citrus Drainage Study
Alternate Two's Phase I by almost 24 percent while achieving essentially the same
level of drainage control on Charlinda Street.
Therefore, it is our recommendation that Alternate One be chosen and that Phase I be
constructed as soon as possible. We also recommend that Phase 11 be designed to'
provide for the construction of a parallel line within a new easement along the
driveway of the lot on the south side of Cameron Avenue adjoining the existing storm
drain.
Alternate Two, would be the more economical choice under the full, development of
these drainage facilities if it is considered desirable to collect the small amount of
cross gutter flow on the east side of Citrus Street at Cameron Avenue.
7
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CHARLINDA I CITRUS
HYDROLOGY MAP
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