1986 Master Plan of DrainageMASTER PLAN OF DRAINAGE PRESENTATION
CITY OF LA QUINTA
CALIFORNIA
Presented by:
BSI CONSULTANTS, INC.
1415 East Seventeenth Street
Santa Ana, California 92701
(714) 558-1952
DECEMBER 15, 1986
OEM
1985 by BSI
in I
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CITY OF LA QUINTA
MASTER PLAN OF DRAINAGE
EXECUTIVE SUMMARY
Introduction
The City of La Quinta has retained BSI Consultants,, Inc. to
prepare a Master Plan of Drainage within its city limits.
The purpose of this study is to analyze the existing
drainage deficiencies and indicate possible solutions. This
Master Plan is also intended to serve as a document for
communication between the City of La Quintal the Coachella
Valley Water District and the residential and commercial
land developers within the City limits.
For the purpose of this study, the overall flood control
system serving the City of La Quinta was divided into two
distinctly different components; "off -site" or regional and
"on -site" flood control systems. The regional flood control
system is a major flood control work planned, designed and
being presently constructed for the Coachella Valley Water
District by Bechtel Incorporated of San Francisco. This
system was designed to collect the runoff from the steep
mountains surrounding most of the City, and to convey it to
the Whitewater River. It will be operated and maintained by
the Coachella Valley Water District.
The "on -site" flood control system is a network of local
drainage facilities. The analyzing, planning and financing
of these local "on -site" facilities, and the feasibility to
convey "on -site" street and lot drainage to the regional
facilities is the subject of this Drainage Master Plan.
This Master Plan of Drainage provides the following:
1. A brief inventory of the "off -site" or regional and
existing "on -site" facilities.
2. An overall concept for "on -site" drainage including
sizes and locations for the required major storm drains,
and priority listings.
3. Recommendations for drainage policies.
4. Cost estimates for proposed facilities.
Methodology Applied
All existing drainage data reports, "as-builts" plans and
land use plans were collected from the City, Coachella
Valley Water District and the consulting engineers serving
- i -
9 21
the land developers within the City.
The study was based on the Riverside County Survey and Road
Department's 1975 aerials, (1 inch 200 feet scale and 4
foot contour intervals) and the City of La Quinta "General
Plan", "Land Use Map" and " Circulation Map."
For the purpose of the Master Plan of Drainage the City was
divided into four areas. (See Exhibit 1) Each individual
area presents similarities in land use, development and
drainage pattern.
Since part of the City is presently undeveloped while other
parts have streets inadequately developed, certain
assumptions were made for the analysis. These assumptions
are as follows:
1. All existing streets without curbs and gutters would
be reconstructed with them in the future. This is
consistent with the City of La Quinta General Plan.
2. During reconstruction, these streets would be lowered
so that the right of way line of the street would be one
foot lower than the finished floor elevations of the
adjacent building pads. (See Exhibit 2)
3. Each existing and future building pad will be
generally drained toward the adjacent street (see
Exhibit 3)
4. In case the above under item 2 and 3 cannot be
accomplished due to existing utility interferences or
impracticality due to major excavation, the drainage
schemes presented on Exhibits 4 and 5 shall be adopted.
Recommendations
The "Master Plan of Drainage Report" recommends the
following:
1. The City shall adopt the methodologies and criteria
set forth by the Riverside County Flood Control and
Water Conservation Districts "Design Manual". As
indicated in Exhibit 6, there shall be one foot of
minimum freeboard between the dwelling pad elevation and
the 100-year water surface elevation which shall be
retained within the street's right of way. This is
consistent with the Federal Emergency Management
Agency's requirement to have the lowest floor elevation
(including basement) at or above the base flood (100-
year flood) level.
2. For Area One it is recommended that Reinforced
Concrete Pipe (RCP) facilities be constructed to convey
runoff to the Bear Creek Channel, the Avenida Bermudas
Detention Basin and the Crystal Canyon Detention Basins
as shown on Plate 1.
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EXHIBIT 2
TYPICAL RECOMMENDED LOT DRAINAGE SCHEME FOR AREAS 1&2
F" B
% %
LOW B High point
10
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A A C C
%
1%
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Curb
PLAN
Mudsill 3'rnin. 4' min.
F- 6" min. jr-- 6 min
POP
BLDG FAD ELE
SECTION C-C
3' min.
6 01 min mudsill
lea a -
SECTION A -A
12" - 18" (Bit min. above pod elevation
Round off top
SECTION B - B
TYPICAL 13ERM DETAIL
4 1
— BLDG. PADI ELEV.—
(—Elev. must be eQual
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or higher
SECTION C-C
d' to IS!' ALTERNATE
EXHIBIT 3
RECOMMENDED LOT DRAINAGE
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EXHIBIT 4
EALTERNATE DRAINAGE SCHEME FOR LOT DRAINAGE AREAS 1&2
HIGH POINT Curb
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B
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3' min.
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MIN 6" min mudsill
High Point
2 % min TIC'minknum
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1% MIN.
ELEV.
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Curb s min. 4'min
PLAN
BLDG. PADI E LEV.
77
Mudsill 3' min. 4' min.
�6" min bow*
76" min od lev. must be equal
C::o BLDG ELEI 17 to bldg. pad elew
or higher.
Competed berm SECTION C-C
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S1 MON C-C ALTERNATE
EXHIBIT 5
RECOMMENDED LOT DRAINAGE/ALTERNATIVE
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-The 100-Year flood shall be contained within street R/W limits.
The 10-Ytar flood shall be contained within the Top of curbs.
Initiate a storm drain or channel when either condition is
exceeded.
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OPEN CHANNEL
NOTES:
Protection criteria shown are the Districts typical minimum requirments. Special conditions,
or other authorities may require stricter controls;ie; for reasons of traffic of pedestrian
safety, maintenance problems behind curbs etc., lower maximum depths of flow in streets
may be required.Also see Riv. Co. Ord. No. 460.
EXHIBIT 6
FLOOD PROTECTION GOALS
The total cost for these improvements is $ 4f882f9OO.
3. For Area Two it is recommended that RCPf
Reinforced Concrete Box (RCB), and grass lined open
channels be constructed to convey runoff to the Bear
Creek Channel and the All -American Canal. This area
also includes the construction of a detention basin.
The total cost for these improvements is $ 51075F100.
4. For Area Three it is recommended that all on going
and new developments shall provide for the flood
protection requirements adopted by this Master Plan.
The total cost for these facilities is absorbed by the
developers of this area.
5. For Area Four it is recommended that RCP and RCB
facilities be constructed to convey runoff to the
Whitewater River and a small portion to the All -American
Canal. The total cost for these improvements is $
28,791,000. However, this amount can be substantially
reduced if the individual developers make provisions to
retain on -site drainage.
The total cost to the City of La Quinta to construct
these improvements is $ 38,749,000 in January 1986
dollars.
Priority Listin
This Master Plan of Drainage recommends the following order
of priority for construction of the recommended on -site
storm drain facilities:
1. Area Two: The facilities that should have top
priority are within Area Two, subareas three and four
(see Plate 2). The facility shall be constructed in
Calle Tampico to the park -detention basin. The next
facility to be built is from the park -detention basin to
Calle Ronda, along the proposed realignment of 52nd
Avenue to the All -American Canal.
2. Area Four: The second priority is in Area Four
subarea six (see Plate 4) . This facility shall extend
from Washington Street along the future 48th Avenue.
This system will eliminate the ponding that frequently
occurs near the intersection of Washington Street and
the future street of 48th Avenue.
3. Areas One & Two: The third priority is in Areas one
and Two (see Plates 1 & 2). It includes all of the
remaining recommended facilities by this Master Plan.
This will provide the existing development with on -site
flood control facilities.
The remaining facilities that are recommended to be
constructed will depend on the order of development.
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Exhibit 7
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Method of Ultimate Runoff Disposal for Area One
The 100-year storm runoff from subarea one will flow into
the Avenida Bermudas Detention Basin. In a similar fashion
the 100-year runoff from subareas two through four will
discharge into the Crystal Canyon Detention Basins. Finally,
the 100-year runoff from subarea five will drain into the
Bear Creek Channel.
Method of Ultimate Runoff Disposal for Area Two
The 100-year storm runoff from subareas one and two will
flow into the Bear Creek Channel and oleander Reservoir.
The 100-year storm runoff from subarea three is recommended
to drain initially to a 36" flap -gated manhole opening at
Calle Amigo and Desert Club Drive. When this system becomes
full, the runoff will drain into the channel along the
proposed realignment of 52nd Avenue. The 100-year storm
runoff from subarea four will drain into the proposed park -
detention basin at Calle Ronda and Avenida Tampico.
Initially, some of the runoff west of Desert club Drive will
drain to a second 36" flap -gated manhole opening at Avenida
Tampico and Desert Club Drive. When this system becomes
insufficient, the runoff will drain to the park -detention
basin. After the park -detention facility develops head the
water will drain through a pipe along Calle Ronda to the
open channel along the proposed realignment of 52nd Avenue.
The channel will continue along the proposed 52nd Avenue
realignment to a point where it meets the existing 52nd
Avenue alignment. At this point the channel will turn
southerly and discharge into the All -American Canal. The
recommended trapezoidal grass lined channel is 3.75 feet
deep, with a 1 foot invert width, and 3:1 grass lined side
slopes.
Method of Ultimate Runoff Disposal for Area Three
The 100-year storm runoff from subarea one will be detained
in the Crystal Canyon Detention Basins and partially drained
into the La Quinta Evacuation Channel via a 60" RCP. The
100-year storm runoff from subareas two and three should
drain into retention facilities on -site.
Method of Ultimate Runoff Disposal for Area Four
The 100-year storm runoff from subareas one, two, and six
will discharge into the La Quinta Evacuation Channel. The
100-year storm runoff from subareas three, four, five, and
eight will drain to the Whitewater River. Subareas three
and eight will flow through part of the City of Indio before
reaching the Whitewater River. Subarea seven will also flow
through part of the City of Indio before reaching the All -
American Canal. The Reflections and the Groves development
will retain the 100-year storm on -site.
- iv -
VIM
I
CITY OF LA QUINTA
MASTER PLAN OF DRAINAGE
PUBLIC MEETING
DECEMBER 15, 1986
AGENDA:
1. INTRODUCTION
11. PURPOSE OF MEETING
Ill. PRESENTATION OF THE STUDY
IV. OPEN DISCUSSION
V. CLOSING STATEMENT
P
CITY OF LA QUINTA
MASTER PLAN OF DRAINAGE
PUBLIC MEETING
DECEMBER 15, 1986
AGENDA:
1. INTRODUCTION
II. PURPOSE OF MEETING
Ill. PRESENTATION OF THE STUDY
IV. OPEN DISCUSSION
V. CLOSING STATEMENT
Aq,
qj
Resolution 86-96
Page 2
OWNER
Calif ornia
Castles, Inc.
DATE AGENDA ITEM #
()APPROVED DEt4IED
() CONTINUED TO
ASSESSOR'S COST TO 25% ADMINI-
PARCEL # ABATE STRATIVE COST TOTAL
773-284-024 $214.50 $53.63 $268.13
Kanner, Myna
774-085-023-0
Kanner, Myna
774-085-024-1
McClelland,
773-315-005
Brennan T.
Overstreet, Emily
773-062-001-2
San Fernando
773-161-014-0
Airpost Corp.
Smith, Donald E.
773-326-022-6
Smith, Trudie
773-163-015-7
Wadworth, Henry J
774-085-018-6
115.50
28.88
144.38
115.50
28.88
144.38
405.00
101.25
506.25
227.50
56.88
284.38
602.50
150.63
753.13
187.50
46.88
234.38
203.50
50.88
254.38
115.50
28.88
144.38
3. The City Manager is hereby directed to transmit a certified
copy of this Resolution to the tax collector of the County of
Riverside and said tax collector is hereby requested to collect
the amount of each assessment herein at the time and in the
manner of ordinary property taxes.
APPROVED and ADOPTED this 2nd day of December, 1986.
MAYOR
ATTEST:
CITY MANAGER/CLERK
APPROVED AS TO FORM:
CITY ATTORNEY