HomeMy WebLinkAbout20180413_Sewer-Water Demand StudyPSOMAS
TECHNICAL MEMORANDUM
To: David Keely
From: Mike Swan
Date: March 12, 2018
Subject: Tentative Tract Map No. NT2017-0004, 4302 Ford Road
Sewer and Water Demand Study
Introduction
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The purpose of this memorandum is to document a sewer and water demand study prepared for
the subject TTM consisting of a proposed 21 unit condominium development on a 1.3-acre
vacant parcel (Assessor's Parcel No. 458-361-09) located at 4302 Ford Road as shown on Figure
1, which also shows the existing sewer and domestic water facilities in the area of the Proposed
Project. The site is just to the southeast of the MacArthur Boulevard/Bonita Canyon Drive
intersection and is accessed by the Ford Road cul-de-sac. An existing AT&T facility is located to
the east of the parcel and the Bonita Canyon Sports Park is to the south.
Sewer
The 21 condominium units are proposed to average 1,916 square feet and the breakdown by
number of bedrooms with the appropriate sewage generation factor (SGF) from the City's
Design Criteria is as shown in Table 1 below.
Bedrooms
2
3
4
Total
Table 1
Sewage Generation
Sewage
Dwelling Generation Factor
Units (gpd)
5 150 per DU
11 190 per DU
5 40 per BDR 1
21
Sewage
Generation
(gpd)
750
2,090
1,150
3,990
1) 190 gpd/DU + 40/additiona I bedroom greater than 3
As shown on Figure 1, there is an existing 8-inch sewer in Ford Road adjacent to the Proposed
Project that currently serves only two buildings, the AT&T building immediately to the east of
the Proposed Project and the Sports Park restrooms to the southwest. This existing 8-inch sewer
runs from MH IDl-557 at the end of the Ford Road cul-de-sac approximately 733 linear feet
easterly in Ford Road to the intersection of Newport Hills Drive West where it turns northerly in
a 12-inch sewer and discharges into the Ford Road Sewer Lift Station wet well. The slope of the
8-inch sewer is 0.020, which would equate to a design capacity of 0.85 cubic feet per second
(cfs) or approximately 550,000 gallons per day (gpd) at a depth-to-diameter ratio of 0.50. Even
doubling the flow from the Proposed Project to account for flow from the AT&T facility and the
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TTM NT2017-0004, 4302 Ford Road-Sewer & Water Demand Study
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March 12, 2018
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Sports Park restrooms and then peaking this average flow at a factor of 5 ( conservative since the
flows will likely not peak at the same time of day), it would equate to a peak flow of about 0.06
cfs and a d/D of O .13, well below the design capacity of the existing 8-inch sewer. In fact, the
additional flow will actually improve the situation in that peak flows will likely now reach just
over 2 feet per second, which is the typical minimum desirable cleansing velocity.
The peak flow experienced by the sewer collection system downstream of the existing sewer lift
station will not be any different than it currently is as the existing pumps will only put out a flow
equivalent to their rated capacity, regardless of the incoming flow rate. The pumps will just
operate slightly longer to pump the minor additional amount of sewage coming into the wet well
from the Proposed Project.
Water
Water demand for the Proposed Project will be equal to the sewer generation (indoor water
demand from Table 1) plus the outdoor water demand. Since all outdoor water use for this
condominium project will be from common landscaped areas, the landscaping water demand has
been estimated using the square footage of planted areas provided by the landscape architect, the
local evapotranspiration rate (Eto ), and the plant types and irrigation system efficiency also
provided by the landscape architect, using the following formula and detailed in Table 2.
ETWU = (Eto)(0.62)[(PFxHA)/IE]
Where:
ETWU = Estimated Total Water Use in gallons per year
Eto = reference Evapotranspiration rate in inches per year (49.9)
0.62 = conversion factor to gallons
PF= Plant Factor from Water Use Classification of Landscape Species (WUCOLS)
HA = H ydrozone Area in square feet ( sf)
IE = Irrigation Efficiency
Table 2
Common Area Landscape Demand
Plant Water
Water Use Plant Landscape Irrigation Demand
Hydrozone Type Factor Area (sf) Efficiency (gal/yr)
1 High -0 -0
2 Medium 0.6 12,940 0.81 296,546
3 Low 0.3 19,409 0.81 222,398
4 Med Tree 0.6 1,040 0.75 25,740
5 Low Tree 0.3 3,560 0.75 44,056
Total 36,949 588,741
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TTM NT2017-0004, 4302 Ford Road-Sewer & Water Demand Study
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March 12, 2018
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As a check, the ETWU must be less than the Maximum Applied Water Allowance (MAW A),
which is calculated based on an Evapotranspiration Adjustment Factor (ET AF) of 0.55 for
residential projects times the total landscaped area (LA) as follows.
MAWA = (ETAF)(Eto)(0.62)(LA) = (0.55)(49.9) (0.62)(36,949) = 628,720 gal/yr
Therefore, the ETWU is less than the MAWA at 94% ofthe MAWA (588,741/628,720).
The total annual landscape demand shown in Table 2 converts to 1,613 gpd (588,741/365).
Therefore, the total water demand is the indoor water demand or sewage generation from Table 1
plus the common area landscape demand from Table 2 or 5,603 gpd (3,990 + 1,613). Using a
conservative factor of2.0 times average demand to get to maximum day demand on the
landscaping demand and assuming the indoor demand will be relatively constant all year round,
the maximum day domestic water demand for the Proposed Project would be 7,216 gpd [(1,613
X 2) + 3,990].
There is an existing 12-inch water main fronting the Proposed Project in Ford Road which is
looped through the Sports Park to the west across MacArthur Boulevard and continuing in Ford
Road further westerly. This same 12-inch water main also runs easterly in Ford Road connecting
to lines in Newport Hills Drive West, Newport Hills Drive East and San Miguel Drive. These
existing domestic water facilities are illustrated on Figure 1.
A fire flow test was conducted on February 5, 2018 at Fire Hydrant #2328 located at the end of
the Ford Road cul-de-sac adjacent to the entrance to the Sports Park parking lot, which is directly
across the street from the Proposed Project. For this test, the static and residual pressures were
measured at Fire Hydrant #2430 located on the southerly side of Bonita Canyon Drive near the
intersection with MacArthur Boulevard, which is the next closest hydrant to the Proposed
Project. Static pressure measured was 112 psi and with the hydrant flowing at 1,519 gpm, the
residual pressure dropped to 102 psi (see attached fire flow test). This calculates to a flow of
5,036 gpm at 20 psi residual, substantially more than required for the Project. Additionally, water
pressure will definitely not be an issue for the Proposed Project, in fact individual pressure
regulators will be required for each service.
Conclusion
As shown above, the average sewage flow from the Proposed Project including 21 condominium
units is 3,990 gpd and no additional sewer system improvements are required to adequately
provide sewer service.
The water demand for the Proposed Project consists of the indoor water demand ( sewage
generation) plus the common area landscaping demand for a total average demand of 5,603 gpd
and maximum day demand of 7,216 gpd. The Proposed project will have excellent water
pressure and more than sufficient fire flow based on the fire flow test and the strong 12-inch
looped system fronting the Project.
Attachments: Figure 1, Fire Flow Test Results
3
Legend
----Sewer Gravity Main
• •• • •■Sewer Force Main
• Sewer Manhole
~ Sewer Direction of Flow
----Water Main 'tr Fire Hydrant
Figure 1
CITY OF NEWPORT BEACH
UTILITIES DEPARTMENT
FIRE HYDRANT FLOW TEST
AMOUNT PAID: $338.00 DATE: 03/05/2018
TIME: 9:30 AM
WEATHER: CLEAR
--------
CHECK NO: --------
TESTNO:
PROJECT:
PROJECT LOCATION: 4320 FORD ROAD
TEST CONDUCTED FOR: HINES
TEST PERFORMED BY: BULLMAN, ALVIDREZ
TEST WITNESSED BY:
FIELD OBSERVATIONS AND FLOW DATA
STATIC HYDRANT#: 2430 LOCATION: 1641 FORD ROAD
F/H MANUFACTURER: JONES NUMBER & SIZE OF OUTLETS: 2-2.5" 1-4" ---------
STATIC PRESSURE, ( Ps , psi), PRE-FLOW: 112
RESIDUAL PRESSURE, (Pr, psi) FLOWING: 102
FLOW HYDRANT# : 2328 LOCATION: 1650 FORD ROAD
F/H MANUFACTURER: JONES NUMBER & SIZE OF OUTLETS: 1-2.5" 1-4"
STATIC PRESSURE, PRE-FLOW (INFO ONLY, NOT FOR TEST CALCS):
F/H OUTLET SIZE ( 2.5 or 4.0): I 2.5 I (d, inches)
FLOW LOSS COEFFICIENT -TUBE C=l .O / BUTT C=0.9 0.9
PITOT GAUGE READING ( p, psi ): 1.----8-2---.
OBSERVED FLOW: THE OBSERVED FLOW FROM A HYDRANT OUTLET IS CALCULATED FROM THE
FOLLOWING EQUATION: Q s = 29.83(Cd 2)-fp
WHERE; Q IS THE OBSERVED FLOW IN GPM; d IS THE OUTLET DIAMETER IN INCHES; p IS THE PITOT GAUGE
PRESSURE IN PSI; AND C IS THE FLOW LOSS COEFFICIENT ( C = 1.0 FOR FLOW TUBES AND C = 0.9 FOR BUTT
FLOW READINGS).
OBSERVED FLOW (Qs, gpm): 1519 IGPM
DISCHARGE CALCS: THE DISCHARGE FOR A GIVEN FIRE HYDRANT CAN BE DETERMINED FROM THE FOLLOWING
EQUATION USING THE INITIAL (STATIC) WATER PRESSURE AND THE RESIDUAL (DYNAMIC)
WATER PRESSURE:
WHERE; Q ( STATIC OR RESIDUAL) IS THE FLOW IN GPM; AND P ( STATIC OR RESIDUAL) IS THE
PRESSURE IN PSI. NOTE: A 10 PSI DROP IS REQUIRED FOR VAUD TEST!
CALCULATED FLOW AT 20 psi (Qr, gpm): ..___5_0_3 6 _ ___.I GPM