HomeMy WebLinkAboutPM 12023 Sewer StudyPage 1 of 7
Sewer System Study
For
McCutchen Commerce Center
Bakersfield, California
April 6, 2016
Prepared For
Beech A/C Properties, LLC
c/o
JB Consulting Services
9519 Lake Superior Drive
Bakersfield, CA 93312
Submitted By
Engineering Solutions
31600 Railroad Canyon Rd, Suite J
Canyon Lake, CA 92587
T (951) 333-1001
Page 2 of 7
INTRODUCTION
This report has been prepared at the request of Jack Brey of JB Consulting
Services who represents the owner of the subject property, Beech A/C
Properties, LLC. The project is a proposed industrial project located at
McCutchen Road and Reliance Drive in Bakersfield, California. The property
consists of approximately 40.0 acres. The proposed development will consist of
approximately 28 buildings with a total of approximately 88 suites of
office/industrial space of varying sizes. The project will be built in phases of 1-
4 buildings each. This report accompanies the first building phase, which
consists of just one building.
Because the proposed sewer system must also take into consideration future
development, this report also takes into account the sewer demands for a
potential future multi-family development on the 40 acres north of the subject
property. These two 40-acre parcels are all that remains in the sewer study area
that do not already have sewer service dependent on other systems, and are
therefore considered to contribute the total potential future sewer demand for
this system.
The subject property is extremely flat, and because of this fact, together with the limited depth of existing sewer lines, conventional gravity sewer lines alone
cannot feasibly provide sewer service to all portions of the proposed
development. The objectives of this sewer study are to determine the location
and number of individual sewer grinder pumps for clusters of buildings for ultimate buildout of the industrial park, and determine the proper pipe
diameter for the force mains as they accumulate flow from increasing numbers
of grinder pumps. The study is also for the purpose of discussion with the city,
and ultimately to serve as a design report to accompany the improvement plans.
Page 3 of 7
Design Concept
The current design concept evolved first from the idea of a single lift station
large enough to accommodate most of the flow from the individual units, to
the idea of a single grinder pump for each suite, based on the basic
development concept of the project. The project consists of multiple
buildings, most of which consist of up to 4 suites such that individual suites
or entire buildings may be sold or leased to tenants. The idea that each suite
could have its own grinder pump with each suite owner responsible for its
own pump seems a feasible alternative to collecting all sewers into a single lift
station. However, since a single grinder pump can serve more than the
volume of sewage produced by one suite, or even one building, it seems more
logical to serve clusters of suites with each grinder pump.
A standard 4” gravity sewer lateral serves each suite in a cluster, and laterals
are collected by a trunk which flows into the grinder pump. The outflow
piping from each pump discharges into a force main that begins as a 1 ¼“
PVC pipe and increases in diameter as more force mains join it on the way to
the ultimate discharge into the existing gravity sewer.
The design of the system begins with determining the estimated flow volume
from each suite which is based on the assumptions and calculations presented
in Table 1, wherein each suite is determined to produce a peak demand flow
equivalent to 14.5 fixture units. Since the conversion from fixture units to
gallons per minute is not a linear function, Table 2 was prepared to show the
accumulated flow rate in gallons per minute in increments of 14.5 fixture
units. Table 3 was prepared to assist in choosing the number of units
necessary to combine for a given pipe diameter at a given slope to maintain
the required minimum velocity of 2.0 feet per second for gravity sewer pipes.
The force main piping is sized by use of proprietary software provided by E-
One, a manufacturer of grinder pumps of the type to be used in this project.
The sizes of all proposed gravity mains and force mains are indicated on
Exhibit A. Table 4, which is based on Exhibit A, indicates the number of
suites contributing to each grinder pump zone, the accumulated number of
units at each junction point, the corresponding peak flow rate in gpm and in
cfs, the diameter of pipe from one node to the next, and the velocity in feet
per second.
Page 4 of 7
Table 1
Fixture Unit Count
Fixture Fixtures/Suite F.U. Equiv. Fixture Units
Toilets 3 3.0 9.0
Urinal 1 1.5 1.5
Lavatory 2 1.0 2.0
Bar Sink 1 1.0 1.0
Floor Drain 2 0.5 1.0
Total per Suite 14.5
Table 2
Fixture Unit/Flow Rate Conversion
No. Suites Fixture Units Equiv. Flow Rate (gpm)
1 14.5 18.8
2 29.0 24.3
3 43.5 27.8
4 58.0 31.9
6 87.0 39.6
8 116.0 46.9
10 145.0 54.0
12 174.0 61.1
14 203.0 67.8
20 290.0 87.7
26 377.0 94.3
28 406.0 114.1
30 435.0 120.7
36 522.0 140.5
38 551.0 148.3
42 609.0 164.0
46 667.0 175.7
52 754.0 193.3
88 1276.0 330.4
Page 5 of 7
Table 3
Gravity Pipe Flow Capacity/Velocity
Pipe Dia. Slope % Flow Depth Q (gpm) V (fps) Suites Served
4 “ 2.00% 80 142 4.24
4 “ 2.00% 70 122 4.16
4 “ 2.00% 60 98 3.99
4 “ 2.00% 50 73 3.72 16
4 “ 2.00% 40 49 3.35 10
4 “ 2.00% 30 29 2.88 4
4 “ 2.00% 20 13 2.29 1
6” 1.00% 90 324 3.87
6” 1.00% 80 59 2.67 12
6” 1.00% 18 23 2.00 2
8” 0.52 25 60 2.00 13
8” 0.60 21 47 2.00 9
8” 0.70 18 39 2.00 7
8” 0.80 16 34 2.00 5
8” 0.85 15.6 31 2.00 3
8” 0.90 15 30 2.00 3
McCutchen Commerce Center
Table 4
1811646.911646.9
1.250.10450.00912.3
21217461.129087.7
2.000.19540.0229.0
3811646.9406114.1
2.500.25420.0347.5
4811646.9522140.5
2.500.31300.0349.2
51014554.0667175.7
2.500.39150.03411.5
6811646.911646.9
1.250.10450.00912.3
768739.620367.8
1.500.15110.01212.3
81217461.137794.3
2.000.21010.0229.6
945831.9435120.7
2.500.26890.0347.9
10811646.9551148.3
2.500.33040.0349.7
1145831.9609175.7
2.500.39150.03411.5
1246667175.71276330.4
4.000.73610.0878.4
Future Multi Family 384.0664384.0
4.000.85560.0879.8
Flow Rate
(CFS)
X‐Section
Area (SF)
Sewer Flow Rate (Demand) By Zone and Accumulative
Zone
Units/
Zone
Flow Rate
(gpm)
Accumulative
Flow (gpm)
Force Main
Dia. (inches)
Velocity (feet
per second)EDU
Accumu‐
lative EDU
SEWER CALCULATIONS
Site Location: McCutchen Commerce Center
cfs =cubic feet per second
fps =velocity in feet per second
GA =gross acres
DV = design volume
GPD =gallons per day
MGD =million gallons per day
Note: Residential
The average family unit shall be 3.01 persons per single family residential unit and
2.77 persons per multi family residential unit.
The average daily discharge of domestic sewage shall be 100 gallons per day per person.
Design discharge per the following formula:
Design Discharge = Peak Factor x Average Discharge
Formula Ave. Discharge Units
where:Peak Factor =2.54 x(Ave. Discharge)-0.1 (MGD)
Peak Factor =2.65 x(Ave. Discharge)-0.1 (cfs)
Land Use Peak Discharge Rate Peak Factor
Commercial -0.012cfs/GA (6,460 GPD/GA)1.8
Industrial0.015cfs/GA (9,695 GPD/GA)2.0
Gross Acres = 40.32
Sewer Pipe Sizing Formula:Design Volume = (GA) x (0.010 cfs/GA) x (Peak) = cfs
Commercial:0.8709cfs
Design Volume = 40.32 x0.4838x1.8 =
Industrial:1.2096cfs
Design Volume = 40.32 x0.6048x2.0 =
Residential: Single Family No. of Units =0.00
People/DU =3.01 Average Daily Discharge
Total Persons =0.000 ÷ 1,000,000 =3E-09mgd
Gal/day/person=100 Peak Factor 18.07
Total gpd =02.54 x (Ave.Discharge)-0.1 =peak factor =
Design Discharge
Peak Factor x Average Ddaily Discharge
18.07 x 0.0000 =0.000mgd
=0gpd
Peak Inflow Into Sewer Pipe =0gpm
Peak Inflow Into Sewer Pipe =0.0000cfs
Residential: Multi - Family No. of Units =664
People/DU =2.77 Average Daily Discharge
Total Persons =1839.28183,928 ÷ 1,000,000 =0.18393mgd
Gal/day/person=100 Peak Factor
Total gpd =183,9282.54 x (Ave.Discharge)-0.1 =peak factor =3.01
Design Discharge
SEWER CALCULATIONS
Site Location: McCutchen Commerce Center
Peak Factor x Average Ddaily Discharge
3.01 x 0.1839 =0.553mgd
=553371gpd
Peak Inflow Into Sewer Pipe =384gpm
Peak Inflow Into Sewer Pipe =0.8562cfs
Note: Trunk and Main sewers may be designed to flow full however; under no conditions may a gravity sewer
be designed to flow under head pressure. Minimum Velocity in sewer is 2 fps
SEWER CALCULATIONS
Site Location: McCutchen Commerce Center
2.1.1 Average Daily Discharge
Sewage flow is calculated per person, per land use. The following assumptions
are based on District and City criteria:
100 gallons per day per person (City Standards)
2.77 persons per dwelling unit (COB Standards - proposed, Section 2.2.1.1a)
664DU *2.77person/DU = 1,839persons
1,839persons *100gpd/person = 183,928gpd =0.183928MGD
Average Daily Discharge = 0.183928MGD
2.1.2 Peak Factor
Peak sewage flow is calculated using the peak factor calculated in City Manual
Section 2.2.1.1b(1).
Peak Factor = 2.54 x (Average Daily Discharge) -0.1
Peak Factor = 2.54 * (0.183928 MGD) -0.1 =3.01
Peak Factor = 3.01
2.1.3 Design Discharge
Design Discharge =Peak Factor x Average Discharge (§2.2.1.1b)
3.01*0.183928MGD =0.553MGD
Design Discharge = 0.553MGD
2.1.4 Peak Flow
The peak flow for the sewer pipe shall be equal to the design discharge.
0.553MGD =553,371gpd
553,371 gpd ÷ 24 hr/d ÷ 60 min/hr =384gpm
Peak Flow =384gpm =0.8562cfs
2.1.5 Pipe Capacity
Proposed Pipe Diameter =10inch
Proposed Slope =0.0400%
Proposed Pipe Material =SDR 35
n - value =0.013
The following calculations assume the pipe is flowing full, but unpressurized:
Flow Area =0.54sq.ft.
Wetted Perimeter =1.30ft
Velocity =8.01ft/s (from Manning's equation)
Flow Capacity =4.34cfs = 1946gpm
2.1.6 Peak Flow Including McCutchen Commerce Center
Peak flow, Future MF384gpm0.8562cfs
Peak flow, Office/Ind.542gpm1.2096cfs
Combined Peak Flow926gpm2.0635cfs
SEWER CALCULATIONS
Site Location: McCutchen Commerce Center
384gpm =0.8562cfs
Hydraulic Calculations:
Pipe Analysis for L.F. of 10 " PVC Pipe 1
invert elevation in-
Q=2.0635 cfs
Props'd Pipe(feet)0.83
Proposed Slope 0.0400
n factor 0.013 (SDR 35 or equal)
Q = A(1.486/n)(R2/3*S1/2)
A=0.541062
1.486/n=114.3077
R2/3=0.350493
S1/2=0.2
Q= (capacity)4.335cfs =48% full
invert elevation out-----------343.50
Velocity
V = (1.486*R2/3*S1/2)/n
constant1.486
R2/3=0.350493
S1/2=0.200000
Velocity=8.01fps
Conclusion: Pipe ok