HomeMy WebLinkAboutAgenda Report - February 1, 1995 (62)OF
CITY OF LODI
COUNCIL COMMUNICATION
c4tFu�'`o
AGENDA TITLE: Plans and Specifications and Advertisement for Bids for Standby Generators for
Water Well and Storm Drain Pumping Stations for Sites 7, 9 and 16
MEETING DATE: February 1, 1995
PREPARED BY: Public Works Director
RECOMMENDED ACTION: That the City Council approve amending the plans and specifications for
the above project and authorize advertising for bids.
BACKGROUND INFORMATION: The City's Water Master Plan recommends that reliable backup
power be available at a minimum of one-third of the well sites.
We currently have twenty-four wells and six standby generators.
The existing generators are mostly 1940's and '50's government
surplus units that were last overhauled in the 1960's. They are obsolete, and repair and replacement
parts are no longer readily available. The controls are unreliable and cannot be considered
"automatic" as they should be. Only four out of the six generators are operational and they all do not
automatically start and operate properly. The four locations are Wells 5, 8, 9 and 16. Well 9 is
currently out of service'. Another unit at Well 7 has not functioned for many years and has been
cannibalized for parts. The sixth unit is at Well 13 and has electrical problems. If we are to maintain
reliable standby power capabilities, these units need to be replaced.
The sites recommended for immediate replacement are those having adjacent storm pump stations for
which the generators will be sized to handle both the well and the storm pumps. These are three of the
City's four major pump stations - Beckman Park (Well 16), Shady Acres (Well 9) and Lodi Lake
(Well 7). The old generators were sized to only run the well or some of the storm pumps.
This project, with two additional sites, was approved for bidding last year. The specifications included
an option for a lease/purchase arrangement due to the poor financial condition of the water utility. The
project was bid twice and both times all bids were rejected due to various problems with the bids and
questions about the project in general.
Staff is again recommending that we move forward on this project and offers the following project
justification and changes in project scope and funding for Council consideration:
Justification
State regulations require that the water system maintain a minimum pressure in the system
under various conditions. In Lodi's system, this is done by two means. The first and foremost is
1 Well 9 has had intermittent problems with bacteria counts exceeding State standards. Based on some preliminary work, we
feel the problem can be solved with an on-site disinfection unit (not chlorine). Since this well is free of DBCP, it is too
valuable to simply abandon the site. Staff wilt be making a recommendation on how to proceed with this well at some time in
the future.
APPROVED: i ivt,
THOMAS A. PETERSON recycled paper
City Manager
CPS&AGE2.DOC %�
Plans and Specifications and Aavertisement for Bids for Standby Generators for Water Well and Storm
Drain Pumping Stations for Sites 7, 9 and 16
February 1, 1995
Page 2
the various well pumps that lift groundwater and pressurize the system. Pumps are turned on
and off to meet customer demands and maintain system pressure. Secondarily, our single
elevated water tank can provide water and pressure under certain hydraulic conditions.
If all the pumps were to stop, the tank would supply water only for a short period of time
depending on the demand. The question of how much standby capacity is needed becomes
more of a risk management issue than a straightforward engineering calculation.
In discussions with Electric Utility staff, it appears the most likely, and also the most severe,
power outage that would affect the water system is a citywide outage. (Smaller area outages
would affect far fewer wells and, unless they occurred during a peak time, would not cause a
major problem. Also, having generators on some wells spread throughout the City would help to
minimize this problem.) Over the past eleven years, we have averaged one citywide outage per
year. They ranged in duration from 4 minutes to 58 minutes. If we were to analyze this similar
to storm events and express it in terms a 100 -year event, we would design for an outage
duration of 72 minutes (see Exhibit A).
If the water tank were called upon to be the sole source of supply, the length of time it would last
would depend on the customer demand and the amount of water in storage at the start of the
power outage. Exhibit B presents this analysis under various demand conditions assuming the
tank starts half full with 50,000 gallons. Under present average day conditions, the tank would
last just over 5 minutes.
One difficulty in further analyzing this problem is that under power -outage conditions, water
demand tends to drop off. The exact amount is unknown and would vary considerably with the
nature of the demand. For example, demands for industrial processes and automatic irrigation
systems would probably drop. Typical domestic uses would be less affected.
Given all these difficulties in analyzing the problem, common practice in the industry is to
provide some level of backup protection, hence the recommendation from our previous
engineering consultants to provide standby power at one-third of our wells.
Additional justification for the three recommended sites is that this will also provide standby
power for the adjacent storm pump stations. We have not analyzed power outages at these
individual locations, but it certainly would seem prudent to provide backup power for critical flood
control facilities.
Project Scope and Fundina
As noted, last year's project was for five sites. Based on the Water Master Plan, we should
have eight wells with standby power. We recommend that the City:
• keep the units at Wells 5 and 8 on-line for a few more years, cannibalizing parts from
the other units as needed. Unneeded parts and/or units would be included in the bid
to be removed;
• purchase the three units listed above, bringing the total to five. Since we have
budgeted lease payments for two years, we have enough funds available to cover
the purchase price without resorting to a lease and corresponding interest payments;
CPS&AGE2.DOc 01124M
Plans and Specifications and Advertisement for Bids for Standby Generators for Water Well and Storm
Drain Pumping Stations for Sites 7, 9 and 16
February 1, 1995
Page 3
• pay for 50 percent of the cost of these three units that will serve the storm pump
stations from the Storm Drain Fund. A recommendation as to the actual amount of
funds to appropriate would be made at the time of award;
• plan to purchase three additional units in two years and another three units in four
years and take the obsolete units at Wells 5 and 8 out of service. This will result in a
total of nine new units, which, by that time, will represent one-third of our wells.
This recommended project is substantially different from last year's project and should attract many
bidders. The specifications for the recommended units will be extracted from the previous
specifications and appropriate changes made to the bid documents to account for the other changes in
the project. The bid opening date will be set by the Public Works Director after the changes are made
and the plans and specifications are ready for bidding.
FUNDING: Originally Budgeted:
Budgeted Fund:
Current Appropriation:
Total Project Estimate:
Prepared by Richard C. Prima, Jr., City Engineer
JLR/RCP/lm
attachments
cc: Purchasing Officer
Water/Wastewater Superintendent
Street Superintendent
City Engineer
1993/94
Water Capital Outlay
$384,000
$350,000
Vzti -
Jack . Ronsko
ublic
Jack
Director
CPSEAGE2.DOC 01/25M
Exhibit A
City -Wide Power Outage Analysis
Date Range: January 1984 thru December 1994 n = 11.0 years
Confidence level assumes normal distribution of outage durations.
z per "Basic Statistical Methods for Engineers & Scientists" 2n4 Ed. 1976, page 159, Table 10-2.
PWR_OUT.XLS
Duration
Date
(minutes)
Time
3/10/85
14
12:46 PM
3/2186
54
12:37 PM
4/8/86
10
9:02 AM
10/21/86
58
10:55 PM
7/16/88
13
2:33 PM
7/6/89
49
12:19 AM
7/29/89
10
6:21 PM
2/16/90
17
1:25 PM
4/16/90
17
1:33 AM
4/4/91
4
8:44 AM
8/24/92
18
3:27 AM
Number of outages:
11
Total Duration:
264
minutes
Average Duration u:
24
minutes
Median Duration:
17
minutes
Standard Deviation 6:
18.7
minutes
Confidence level
z
Outage duration (N+z Q)
90%
1.645
55 minutes
95%
1.960
61
98%
2.326
67
99%
2.576
72
Confidence level assumes normal distribution of outage durations.
z per "Basic Statistical Methods for Engineers & Scientists" 2n4 Ed. 1976, page 159, Table 10-2.
PWR_OUT.XLS
Exhibit B
Water System Demand & Storage Tank Capacity
Tank Capacity: 100,000 gallons (full)
Available Storage: 50,000 gallons (assumed)
Avg. Flow Available for 60 minutes: 833 gpm
Demand year:
1993
2007
Avg. Day, gpm:
9,000
15,000
Max Day, gpm:
17,000
34,000
Peak Hour, gpm:
25,000
50,000
Flow Time from Available Storage
year:
1993
2007
Avg. Day, minutes:
5.6
3.3
Max Day, minutes:
2.9
1.5
Peak Hour, minutes:
2.0
1.0
PWR OUT.XLS