HomeMy WebLinkAbout04.b. Review draft Position Paper to approve the Phase 2 - Aeration Basins Diffuser Replacement and Seismic Upgrades Project in the Fiscal Year 2020-2021 Budget and funding from the Steam and Aeration Blower Systems Renovations, District Project 7349; an Page 1 of 18
Item 4.b.
CENTRAL SAN BOARD OF DIRECTORS
POSITION PAPER
DRAFT
MEETING DATE: APRIL 20, 2021
SUBJECT: REVIEW DRAFT POSITION PAPER TO APPROVE THE PHASE 2 -
AERATION BASINS DIFFUSER REPLACEMENTAND SEISMIC
UPGRADES PROJECT IN THE FISCAL YEAR 2020-2021 BUDGETAND
FUNDING FROM THE STEAM AND AERATION BLOWER SYSTEMS
RENOVATIONS, DISTRICT PROJECT 7349; AND AUTHORIZE THE
GENERAL MANAGER TO AMEND AN EXISTING AGREEMENT WITH HDR,
INC. TO INCLUDE FINAL DESIGN SERVICES IN AN AMOUNT NOT TO
EXCEED $1,856,000, INCREASING THE COST CEILING TO $5,326,000
SUBMITTED BY: INITIATING DEPARTMENT:
NITIN GOEL, SENIOR ENGINEER ENGINEERING AND TECHNICAL SERVICES-
PDS-ASSET MANAGEMENT
REVIEWED BY: DANEA GEMMELL, PLANNING AND DEVELOPMENT SERVICES DIVISION
MANAGER
EDGAR J. LOPEZ, CAPITAL PROJECTS DIVISION MANAGER
JEAN-MARC PETIT, DIRECTOR OF ENGINEERING AND TECHNICAL
SERVICES
STEVE MCDONALD, DIRECTOR OF OPERATIONS
ISSUE
The Board of Directors (Board) authorization is required for the General Manager to amend an existing
professional engineering services agreement in an amount greater than $200,000.
BACKGROUND
Recently, the existing aeration system has not been able to reliably maintain a desired dissolved oxygen
levels across the basins. Proper oxygen transfer is an essential element of a biological activated sludge
treatment process. This has contributed to a steady deterioration (increase) in sludge volume index (SVI),
which is a key secondary process operational parameter for activated sludge settleability and compaction.
The increase in the SVI has in turn, led to concerns over the ability to consistently meet National Pollutant
Discharge Elimination System (NPDES) discharge limitations. While Central San continues to meet
NPDES discharge permit limits, further deterioration in performance of the aeration system will cause
more challenges overtime, which would also lead to poor settleability in the secondary clarifiers and would
impact the performance of the UV disinfection system.
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Staff updated the Board and Engineering and Operations (E&O) Committee at several meetings, including
on December 20, 2018, when authorization was granted to enter into an agreement with HDR, I nc. (HDR)
for the condition assessment and preliminary design of the Steam and Aeration Blower Systems
Renovations, District Project(DP) 7349 (Steam Project). This decision was made after a very competitive
and formal solicitation process and selection that included four qualified consulting engineering firms.
At the Board Meeting on July 16,2020, staff proposed phasing the design of the Steam Project into
multiple projects. The Board also approved the first phase of the project- Electric Blower Improvements,
DP 7377 (now DP 10015). Based on detailed evaluations, completed as part of the Steam Project on the
aeration system and structural integrity of the aeration basins, as well as operational reliability concerns,
staff now recommends proceeding with the final design of Phase 2 -Aeration Basins Diffuser
Replacement and Seismic Upgrades (Aeration Project).
Summary
A detailed condition assessment was completed as part of the Steam Project that evaluated the condition
of the aeration system (diffusers and other associated mechanical assets) and the structural integrity of the
aeration basins, with an emphasis on meeting current seismic code. The condition assessment and
comprehensive asset evaluations recommend diffuser replacement, mechanical asset
rehabilitation/replacement, controls upgrade, concrete repairs, and structural improvements to prolong the
remaining useful life of the aeration basins and improve resiliency.
Aeration Basin Diffusers
Based on the Steam Project condition assessment task, the existing diffusers are from the early 1970s,
are reaching the end of their useful life, and require replacement. The four aeration basins contain 9,600
ceramic fine bubble diffusers located in plenum boxes on the basin floor. Diffusers convert air from air
distribution piping into fine bubbles to provide oxygen to activated sludge bacteria. In 2009 and 2010
during the Aeration Air Renovations, DP 7207 and Aeration Air Renovations-Phase 2, DP 7274, plenum
grout injection was completed to seal cracks and reduce air leaks, 15 percent of diffusers were replaced
in-kind (1,440), new actuators valves were installed, new pressure relief valves were installed, and other
miscellaneous repairs were completed.After many years of service and based on the evaluations
described below, replacing only the non-functional diffusers would still very likely continue to pose risk due
to fouling and porosity differences between new and older diffusers as seen from the last replacement.
Diffusers and Mechanical Assets Condition Assessment Findings
Based on evaluations of the diffusers in two of the four basins, an estimated 50 percent of diffusers are
non-functional due to fouling/clogging attributed to the number of years in service. Basin gates and
downcomers require rehabilitation or replacement due to corrosion. The concrete structures are in fair
condition with some locations requiring surface repairs.
Seismic Evaluation Findings
There are structural evaluation standards for existing structures and tanks or the 1970s aeration basins
developed to assess the seismic vulnerability of aged infrastructure and these standards were developed
from lessons learned based on structural damage and behavior after major earthquakes, such as Loma
Prieta in 1989 and Northridge in 1994. The previous codes designed for lower-than-expected ground
shaking incorporate insufficient member ductility to remain undamaged after an earthquake. HDR
completed a seismic evaluation using the 2019 California Building Code and California Existing Building
Code, which references American Society of Civil Engineers (ASCE)41 for Existing Building Design.
Structural analysis identified a need to strengthen overstressed walls and beams and repair expansion
joints to wall connections.
Diffusers Performance Testing Findings
The existing aeration system performance has deteriorated over time. The oxygen transfer efficiency of
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the diffusers is 0.3 percent per feet, which is much lower than typical values observed at conventional
activated sludge treatment plants of 0.6 to 1.1 percent per feet. Professor Michael Stenstrom from UCLA
performed the oxygen transfer efficiency testing of the existing diffusers in 2019 (as a part of Steam
Project), as well as in 1997, and 1991 as part of past projects. He found that the diffuser performance in
2019 has deteriorated significantly compared to the past diffuser performance. Staff prepared a business
case evaluation (BCE) comparing replacing existing ceramic diffusers in-kind and repairing the plenum
versus installing new membrane diffusers without the plenum. Staff concluded that the replacement with
the latest technology membrane type diffusers without the plenum was preferable as the long-term
solution. The BCE was based on capital cost, net present worth cost, as well as cost benefit ratio.
Operational Concerns with Secondary Process and Permit Impacts
Due to the large number of manual control valves and non-functional diffusers, required air flow distribution
to maintain the desired oxygen transfer for the activated sludge process across the basin is challenging to
maintain. As a result, the existing aeration system is not able to maintain a desired dissolved oxygen levels
across the basin. This has contributed to a steady deterioration in settleability illustrated by an increase in
the SVI and has increased concerns by operational staff over the ability to reliably meet NPDES
discharge limitations in the future.
Government Code Section 1090 (Section 1090) Compliance:
HDR will be performing the technical work for the final design of Aeration Project, which is in compliance
with Section 1090. HDR has not been precluded from continuing with the final design of the Aeration
Project and associated potential subsequent engineering services during construction of the elements
identified as part of the Aeration Project and other phases of the Steam Project based on the following
premises:
1. The publicly advertise scope of the Steam Project for consultant selection included from its
inception elements for the Aeration Project, related work as well as other phases;
2. HDR role and scope on the project during the preliminary design, BCE, and assessments were
limited to technical evaluations in nature only and did not include any recommendations independent
from staff;
3. HDR was not acting in a capacity similar to that of a Central San employee or staff;
4. HDR did not perform work that independently defined the scope of the subsequent contract
amendments;
5. HDR did not influence the decision making of Central San regarding the subsequent work; and
6. Board Committee meetings and Board presentations were prepared, presented, and
recommendations created by Central San staff.
The elements identified as part of the Steam Project will be implemented in Phases:
• Phase 1: New Electric Blowers - DP 10015 (Currently in Final Design)
• Phase 2: Aeration Basins Diffuser Replacement and Seismic Upgrades (Aeration Project)
• Phase 3: Secondary System Improvements
• Phase 4: Steam System and Existing Aeration Blower Renovations
The major elements of the scope of the Aeration Project is described below:
The Aeration Project will develop the final design drawings and specification for structural
upgrades, mechanical assets rehabilitation/replacement, concrete repairs, diffuser system replacement or
upgrades, demolishing the existing air plenums, and installation of with state of industry systems such as
membranes. This project will also be replacing some of the air piping, reconfigure the aeration basins
(a.k.a.A/N Tanks)to maximize the use of unused channels to optimize the activated sludge process using
available volume and tankages, as well as implementing instrumentation and controls upgrades to improve
air flow distribution to match process oxygen demands.
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California Environmental Quality Act(CEQA)
Staff has concluded that this Project is exempt from CEQA under Section 15262 of Central San's CEQA
Guidelines, since it allows for further planning and feasibility studies for possible future actions which
Central San has not approved, adopted, or funded, and the outcome of these tasks will not have a legally
binding effect on later activities. Central San will conduct an environmental evaluation of any capital project
that is proposed in the future as a result of the tasks authorized herein to determine the need for any
additional CEQA documentation.
ALTERNATIVES/CONSIDERATIONS
Alternative 1: Status Quo - Do Nothing Alternative, replacement in-kind of only non-functional diffusers
(-50 percent of existing diffusers) overtime during preventative maintenance shutdowns. Replacing only
non-functional diffusers is considered high-risk due to fouling and porosity differences between new and
existing diffusers that may result in compatibility issues.
Alternative 2: Exclude some elements of the Project, such as the mechanical rehabilitation/replacement,
controls upgrade, concrete repairs, or structural improvements. The mechanical replacement, diffusers,
and the concrete repairs are needed immediately. Seismic upgrades should be completed during the
renovation of the diffuser system and the demolition of the air plenums. Performing the seismic upgrades
later would be more expensive and most likely result in re-doing the mechanical systems.
These alternatives are not recommended.
FINANCIAL IMPACTS
The total anticipated cost for the final design of the Aeration Project is $1,056,000, which includes bidding
services. The current cost ceiling of HDR's Steam Project agreement is $3,470,000. If the Board
approves the additional $1,856,000, this will result in a new HDR contract value or cost ceiling of
$5,326,000, as shown in the table below.
Services Fees Board Approval
Original Agreement with HDR for Steam Project $2,590,000 December 20, 2018
Phase 1 - Electric Blower Improvements DP July 16, 2020
10015- Final Design and Bidding Services $880,000
Current HDR Agreement $3,470,000
Phase 2 -Aeration Basins Diffuser Replacement
& Seismic Upgrades Project- Final Design and $1,856,000
Bidding Services
Total Contract Value with Amendment $5,326,000
There are adequate funds within the current budget of the Steam Project, DP 7349 to fund the Aeration
Project- Final Design and Bidding Services. The total estimated construction cost is $22,900,000, which
equates to roughly 8.1 percent of the design fee for HDR. A future amendment to the agreement is
anticipated if the Phase 2 project is awarded for construction.
COMMITTEE RECOMMENDATION
The Engineering and Operations Committee reviewed this matter at its meeting on April 20, 2021 and
recommended
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RECOMMENDED BOARD ACTION
Staff recommends the following:
1. Approve the Phase 2-Aeration Basins Diffuser Replacement and Seismic Upgrades Project in the
Fiscal Year 2020-21 Budget and funding from the Steam and Aeration Blower Systems
Renovations, District Project 7349; and
2. Authorize the General Manager to amend an existing professional engineering services agreement with
HDR, Inc. to include final design for Phase 2-Aeration Basins Diffuser Replacement and Seismic
Upgrades Project in an amount not to exceed $1,856,000, increasing the agreement cost ceiling to
$5,326,000.
Strategic Plan Tie-In
GOAL TWO:Environmental Stewardship
Strategy 1—Achieve 100%compliance in all regulations, Strategy 2—Anticipate and prepare for potential regulatory
changes
GOAL FIVE:Infrastructure Reliability
Strategy 1—Manage assets optimally to prolong their useful life, Strategy 2—Execute long-term capital renewal and
replacement program
GOAL SIX.Innovation and Optimization
Strategy 1—Implement the Central San Smart 1 nitiative, Strategy 2—Improve and modernize operations through
technology and efficiency measures
ATTACHMENTS:
1. Presentation
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PHASE 2 - AERATION BASINS DIFFUSER
REPLACEMENT & SEISMIC UPGRADES PROJECT
(PART OF STEAM &AERATION BLOWER
SYSTEM RENOVATIONS, DISTRICT PROJECT (DP) 7349)
Jean-Marc Petit, Director of Engineering and Technical Services
Steve McDonald, Director of Operations
Engineering and Operations Committee Meeting
April 20, 2021
1
BACKGROUND
Iz
2
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ACTIVATED SLUDGE PROCESS
The heart of the liquid treatment is the secondary activated sludge process which
requires oxygen for the biological treatment. Oxygen is provided by aeration blowers to
the aeration basins (A/N Tanks).
SECONDARY PROCESS SYSTEM
77
MW-AWA
CFNTPAt SAN
3
AERATION SYSTEM OVERVIEW
Anaerobic Selector _
(No Air Added) v� "�• Aerobic Aeration basins
♦ (Air Added)
4 basins Each
.I a (2 Passes per basin)
Secondary Process Starting Point: 1
Influent&Return Activated Sludge
Nial Mai
IIIIIIII DO Probe(8 total) 1W an
■,ei rom
4 w One actuator controls
air per pass(8 total)
CFNTPAL SAN
4
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AIR PIPING DOWN COMERS, PLENUM, AND DIFFUSER CONFIGURATION
y �
— - A1libA A1W&I
`♦
""Ou
wPww ft J
. � � cgaa�cama
CFNTPAt SAN
s
5
9,600 DIFFUSERS IN CENTRAL SAN AERATION BASINS
Central San Secondary Process
Aeration System Summary:
4 basins �ti ;„:•-� ��
• 2 passes per basin (8 total)
• 1 actuators per pass(8 total) -
• 11 drop legs per pass(88 total) fir- :ate
• 1,200 diffusers per pass(9,600 total)
aSBY
CFNTPAL SAW
6
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OPERATIONAL CHALLENGES WITH SECONDARY
PROCESS SLUDGE VOLUME INDEX (SVI)
• SVI is an indicator of settleability: lower 400
values are desired. 4
350 -------F .' -------- ------ ------------------------#------
• Central San continues to meet permit 300 � ? t-.'= --'- k- =•:�
limits. However, an increasingSVI likely
due to an Ineffective aeration system will` 250 'j j �► -----
A:
rn .: • Al
cause more issues over time. 200 '
II ., II► I
• Impacts include secondary process 150
capacity and more challenges with 100 1 -- -- ----
effluent total suspended solids (TSS)
.:
limits. so -- -- ------ ---- ---- - •----- - -- ----- - L----- ----- -----
0
nAa O9 A� 1 r,12 �A5 �6 r,0 .0 \s r20 71
Mixed liquor suspended solids(MLSS)saso,"'�a Ia �a �a �a �a ya Ia Ia Ia ja sa
Moving (Mov.) ♦ MLSS Channel,SVI
Milliliter per gram (mL/g) —Linear(MLSS Channel,SVI)
—30 per.Mov.Avg.(MLSS Channel,SVI)
For Central San's process, SVI of 100 to 150 mL/g is considered good '
CFNTPAI SAN
CENTRAL SAN DIFFUSER
PERFORMANCE IS DETERIORATING 1.6 * 1991 (Split Treatment)
OVER TIME 1997
♦ 2019
• Performance of Diffuser is directly correlated
to aSOTE/Z(higher the better)
• Typical aSOTE/Z Values:
• Secondary Treatment: 0.6–1.1 %/ft
LU
• Nitrification: 0.9–1.35%/ft I—
O
• Nitrification/Denitrification: 1.05- 1.45%/ft cn
• How does Central San fare? 0.8-
1991
.a 1991 aSOTE/Z was 0.52%/ft
0 1997 aSOTE/Z was 0.54%/ft iii [�inDr.
f Typical Values at Various SRTs
♦ 2019 aSOTE/Z was 0.30%/ft nstrom's Database
• aSOTE/Z=0.30 might be the lowest HDR.Inc.
0.4
and Professor Stenstrom have ever seen
MCRT & i MCRT i i i i i MCRT
(d) �6 (d) 106:1712M (d) 11
0.2 0 114 18
Se ndary Nitrifying Only Nitrification/
Alpha Standard Oxygen Transfer Efficiency in process water per depth(aSOTE/Z) Treatment Den'
Solids Retention Time(SRT) _
Mean Cell Residence Time(MCRT)also known as sludge age Days(d)
8
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STEAM SYSTEM AND AERATION PROJECT, DP 7349 SCOPE
Sub 33
irsrr� '�`• ��
r
-
O���iK']i
« !3/ Sub 52 _'Iii
-- _� Sub 34 •may
4W J
ita
i!1 i
Sub 73
lCIClClP:lRE!!!lEF: I � r.
_. ElAN ll:lLLCl[LI1GILyE�^
) 9
9
STEAM PROJECT PHASING
Phase 1: Refurbish and add New Electric Blowers in Pump & Blower
Building.
Phase 2: Secondary Process Improvements including Aeration Tanks,
associated Electrical and Controls Systems.
Phase 3: Secondary Process Improvements including Mixed liquor division
box, Secondary Clarifiers, and associated Electrical and Controls Systems.
Phase 4: Complete the Evaluation of Steam System and Determine
Upgrade of Existing Steam System vs. Conversion to Electric with Steam
Turbine Power Generator Included in Ten-Year CIP
ZA J
CFNTPAt SAN
10
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Wk.UN
--
:i10 � t � DRAFT Secondary Process and rl ;� DRAFT Steam System
Aeration System Comprehensive i, Comprehensive Asset
Fl - Asset Evaluation Evaluation
t I_
k Steam and Aeration Blower System ie Steam and Aeration Blower System
d;I' Renovatlon Project,BP 7349 4=i� Renovation Project,BP 7349
`iaHFLrie��ii FN
September 2020
August 2020 -„ _
EVALUATIONSCOMPREHENSIVE ASSETS
Mimi Central San Steam Project
Comprehensive Asset Evaluation for
- Electrii
Odobrr 20200
11
11
Asset Name Location
Aeration Air Filters SArm9 -
Aeration Shakers19Blower Inlet Inlet Guide Vanes#1 and#2
Blower Inlet Guide Vane#3 2g .Ip(�s�• \/�/�\���
Blowers#1 and#2 ;q 11 11 I;�/ \�
Blower#3,#4,and#5 3g ���///\�'� O
14 •�� i7 15 12 F'
iiia•. i'< - r
11 +.- -a+aays�a ea 11 11 '-. rr•
Aeration Basi 9
]���rr 2A I I�•,
Secondary Clarifier Basins 11 ' • 6 •, —
y
38 2B A 3A c:
- _ 1
Secondary Clarifier Inlet Gates 14&15
['f 1A I' A
- 1g I
Tunnels 20 C� Phase 1:New Electric Blowers(In Final Design DP-10015)
Structural Strengthening of Aeration Tanks 0 Phase 2:Aeration Basins Diffuser Replacement&Seismic Upgrades
Rehabilitate Unused Selector 22
Secondary Launders 23 Phase 3:Secondary System Improvements
O Existing Secondary System
* Pending inspectionO f
Phase 4:Steam and Existing Aeration Blower Renovations
12
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AERATION BASINS DIFFUSERS REPLACEMENT &
SEISMIC UPGRADES PROJECT
i. Project Focus Areas:
.I
-;-6 ; • Diffusers and Other Existing
I Mechanical Assets
=„ /Iv Tanks Aeration Improvements (for
Sub 52 `s _ example, Gate
. f __= __====� ti , Rehabilitation/Replacement,
etc.)
Aeration Piping and Isolation
= Buried Air Piping and Valves
� • Butterfly Isolation Valves
Instrumentation and
Controls Upgrades
Structural and Seismic
Upgrades
CENTRALSAN
tlnnnt{tn{u�; � -
WHY INITIATE THE DESIGN
OF PHASE 2A NOW?
CENTPAL SAN
14
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DRIVERS FOR AERATION BASINS DIFFUSER REPLACEMENT &
SEISMIC UPGRADES PROJECT
1 . Replace aeration diffusers
2. Address Mechanical Deficiencies
3. Improve aeration system controls
4. Aeration basin seismic upgrades
CENTRALSANi
15
IMPLICATIONS OF SVI ON SECONDARY TREATMENT CAPACITY:
DETERIORATING SVI = NEARING CAPACITY
100
90 -------------------------------------------------------------- 2019 SVI Data: -----------------------------------------------------------------
180 mL/g Ave.Annual
80 240 mL/g Max.Month ------------------------------------------------------------------
71
E70 ---------- ---------------- ---------------------------------------------------------
Permitted ADWF
Z60 ------------------------------------- ------------------------------------------------------------------------------------------------------------------ 53.8 mgd
CL ia
M
U50 ------------- ------------------------------- -------------------------------------
43
2045 ADWF
40 ------------- ------------------------------ ------------------------------ ------------------------------------------------------------- 42-45 mg
0
v
in30 ------------------------------ ------------------------------ ------------------------------- --------------- 2019 ADWF
LL
34 mgd
0 20 ------------- ---------------------- ------------------------------ ------------------------------- ---------------
Q
10
0
SVI=150 mL/g SVI=190 mL/g SVI=235 mL/g SVI=260 mL/g
=y Average Dry Weather Flow(ADWF) Million Gallons Per Day(mgd) CFNTPAL SAN
f
Sf!
16
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AERATION BASINS DIFFUSERS REQUIRE IMMEDIATE ATTENTION
1. Diffusers are original equipment type (1970's)and nearing end of
useful life:
• About 50% of them are non-functional
(combination of blanks and non-functional diffusers)
• Inefficient and ineffective at maintaining dissolved oxygen set-points
across the basins (as documented in the off-gas report performed by
Professor Michael Stenstrom, UCLA)
• Challenging to control air distribution to desired basin zones
2. Operational Impacts: inability to maintain sufficient dissolved oxygen _
levels likely contributes to long-term solids settleability deterioration
and may compromise permit compliance -_ _ _
Page 15 of 18
INSTRUMENTATIONS AND CONTROLS: CHALLENGES MAINTAINING CONSISTENT
DISSOLVED OXYGEN (DO) ACROSS AERATION BASINS
2.5
23 Set-point2 25
21 g/L
Set-point 2.0 mg/L ------ ----- --- ------
E 1.8 .IIIIIT W,a-
1.5 IIT' 7
X1.3 •I 1'
v 1.0 i
0.8
0.5
03 III
0.0 I
1 2 3 4 5 6 7 8 9 10
Location(45 ft intervals from inlet)
0Tank1A/1B ■Tank1C/11D ■Tank2C/2D Tank 2A/2B
• DO levels across the basins are random and challenging to
control. Importance: 7 ,
• Low DO levels foster growth of filaments
• Filaments compromise settleability and in turn could impact a �
the ability to meet National Pollutant Discharge Elimination
System(NPDES)discharge limits — l�
• Reasons:difficult to control air distribution with manual drop legs DO Probe(8 total)
and number of non-functional diffusers in each zone is likely
uneven.
19
STRUCTURAL EVALUATION RESULTS
Seismic Evaluation: developed three-
End wall strengthening "— dimensional (3-d)finite element analysis
model and evaluated with 2019
over5tre56ed California Building Code and California
top blab __ Existing Building Code which references
beams ——
American Society of Engineers 41 for
Existing Building Design
. .E
! —Longitudinal wall strengthening
7 I End wall strengthening �..
North-south expansion joint not • •r
continuous,resulting in cracking in wall
CFNTPAL SAW
20
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ESTIMATED PROJECT COST &
FUNDING SCHEDULE
BOARD ALTERNATIVES &
RECOMMENDED BOARD ACTION
21
AERATION BASINS DIFFUSER REPLACEMENT &
SEISMIC UPGRADES PROJECT
TOTAL ESTIMATED PROJECT COST
IProject Components
Istimated Construction Cost $22.9 M
Total Estimated Project Cost $25.8 M
Funding from the Steam and Aeration Blower Systems Renovations,DP 7349 has a total project budget of$51 million(M)in
Fiscal Year(FY)2020-21 Budget.
CFNTPAL SANI
22
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SCHEDULE FOR
AERATION BASINS DIFFUSER REPLACEMENT &
SEISMIC UPGRADES PROJECT
Year 2021 Year 2022-2024 01
Iff _ Jul Oct
May Jul Oct Feb Apr-May 2022-Sep
I'll, 11111�
2021 2021 2021 2022 2022 2024
2023 `
• • 1
Board 10% Design Equipment Submittal
Bid/Award Construction Completion
Approval Submittal Procurement
Documents& Goal: 1-2 basins per dry
30%Submittal weather construction
season (—Mar-Sep) 23
CFNTPAt SAN
23
BOARD ALTERNATIVES
• Alternative 1: Status Quo - Do Nothing Alternative, replacement in-kind
replacement of only non-functional diffusers (-50 percent of existing
diffusers) over time during preventative maintenance shutdowns. Replacing
only non-functional diffusers is high risk due to fouling and porosity
differences between new and still functional existing diffusers may result in
compatibility issues.
• Alternative 2: Replace all diffusers in all aeration basins and exclude the
mechanical asset rehabilitation/replacement, controls upgrade, concrete
repairs, and structural improvements from the Phase 2 -Aeration Basins
Diffuser Replacement and Seismic Upgrades Project. Mechanical asset
rehabilitation/replacement, concrete repairs, and structural improvements
are required to prolong the remaining useful life of the aeration basins.
These alternatives are not recommended.
,en@,'KJ
L24
CENTRALSAN
24
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RECOMMENDED BOARD ACTION
• Approve the Phase 2 - Aeration Basins Diffuser Replacement
and Seismic Upgrades Project in the Fiscal Year 2020-21
Budget and funding from the Steam and Aeration Blower
Systems Renovations, District Project 7349; and
• Authorize the General Manager to amend an existing
professional engineering services agreement with HDR, Inc. to
include final design for the Phase 2 - Aeration Basins Diffuser
Replacement & Seismic Upgrades Project for an amount not to
exceed $1 ,856,000, increasing the agreement cost ceiling to
$5,326,000.
CENTRALSAW
25
QUESTIONS?
CENTPAL SAN
26
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