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Combined Sewer System Permit
and Long Term Control Plan Update
CSS Stakeholder Group Meeting #4
February 1, 2018
City of Alexandria and Alexandria Renew Enterprises
• Welcome
• Purpose and Goals
• Green Infrastructure Update
• Summary of CSO Program Options and Performance
• Life Cycle Cost Estimates, Schedule, Community Impact, O&M, and Adaptability
• Public Comment and Questions
• Wrap-Up
Presentation Outline
CSS Stakeholder Group Meeting #4 2
Public Participation Goals
CSS Stakeholder Group Meeting #4 4
Increase stakeholder
awareness of the City’s
combined sewer
system and the Long Term
Control Plan Update
program.
Develop basic
understanding of the
Long Term Control Plan
Update recommended
strategies.
Awareness, consideration
and responsiveness on the
Long Term Control Plan.
Solicit feedback on the
combined sewer
control strategy
recommendations.
Resolution No. 2781
• Provide recommendations on how a primary combined sewer system control strategy can accomplish the City’s goals and permit requirements while minimizing impacts to the community
• Review and monitor the preparation of the Long Term Control Plan
• Permit and regulatory issues
• Engineering and analysis of infrastructure alternatives
• Implementation plan schedule and funding strategy
• Serve as a central information receiving/dissemination body related to the Long Term Control Plan
• Additional engagement opportunities following submission of the plan (working groups, implementation groups)
Stakeholder Group Charge
CSS Stakeholder Group Meeting #4 5
Alexandria’s Goals for the CSO Program
CSS Stakeholder Group Meeting #46
WATER QUALITYEnhance local infrastructure to improve the
water quality of Alexandria’s waterways.
INVESTMENT STEWARDSHIPBe good stewards of the rate payers’ investments in
both the short term and long term.
COMMUNITY BENEFITS AND CONSTRUCTION IMPACTSEngage the community, explore opportunities,
and be a good neighbor.
LEGISLATIVE MANDATEImplement the CSO Program to meet the legislative mandate.
• City is refining the evaluation of Green Infrastructure (GI) and will report to the Group:
• Lessons learned from City’s experience and other CSO programs
• Opportunities and challenges in the combined sewer area
• Cost/benefit analysis of GI in the combined sewer area
• Potential GI strategies
• Present results at Stakeholder Meeting #5
Green Infrastructure Update
CSS Stakeholder Group Meeting #4 8
City: ~15.2 square miles
CSO Area: ~540 acres, 6% of the city
Four permitted outfalls by DEQ:
•CSO-001 (Oronoco Bay)
•CSO-002 (Hunting Creek)
•CSO-003/004 (Hooffs Run)
Alexandria’s Combined
Sewer System
Combined Sewer
Service Area
Duke St.
CSO-003 & CSO-004
Pendleton St.
CSO-001
Royal St.
CSO-002
Hunting
Creek
Hooffs Run
Po
tom
ac R
ive
r
Alexandria Renew
Enterprises Water
Resources Recovery
Facility
CSS Stakeholder Group Meeting #4 10
Existing CSO System
CSS Stakeholder Group Meeting #4 11
CSO-002
Combined
Sewer
Area
CSO-001
AlexRenew
WRRF
Ho
off
s R
un
Hunting Creek
Po
tom
ac R
ive
r
Cameron Run
Oronoco
Bay
AlexRenew
Plant Outfall
CSO-003
CSO-004
(to be relocated)Final Effluent Outfall
Existing CSO
Existing Conveyance
Piping
Option ASeparate Tunnels with Wet Weather Treatment
CSS Stakeholder Group Meeting #4 12
AlexRenew
WRRF
CSO-002
Co
nve
yan
ce
Tu
nn
el
Wet Weather
Treatment
Sto
rage
Tu
nn
el
Treated Wet
Weather
Outfall and
Relocated CSO
004
CSO-003
CSO-004
(to be relocated)
CSO-001
Ho
off
s R
un
Hunting Creek
Po
tom
ac R
ive
r
Cameron Run
Oronoco
Bay
AlexRenew
Plant Outfall
New Conveyance
Piping
Final Effluent Outfall
Existing CSO
Existing Conveyance
Piping
Option BUnified Storage Tunnel
CSS Stakeholder Group Meeting #4 13
Ho
off
s R
un
Po
tom
ac R
ive
r
Cameron Run
AlexRenew
WRRF
CSO-002
2.2
MG
Sto
rage
Tu
nn
el
Storage and Conveyance Tunnel
Relocated CSO-004
CSO-003
CSO-004
(to be relocated)
AlexRenew
Plant Outfall
CSO-001
Hunting Creek
Oronoco
Bay
New Conveyance
Piping
Final Effluent Outfall
Existing CSO
Existing Conveyance
Piping
Ho
off
s R
un
Po
tom
ac R
ive
r
Cameron Run
AlexRenew
WRRF
CSO-002
CSO-001
CSO-003
CSO-004
(to be relocated)C
on
ve
yan
ce
Tu
nn
el
Storage
Tank
Storage
Tank
AlexRenew
Plant Outfall
Wet Weather
Treatment
Hunting Creek
Oronoco
Bay
New Conveyance
Piping
Final Effluent Outfall
Existing CSO
Existing Conveyance
Piping
Option CTunnel for 003/004 with Wet Weather Treatment and Tanks for 001/002
CSS Stakeholder Group Meeting #4 14
Treated Wet
Weather
Outfall and
Relocated CSO
004
0 10 20 30 40 50 60 70 80 90
CSO-001
CSO-002
CSO-003
CSO-004
Number of Overflow Events
Average Number of Overflows 2000-2016
Option A, 2Option B, 2Option C, 3
Existing, 78
Option A, 3Option B, 4
Option C, 3
Existing, 35
Option A, <1Option B, <1Option C, <1
Existing, 68
Option A, 1Option B, <1Option C, <1
Existing, 71
15CSS Stakeholder Group Meeting #4
* Preliminary performance
data, subject to change due
to further refinement
4-6 overflows/year
150.2 MG
18.7 MG
42.6 MG
20.8 MG
0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0
Existing
Option A
Option B
Option C
CSO Volume (MG)
CSO-001 CSO-002 CSO-003 CSO-004
Average Volume of Overflows 2000-2016
16CSS Stakeholder Group Meeting #4
* Preliminary performance
data, subject to change due
to further refinement
Existing
Option A
Option B
Option C
68%
96%
91%
96%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent Capture
Average Percent Capture 2000-2016
17CSS Stakeholder Group Meeting #4
* Preliminary performance
data, subject to change due
to further refinement
Existing
Option A
Option B
Option C
85%
Performance Conclusions
CSS Stakeholder Group Meeting #4 18
Option A
Separate Tunnels
Option B
Unified Storage
Tunnel
Option C
Tunnel for 003/004
and Tanks for
001/002
Meet Hunting Creek TMDL ✓ ✓ ✓
Reduce overflows to 4 per year (or less)
on average✓ ✓ ✓
Provide 85% capture ✓ ✓ ✓
Evaluation Criteria Survey Score Description
Life Cycle Costs 4.07• Optimize the solution to minimize the impact to ratepayers
• Capital costs: planning, design, and construction
• Annual Operation and Maintenance Costs
Schedule 3.43• Risk of compliance with the mandated schedule
• Ability to secure necessary construction permits in a timely manner from local, state,
and federal agencies
Community Impact 3.93
• Minimize disruption to the community during construction.
• Minimize disruption to the community caused by regular Operation and Maintenance
activities.
• Maximize opportunities to incorporate community benefits.
O&M Complexity
and Reliability4.07
• Maximizes reliability of meeting VPDES permit
• Combined Sewer System Permit
• AlexRenew Wastewater Treatment Facility Permits
• Minimizes location and number of facilities to operate and maintain
Adaptability 3.93
• Ability to meet future capacity, environmental, or regulatory needs and navigate
climate change impacts
• Provides for opportunities for adaptive management and resiliency
• Integrate other planned City project needs if feasible
• Opportunities for complementary Green Infrastructure
Evaluation Criteria
CSS Stakeholder Group Meeting #4 20
Evolution of Program Costs
CSS Stakeholder Group Meeting #4 22
100%
80%
60%
40%
20%
0
-20%
-40%
-60%
-80%
-100%
100
50
3020
15
0
-50
-30-20
-15 -10
Pre
limin
ary
Desig
n
Pa
rtia
l D
esig
n
Com
ple
te F
ina
l
Desig
n (
Bid
)
Con
str
uctio
n
Com
ple
te
Cost Opinions
Lower Range of Probable Cost Upper Range of Probable Cost
PROGRAM STAGE
Ea
rly C
on
ce
pt (N
o S
ke
tch
es)
Con
ce
pt
(With S
ke
tch
es)
Capital Cost Estimates
23
WRRF Upgrades
CSO 003/4 Tunnel + Pumps
Wet Weather Facility
CSO 001/2 Tunnel
CSO 001/2 Tanks
TOTAL ESTIMATES
2.7
130
92
200
--
2.7
130
--
213
--
2.7
130
92
--
147
424 346 371
+50% TOTAL ESTIMATES 635 520 560
Cost $ Millions
(escalated to the midpoint of construction)
Option ASeparate Tunnels
Option BUnified Tunnels
Option CTunnel and Tanks
CSS Stakeholder Group Meeting #4
What are Life Cycle Costs?
CSO 003/4 Tunnel Example
24
Life Cycle Costs
Capital Costs (soft and
construction costs)
Operations Costs
Maintenance Costs
Capital Costs (present) $112M
O&M
Annual ($0.26M)
20 years @ 3% $4M
Net Present Worth $116M
Escalated to Midpoint (January 2023) $134M
CSS Stakeholder Group Meeting #4
Capital Cost Estimates
O&M Cost Estimates
TOTAL LIFE CYCLE ESTIMATES
+50% TOTAL LIFE CYCLE
ESTIMATES
Option ASeparate Tunnels
Option BUnified Tunnels
Option CTunnel and Tanks
Life Cycle Cost Estimates (20 years)
CSS Stakeholder Group Meeting #4
424
14
346
8
371
18
Cost $ Millions
438 354 389
657 531 583
25
Option B has the lowest estimated capital and life cycle costs
Cost Estimate Summary
CSS Stakeholder Group Meeting #4 26
0
50
100
150
200
250
300
350
400
450
Option A Option B Option C
$ M
illio
ns
Capital Life Cycle (20 years)
Evaluation Criteria Description
Life Cycle Costs• Optimize the solution to minimize the impact to ratepayers
• Capital costs: planning, design, and construction
• Annual Operation and Maintenance Costs
Evaluation Criteria
CSS Stakeholder Group Meeting #4 27
2018 2019 2020 2021 2022 2023 2024 2025
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
WRRF Upgrades
CSO 003/4 Tunnel
Wet Weather Facility
CSO 001/2 Tunnel
Option A
CSS Stakeholder Group Meeting #4 29
Design Procurement ConstructionPlanning, Permitting, and
Interagency Coordination
Option B
CSS Stakeholder Group Meeting #4 30
2018 2019 2020 2021 2022 2023 2024 2025
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
WRRF Upgrades
CSO 003/4 Tunnel
CSO 001/2 Tunnel
Design Procurement ConstructionPlanning, Permitting, and
Interagency Coordination
2018 2019 2020 2021 2022 2023 2024 2025
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
WRRF Upgrades
CSO 003/4 Tunnel
Wet Weather Facility
CSO 001/2 Tanks
Option C
CSS Stakeholder Group Meeting #4 31
Design Procurement ConstructionPlanning, Permitting, and
Interagency Coordination
Item Option A Option B Option C
Ability to meet
legislative milestone
• High risk, no schedule
flexibility for delays
• High risk, schedule
flexibility for delays
• Moderate risk, limited
flexibility for delays
Concurrent
construction projects
• High risk
• Complex coordination
at WRRF
• Single delay can affect
critical path
• Lowest risk, less
complex coordination
• Moderate risk
• Majority of projects
require coordination at
WRRF
• Single delay can affect
critical path
Construction and
regulatory
permitting
• Moderate risk since most
facilities are below-grade
• Moderate risk since
most facilities are
below-grade
• Highest risk due to temporary
and permanent footprint and
above-grade structures
Easements and
property acquisition
• Low risk due to small size
of temporary and
permanent surface
footprints
• Low risk due to small
size of temporary and
permanent surface
footprints
• High risk due to large size of
temporary and permanent
surface footprints
All options meet the legislative milestone
Key Schedule Risks
33
Evaluation Criteria Description
Schedule• Risk of compliance with the mandated schedule
• Ability to secure necessary construction permits in a timely manner from
local, state, and federal agencies
Evaluation Criteria
CSS Stakeholder Group Meeting #4 34
Shafts Tunnels TanksWet Weather
Treatment
Option A ✓ ✓ ✓
Option B ✓ ✓
Option C ✓ ✓ ✓ ✓
Different Facilities Have Different Impacts
CSS Stakeholder Group Meeting #4 36
How Do We Build Surface Facilities?
Excavation Support
Excavation
Permanent Construction
Restoration and Commissioning
CSS Stakeholder Group Meeting #4 38
Types of Excavation Support
Soldier Pile and Lagging
Slurry Wall
DewateringSecant Piles
Secant Pile Rig
Sheet Piling
CSS Stakeholder Group Meeting #4 39
Excavation
CSS Stakeholder Group Meeting #4 40
Shaft Excavation
Structure Excavation
Tank Excavation
Permanent Construction
Formwork
Rebar Installation
Concrete Pours and Finishing
CSS Stakeholder Group Meeting #4 41
CSS Stakeholder Group Meeting #4
Footprints During Construction
46
75% of a football field 150% of a football field
Tunnels Tanks
SHORT-TERM Option A Option B Option C
Footprint (football field) 75% 75% 150%
Construction Duration (years) 2 2 3
Construction Work Hours 7AM – 6PM 7AM – 6PM 7AM – 6PM
Typical Hauling Rates
(trucks/hour)
2-10 2-10 5-20
Piles No No Yes
Impacts by Site – CSO 001 (Oronoco Bay)
49
LONG-TERM Option A Option B Option C
Above-grade Structure(s) Electrical cabinet Electrical cabinet Odor control,
electrical cabinet
Maintenance Frequency Monthly Monthly Weekly
CSS Stakeholder Group Meeting #4
SHORT-TERM Option A Option B Option C
Footprint (football field) 30% 30% 150%
Construction Duration (years) 2 2 3
Construction Work Hours 7AM – 6PM 7AM – 6PM 7AM – 6PM
Typical Hauling Rates
(trucks/hour)
2-10 2-10 5-20
Piles No No Yes
Impacts by Site – CSO 002 (Hunting Creek)
50
LONG-TERM Option A Option B Option C
Above-grade Structure(s) Electrical cabinet Electrical cabinet Odor control,
electrical cabinet
Maintenance Frequency Monthly Monthly Weekly
CSS Stakeholder Group Meeting #4
SHORT-TERM Option A Option B Option C
Footprint (football field) 30% 30% 30%
Construction Duration (years) 2 2 2
Construction Work Hours 7AM – 6PM 7AM – 6PM 7AM – 6PM
Typical Hauling Rates
(trucks/hour)
2-10 2-10 2-10
Piles No No No
Impacts by Site – CSO’s 003/4 (Hooffs Run)
51
LONG-TERM Option A Option B Option C
Above-grade Structure(s) Electrical cabinet Electrical cabinet Electrical cabinet
Maintenance Frequency Monthly Monthly Monthly
CSS Stakeholder Group Meeting #4
SHORT-TERM Option A Option B Option C
Footprint (football field) 300% 200% 300%
Construction Duration (years) 5 3 4.5
Construction Work Hours 24/7 (mining only) 24/7 (mining only) 24/7 (mining only)
Typical Hauling Rates
(trucks/hour)
5-20 5-20 5-20
Piles Yes No Yes
Impacts by Site – AlexRenew
52
LONG-TERM Option A Option B Option C
Above-grade Structure(s) Odor control,
operations building,
electrical, screens
Odor control, operations
building, electrical,
screens
Odor control,
operations
building,
electrical, screens
Maintenance Frequency Daily Daily Daily
CSS Stakeholder Group Meeting #4
• Soil Disturbances From excavation and grading activities
• Impacts to Groundwater From dewatering activities
• Noise and Vibrations Generated from construction activities
• Dust and Emissions Generated from construction activities
• Temporary Lane Closures Resulting in disruptions to traffic, parking,
and Restrictions public transportation
• Disruptions to Utilities i.e. water, gas, and electricity during
relocation activities
• Construction Activities May require the removal and proper disposal
of contaminated soil and groundwater
Other Potential Short-term ImpactsApplicable to all options
CSS Stakeholder Group Meeting #4 53
Option C has highest short and long-term impact
Community Impact Summary
CSS Stakeholder Group Meeting #4 54
Impact Option A Option B Option C
Short-term Minimal impact over
larger area
Minimal impact over
larger area
Highest impact in a
concentrated area
Long-term Low impact
• Most mechanical
equipment located
at WRRF
Low impact
• Most mechanical
equipment located
at WRRF
High impact within
community:
• Permanent above-
grade facilities
• Mechanical
facilities in
community
• Requires frequent
visits to tank
locations
Evaluation Criteria Description
Community Impact
• Minimize disruption to the community during construction.
• Minimize disruption to the community caused by regular Operation and
Maintenance activities.
• Maximize opportunities to incorporate community benefits.
Evaluation Criteria
CSS Stakeholder Group Meeting #4 55
Major Equipment
57CSS Stakeholder Group Meeting #4
Pumps Screens Odor Control Flushing (Tanks only)
Electrical
Wet Weather Treatment Facility Use
0
5
10
15
20
25
30
35
40
45
50
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
20
15
20
16
An
nu
al
Ho
urs
Year
58CSS Stakeholder Group Meeting #4
Option B is the simplest to maintain due to centralized location of facilities and no wet weather treatment
O&M Complexity Summary
CSS Stakeholder Group Meeting #4 59
Item Option A Option B Option C
Location of
mechanical
facilities
• Low complexity since
mechanical equipment is
centralized at WRRF
• Least complexity since
mechanical equipment is
centralized at a single
location (at WRRF)
• Highest complexity due
to multiple locations of
mechanical equipment
Residuals
(solids and
floatables)
handling
• Low complexity due to
self-cleaning and
centrally located
residuals facilities
• Least complexity due to
self-cleaning and single
location for handling
residuals
• Highest complexity due
to routine access,
multiple residuals
handling locations, and
flushing system
New treatment
facilities
• Complex since limited
operation requires
equipment exercising
• Least complex, no wet
weather treatment facility
• Complex since limited
operation requires
equipment exercising
Evaluation Criteria Description
O&M Complexity
and Reliability
• Maximizes reliability of meeting VPDES permit
• Combined Sewer System Permit
• AlexRenew Wastewater Treatment Facility Permits
• Minimizes location and number of facilities to operate and maintain
Evaluation Criteria
CSS Stakeholder Group Meeting #4 60
Option B provides the most adaptability due to connectivity with WRRF
Adaptability Summary
CSS Stakeholder Group Meeting #4 62
Item Option A Option B Option C
Flexibility for future
changes (e.g.
regulatory, climate)
• Flexible
• Connects to WRRF
• Add pumping and
expand treatment
• Most flexible
• Unified system at
WRRF
• Add pumping and
treatment
• Least flexible
• Requires new
tankage or remote
treatment
• Connectivity to
WRRF limited by
interceptor
Evaluation Criteria Description
Adaptability
• Ability to meet future capacity, environmental, or regulatory needs and
navigate climate change impacts
• Provides for opportunities for adaptive management and resiliency
• Integrate other planned City project needs if feasible
• Opportunities for complementary Green Infrastructure
Evaluation Criteria
CSS Stakeholder Group Meeting #4 63
Long Term Control Plan Update Timeline
DEQ
Direction
CSS
Stakeholder
Meetings
Public
Meeting
30-Day
Public
Comment
Period
City
Council
Legislative
Session
Oct 2017 –
Mar 2018
March -
April
Apr 10,
2018
Early
April
AlexRenew
Board
Meeting
April 17,
2018
City
Council
Public
Hearing
April 28,
2018
Submit
LTCPU to
DEQ
Release
Draft
LTCPU
June 1,
2018
CSS Stakeholder Group Meeting #4
July 1,
2018
Late
March
CSS Stakeholder Meeting Schedule
CSS Stakeholder Group Meeting #4 66
Introduction/
Background
Evaluation
Criteria and
Shortlist of
Alternatives(all four outfalls)
Layouts of
Options and
Performance
Additional
Detail of
Options
Recommended
OptionWrap-Up
Discuss the
CSS/WW Plan
history, the 2016
LTCPU
submission, and
the new
legislation.
Introduce the
technologies
under
consideration
Introduce the
shortlist of
alternatives.
Review and
discuss the
evaluation criteria
and process
Review conceptual
layout of options.
Present
performance
Review options
with respect to
schedule, cost,
community
acceptance,
O&M, and
adaptability
Summarize scoring
and discuss
recommended
option. Review
potential rate
impacts. Green
Infrastructure
evaluation and
discussion. Discuss
Stakeholder
Recommendation
Process
Wrap-up and
present draft plan.
Stakeholder
Recommendation
discussion
Oct 12,
2017
Nov 20,
2017
Jan 10,
2018
Feb 22,
2018
March
2018
Feb 1,
2018
For more information, contact:
William.Skrabak@alexandriava.gov
703.746.4065
Erin.BevisCarver@alexandriava.gov
703.746.4154
www.alexandriava.gov/CleanWaterways
Questions, Suggestions and Comments
CSS Stakeholder Group Meeting #4 67
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