LOWER COLMA CREEK
CAP 103 PROJECT
SOUTH SAN FRANCISCO CITY
COUNCIL BRIEFING ON TENTATIVELY
SELECTED PLAN
May 25, 2022
SPD Regional CAP Production Center
San Francisco District
City of South San Francisco
City of South San Francisco and San Bruno
Water Quality Control Plant
2 PROJECT AUTHORITIES
Congressionally
Authorized
• General Investigation Studies
(GI)
Projects typically large & complex
• Study & construction authorizations based
in law (from Congress)
• Requires appropriations for funding
• Typically, 5+ years from initial funding of
study to start of construction
Delegated Authorities
• Continuing Authorities
Program (CAP)
• Tribal Partnership Program
(TPP)
Smaller Projects: Start quickly &
build sooner
• Limited scope and complexity
• Congress does not need to specifically
authorize projects or provide projectspecific funding
• Typically, 3-5 years from initial funding of
study to start of construction
Tech. Assistance
Programs
• Flood Plain Management
Studies (FPMS)
• Planning Assistance to States
(PAS)
• Emergency Preparedness &
Response
Assistance only: No construction
• General Technical Services
• General Planning Assistance
• No project construction
PLANNING AND CONSTRUCTION PLANNING & TECH ASSISTANCE
3 THE CAP AUTHORITIES
Authority
(Section)
Project
Type
Design & Implementation Cost Share
(Federal / Non-Federal %)
Federal Limit
(Project)*
14 Emergency Stream Bank and Shoreline
Protection
65% / 35% $5,000,000
103 Hurricane and Storm Damage Reduction;
Beach Erosion
65% / 35% $10,000,000
107 Navigation Improvements Varies, based on depth $10,000,000 111 Mitigation to Shore Damage Attributable to
Navigation Works
Shared in same proportion as project
causing damage
$10,000,000
204 Regional Sediment Management 65% / 35% $10,000,000
205 Flood Damage Reduction 65% / 35% $10,000,000
206 Aquatic Ecosystem Restoration 65% / 35% $10,000,000 1135 Project Modifications for Improvements to
the Environment
75% / 25% $10,000,000
*Only includes the statutory federal limit
Feasibility cost is part of total allowable project cost 4 BRIEF
PROJECT
OVERVIEW
• NFS City of South San Francisco / SSF WQCP
• CAP Section 103 (Coastal, <$10 M fed, simple)
o includes protecting single non-federal public properties and facilities against damages caused by storm driven
waves and currents.
• 165,000 full time residents + the daily population of San Francisco International Airport rely on plant.
• The WQCP plant & pump station 4 currently at risk for coastal flooding by storm driven waves
• Flood risk is expected to increase over time due to the location in a low-lying coastal area & SLR
• Coastal storm risk flood events could cause:
➢ Damage to critical infrastructure
➢ Disrupted wastewater treatment services/pumping
➢ Raw sewage backups in homes, businesses, and streets
➢ Release of untreated raw sewage into the Bay
• Unpermitted discharges and mixing of contaminated water during flooding events could result in environmental
degradation in nearby sensitive habitat
PROJECT OVERVIEW
5 STUDY AREA MAP
Lower Colma CAP 103
5 San
Francisco
Bay
South San Francisco
Wastewater Quality Control
Plant (SSF WQCP)
Pacific
Ocean
6 COASTAL WATER LEVELS – SEA LEVEL CHANGE
(SLC) AND EXTREME WATER LEVELS (EWL)
5/10/2022
– USACE ER1100-2-8162 “Incorporating Sea Level Change in Civil Works Programs” – Basis for Lower Colma Creek Extreme Water Levels
• BakerAECOM/FEMA 2016 Tidal Datum & Extreme Water Levels Study • Relative SLC Redwood City, CA NOAA tide gauge
• USACE Sea-Level Change Curves (low, intermediate, high) – Max SLR elevation modeled was 14.09 ft NAVD88 in 2073, .2% AEP • Extreme water levels will be used as downstream boundary condition – Water Levels defined for 153 Scenarios
• 8 return period events; 100% (1-year) through 0.2% (500-year) events • 2023(L/I/H), 2033(I/H), 2043(I/H), 2053(I/H), 2063(I/H), 2073(L/I/H) 7 EXISTING FLOOD HAZARD
Base year (2023) 1% AEP Flood Inundation with Intermediate sea level rise, stage = 10.32 ft Pump Station 4
SSF WQCP
Depth
(ft NAVD88)
8 EXISTING FLOOD HAZARD
Base year (2023) 0.2% AEP Flood Inundation with Intermediate sea level rise, stage = 11.42 ft Pump Station 4
Breakout occurs
from north bank
Depth
(ft NAVD88)
9 EXISTING FLOOD HAZARD
• Presents coastal flood risk to the
SSF WQCF.
• Colma Creek right bank is
not expected to contain the
1% annual exceedance
probability (AEP) coastal
event.
• This analysis was only for
coastal events, does not
include Colma Creek.
• Flooding could be
exacerbated by flows in
Colma Creek.
• New model uses 2017 San
Mateo County LiDAR
• New model uses Extreme Tide
Elevations from USACE SLR
curves and Redwood tide
gauge.
• Water overtops the north bank at
10.47 ft water elevation, at the
South bank at 11.74 ft, and
overland from the west at 13 ft.
50 years (2073) 1% AEP Flood Inundation with Intermediate sea level rise, stage = 11.24 ft
SSF WQCP
Breakout occurs
from north bank
Pump Station 9 Pump Station 4
Pump Station 11
Depth
(ft NAVD88)
10 EXISTING FLOOD HAZARD
50 years (2073) 0.2% AEP Flood Inundation with Intermediate sea level rise, stage = 12.34 ft Pump Station 4
SSF WQCP
Breakout occurs
from north bank
Breakout occurs
from south bank
Breakout
occurs overland
from west
Depth
(ft NAVD88)
11 Natural and Nature-Based Features (NNBFs)
(structural)
Screened Areas most suitable for NNBFs do not correlate well with where NNBFs would be needed for managing coastal storm risk
Improvements to SF Bay Trail (recreation) Screened Routing the trail along the Bay adjacent to the WQCP poses an unacceptable safety /security threat to critical infrastructure. Alternative route identified has a high estimated cost and would not substantially improve recreational experience from the existing experience.
Temporary /deployable flood barriers (structural) Screened Not cost effective compared to floodwalls.
Storm surge barrier at the mouth of Colma Creek
(structural)
Screened Exceeds the cost limit of CAP
Ecotone levee combo with floodwall (structural) Screened Insufficient space, would fill in the entire creek width in order to provide sufficient flood risk management
CSRM Improvements to Finger Piers (storage and
parking area) (structural)
Screened Insufficient damages to support CSRM measures in this location. Good potential mitigation location if mitigation is required.
Drainage pump system (structural as they would be
implemented in combination with tide gates or storm
surge barriers)
Screened Exceeds the cost limit of CAP
Standard Levee (structural) Screened Insufficient space Standard levee/floodwall combo (structural) Screened Insufficient space Dredging Colma Creek (structural) Screened Not effective in addressing coastal flood risk / meeting objectives Relocate entire treatment facility (non-structural) Screened Cost (in the billions of dollars) exceeds benefits and CAP cost limit Relocate structures of concerns (non-structural) Screened Infeasible/not cost efficient Leverage another treatment facility (non-structural) Screened Not effective as other nearby treatment facilities are also at risk for coastal flooding
Tide gates (structural) Screened Exceeds the cost limit of CAP
INITIAL SCREENING
12 Floodwall (structural) Retained There is sufficient space to site a floodwall and cost estimate is within CAP cost limit. Alignment can be pulled back from shoreline as much as possible to avoid impacts to adjacent marsh near bridge on north end of WQCP. Plant operability and performance is high up to design event. Can be made adaptable to sea level rise.
Flood proofing of key structures (nonstructural)
Retained Depths of flooding are shallow and velocities are low, which makes flood proofing a viable potential measure. Cost is competitive compared to other measures. SLR adaptability would be to seal plant more frequently. May impact operability and performance of plant, which needs investigation.
Operating during flood conditions could endanger workers at the plant, so a safety assessment is needed.
Flood warning system (non-structural) Retained For the non-structural operation, the flood warning system is necessary to ensure flood proofing is sealed and in place, which is operated manually.
Ring Levee (non-structural) Screened for main
WQCP
Retained for pump
station 4
Insufficient space
For pump station 4, there is room for a small retaining wall type concrete floodwall around the perimeter station, with a stop log gate for vehicular access. Cost is well within CAP cost limit.
Raise critical assets in place (non-structural) Screened for most assets
Retained for electrical
system only
Infeasible/not cost effective compared with floodproofing It is not feasible to floodproof the entire network of subterranean electrical system, which is particularly hazardous if flooded. Raising electrical only was retained.
INITIAL SCREENING – RETAINED MEASURES
13 ALTERNATIVE 1
Alt 1: North floodwall (1BN plus 1AN), shown in left image, plus full perimeter concrete floodwall with stop log gate around pump station 4, and flood warning system, pictured right.
Pump Station 4 Main WQCP
14 ALTERNATIVE 2
Alt 2: North and south floodwall (1BN + 1AN+2S), plus full perimeter floodwall with stop log gate around pump station 4 and flood warning system
23 Buildings to be floodproofed
Each structure /facility in a yellow box was
individually assessed for flood risk based on their
structure type, elevation, material, and contents.
Structures that do not flood in the without project
condition, or do not incur damages, or damages are
negligible are marked in red and were excluded.
Total = 23 structures to be floodproofed
This alternative also includes raising the electrical
system (next slide) and emergency exits/walkways
(not costed/designed)
ALTERNATIVE 3: NONSTRUCTURAL
16 EVALUATING THE ALTERNATIVES
Team started off by looking at
the four planning criteria—
1. Effectiveness
2. efficiency
3. completeness (whether
the benefits can be
realized without future
action from others)
4. acceptability (whether it’s
legally implementable)
This evaluation informed
iterative plan development,
including adding electrical
raising to the non-structural
only plan to make it complete/
safe for plant operators.
17 Damages included in this analysis include:
• A structural inventory of structures and contents within the WWTP facility.
• All building characteristics considered in the evaluation, including information on:
➢ foundation height,
➢ values of building and its contents,
➢ depreciation,
➢ information about how the plant operates
➢ and the number of sewer lateral connections
• The second and largest source of damages are from the clean-up cost associated with a failure to the electrical components to the WWTP and/or to Pump Station #4.
• I.e. back up of raw sewage to some or all of the lateral connections:
» City of South San Francisco – Approximately 19,000
» City of San Bruno – Approximately 10,586
» City of Daly City – Approximately 471
» Town of Colma – Approximately 77
ECONOMIC DAMAGES
• The Economic Period of Analysis is 50 years and was calculated using the FY 22 Federal Interest rate of 2.25%
• Economic Computations used the Intermediate Sea Level Rise Curve 18 COMPREHENSIVE BENEFIT COMPARISON
• Simple qualitative
initial screening
• Developed
screening criteria
through charettes,
research, and team
discussions,
including with VT
• Used information
learned through
formulation and
analysis to support
PDT comparison of
each screening
criteria
• Maximal Benefit
Plan = NED Plan
• No need to perform
more quantitative
analysis to support
TSP selection
19 - Site visit on November 4, 2021 with Fish and Wildlife Services - Resource agency meeting January 10, 2022
- Tribal and historical society letters sent March 8, 2022 - Colma Creek Citizen Advisory Committee presentation March 8, 2022 - Agency specific coordination held March-May 2022
- One Shoreline coordination, ongoing
- Resource agency TSP presentation – coming soon
- Public meeting will be held once Draft Report is released for comment
AGENCY, TRIBAL, & STAKEHOLDER COORDINATION
What stakeholder
groups do you
recommend we reach
out to? How can we
reach vulnerable
communities in
particular?
20 PATH TO THE FINAL REPORT APPROVAL
MILESTONE / SCHEDULE
• Tentatively Selected Milestone - March 31, 2022 (Met) • Finish Draft Detailed Project Report / Environmental Assessment (DPR/EA) – NLT April 22, 2022 (Met) • District Quality Control Review - Ongoing
• Release Draft DPR/EA - Early Summer 2022
• Hold interagency coordination & public meeting
• ATR/Public/Policy & Legal Reviews of Draft DPR/EA— Spring/Summer 2022 • Complete Final Report –January 23, 2023
• Final Report Milestone – March 7, 2023
21 DISCUSSION / QUESTIONS?
22 BACKUP SLIDES
23 FUTURE SEA LEVEL RISE AND ANNUAL EXCEEDANCE
PROBABILITY (AEP) SCENARIOS
All extreme tide elevations scenarios modeled.
Maximum
Electrical Raising– Overall Electrical Single-Line Diagram of the WQCP ALTERNATIVE 3: NONSTRUCTURAL (CONTINUED)
25 Problems
For the following problem statements, flood risk is expected to increase in frequency and magnitude as a result of sea level change.
1. Storm driven waves and currents cause coastal flood
risk to the SSF WQCP which risks economic damages
resulting from damage to infrastructure and contents,
plant service shutdown, and cleanup costs from the
backup of untreated effluent in homes, businesses, and
streets throughout the service area.
2. Should significant flooding occur at the SSF WQCP or at pump station 4, there is a risk of service disruption to their roughly 112,000 customers resulting in potential
business and household economic losses.
3. Public and environmental health is at risk should coastal flooding cause the need for emergency releases of
untreated effluent into Colma Creek and San Francisco Bay.
4. The coastal flood risk endangers human life and safety of the WQCP workers and operators should the plant
flood.
5. Human safety is endangered from direct exposure to
untreated sewage backing up in the sewer system and
overflowing in toilets and manholes in the service area of the SSF WQCP in the event of a plant shutdown caused by coastal flooding.
PLAN FORMULATION
Opportunities
1. There is an opportunity to avoid or reduce discharges of untreated effluent into the Bay and avoid water quality degradation and associated impacts to human health and the environment.
2. Opportunities to improve habitat values and the aesthetic and recreational experience in the study area were also investigated.
Constraints
1. The project cannot compromise the safety and security of the SSF WQCP, which is critical infrastructure for the region.
2. There is also the universal constraint that the project must comply with applicable federal laws, regulations and policies.
Planning Objectives
1. Manage the risk of flooding at the SSF WQCP and its pump stations.
2. Manage risk to human life and safety due to flooding at the SSF WQCP and its pump stations.
3. Reduce the economic damages that result from flooding of the WQCP (including pump stations), and the associated potential service disruptions and/or plant shutdowns.
4. Reduce damages to the environment (people and other living things) that result from flooding and the associated releases of untreated effluent into Colma Creek or San Francisco Bay.
26 FOCUSED ARRAY
Alternative Formulation
Strategy
No Action Plan No Action
Alt 1: North floodwall (1BN plus 1AN), plus full
perimeter concrete floodwall with stop log gate
around pump station 4 and flood warning
system
Cost Effectiveness
Alt 2: North and south floodwall (1BN +
1AN+2S), plus full perimeter floodwall with stop
log gate around pump station 4 and flood
warning system
Effectiveness/
Meeting Objectives
Alt 3: Non-structural only. Floodproof 23
structures on main plant, ring floodwall with
stop log gate around pump station 4, and flood
warning system
Maximize
Nonstructural
27 TRIBAL COORDINATION
Tribal Consultation Summary
• Formal Section 106 tribal consultation letters sent out on 8 Mar 2022
• Consultation with the Ohlone Indian Tribe by phone on 17 Feb 2022. Requested subsurface testing to
determine presence of CA-SMA-45. Tribal monitors
requested for all ground disturbance work
• No other responses from tribes received to date. No
tribal attendance during the agency meeting
Tribes and Section 106 Tribal Consulting Parties
• The Ohlone Indian Tribe (consultation ongoing and occurred early on in April 2021)
• The Amah Mutsun Tribal Band of Mission San Juan Bautista • The Costanoan Rumsen Carmel Tribe
• Indian Canyon Mutsun Band of Costanoan
• Muwekma Ohlone Indian Tribe of the SF Bay Area
• Rumsen A:ma Tur:ataj Ohlone
Tribes fall under these eight Ohlone cultural groups
throughout the California Bay Area
28 Activity Status
Fish and Wildlife Coordination Act Draft Coordination Act Report (CAR) received Clean Water Act Section 404(b)(1) Draft concurrent with draft report Clean Water Act Section 401 Draft application to be released with draft report Coastal Zone Management Act Draft consistency determination to be released with draft report Endangered Species Act Informal consultation to be initiated in early May National Environmental Policy Act Draft Integrated Detailed Project Report/ Environmental Assessment (DPR/EA) scheduled for release in May
National Historic Preservation Act
(Section 106)
Section 106 initiated with SHPO agreement on Area of Potential Effects (APE), tribal consultation formally initiated
ENVIRONMENTAL COMPLIANCE STATUS