Stormwater Master
Plan Update
City of San Mateo - City Council
January 26, 2026
Public Works Department – Jimmy Vo, PE
Schaaf and Wheeler – Dan Schaaf, PE
Council Feedback
Staff requests feedback on the following items:
• General comments on project prioritization and cost estimates • Funding strategies for “Very High” projects ($39.1 M) and support for using stormwater fee revenues for bonding
• Setting aside limited annual funding for minor stormwater projects outside the Stormwater Master Plan priorities
• Reviewing private development stormwater management to reduce City’s system impacts and address future climate conditions
Presentation Outline
• Context for Stormwater Planning
• Master Plan Update Approach
• Technical Analysis
• Capital Improvement Program Summary
• Key Findings
• Funding Approach
• Public Engagement
• Council Feedback and Next Steps
• Exposure to flooding risks
due to aging infrastructure
• Recent storms highlighted
system vulnerabilities
• Over 20 years since last
Stormwater Master Plan
Update
• Stormwater Fee supports
long-term planning
Planning Context
LiDAR Aerial Survey
• Reassess stormwater system
condition and capacity
• Identify system constraints
and deficiencies
• Develop a prioritized capital
improvement framework
Purpose of Master
Plan Update
Project Overview
• Holistic Study of Drainage
Infrastructure
• Condition
• Capacity
• Reliability
• Climate Impacts
• Capital Improvements
• Design/Fund/Build
• Resilience/Adaptation
Condition Assessment
Pump Stations:
• Site visits of 9 pump stations
• Data collection: capacity,
condition, and station layout
• Feedback from O&M staff
Conveyance System
• 11,000 LF CCTV
Ranking Structural O&M
1 2% 4%
2 14% 41%
3 18% 19%
4 27% 19%
5 38% 17%
System Model
• The City has ~150 miles of
pipes and drainage ditches, and
~15 miles of significant
channels (including Marina
Lagoon)
• Eight pump stations perform a
crucial function in handling
stormwater
• There are three dams (Marina
Lagoon + two Laurel)
System Model
• Example: Sunnybrae
• Existing conditions model
mirrors actual drainage
issues
• CIPs developed
iteratively:
• Try upsizing pipe or adding
new pipe Run model
• Adjust or upsize/add
additional pipe
10-year storm:
Ø 10” max depth
Ø Water in street
for >6 hours
Capacity Criteria
• “Design Storm”-Based
• 10-year Storm (10% Annual
Chance)
• Closed conduit systems
• Smaller pump stations
• 100-year Storm (1% Annual
Chance)
• Open Channels
• Larger, terminal pump stations
(Marina Lagoon, Coyote, Poplar)
Pipe System Capacity
• Existing systems (pipes, ditches, creeks) modeled for various storms
Animated Depth for 10-year Storm, Existing Conditions
(Around San Mateo Creek)
Capital
Improvement
Program (CIP)• Prioritized based on:
• Severity and frequency of
flooding
• Properties impacted
• Pre-requisites (Are other
projects required first)
• Safety issues
• O&M Burden
• Within Equity Priority Area
• Overlapping or Near other
CIP Projects
• Cost
• Factors are not equally
weighted
10-year Storm Side-by-Side
> 1 ft
Existing With CIP
10-year storm:
Ø 10” depth
Ø Water in street
for ~6 hours
Climate Change Predictions
• Precipitation: EPA SWMM-CAT and CalAdapt
• Increases in 72-hour Storm Precipitation:
• Sea Levels: Ocean Protection Council
• Increases in Extreme Tide Levels:
Storm 2050 2100
10-year +10% +30%
100-year +8% +20%
2050 2100
Increase: +0.8 ft +3.1 ft
With CIP +
Climate
Change
10-year storm:
Ø 3” depth
Ø Water in street
for ~1-2 hours
Impact on Pipe Systems (2050)
> 1 ft
Existing
10-year storm:
Ø 10” depth
Ø Water in street
for ~6 hours
In most cases, recommended
CIPs provide an acceptable
degree of resilience against
climate change impacts
Summary
Work Completed
• Full suite of HEC-HMS, HEC-
RAS, and MIKE+ models have
been developed
• CIP scenarios are complete
• Climate Change has been
incorporated into the analysis,
with cost impact estimated
Next Steps
• Finalize CIP prioritization and
cost estimates
• Preliminary designs for the
highest priority projects
• Work with the City to evaluate
funding strategies
Key Findings
1. CCTV inspections show most pipes are in good condition, but additional field verification may be necessary to understand the full scope of system repair and replacement needs.
2. Although recent maintenance has extended the Marina Lagoon Pump Station’s life, it is nearing the end of its service life with insufficient capacity for future tide and sea level rise conditions.
3. Most pump stations meet current design standards, but accommodating future climate impacts will require full implementation of priority upgrades, including added pumps at Marina Lagoon and potentially a new tide gate and pump station at San Mateo Creek.
Key Findings
4. While some properties remain in FEMA flood zones, updated modeling may remove 16th Ave/Palm from designation, and additional projects are planned for 3rd Ave/Norfolk and Hillsdale/McLellan.
5. Larger regional challenges like shoreline and San Mateo Creek protection will require significant future investment and multi-agency coordination.
6. Open channel maintenance is essential to maintaining system capacity and the City is pursuing a multi-agency Citywide Creek Maintenance Permit to facilitate maintenance work.
Private
Development
Opportunities
• Strengthening runoff
management requirements
• Aligning private improvements
with City system capacity and
climate impacts
• Council direction ultimately
needed to expand stormwater
obligations
LiDAR Aerial Survey
Funding
Considerations
• Stormwater Fee provides a
stable funding source for
most projects
• Additional financing needed
for larger capital projects
(Marina Lagoon)
• Grant and bond options
under evaluation
Priority Number of
Projects*
Estimated Cost
(in Millions)
Est. Cost without
Marina Lagoon
PS (in Millions)
Very High 11 $160 $39
High 33 $27 $27
Medium 35 $22 $22
Low 58 $24 $24
Total: 137 $233 $112
• Climate Change will add an additional $34
million to the CIP – Total Cost $267 million
• Marina Lagoon Pump Station Improvements
total approximately $121 million
Localized Ponding
• In general, focus investment in high-
risk locations to deliver
greater systemwide benefit per
dollar invested
• Continue to invest in localized street
ponding (typically shallow and low
risk) to reduce resident impacts
• Keep localized ponding projects
strategic:
• Deliver noticeable improvements
through modest investment
• Proactively prioritize projects
based on benefit and risk
• Prioritize vulnerable populations
(e.g. walking routes near schools
and senior centers)
LiDAR Aerial SurveyPublic Engagement
• Stormwater Mapping Tool
• Draft Master Plan release for
public review in late
February
• Two public engagement
meetings to be schedule in
Spring 2026
Feedback Given by Commission
1. The commission is supportive of evaluating potential changes that would encourage private development to contribute toward stormwater solutions.
2. Commissioners broadly supported continuing and potentially increasing investment to address localized ponding projects
3. Many emphasized prioritizing highly visible and heavily used areas like major roads, schools, and parks
4. Some expressed interested in more public engagement beyond the two meetings to build trust and support future investment
Next Steps
1. Complete internal review and finalize the draft Master Plan
2. Release the draft Master Plan for public review in March 2026
3. Planning for 2 community engagement meetings in Spring 2026
4. Return to Commission City Council with formal adoption by June 2026
5. Initiate design for a subset of “Very High” priority projects in FY 2026–27
6. Continue evaluating funding options for identified capital improvements Council Feedback
Staff requests feedback on the following items:
• General comments on project prioritization and cost estimates • Funding strategies for “Very High” projects ($39.1 M) and support for using stormwater fee revenues for bonding
• Setting aside limited annual funding for minor stormwater projects outside the Stormwater Master Plan priorities
• Reviewing private development stormwater management to reduce City’s system impacts and address future climate conditions
Additional Questions