HomeMy WebLinkAboutPA2023-0076_20230403_Coastal Hazards report dated June 2022
Attachment 4b
Coastal Hazards Report
Memo
SUBJECT PROJECT
Coastal Hazards Analysis Bay Bridge Pump Station
Replacement Project (5-67)
TO DATE
Orange County Sanitation District June 2022
Introduction
This memorandum summarizes the analysis for coastal hazards for the Bay Bridge Pump Station (BBPS)
Replacement Project, Newport Beach, Orange County, California. The Orange County Sanitation District (OC
San) proposes to replace the existing BBPS with a new pump station and force main infrastructure. The existing
BBPS is over 50 years old, outdated, and no longer meets structural, electrical, and maintenance standards. The
Project includes replacing the existing pump station and force mains with a new pump station, replacement force
mains, a new electrical building, a new emergency generator building, and an odor control structure.
The new pump station will include a trench-type wet well and a dry well for housing the pumps, motors, and other
mechanical equipment. As shown on Figure 1, the pump station site also includes an electrical building, a
generator building, and an odor control structure. The proposed electrical building includes the electrical
equipment, instrumentation, control equipment, and restroom. The electrical building has a finished floor elevation
of 15.50 feet NAVD88 and is elevated from the grade level. The entrance to the underground pump station dry
well is at the same elevation of the electrical building finished floor. The generator room finished floor is 14.17 feet
NAVD88 and the generator will be mounted on a 2-ft-high belly fuel tank. The odor control structure finished floor
is 14.00 feet NAVD88. The new force main will be installed beneath the Newport Bay Channel and would not be
affected by coastal processes and is not included in the analysis.
This memorandum summarizes the potential impacts on the BBPS resulting from anticipated sea level rise,
coastal geologic instability, and flooding per the requirements of the Newport Beach Local Coastal Plan Policies
LUPs 2.8.1-1, 2.8.-2 and 2.8.1-4 and per Section 30253 of the Coastal Act.
Site Characteristics and Land Use
The Project site is located within a fully developed and urbanized area north of East Coast Highway. The existing
BBPS is approximately 4,800 square feet, occupied by a single-story pump station building. The perimeter of the
pump station building is surrounded by concrete masonry walls on all sides with two entrance gates. The existing
facility is located on a parcel that is surrounded to the north, east, and west by a recreational vehicle storage area.
Seven acres of the site are planned for a mixed-use development. Surrounding land uses include residential,
commercial, and commercial recreational marine uses. Within the vicinity of the Project, East Coast Highway, also
known as State Route 1 is a 7 to 8 lane roadway including a bridge that crosses the Newport Bay Channel.
Bayside Drive is located to the east of the Project and is a 4 lane, designated secondary road.
Sea Level Rise Evaluation and Flooding
Several analyses have been conducted to understand the potential for anticipated Sea Level Rise (SLR) to impact
the BBPS and whether the facility is at risk.
In 2019, OC San prepared the Resiliency Study SP-152 (Resiliency Study) which examined the potential climate
change impact, including SLR on OC San facilities throughout its service area. The Resiliency Study used SLR
projections from the Rising Seas Report and California’s Fourth Assessment (Hall 2018) as representing the state
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of science for SLR for the Orange County area. Relying on Hall 2018, OC San used SLR increases of 1.54 feet
for 2050 and 3.71 feet for the year 2070 (Hazen 2019) to determine the potential risk of SLR in 2050 and 2070.
Using the 2050 and 2070 projections, the Resiliency study did not identify the BBPS site as having a significant
risk associated with SLR in Year 2050 or 2070 (Hazen 2019).
Additional analysis of the potential impacts on the BBPS has been conducted using the Coastal Commission’s
Sea Level Rise Guidance Policy. According to the State Sea-Level Rise Guidance, under the H++ SLR scenario,
2.7 feet of SLR can be expected by 2050, 6.6 feet by 2080, and 10.2 feet by 2100 (California Coastal Commission
2021). The life expectancy of the new pump station will be around 50 years and the 6.6 feet SLR of Year 2080 will
be used for evaluation. The Our Coast Our Future (OCOF) map with projection of 6.6-ft SLR above mean high
water (MHW) is shown on Figure 2. A portion of the existing site is shown inundated based on the 2080 SLR of
6.6-ft SLR Above MHW (11.15 feet NAVD88).
In developing the design for the new BBPS, the engineers used both SLR and potential tsunami run up elevations
when determining ground elevations for the Project. The BBPS design took a conservative approach of designing
to a minimum floor elevation of 14.00 feet NAVD88 as shown on Figure 1. Using this minimum floor elevation,
construction of the new BBPS would avoid SLR impacts for the anticipated life of the facility.
Flooding & Tsunami
According to the Federal Emergency Management Agency (FEMA) 2019 FIRM map, the Project is not located
within the 100 year flood hazard zones (Figure 3). As analyzed in the 2020 Recirculated Environmental Impact
Report (Michael Baker International 2020), less than significant impacts are anticipated in the event of the 100-
year flood.
The Project site is located within the designated tsunami zone (California Department of Conservation 2022).
During design of the BBPS, the engineers used the American Society of Civil Engineer’s (ASCE) Tsunami Design
Zone (TDZ) to determine the Maximum Considered Tsunami (MCT)In the event of a tsunami, the Project site
could be expected to see some minor flooding and the run up elevation at the Project site is 7.24 feet above MHW
or 11.74 feet NAVD88 (Figure 4 and 5). Figure 4 shows that in the event of tsunami, the parking areas may be
expected to see minor flooding. However, because the minimum floor elevation of the new BBPS would be 14.00
feet NAVD88, the new facilities would not be subjected to inundation.
Furthermore, onsite drainage is routed to the BBPS. The pump station is designed to operate even if the site is
inundated. Therefore, the risk of flooding the pump station is minimal.
Ground Improvements and Shoring
The Project site is located in an area of potential liquefaction. To mitigate the potential for liquefaction, static
settlement, and differential settlement, the new pump station will be excavated over 35 feet deep such that the
impacts from liquefaction are not anticipated. The ground improvement plan for the overall pump station site can
be referenced to the Geotechnical Design Report enclosed in the permitting package. Deep excavation will
require shoring and design is exploring several techniques including, but not limited to slurry diaphragm wall,
secant pile wall shoring, solid sheet pile wall, or a combination of shoring techniques.
Erosion and Shoreline Loss
The location of the BBPS is located within a developed area and is not located at the shoreline or at the bank of
the Newport Bay Channel. The Project site is not subject to erosion and shoreline loss. The BBPS would not be
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subjected to erosion or shoreline loss as a result of waves or wave run up. The Project does not include, and
does not require shoreline protection.
Summary and Conclusion
The BBPS Project has been analyzed with regards to postal coastal hazards, including SLR, flooding, tsunami,
and geologic stability. The new BBPS will be located in a developed area, including the location of the existing
BBPS. The new BBPS is designed to ensure that the facilities would not be subjected to the SLR and tsunami
impacts.
References:
Michael Baker International. 2020. Bay Bridge Pump Station and Force Mains Replacement Project (Project No.
5-67) 2020 Recirculated Environmental Impact Report. May 2020.
Arcadis. 2022. Preliminary Design Report Project No. 5-67 Bay Bridge Pump Station Replacement.
California Coastal Commission. 2021. Critical Infrastructure at Risk: Sea Level Rise Planning Guidance for
California’s Coastal Zone. Final Adopted Guidance. November 17, 2021.
California Department of Conservation. 2022. Orange County Tsunami Hazard Areas. Website located at
https://www.conservation.ca.gov/cgs/tsunami/maps/orange. Retrieved June 17, 2022
Our Coast Our Future Mapping Tool. 2022. Website located at: https://ourcoastourfuture.org/ retrieved June 10,
2022
Hall, Alex, Neil Berg, Katharine Reich. (University of California, Los Angeles). 2018. Los Angeles Summary
Report. California’s Fourth Climate Change Assessment. Publication number: SUM-CCCA4-2018-007
Hazen. 2019. Climate Resiliency Study. Final Report. SP-152. November 27, 2019.
Enc. [Enclosures]
Figure1
Site Plan
Orange County Sanitation District
Bay Bridge Pump Station Replacement Project
TRANSFORMER
ACCESS HATCH
GENERATOR
ROOM
RAISED
PLATFORM
ELECTRICAL
ROOM
ODOR CONTROL
AREA
PUMP STATION
(BELOW GRADE)
NORTH GATE
24' WIDE SWING GATE
SOUTH GATE
24' WIDE SWING GATE
WEST GATE
18' WIDE CANTILEVER
SLIDING GATE
MANHOLE COVERS, TYP.
SEE STRUCTL DWGS
RAISED
PLATFORM
45.57'
16.23'
9.52'
TOW = 29.33'
PEDESTRIAN GATE
8' HIGH WALL
10' HIGH WALL
8' HIGH WALL
F U T U R E A C C E S S R O A D
P A C I F I C
C O A S T HI G H W A Y
(E) BUILDING
STRUCTURE
OUTLINE
10' HIGH WALL
8' HIGH WALL
10' HIGH WALL
15' HIGH WALL
15' HIGH WALL
A2001
1
A20012
A2001 3
A2001
4
173.84'
57.26'
18.00'
4.44'
EXTERIOR WALL
BOUNDARY
SWITCHBOARD
106.32'
133.53'
39.48'
24.00'
43.99'
LANDSCAPE AREA
(SEE LANDSCAPE DWGS)
6' - 5 1/8"
LANDSCAPE AREA
(SEE LANDSCAPE DWGS)
TOW = 24.00'
TOW = 24.00'
TOW = 24.00'
TOW = 24.67'
TOW = 23.33'
TOW = 22.00'
TOW = 22.00'
6' - 10"
23' - 7 5/8"
41' - 7 7/8"
TOW = 22.00'
9
TOW = 24.67'
TOW = 29.33'
5.07'
TOW = 23.33'
TOW = 23.33'
TOW = 29.33'
TOW = 29.33'
SWITCHBOARD
PLATFORM
(REMOVABLE)
SCALE: 1/8" = 1'-0"
SITE PLAN
FF = 14.17
FF = 15.50
FF = 14.00
Figure2
6.6-Foot Sea Level Rise Map
Orange County Sanitation District
Bay Bridge Pump Station Replacement Project
Project Location
Source: Our Coast Our Future: https://ourcoastourfuture.org/hazard-map/
BAY BRIDGE PUMP STATION
PROJECT SITE
Figure3
FEMA Map
Orange County Sanitation District
Bay Bridge Pump Station Replacement Project
Legend
Offshore Tsunami Amplitude
Runup Elevation Point
Inundation Depth Point
Earthquake Induced Regional Ground
Subsidence (ft)
Tsunami Design Zone
World Imagery
Low Resolution 15m Imagery
High Resolution 60cm Imagery
High Resolution 30cm Imagery
Citations
60cm Resolution Metadata
Maxar | City of Newport Beach, County of Los Angeles, Esri, HERE, Garmin, INCREMENT P, USGS, Bu
Orange County Sanitation District
Bay Bridge Pump Station Replacement Project
GENERATOR BLDG
ELECTRICAL BLDG
ODOR CONTROL AREA
ASCE Tsunami Hazard Tool with Bay BridgePump Station
BAY BRIDGE
PUMP STATION
Source: ASCE Tsunami Hazard Tool - ASCE Tsunami Design Geodatabase Version 2016-1.0
Figure
4
Legend
Offshore Tsunami Amplitude
Runup Elevation Point
Inundation Depth Point
Earthquake Induced Regional Ground
Subsidence (ft)
Tsunami Design Zone
World Imagery
Low Resolution 15m Imagery
High Resolution 60cm Imagery
High Resolution 30cm Imagery
Citations
60cm Resolution Metadata
Maxar | City of Newport Beach, County of Los Angeles, Esri, HERE, Garmin, INCREMENT P, USGS, Bu
Runup Elevation Point
Latitude Longitude Runup Elevation (MHW) (ft.)Runup Elevation (NAVD88) (ft.)
33.61667 -117.90222 7.24 11.74
Earthquake Induced Regional Ground Subsidence (ft.): 0
Zoom to
ASCE Tsunami Hazard Tool with RunupElevation
Orange County Sanitation District
Bay Bridge Pump Station Replacement ProjectSource: ASCE Tsunami Hazard Tool - ASCE Tsunami Design Geodatabase Version 2016-1.0
Figure5