PISMO BEACH COUNCIL AGENDA REPORT
Agenda Item #12.B
SUBJECT/TITLE:
OPTIONS FOR THE PIER AVENUE STAIRS
RECOMMENDATION:
Review options for the Pier Avenue Stairs and provide staff with direction on how to proceed.
BACKGROUND:
The Pier Avenue Stairs have been a fixture of Shell Beach dating back to the 1970s.
Records of the construction of the stairs are no longer available; however, based upon historic photographs from the California Coastal Records Project1, it appears the stairs date back to at least May of 1979 and possibly as far back as 1972. This means that the stairs are 40 or more years old, and are nearing or past the end of their design service life. The City has regularly maintained the stairs, including a significant repair project in August of 2005.
The Pier Avenue Stairs provided access to approximately 800 feet of coastline within an isolated pocket beach, extending from the intersection of Ocean Boulevard and Windward Avenue to the north, to the tip of Margo Dodd Park to the south.
On October 26, 2021, the City closed the stairway due to a lower bluff failure caused by storm activity, which left a portion of the third landing (from the top down) unsupported and hanging in space. In addition, it appears the storm sheared the supports of the bottom section of the stairs from their footings. With the closure of the Pier Avenue Stairs, there is no beach access south of Boeker Avenue until the beach access located at the Inn at the Cove, which is approximately a half-mile walk from Margo Dodd Park.
Staff retained the services of ENGEO Incorporated (ENGEO), formerly TerraCosta Consulting Group, Inc., to inspect the stairs and adjacent bluff and to make recommendations to restore beach access in this part of Shell Beach.
In its report (Attachment 1), ENGEO noted several portions of the coastal bluffs that are experiencing erosion, including a sea cave, previously noted by staff, that extends under the shoulder of Ocean Boulevard near the intersection with Windward Avenue. ENGEO also noted that the existing seawall protecting the bluff near Margo Dodd Park is in critical need of maintenance to reduce the risk of accelerating the loss of public resources and access, including potentially a portion of Ocean Boulevard.
1 www.californiacoastline.org
Options for Repair/Replacement of the Pier Avenue Stairs ENGEO examined the existing conditions of the bluff from Windward Avenue to Margo Dodd Park, the available parking along the bluff top and anticipated future site conditions, taking into account sea level rise and developed the following options.
Option 1 – Temporary Repairs to Existing Stairway, $1,500,000 This option includes the minimum interim temporary repairs to reopen the Pier Avenue Stairs to the public. The project includes the installation of a 4-foot-diameter concrete pier extending from the middle of the partially-unsupported third landing down into the shore platform bedrock. This would require the removal of the third landing and the installation of temporary shoring of the second and third flight of stairs.
The anticipated cost of this project is $1,500,000 and does not include repair of the lower stainless steel foundations or any Building Code-required upgrades, nor does it include repairs to the sea wall near Margo Dodd Park.
Because the rest of the staircase is past its useful life and may need to be rebuilt within 3–5 years in its entirety, in addition to the cost of this repair, staff does not recommend this option.
Option 2 – Replace Stairway within Existing Alignment, $2,350,000 This option includes the installation of new, deepened foundations at all of the landings and an entirely new stairway system. The new deepened foundations would provide long- term survivability of the stairway as additional erosion and bluff failures continue to reduce the size of the existing headland that currently supports the stairway. ENGEO provided the option for a solid pedestrian parapet on the bottom section of stairs, similar to the Memory Park Stairs, or an open pedestrian parapet with the installation of either real or faux rocks at or slightly above the High Tide Line to dissipate wave energy within the cove.
The anticipated cost of this project is $2,350,000 and does not include repairs to the seawall near Margo Dodd Park. While this option results in a new staircase, the staircase is vulnerable to wave energy and further erosion, and it does not protect the bluff from further erosion.
Option 3 – New Stairway with Beach Access from Margo Dodd Park, $4,800,000 Option 3 involves construction of a new public beach access stairway near the entrance to Margo Dodd Park. The new stairway would be incorporated into the Margo Dodd seawall repairs and outlet onto the beach immediately upcoast and behind the existing headland having two existing sea caves. Moving the stairs to Margo Dodd Park also has the advantage of approximately 30 more parking spaces in close proximity.
The beach at this location is relatively narrow, but it is less exposed to direct wave energy than the existing landing of the Pier Avenue Stairs. However, the adjacent steep bluff is vulnerable to collapse and therefore it is recommended that additional bluff scaling be performed to create a buffer for the bottommost stairway landing. This project also
includes the infilling of the two sea caves to maximize public safety and revitalize the natural protection to the bottom section of the proposed stairway.
The anticipated cost of this project is $4,800,000 and includes the repair of the existing seawall, sea caves and stabilization, by scaling and laying back the steep bluff near the bottom section of the stairs.
Option 4 – New Stairway with Beach Access from Palisade Avenue, $5,200,000 This final option is similar to Option 3, however the entrance to the new stairway would start across from Palisade Avenue instead of at Margo Dodd Park. This option calls for the stairway to be built on-grade. One possible advantage of this option is that the upper portion of the stairway would provide a more gradual and natural descent down the upper portion of the bluff, providing a more visually and physically comfortable user experience when compared to Option 3. However, this option also has the disadvantage of the entrance not being as favorable for accommodating congregating when compared with the Margo Dodd Park access.
The anticipated cost of this option is $5,200,000.
Option 5 – Removal of the Existing Stairway, $430,000
Staff also prepared an estimate to remove the existing stairs and restore the beach and bluff. This project would be anticipated to cost $430,000.
Exploring Potential Partnerships
In addition to making repairs to the stairway and bluff area, there are also bluff issues and a need to repair drainage at the end of Cliff Ave. Including this work in the project would be advisable for a complete repair of the bluff area along Ocean Boulevard and could increase total repair costs to $10-15 million dollars. In this instance, the City may wish to pursue partnerships with other state and federal agencies to bring in additional dollars and technical assistance to the project. The City has partnered with the Army Corps of Engineers in the past on a CAP 103 project to build the stairs and protect the lift station in the St. Andrews Tract. Due to the significant cost of these projects, the City Council may wish to direct staff to pursue partnerships like these before determining which option to proceed with.
Conclusion and Recommendation
The Pier Avenue Stairs are currently unusable and could be a hazard to public health and safety should the public not obey the closure signs. Staff recommends that the City Council discuss options for the Pier Avenue Stairs and provide staff with direction on how to proceed.
FISCAL IMPACT:
The fiscal impact of the Pier Avenue Stairs depends on which option is implemented.
These potential costs range from $430,000 to $5,200,000, which would need to be supported by the General Fund. Depending on the option chosen and the cost, it is likely
that Council will need to consider delaying or reducing other planned projects. Staff would come back to Council to appropriate the funds.
ALTERNATIVES:
1. Do not provide direction at this time.
2. Request more information.
ATTACHMENTS:
1. ENGEO Alternative Analysis
Submitted by: Meeting Date: November 15, 2022
Benjamin A. Fine, P.E., Director of Public Works/City Engineer City Manager Approval:
GEOTECHNICAL
ENVIRONMENTAL
WATER RESOURCES
CONSTRUCTION SERVICES
COASTAL/MARINE GEOTECHNICS
Project No.
19892.000.001
November 4, 2022
Mr. Eric Eldridge
City of Pismo Beach
760 Mattie Road
Pismo Beach, California 93449
Subject: Pier Avenue Stairs
Pismo Beach, California
ALTERNATIVES ANALYSIS
Dear Mr. Eldridge:
We are pleased to present the following alternatives analysis for repairing, replacing, and/or creating additional points of public beach access in the vicinity of the Pier Avenue Stairs, located near the intersection of Ocean Boulevard and Pier Avenue in Pismo Beach, California. Our alternatives analysis is based upon our preliminary site reconnaissance performed with you on October 29, 2021, our more thorough site reconnaissance performed on March 27, 2022, our review of freely available historic imagery of the project site area, and our work on other nearby projects having similar geotechnical and marine characteristics. This includes our 40+ years of experience associated with designing, permitting, and constructing these types of specialty coastal projects. Provided below is a discussion of the background, geologic setting, existing site conditions, anticipated future site conditions, stairway alternatives, and preliminary construction cost estimates for each stairway alternative.
BACKGROUND
Based on our review of the historic photographs available on the California Coastal Records Project website ( www.californiacoastline.org) , we believe some version of the Pier Avenue public access stairway may have existed in May of 1979, and possibly as far back as 1972. However, the quality and resolution of these early photographs make it difficult to determine the year in which the beach access stairway was established. Minimally, we would suggest that the stairway may now be approximately 40+ years in age (nearing its design service life). However, the stairway also appears to have been regularly maintained and had significant repairs completed in August 2005, based on our review of the City-provided Garing Taylor & Associates as-built plans.
While a majority of the stairway’s treads are now pressure-treated timbers, a number of the original concrete treads still exist within the upper two flights of the stairway. The hand railings and balusters within the upper three flights are painted galvanized steel (upper approximately 80%), while the hand railings and balusters within the lowest flight (lower approximately 20%) are stainless steel, designed as a result of being located more proximally to the corrosive wave impact zone.
On October 26, 2021, the stairway was closed due to a lower bluff failure (resulting from storm damage) that left a portion of the third landing (from the top down) unsupported and hanging in Council Agenda 11-15-2022 12.B-1
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 2
space (Photo 1, Figure A1 in Appendix A). In addition, the storm appears to have damaged the lowest flight of the stairway (the stainless steel section), which is now bent and sheared from two of its footings, slightly shifting the bottom alignment of the stairway landward (Photo 2, Figure A1).
During our two site visits, we also observed spalling concrete and exposed rebar within many of the existing shallow footings (Photo 3, Figure A1), corrosion of the painted galvanized steel railings and balusters in the upper three flights (Photo 4, Figure A1), and spalling concrete in a majority of the original treads (Photo 5, Figure A1), including loose screws and graffiti along the stringers of the lowest flight (Photo 6, Figure A1).
With respect to coastal access in this general area, the closure of the Pier Avenue stairway, accompanied by the closure of the Morro Avenue stairway in October 2015 (also due to storm damage), currently leaves approximately 1.2 miles of coastline inaccessible to the public between the next two closest beach access stairways located at Vista del Mar Avenue and the privately owned Inn at the Cove (Vicinity Map, Figure 1). Given the relatively tall bluff along this section of coastline, which further limits beach access and also intensifies and concentrates public use at the few available remaining access locations, it is no surprise that the public has been regularly observed circumventing the closure barriers/warnings and continuing to use the stairway despite its aged and damaged condition, making it apparent that additional points of public beach access are needed in this region. Exhibit 1 provides a view of the lower portion of the stairway, and exemplifies the potential danger that the stairway presents to beachgoers.
Recognizing the significant public use of the area (via official and unofficial means) and the California Coastal Commission’s goals of providing vertical public beach access along the coastline at an approximately 500-foot interval (where feasible), temporarily repairing the existing access and, for the long term, providing additional public access alternatives would aid in dispersing concentrated public use along what is currently about a 1.2-mile gap between the limited number of available points of public beach access.
EXHIBIT 1: Pier Avenue Stairway (Source: ENGEO Incorporated, March 2022)
Council Agenda 11-15-2022 12.B-2
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 3
GEOLOGIC SETTING
The Pier Avenue stairway provides access to an approximately 800-foot stretch of coastline within an isolated pocket beach, extending from the intersection of Ocean Boulevard and Windward Avenue at the upcoast end of the cove, to the western tip of Margo Dodd Park at the downcoast end of the cove (Figure 2). The entrance to the stairway sits atop an approximately 40-foot-tall coastal bluff that is part of the gently southwesterly sloping coastal terrace between the Pacific Ocean shoreline and the lower foothills of the San Luis Range in the Coast Ranges geologic and geomorphic province.
Structurally, the project area is situated on the southwesterly flank of a long synclinal (concave) fold with a northwest/southeast-trending axis of the Pismo Syncline (Figure 3). This major structural feature (estimated to be 4- to 5-miles wide and 25± miles long) was formed, along with associated faulting, during a long period of regional tectonic activity and continued to grow throughout most of Miocene and Pliocene time, thus creating the Pismo Depositional Basin, which extends from Arroyo Grande on the southeast to coastal Point Buchon on the northwest.
Our review of California Geological Survey’s Special Publication 42 indicates that the coastal bluff along Ocean Boulevard is not located within or crossed by a State-delineated Alquist-Priolo Earthquake Fault Zone. Alquist-Priolo Earthquake Fault Zones are typically delineated along active faults. An active fault is defined as one that has “had surface displacement within Holocene time” (approximately the last 11,000 years). At the top of the coastal bluff at the Pier Avenue stairs, the cove area is underlain by late Pleistocene-age marine terrace deposits consisting of beach and nearshore sands and gravels covered by alluvium and colluvium. Underlying these deposits is an older emergent wave-cut shore platform that has been regionally uplifted (tilted and folded), and locally consists of Miocene-age Obispo Formation. The Obispo Formation is predominantly comprised of yellow to brown tuffacous siltstone and claystone. The Obispo Formation is the predominant relatively resistant basal cliff-forming unit that is observed and mapped locally along this section of coastline and, more importantly, is within the tidal/wave impact zone. When this unit is exposed to wave energy over time, the folded broken up and softer layers within the unit slowly erode, leading to surge channel development, overhanging notches, sea caves, and eventually roof collapse with upper-bluff failures eventually extending up through the terrace deposits. An example of this long-term geologic process can be seen at the nearby Dinosaur Caves Park with its multitude of sea caves that are in various stages of growth and collapse, which can be sudden and may not necessarily coincide with a storm event. It is also worth noting that this geology (tilted bedding), coupled with marine-based erosion occurring along the toe of bluff, contributes to the ominous nature of the locally overhanging bluffs, particularly at the bottom landing of the Pier Avenue stairway, which should be addressed to mitigate potential public safety issues.
EXISTING SITE CONDITIONS
On October 29, 2021, just a few days after the lower bluff failure occurred at the Pier Avenue stairway, we performed a preliminary site reconnaissance with you. We observed the clearly visible unsupported third landing. However, the high tide and rough surf conditions at the time did not allow for an in-depth evaluation. To perform a more thorough observation of the stairway and the entire Pier Avenue beach area in which alternative public access could be implemented, we performed an additional site reconnaissance on March 27, 2022, and again on May 18, 2022, both during tidal lows. The following subsections discuss the existing Pier Avenue cove area Council Agenda 11-15-2022 12.B-3
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 4
conditions based on our site visits and review of freely available historic imagery, starting at the upcoast end of the cove near the intersection of Ocean Boulevard and Windward Avenue, and making our way toward the western tip of Margo Dodd Park at the downcoast end of the beach.
Region Upcoast of Pier Avenue Stairway
Exhibit 2 provides an oblique aerial view in 2018 of the region upcoast of the Pier Avenue stairway.
EXHIBIT 2: View of Region Upcoast of the Pier Avenue Stairway (Source: Shell Beach Coastal Conservancy Preserve, Steve Perry, February 2018)
The furthest point upcoast within the cove is defined by a northwesterly trending, developing sea cave and two northerly wave-cut notches (Photos 7 and 8, Figure A2), the approximate landward limits of which are depicted below on Exhibit 3, and is essentially where public parking along the seaward side of Ocean Blvd begins. Notably, we estimate that there are currently approximately 15 parallel parking spaces (9’x22’) between Windward Avenue and the Pier Avenue Stairway, and another 30 potential parking spaces downcoast of the stairway towards Margo Dodd Park and Cliff Avenue, suggesting this stairway handles significant pedestrian traffic, including kayaking and youth day camp field trips to the area.
Council Agenda 11-15-2022 12.B-4
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 5
EXHIBIT 3: Limits of Sea Cave and Notches in the Region Upcoast of the Pier Avenue Stairway (Source: Nearmap, August 2019)
The northwest portion of this large section of overhanging bluff currently extends approximately 35 feet horizontally beneath the top-of-bluff (and the adjacent unimproved roadway shoulder).
The two adjacent notches currently extend horizontally between approximately 10 and 15 feet beneath the top-of-bluff. The supporting roof material currently consists of 20± feet of a relatively thick section of the Obispo Formation. While this area is not presently a concern, the roof rock thickness should continue to be monitored for potential future loss of the existing relatively thick roof rock section. Based on rough order of magnitude field measurements, the distance between Ocean Boulevard and the top-of-bluff in this area ranges from 25 to 30 feet. Our review of California Coastal Records Project ( www.californiacoastline.org) aerial photographs dating back to 1972 (Image 7227066, Image 7940042, Image 8708072, Image 8910119, Image 2356, Image 200403918, Image 200510183, Image 201007243, Image 201317456, Image 201503102, Image 201902554) suggests this overhanging bluff area has existed for at least the past 50 years. The 2002 California Coastal Records Project photographs, which are of higher quality than many of the earlier historical photographs, also suggest that only a couple feet of erosion may have occurred in this area over the last 20 years. This is in stark contrast to the 20 to 30 feet of documented erosion that has occurred in other nearby regions of the Pismo/Shell Beach area over the last 20 years. At this location, it is our opinion that this localized lower erosion rate is likely attributable to the relatively consistent presence of many large nearshore formational outcrops within the shore platform that help dissipate wave energy originating from both the north and south.
As we move downcoast from this overhanging bluff area, there are three distinct northeasterly trending erosional features (nooks/recesses) within the bluff and back beach immediately upcoast Council Agenda 11-15-2022 12.B-5
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 6
of the Pier Avenue stairway (Photos 9 through 12, Figure A2). Based on our review of the offshore bathymetry, aerial imagery, and geologic maps, we infer that there likely exists a relatively small nearshore localized depression in the bedrock shore platform allowing increased wave energy from the south/southwest, locally increasing erosion within the Obispo Formation (see Exhibit 4).
The increased wave energy within the depicted westerly corridor is likely contributing to the overhanging bluff condition previously discussed and shown on Exhibit 3, along with the nook/recess development and erosion in the vicinity of the Pier Avenue stairway. Horizontal depth measurements of the southerly two (larger) nooks/recesses are approximately 60 to 70 feet landward from the adjacent headlands. Our review of the available aerial imagery suggests these features may have advanced tens of feet landward over the last 50 years. Along the top-of-bluff, there is approximately 10 feet between the Ocean Boulevard curb, just above the middle nook/recess, which then descends to beach level at an approximately 1/2:1 (H:V) gradient. At the nook/recess immediately upcoast from the Pier Avenue stairway, there is approximately 13 feet between the Ocean Boulevard curb and the top-of-bluff (which is reduced to approximately 5 feet from the top-of-bluff if you include the shoulder parking area). From the top-of-bluff, this nook/recess descends at a near-vertical slope down to beach level. It should also be noted that a storm drain outfall pipe and top-of-bluff concrete headwall existed in this nook/recess until about 2005, which may have been rerouted/abandoned. Overall, the City should anticipate that these nooks/recesses will continue to expand (growing landward and laterally), and will eventually threaten both Ocean Boulevard and the Pier Avenue Stairway.
EXHIBIT 4: Nearshore environment of the Pier Avenue Stairway (Image Source: Google Earth, September 7, 2018)
Pier Avenue Stairway Region
Currently, the Pier Avenue Stairway is located on a headland that extends approximately 80-feet seaward of Ocean Boulevard. Due to the overall height and topography of the bluff, the stairway Council Agenda 11-15-2022 12.B-6
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 7
is comprised of a circuitous series of four flights and five landings, shown in Exhibit 5), and where the overall alignment takes advantage of the existing topography, to descend down the face of the bluff. Additionally, there exists a lower-bluff shelf within the Obispo Formation in which Landing 3 is founded, which is now partially unsupported due to the bluff collapse that occurred on October 26, 2021 (forcing the City to close the stairway). Based on our site visits and review of readily available historical imagery, we estimate that approximately 8 feet of erosion/bluff loss occurred during this single event. We believe that the failure is also associated with the presence of a relatively small sea cave that is located directly beneath the landing. Post-collapse, the remaining portion of the sea cave is now on the order of 6’x6’x6’ (LxWxH), noting that the mid-interior of the cave balloons to approximately 12 feet in width. Coastal Records 2002 image 2356 provides historic context of the stairway, landings, geologic site conditions (including the lower-bluff shelf), and the sea cave almost 20 years prior to the recent bluff collapse.
EXHIBIT 5: Existing Condition - Pier Avenue Stairway (Image Source: Nearmap, July 3, 2021)
With respect to the current stairway alignment and bottommost landing, we believe it has been as optimally located as possible given the need to strike a balance between the two main potential public safety issues (i.e., rockfall and wave impacts). Historically, it has withstood continued erosion and the developing steepening and overhanging bluff condition within this overall beach area. In the future, the coastal bluffs around this isolated pocket beach will continue to steepen, requiring ongoing scaling of the bluffs. With any additional loss of sand or sea level rise, there is also a narrowing of the beach face, forcing the public closer to the coastal bluffs.
Region Downcoast of Pier Avenue Stairway (Margo Dodd Seawall and Park) Exhibit 6 provides an oblique aerial view from 2018 of the region downcoast of the Pier Avenue stairway, from the existing CMP storm drain outfall pipe to the western tip of Margo Dodd Park.
Council Agenda 11-15-2022 12.B-7
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 8
As mentioned previously, we estimate that there exists double the available parking in this area on the downcoast side of the Pier Avenue stairway, approximately 30 parallel parking spaces (9’x22’) along the seaward side of Ocean Boulevard, adjacent to Margo Dodd Park, and ending near the intersection of Cliff Avenue, making it an approximately 1,000-foot trek to the beach below. While not a significant distance, it is the likely impetus contributing to the numerous unofficial goat paths that have developed over the years around Margo Dodd Park and along the top of the Margo Dodd seawall. Arguably, the area along the top of the seawall is attractive for fishing and exploration, and we have regularly observed visitors in these areas during our site visits over the years.
EXHIBIT 6: View of Region Upcoast of the Pier Avenue Stairway. Orange arrow points to recent bluff failure discussed below (Source: Shell Beach Coastal Conservancy Preserve, Steve Perry, February 2018)
Our review of the bluff between the existing CMP storm drain outfall pipe (located approximately 85 feet southeast of the Pier Avenue stairway) and the downcoast end of the Margo Dodd seawall suggests that only a few feet of erosion has occurred over the last 20 years. However, the bluff face in this region has become noticeably steeper over the last 50 years. Typically, an oversteepening of the coastal bluff eventually leads to episodic increased bluff failures and landward migration of the top-of-bluff. This is exemplified where the orange arrow is shown on Exhibit 6, where a sizeable bluff failure occurred in between two of our site visits in the absence of any large storms. Presently, the distance between Ocean Boulevard and the top-of-bluff in this area ranges between 30 and 55 feet.
Immediately upcoast of the Margo Dodd seawall, there exists a westerly extending headland with two sea caves that we used to access the front face of the wall (Photos 13 through 16, Figure A3). The larger, more landward sea cave is approximately 24-feet long in the north-south direction, ranges from 20- to 32-feet long in the east-west direction, and ranges from 4 to 9 feet in height, while the smaller, more seaward sea cave is approximately 17-feet long in the north- south direction, ranges from 6- to 27-feet long in the east-west direction, and ranges from 4 to 6 feet in height.
Council Agenda 11-15-2022 12.B-8
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 9
Based on our review of the City-provided background information associated with the Margo Dodd seawall, our understanding is as follows:
1. The seawall is an existing approximately 150-foot-long by 21-foot-tall wall (18-feet tall with an average 3-foot concrete keyway) located immediately upcoast from Margo Dodd Park.
2. While there exists very little information to review pertaining to the age and design of the original triangular-shaped multi-tiered concrete gravity mass seawall, the documentation suggests erosion and wave overtopping were of concern to both a resident (428 Ocean Boulevard ) and the City in the late 1980s.
3. Mr. Fred Schott was retained to design an approximately 8-foot-tall wall extension that was constructed atop the original triangular mass, circa 1991. This repair primarily consisted of placing a thin wearing surface or architectural cladding over the front face of the existing triangular mass, adding a 7’8”-tall by 1’3”-thick wall extension with wave deflector, thereby increasing the overall wall height, and constructing a series of shallow counterforts with footings along the landward side of the wall extension spaced roughly 20 to 28 feet apart. Negating the tiedowns and doweling into existing concrete or formation that is a signature of Mr. Schott’s designs, these counterforts and footings do not extend (vertically) lower than the top-of-tier of the original triangular gravity mass.
4. Circa 1993, Mr. Dennis Schallenberger with Earth Systems Consultants performed a site reconnaissance to observe a developing erosional void behind the southern wall end and recommended filling the void with slurry. However, it is not clear from the documentation (and our recent site visits) if this infilling actually occurred.
5. In early February 1998, Mr. Schallenberger and Mr. Rick Gorman (both with Earth Systems Consultants) performed another site reconnaissance to observe a much larger void developing in the same area along the southern end of the wall, which revealed several interconnected caves. At the time, they opined that collapsed formational blocks from the outer cave would form a pile near the entrance of the inner cave, forming a protective barrier that reduced the potential for future erosion. However, their recommendations also describe a series of steps for repairing the void in the wall to mitigate additional surficial slope failures that could eventually propagate further into the park near the gazebo. Again, based on our review of the provided information and our site visits, it is not clear if these repairs were completed.
Regardless of whether or not the suggested 1993 and 1998 erosional maintenance infill repairs were completed, it has been 30 years since the Fred Schott wall extension was completed. Given our contemporary review of the nearshore and offshore environment in this region (e.g., wave exposure depicted on Exhibit 4), it is our opinion that this approximately 150-foot-long seawall and the adjacent geologic outcrops (Photos 17 and 18, Figure A4) continue to provide vital protection to the coastal bluff, Margo Dodd Park, and the Ocean Boulevard corridor, and equally important, preserve public access and recreational opportunities along this scenic section of Pismo Beach. Today, based on our assessment of this wall, it is our opinion that it is time to perform critically needed maintenance or risk accelerating the loss of these public resources and a portion of the roadway. This is based on the following observations:
Council Agenda 11-15-2022 12.B-9
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 10
1. The 3-foot-thick concrete keyway (original triangular gravity mass wall) at the toe of the seawall is now notched and scoured, and no longer in intimate contact with the underlying formational shore platform laterally along the wall in numerous locations, with some of these voids extending as much as 6.5-feet deep from the seaward face of the concrete keyway, and others typically on the order of 2.5 feet in depth (Photo 19, Figure A4).
2. At the downcoast end of the seawall, a sea cave extends under Margo Dodd Park, wrapping around and behind the wall, which opens up to a large void where extensive piping (soil loss) of the wall backfill has occurred (Photo 20, Figure A4). While it is unclear if this area has been previously repaired, it is apparent from the historical imagery that there exists regular uncontrolled public use of the area, as noted by the presence of orange construction fencing visible in the 2002 California Coastal Records Project photographs ( www.californiacoastline.org , Image 2357). This construction fencing was likely installed in the vicinity of the top-of-wall to alert the public using the unofficial access to the presence of the developing void.
3. More recently, possibly sometime in 2019 or later, an additional void began to develop behind the middle section of the seawall (Photos 21 and 22, Figure A4). The location of this void is directly above a 6.5-foot-deep (horizontal) void extending beneath the concrete keyway at the bottom of the original triangular gravity mass wall. As these voids continue to extend landward beyond the more resilient concrete face and into the weaker formation, erosion from wave energy accelerates, eventually leading to the observed slumping and collapse of the fill soils above/behind the Fred Schott repairs.
4. Beyond the downcoast end of the seawall, a southwesterly trending headland extends from the western end of Margo Dodd Park. The headland has a number of developing sea caves and notches, varying between 4 and 12 feet in depth from the dripline. Based on our review of historic photographs, it is difficult to determine if these sea caves have experienced significant growth over the last 50 years.
Overall, and regardless of the alternatives or additional beach access locations that the City ultimately decides upon, it is our opinion that this seawall should be made a priority for rehabilitation as soon as feasible to help preserve its vital function. Also, and in consideration of the type of repairs that would be involved, including contractor ingress/egress and staging and phasing (disturbance footprint), it is our opinion that this repair work would be an ideal opportunity for the City to add formal public beach access in the vicinity of Margo Dodd Park for the following reasons:
1. There exists double the amount of available parking opportunities downcoast and nearer the Margo Dodd Park seawall, and the public already navigates a number of unofficial, and arguably unsafe, bluff-top paths to access this area, further legitimizing the need for developing additional official access in this location.
2. It would facilitate achieving the previously discussed goals of the California Coastal Commission to provide public beach access at regular intervals along the coastline.
3. While arguably a maintenance project, adding a public access component to the repair work should help facilitate regulatory approvals needed to repair the wall.
Council Agenda 11-15-2022 12.B-10
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 11
4. Enhances the attributes and functionality of Margo Dodd Park.
5. Access along the top of the Margo Dodd seawall would provide a long and wide intermediate bluff landing that may be an attractive alternative to the steep, narrow, and circuitous Pier Avenue stairway, and may be more desirable for kayak/paddle board portage, where there exists a larger available staging area at the top-of-bluff in the park.
6. Adding a walkway with a pedestrian parapet and wave deflector also enhances the wall for wave overtopping and sea level rise, providing improved protection for the fill slope above the wall and Ocean Boulevard.
ANTICIPATED FUTURE SITE CONDITIONS
Past and possible future changes in mean sea level (MSL) are of interest in design and planning for coastal projects, with the subject beach access stairway project being no exception. Global mean sea level rose at least 300 feet, and perhaps as much as 400 feet, during the past 18,000 years or so (CLIMAP, 1976). Exhibit 7 shows the relative sea level trend observed at the Port San Luis Tide Gauge from 1945 to 2021. These data are routinely tabulated by the National Oceanic and Atmospheric Administration (NOAA) as part of their national tide gauging program (Flick et al., 2003). The sea level trend from 1945 through 2021 has been relatively linear over the past century, with the relative sea level trend of 0.97 mm per year equivalent to a change of 0.32 foot in 100 years.
EXHIBIT 7: Relative Sea Level Trend for Port San Luis, 1945-2021 (Source: NOAA, 2021).
While mean sea level rise (MSLR) has increased linearly at a relatively slow rate over the past century, it is generally concluded that MSLR will likely accelerate along the California coast over the next few decades (OPC, 2018). The Ocean Protection Council’s (OPC’s) 2018 update to the State of California Sea-Level Rise Guidance document offers a new strategy for presenting MSLR trajectories as functions of emission scenarios as well as probability of occurrence. For example, for Port San Luis, the low-emissions 2100 endpoint value of 1.3 feet of MSLR has a 50 percent chance of being exceeded, while the corresponding high-emissions 2100 endpoint is 2.1 feet. For additional perspective, the low-emissions 2100 MSLR value has a 66 percent chance of rising between 0.7 and 2.1 feet, while the high-emissions range suggests 1.3 to 3.1 feet. Notably, there is a 5 percent chance that MSLR will be 2.9 feet (low) or 4.1 feet (high) by 2100, and a 0.5 percent chance of 5.4 feet (low) or 6.7 feet (high). Finally, the extreme scenario postulates 9.9 feet MSLR by 2100 in case of rapid Antarctic ice loss (see Exhibit 8).
Council Agenda 11-15-2022 12.B-11
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 12
EXHIBIT 8: Projected Sea-Level Rise for Port San Luis (Source: Table 19, OPC, 2018).
Council Agenda 11-15-2022 12.B-12
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 13
Minimally, it should be anticipated that any increase in sea level will result in increased rates of coastal erosion and a narrowing of the available beach. While annualized erosion rates for the subject area over the past 20 years appear to be on the order of 0.1 to 0.2 foot per year, we anticipate that erosion rates may double over the next few decades, particularly given the observed steepening of the bluff face.
Given the preceding, we have developed the following stairway alternatives for the City’s use in the further evaluation of providing and maintaining coastal access to this heavily utilized area.
PIER AVENUE STAIRWAY ALTERNATIVES
Option 1 – Temporary Repairs to Existing Stairway
Option 1 involves implementing the minimum interim temporary repair measures necessary to reopen the Pier Avenue stairway to the public (Figure 4). The most significant component of this repair consists of installing a single 4-foot-diameter, steel-reinforced concrete pier extending from the middle of the partially unsupported third landing down into the underlying shore platform bedrock. Logistically, this likely involves temporarily shoring in-place the second and third flight of stairs before detaching/dismantling the third landing; excavating and scaling approximately 20 feet of overhanging fractured and loose formational material within the mid-bluff shelf to create a clear unobstructed vertical space and a safe work area; placing a reinforcing cage into the drilled hole; placing a sonotube up to within a couple feet of the bottom of the landing; pumping concrete; and subsequently structurally connecting the landing to the new pier.
The City should also:
1. Preemptively excavate/scale and lay back the surrounding tall bluff above the bottommost Landing 5 and Flights 3 and 4, and repair the storm-displaced existing lower stainless steel flight with new foundations.
2. Have our structural engineer observe the condition of the structural connections at each of the flights and landings to determine if any other maintenance repairs should be completed as part of this work.
3. Determine if any other code upgrades become necessary as part of completing interim repairs.
Given the age of the overall structure it might be prudent to also consider installing drilled piers at Landings 4 and 5 in lieu of reattaching the bent flight to the existing shallow foundations for the interim.
Option 2 – Replace Stairway within Existing Alignment
Option 2 involves new deepened foundations at all of the landings and an entirely new stairway system that could consist of a combination of either stainless steel or possibly FRP (Fiber Reinforced Polymer) at the top of the bluff, and transitioning to reinforced concrete (with a solid parapet and wave deflector) when the flights and landings descend below approximately elevation 30 feet NAVD 88 within the wave runup and impact zone. The deepened foundations are intended to provide long-term survivability of the stairway access as additional erosion and bluff failures Council Agenda 11-15-2022 12.B-13
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 14
continue to reduce the size of the existing headland in which the stairway currently rests. While FRP has clear advantages for corrosion resistance, lower cost, and lightweight properties, we cannot endorse implementing FRP within the wave impact zone due to longshore transient sediment abrasion issues. Additionally, it remains uncertain to us if FRP implemented above the wave impact zone would withstand the intense public use of this area (e.g., top rail being used as a sliding surface to help portage heavy plastic kayaks down to the beach).
While we generally prefer to not have an open railing surface within the wave impact zone, the existing robust stainless steel (Flight 4) has performed well at this location, suggesting the continued use of robust stainless steel. Also, and in lieu of having a solid concrete pedestrian parapet with a wave deflector within the wave impact zone, this option could include strategically placing a couple of 8-ton rocks or faux carved and colorized concrete rocks embedded into the formational shore platform at or slightly above the High Tide Line (6.85 feet NAVD 88; Exhibit 9), possibly mitigating the need for a solid parapet, but also allowing the existing bottom landing to remain aligned in the current position. Also, these real or fake rocks would benefit the area by dissipating wave energy within the cove and protect anyone caught unaware in the wave runup zone near the bottom landing.
EXHIBIT 9: Example of faux rocks we have designed and implemented at a limited- access site to reduce wave energy impacting a nearby walkway, Sunset Cliffs area, San Diego (Source: ENGEO, April 2022)
Note that we only recommend the implementation of faux rocks for limited access sites when it is cost-prohibitive to mobilize large equipment needed to place so few rocks. Given that a crane would likely be needed for the minimum repairs, and that pumped concrete is also a component of the work, the City has the option for either real or faux rocks should this be desired for the Pier Avenue stairway. Negating cost comparisons, the faux rocks may be more desirable in that they can be in-situ custom-shaped for the appropriate anchorage and wave baffling effect, and would Council Agenda 11-15-2022 12.B-14
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 15
also blend in with the surrounding natural formational outcrops. Otherwise, large rocks that would be obtained from a quarry and placed with a crane should likely be hand-selected for similar favorable attributes. Option 2 also renews the service life of the stairway on the order of 40+ years with regular maintenance.
With either option, there is still a concern over public safety. If the landings are located or rotated toward the back beach, then additional stabilization measures will likely be necessary to mitigate rockfall and bluff collapse. With regard to opening handrails in the presence of kelp wrack and debris (which can accumulate on an open railing system), high wave loads on this accumulated debris can destroy the railing system. Recognizing that these loads can be very high, we have determined that solid concrete parapets in the lower flights are preferred to help mitigate both the wave impact safety hazard and reduce the available surface area in which kelp and debris can attach/accumulate. That is not to say that we believe the existing stainless steel lower flight needs to be replaced, as it appears to have performed well in this environment despite being bent and dislocated from the footings. However, this recent damage illustrates the high periodic wave forces acting on these structures.
MARGO DODD PARK AND SEAWALL STAIRWAY ALTERNATIVES
Option 3 – New Stairway with Beach Access from Margo Dodd Park
Option 3 involves construction of an additional public beach access stairway downcoast of Pier Avenue near the entrance of Margo Dodd Park (Figure 6). The stairway would be incorporated into the previously discussed Margo Dodd seawall repairs, and outlet onto the beach immediately upcoast and behind the existing headland having two existing sea caves (Exhibit 10).
Council Agenda 11-15-2022 12.B-15
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 16
EXHIBIT 10: Stairway Landing Area, Options 3 and 4, prior to bluff failure - arrows point to approximate area (Source: ENGEO, March 27, 2022)
While the beach at this location is relatively narrow, it is less exposed to direct wave energy when compared to the exposure at the Pier Avenue stairway, as shown previously on Exhibit 4.
However, the adjacent steep formational bluff is vulnerable to collapse, as shown on Exhibit 11.
Although there has been a bluff failure at this location, we would recommend that additional bluff scaling is still warranted, particularly to create a buffer for the bottommost stairway landing originating from the top of the repaired Margo Dodd seawall. With the introduction of a stairway over the unofficial trail, we would also recommend infilling of the two sea caves within this headland to minimize public safety/nuisance issues, and also to revitalize the natural protection to the bottom section of the stairway shown on Figure 6.
Council Agenda 11-15-2022 12.B-16
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 17
EXHIBIT 11: Stairway Landing Area, Options 3 and 4, subsequent to bluff failure that occurred between March 27 and May 18, 2022 (Source: ENGEO, May 18, 2022)
To rehabilitate the seawall and incorporate a stairway and walking path, we would suggest the following measures (as conceptually shown on Figures 6 and 7):
1. Filling the voids along the front face of the existing wall beneath the keyway and bedrock shore platform with an estimated 30 cubic yards of pumpable 3-sack slurry or controlled low strength material (CLSM).
2. Sawcutting, demolishing, and removing the existing wave deflector atop the 1991 Fred Schott wall repairs.
3. Placing approximately 275 cubic yards of a 5,000 psi shotcrete tied-back structural skin over both the original triangular mass concrete gravity wall and the Fred Schott repairs, keyed into the formational shore platform a minimum of 2 feet, and extending vertically above the top of the existing wall an additional 5 feet to form a new parapet and wave deflector (see Figure 7). At this time, we estimate that this would likely include two rows of tiebacks spaced 10 feet on center, horizontally and vertically, over the entire length of the existing wall (approximately 150 feet), totaling 30 tiebacks.
4. Placing approximately 165 cubic yards of 12-inch-thick carved and colorized architectural sculptor coating over the structural skin.
5. Infilling the existing sea cave at the downcoast end of the wall with an estimated 20 cubic yards of pumpable 3-sack slurry or CLSM. This includes removal of all transient sand and loose cobble from the floor of the sea cave (to be left on the beach) prior to infilling.
Council Agenda 11-15-2022 12.B-17
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 18
Depending upon contractor means and methods, work to infill the sea cave may also require temporary shoring of the outside face of the sea cave to allow for worker safety.
6. Backfilling and compacting the large void behind the downcoast end of the seawall with on the order of 100 to 150 cubic yards of 3-sack slurry or CLSM, along with the small void behind the middle portion of the seawall with approximately 10 cubic yards of 3-sack slurry or CLSM.
7. Infilling the larger, more landward sea cave associated with the westerly extending headland at the upcoast end of the seawall with an estimated 150 cubic yards of 3-sack slurry or CLSM. We would also recommend including integral color or applying an architecturally carved and colorized surface to any exposed faces of the slurry or CLSM to blend the appearance with the adjacent natural formational outcrops. This would include infilling the smaller, more seaward sea cave associated with the westerly trending headland with an estimated 40 cubic yards of slurry or CLSM, totaling 190 cubic yards.
8. Removing the existing elevated upcoast section of the headland that the seawall is tied into to prevent the walking path from going up and then down, and to allow for westerly drainage resulting from slope runoff or wave splash/overtopping.
9. Constructing an approximately 1,720-square-foot new variable-width concrete walking surface with seat wall along the top perimeter of the wall totaling approximately 120 cubic yards.
10. Installing two new sections of pile-supported stainless steel stairway on either end of the rehabilitated Margo Dodd seawall. At this time, there is insufficient topographic information from which to prepare representative concepts for the stairs, recognizing that building codes require that landings be placed vertically not more than every 12 feet, and also distributed equally along the alignment.
11. Scale and lay back the steep bluff in proximity to the bottommost stairway se ction on the beach.
Option 4 – New Stairway with Beach Access from Palisade Avenue
Option 4 is similar to Option 3, except that the entrance to the new stairway would start across from Palisade Avenue (Figure 8) instead of at Margo Dodd Park. For this option, we suggest that the stairway be on-grade at this location given the proximity to the retreating bluff that we are recommending for further scaling, which may eventually require alteration of the alignment to accommodate additional erosion in this area. One possible advantage of this option is that the upper portion of the stairway would provide a more gradual and natural descent down this portion of the bluff, providing a more visually and physically comfortable user experience when compared to Option 3. One disadvantage of this option is that the entrance is not as favorable for accommodating congregating when compared with the Margo Dodd Park access.
Council Agenda 11-15-2022 12.B-18
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 19
GENERAL RECOMMENDATIONS
1. Possibly on an emergency basis, the City might consider scaling the tall and overhanging bluff encircling the cove where the Pier Avenue stairway exists, and place all excavated materials within the cove and on the beach above the HTL.
2. Implement the minimum necessary repairs to enable reopening the Pier Avenue Stairway, including:
a. Inspect all existing structural connections at landings and flights, and determine suitability for continued use (e.g., maintenance repairs to treads and galvanized railings where applicable).
b. Construct drilled pier at Landing 3.
c. Consider adding two additional drilled piers at Landings 4 and 5. d. Reattach/anchor stainless section (Flight 4) to new piers. e. Consider strategically placing three to four 8-ton rocks (or faux rock) in front of Flight 4 and Landing 5.
3. In parallel, develop and permit repair plans for the Margo Dodd seawall rehabilitation incorporating additional new public beach access at Margo Dodd Park and along the top of the seawall down to the beach behind the headland, including infilling of the sea caves and scaling the nearby bluff.
In consideration of the currently estimated construction costs for the options discussed below, notably the high costs associated with what are arguably temporary repairs to the Pier Avenue Stairs (due to the challenging site conditions), it might be more appropriate for the City to focus on the significant repairs that are needed for the Margo Dodd Seawall, and incorporate improved public access as part of that work. If that is the direction the City ultimately decides upon, we would then suggestion demolition and removal of the existing stairway, costs for which are outlined below.
PRELIMINARY CONSTRUCTION COST ESTIMATES
Based on our prior construction-related experience, we contacted J.C. Baldwin Construction (information below), who specializes in limited-access coastal stabilization and construction projects, to discuss the site constraints and stairway repair and replacement alternatives.
J.C. Baldwin Construction
Paul McKee and Danny Cohen
2469 Impala Drive, Carlsbad CA 92010
Website: http://jcbaldwin.com
Phone: (760) 438-9274
J.C. Baldwin Construction provided preliminary (rough order of magnitude) cost estimates for the five stairway options as shown in Table 1. The cost estimates are based upon providing this letter and figures to the contractor, along with a phone call to discuss the background information and drawings.
Council Agenda 11-15-2022 12.B-19
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 20
TABLE 1: Preliminary Construction Cost Estimates
Stairway Alternative
Preliminary
Construction Cost
Estimate
Option 1 $1,500,000
Option 2 $2,350,000
Option 3 $4,800,000
Option 4 $5,200,000
Demo & Remove
Existing Pier Ave
Stairway
$360,000
With respect to contractor selection, there exists a multitude of potential contractors (large and small) from which bids could be solicited. However, this type of work is highly specialized, involving work within a fluctuating marine, tidally influenced environment that is prone to wave impacts, variable site conditions, and unstable bluffs. As a result, the selected contractor will need to be able to anticipate problems that will arise throughout the duration of the project. This includes work in a corrosive (saltwater) beach environment, dynamic wet conditions, additional site safety measures (such as temporary shoring), and shortened work days due to unfavorable tides limiting access to areas of work, which routinely slow progress, increasing the time and costs to complete a project.
With respect to construction costs, construction activities for all types of projects have remained at a heightened level during the entirety of the COVID-19 pandemic. As a result, price increases are being reported by contractors and material suppliers associated with not only increased demand for construction materials, but also limited availability of inventory due to past disruptions (complete stoppage in some cases) in manufacturing and delivery supply chains. Contractors are also reporting that typical price guarantees (fixed pricing) on material quotes are being removed from estimates, further contributing to uncertainty in overall project costs.
While we have done much preliminary work to help estimate the anticipated construction costs, there remains additional detailed design work that would need to be completed should you decide to proceed with the recommended repairs, including:
1. Obtain detailed topographic site surveys at both Pier Avenue and Margo Dodd Park and seawall.
2. Prepare a formal geotechnical report, including a more detailed discussion on sea level rise.
3. From topographic survey data, evaluate rise and run of new flights of stairway sections to optimize the configuration and alignment.
4. Develop site-specific sand mitigation fee calculations.
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City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 21
5. Prepare supporting structural calculations and detailing.
6. Develop formal design plans for permitting and contractor bidding.
7. Perform preliminary environmental site reviews for (avoidance of) cultural resources and possibly old dump/burn pits.
LIMITATIONS AND CONDITIONS OF USE
This document is intended to provide the City of Pismo Beach with a preliminary understanding and overview of site conditions, and alternatives for possible repairs and opportunity for additional points of public beach access, including preliminary (order of magnitude) estimates of potential construction costs for the various alternatives presented. As such, it should be anticipated that the information and order of magnitude probable costs are subject to change, particularly given the absence of detailed topographic survey data.
We strived to perform our professional services in accordance with generally accepted principles and practices currently employed in the area; there is no warranty, express or implied. Risks of earth movement are inherent of development within the coastal environment, and it should be expected that there will continue to be changes to the site, which may be sudden and episodic.
As we are unable to eliminate all risks, we cannot guarantee or warrant the results of our services.
CLOSING
If you have any questions or comments regarding this letter, please call and we will be glad to discuss them with you.
Sincerely,
ENGEO Incorporated
Gene Spineto Walter F. Crampton, GE, D.CE
Senior Project Manager Principal
gds/wfc/crh/jg
Attachments: Select References
Figures
Appendix A – Site Photographs
Council Agenda 11-15-2022 12.B-21
Attachment 1
City of Pismo Beach 19892.000.001
Pier Avenue Stairs November 4, 2022
ALTERNATIVES ANALYSIS Page 22
SELECT REFERENCES
Bromirski, P.D., A.J. Miller, R.E. Flick, and G. Auad, 2011, Dynamical Suppression of Sea Level Rise Along the Pacific Coast of North America: Indications for Imminent Acceleration, J.
Geophys. Res. C., 116, C07005.
CLIMAP, 1976, The Surface of the Ice-Age Earth, Science, 191, 1131-1137.
Flick, R.E., Murray, J.F., and Ewing, L.C., 2003, Trends in United States Tidal Datum Statistics and Tide Range, J. Waterway, Port, Coastal and Ocean Eng., Amer. Soc. Civil Eng., 129(4), 155-164.
Fugro West, Inc., April 24, 2002, 1992 Bluff Erosion Study Update, Private Lots, North Cypress Street to Bluff Drive, Pismo Beach, California.
NOAA, Tides & Currents, Tides/Water Levels website,
https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?id=9412110 accessed on 4/21/2022.
Ocean Protection Council, 2018, State of California Sea-Level Rise Guidance, 2018 Update, https://opc.ca.gov/webmaster/ftp/pdf/agenda_items/20180314/Item3_Exhibit- A_OPC_SLR_Guidance-rd3.pdf
Wiegers, M.O., 2011, Preliminary Geologic Map of the Pismo Beach 7.5’ Quadrangle, San Luis Obispo County, California, published by the California Geological Survey.
Council Agenda 11-15-2022 12.B-22
Attachment 1
19892.000.001
November 4, 2022
FIGURES
Figure 1 – Vicinity Map with Beach Access Stairways
Figure 2 – Overall Site Plan – Pier Avenue & Margo Dodd Park Figure 3 – Geologic Map
Figure 4 – Option 1 - Temporary Repairs to Existing Stairway Figure 5 – Option 2 – Replace Existing Stairway
Figure 6 – Option 3 - Beach Access from Margo Dodd Park Figure 7 – Seawall Rehabilitation – Section
Figure 8 – Option 4 - Beach Access from Margo Dodd Park
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APPENDIX A – SITE PHOTOGRAPHS
Figure A1 – Photos of Existing Stairway Condition
Figure A2 – Photos Upcoast of Stairway
Figure A3 – Photos of Sea Caves near Margo Dodd Seawall Figure A4 – Photos of Margo Dodd Seawall
Council Agenda 11-15-2022 12.B-32
Attachment 1
PHOTO 1 - SUSPENDED SUPPORT LEG AND FOOTING PHOTO 2 - SUPPORT LEGS SHEARED OFF OF FOOTINGS PHOTO 3 - SPALLING CONCRETE AND EXPOSED REBAR IN
FOOTING
PHOTO 4 - CORRODING RAILING AND BALUSTERS
PHOTO 5 - SPALLING CONCRETE TREADS PHOTO 6 - LOOSE SCREWS AND GRAFFITI
PHOTOS OF EXISTING STAIRWAY CONDITION
PIER AVENUE STAIRS
PISMO BEACH, CALIFORNIA
PROJECT NUMBER: 19892.000.001
SCALE: NO SCALE
DRAWN BY: CRH CHECKED BY: WFC
FIGURE NO.
A1
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Attachment 1
PHOTO 7 - NOTCHES EXTENDING UNDER BLUFF PHOTO 8 - NOTCH EXTENDING UNDER BLUFF PHOTO 9 - FIRST NOOK/RECESS PHOTO 10 - SECOND NOOK/RECESS PHOTO 11 - THIRD NOOK/RECESS PHOTO 12 - COLLAPSED ROCK IN THIRD NOOK/RECESS
PHOTOS UPCOAST OF STAIRWAY
PIER AVENUE STAIRS
PISMO BEACH, CALIFORNIA
PROJECT NUMBER: 19892.000.001
SCALE: NO SCALE
DRAWN BY: CRH CHECKED BY: WFC
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Council Agenda 11-15-2022 12.B-34
Attachment 1
PHOTO 13 - VIEW OF SEA CAVES LOOKING EAST PHOTO 14 - VIEW OF SEA CAVES LOOKING NORTH PHOTO 15 - VIEW OF SEA CAVES LOOKING NORTH PHOTO 16 - VIEW OF SEA CAVES INCLUDING SEAWALL
PHOTOS OF SEA CAVES NEAR MARGO DODD SEAWALL
PIER AVENUE STAIRS
PISMO BEACH, CALIFORNIA
PROJECT NUMBER: 19892.000.001
SCALE: NO SCALE
DRAWN BY: CRH CHECKED BY: WFC
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.
Council Agenda 11-15-2022 12.B-35
Attachment 1
PHOTO 17 - VIEW OF WESTERN END OF WALL PHOTO 18 - VIEW OF EASTERN END OF WALL PHOTO 19 - TYPICAL VOID BETWEEN CONCRETE KEYWAY AND
SHORE PLATFORM
PHOTO 20 - VOID AT DOWNCOAST END OF WALL
PHOTO 21 - VOID IN MIDDLE OF WALL PHOTO 22 - VIEW OF SEAWALL FROM MARGO DODD PARK
PHOTOS OF MARGO DODD SEAWALL
PIER AVENUE STAIRS
PISMO BEACH, CALIFORNIA
PROJECT NUMBER: 19892.000.001
SCALE: NO SCALE
DRAWN BY: CRH CHECKED BY: WFC
FIGURE NO.
A4
ORIGINAL FIGURE PRINTED IN COLOR
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Council Agenda 11-15-2022 12.B-36
Attachment 1