944 and 960 West Cliff Drive Emergency Storm Damage Project

944 and 960 West Cliff Drive Emergency Storm Damage Project

Starting December 28, 2022, through January 2023, high wave events damaged several sections of coastline along West Cliff Drive, including sections in and along the public right-of-way across from 944 and 960 West Cliff Drive. This period was subsequently declared a California state disaster (DR-4683-CA) across Santa Cruz County by California Governor Gavin Newsom. The sites have continued to suffer damage and erosion from the winter 2023/2024 storm season. Located approximately 500 feet and 700 feet west of Columbia Street along West Cliff Drive, two seawall structures built to protect public recreational pathways and parking areas, experienced extreme winter storm events. At 944 West Cliff Drive, the storms removed the rip-rap protection at the toe of the wall and exposed the softer bedrock formation under the base of the wall. An undercut formed, jeopardizing the wall foundation. Further erosion of the exposed backfill soils created a void under the public walkway paving that led to the formation of a 16-feet deep sinkhole behind the seawall. At 960 West Cliff Drive, wave action during the same winter storm events outflanked and undermined the same wall, resulting in loss of existing rip-rap protection and terrace deposits that previously supported the end of the wall. The loss of backfill behind the wall and below the footings resulted in damage to the public pathway above. Currently, this exposed portion of the wall is unsupported and vulnerable to wave attack. To repair the seawall at 944 West Cliff Drive, the proposed project involves excavating the loose materials in the sinkhole, placing an underdrain system in the damaged area at the base of the sinkhole, and backfilling the void on the interior of the wall with 450 cubic yards of slurry cement backfill. In addition, the proposed project will repave the damaged parking area, curb, gutter and recreational path. There will also be replacement of 160-250 tons of lost rock slope protection (RSP) at the toe of the wall, above the mean high tide elevation. Soil nails for the seawall will not be cut or damaged. At 960 West Cliff Drive, the project includes a 25-feet long, pile supported wall and 56-feet long, secant pile wall west of the damaged soil nail wall. The proposed repair will remove the last 5 feet of the current soil nail wall and abandon the soil nails in place. Then, the 25-feet long concrete wall will be constructed in front of the void created by the lost terrace deposits using drilled piers. Once the wall is in place, the void can be backfilled. At the bend in the public pedestrian pathway, the new, 56-feet long secant pile wall system will be constructed behind the existing terrace deposit bluff. The first series of spaced piers will be drilled with a slurry cement infill, and the second series of piers will be drilled between and into the first slurry piers. These piers will be reinforced and infilled with concrete, resulting in a continuous concrete wall. A concrete grade beam will be constructed at the top 3 to 4 feet of wall for continuity. The project includes best management practices (BMPs) to prevent erosion, sedimentation, and the discharge of pollutants during construction, protecting marine resources. For example, silt fences and catch basin protections will be used for the duration of construction, and straw bales, pumps, curtain enclosures, and other containment/soaking devices will be used in case of spillage. Additionally, construction will take weather into account by scheduling excavation and concrete pours outside of forecasted rain events, high surf, high tide, storms, and covering soil stockpiles and safety positioning equipment and materials at the end of each shift. The suite of BMPs will ensure that no debris, soil, silts, sand, rubbish, cement or concrete or washing thereof, oil or petroleum products or other earthen material from any construction or associated activity will be allowed onto the beach below or adjacent marine environment. Therefore, the proposed project conforms to the applicable marine resources policies of the Coastal Act.

Santa Cruz

Santa Cruz

San Francisco Bay Area

Santa Cruz