The precast wall was an alternate in the Woodward-Clyde bid package and was selected by Granite Construction over the MSE wall alternate. An integral wave deflector was monolithically cast with the top wall panels instead of the field cast cap that would shown for the MSE wall.
Prior to the wall installation a trench was cut into the slope and a cip cut off wall was constructed behind rip rap. The precast wall components were then installed. Since sand was used for wall fill filter fabric/geotextiles were placed over the fill side of the precast elements.
The wall has been subjected to many extreme load conditions compared to a typical seawall/erosion control structure. Locals claim that the tallest wave ever recorded in North America occurred at Pacifica. There are shots of these giant waves at local establishments. Some smaller waves are shown crashing into the wall in the shots.
Also the wall was impacted by the San Francisco earthquake which hit shortly after the wall was completed. The existing MSE wall north of the fishing pier has not fared so well. We understand that due to the corrosion of the metal soil reinforcement and movement fill has been lost from behind the wall. To address this issue the city has apparently refilled voids with concrete fill. There have been no issues with the Stresswall Structure.
SR 31 @ Canadian Border
||City of Pacifica Client
|| Scope Of Work
Single tier seawall structure placed along WashDOT SR31 at the Canadian Border.
The counterforts were placed in slots cut into the existing roadway embankment. Due to the constant border traffic it was necessary to construct the wall as one lane was kept open. Other wall options would have required shoring.
Cut material was utilized for wall fill.
||Seawall for Embankment Support Scope Of Work
This 1.5 mile 8′ high wall was constructed in the spring when there are typically no hurricanes or major storms. Although unfortunately that was not the case the wall components were placed quickly and reaches filled between high wave events.
The other bid option was a panel MSE wall system. Due to the fact that the counterfort wall can be designed to use a wide range of wall fill including the “clayey” site material the low bidder selected Stresswall partially due to the fill savings compared to the spec. fill for the MSE wall option
The 8′ high ‘seawall counterforts” were cast at Manco in San Antonio and delivered to the site. The shots show the counterfort elements stored on the beach in front of the wall. By working off of the existing embankment excavators placed the counterforts into slots cut into the existing slope. The excavation costs were therefore substanially less for Stresswall than would have been the case for the MSE option.
The “elevated base seawall” counterfort has a unique configuration which results in the minimum excavation volume as well as providing the counterfort support base at a higher elevation than the bottom of the wall elevation. This element geometry facilitates an efficient component erection even in high tide conditions. Also, since the counterfort base is elevated compared to the bottom of the counterfort face, the resultant earth and surcharge loads passes through the counterfort base so the overturning moment is at a minimum. Due to the elevated base the wall foundation loading approaches the minimum value of gamma times h where h is the wall height.
||Matagorda County Client
||1.5 mile 8' high seawall Scope Of Work