A sampling from the eight-mile-long concrete seawall containing the waters of Marina del Rey shows corrosion damage that could mean an immense repair bill for Los Angeles County, officials said.
Larry Charness, chief of planning for the Los Angeles County Department of Beaches and Harbors, said that if damage throughout the wall is found to be as extensive as is shown in 61 samples, necessary repairs would cost at least $10 million.
Technical experts from the U. S. Army Corps of Engineers in Vicksburg, Miss., were called in last week to test selected portions of the 60-foot-thick concrete seawall with a new kind of sonar system, Charness said.
Results of their tests were not immediately available, officials said Thursday.
Charness said county officials got their first inkling of problems in the massive seawall that separates land and water at Marina del Rey last spring when one panel of concrete near the Charthouse restaurant fell into the harbor waters during a rainstorm.
Officials found that steel pins holding the concrete panel to its footings had become corroded by seawater after seals protecting the metal apparently ruptured, Charness said.
Engineers are concerned because it is the steel that gives the wall strength by holding the concrete in place, he said.
County engineers took 61 samples, representing about 1% of the seawall, to determine the extent of damage at the 22-year old marina, staff members told the county Small Craft Harbors Commission earlier this month.
The results of the sampling were "sobering," department director Ted Reed told the commission.
"If the samples show what we think they do, we are looking at a tremendous expense that would be out of the possibility of one-year financing," Reed said.
Bond Issue Needed
If the problem is as extensive as is feared, he said later in an interview, a bond issue would be required to repair the seawall.
The original financing of the marina included a $13-million bond issue approved by county voters in 1956. The total initial public cost of the marina, which was officially opened in 1965, was $36.3 million, according to county officials.
One of the problems in assessing the damage is finding a nondestructive way of testing the seawall, officials said.
The equipment the Corps of Engineers employed last week at the marina is a prototype of a new kind of "pulse-echo" sonar system that the federal agency has been developing during the past half-decade, Charness said.
Older methods require that equipment be placed on both sides of a wall to measure how sound passes through it, but this new experimental method could be used on dams and other structures where engineers can only reach one side, he said.
The new equipment used last week at the marina sends a signal through the thick concrete walls and monitors the signal when it bounces back from the earth behind the wall, he said.