The concern is that portions of the dam added later could liquefy in a major quake, causing it to fail. Most of the water in the lake northeast of Escondido comes from Lake Henshaw and is channelled through the Escondido Canal.
The lake is a source of water for the cities of Escondido and Vista. In 1924, authorities added 7.4m to the height of the dam using silt and sand and reinforced the landward side with similar materials. But the materials were not properly placed.
Although the dam passed state tests in the intervening years, the integrity of the sand-and-silt construction is suspect when subjected to a Richter 7.5 magnitude earthquake loading.
Since then, the Escondido has kept Lake Wohlford at half-capacity. The level of the reservoir is kept below the height of the original rock dam, which was shown in the federal tests to be strong enough to withstand earthquakes and floods.
The consultant’s report should be completed by July this year.
