The San Jose Creek Channel was constructed in the 1960's to provide storm and groundwater drainage for an extensive area in Los Angeles County near the cities of Walnut and Industry. It consists of a reinforced concrete channel bottom with vertical reinforced concrete retaining walls. The walls have a construction joint a few inches above the channel bottom and between adjacent wall panels. A 60 ft. long section of the channel wall failed during a storm in 1991, and a second wall panel experienced extreme distress in 1998. 

The Los Angeles County Department of Public Works (LADPW) hired WDP in early 1998 to conduct an investi- gation into the cause of the failures. After selected impact-echo and corrosion testing, it was determined that there was extensive corrosion in some locations at the base of the wall adjacent to the cold joint between the channel bottom and walls. A prototype study and subsequent structural analysis and reliability studies were conducted by WDP in the Fall/Winter of 1998. The studies showed conclusively that the principal cause of the deterioration was corrosion of the flexural reinforcing steel in the channel walls. It was determined that the failure probability of a typical panel was approximately two orders of magnitude greater than what would be expected for new designs utilizing modern codes. WDP developed and refined a testing and evaluation protocol for the panels where results could be used in conjunction with hand computations and finite-element structural models to allow for the most appropriate and cost-effective repair design. 

An outgrowth of the recommenda- tions of WDP's prototype studies was the development of a comprehensive repair/retrofit program by LADPW for the entire 4.4 mile reach of channel defined in the initial studies. WDP responded to a request for proposals by LADPW and was awarded a contract on April 7, 1999 to provide structural engineering and testing that would ultimately result in the design of a cost-effective retrofit/repair for the channel wall panels. 
 

The work under the contract was multifaceted and included: impact-echo testing and visual analysis of each of approximately 830 wall panels, geotechnical investigation, development of a project database, determining the condition of the back face reinforcing on two adjacent panels, preliminary seismic analysis, evaluation of invert cracking and subgrade condition, field testing relating to the design of a cathodic protection system, a forensic investigation and report, and the development and design of required repairs/retrofit for the channel wall panels.

Services WDP used on this project included:

• Impact-Echo Testing
• Corrosion Investigation
• Development of Computer Database of  Nondestructive Evaluation Results for Facility Management
• Geotechnical Investigation
• Structural Analysis
• Seismic Analysis, Retrofit and Seismic Upgrade Design 
• Preparation of Contract Structural Drawings and Specifications