As a continuation of a project to develop a large scale accelerated laboratory test for the durability evaluation of materials used in the construction of preserved wood foundations, hemfir plywood panels treated to two retention levels with CCA-C and ACA preservatives and installed in PWF test boxes at the Ottawa laboratory are being examined for durability performance after four years in service. This interim progress report has been prepared pending completion of the inspection, at which time a final report will be prepared.