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_DESIGN~ Memorandum Page 2 of 3 information, it would somewhat defeat the purpose of the demonstration; correlating pavement thickness data will not be available as part of the demonstration. As we discussed with you, GEOVlsion's interpretations are based on an assumed dielectric constant of the asphalt pavement. This electrical property affects the speed at which electromagnetic waves, like radar, travel through the asphalt. This travel time is what is used to measure thickness. As asphalt mixes vary in density and porosity, the rate at which waves travel varies. We anticipate that the maximum variation associated with variable asphalt mixes wou'ld result in a corresponding maximum variation in the precision of the GPR interpretations of about 10 percent. Once provided with pavement core data, as planned for our evaluation of the Artesia Pilar neighborhood, the degree of precision of the GEOVision interpretations would be near 100 percent at and near the core locations, and would vary elsewhere to the extent the asphalt characteristics are different. Therefore, when evaluating the results of the test section, it should be understood that the degree of precision allowed without pavement and base thickness data to calibrate the GPR interpretations is limited to be plus or minus 10 percent of the actual thicknesses. In this case, for a pavement thickness of 10 inches, a successful GPR interpretation would be plus or minus 1 inch and Similarly for a pavement thickness of 5 inches, a successful GPR interpretation would be plus or minus 0.5 inch. SCHEDULE AND LOGISTICS OF TEST SECTION AND PLANNED WORK As we discussed, GPR for the test section is currently planned for Monday, July 14, and the results of the field screening will be interpreted and presented to the City on Tuesday, Juiy 1 5. If the results are acceptable to the City, the remaining fieid work would be performed July 16 and 17. In this scenario, a formai contract would need to be available for execution on July 15. To the extent possible, we respectfully request advanced confirmation from you that if in fact the test section is deemed successful, our team will be awarded this work in the time frame outlined in the above paragraph. If we are not awarded the work as outlined above, it will be at least one month before the necessary equipment is available to compiete the work. Pavement coring would be scheduled to commence as outlined in our proposal dated June 27, 2008. CLOSING We sincereiy appreciate the opportunity to provide professional services to assist your overall pavement evaluation and improvement projects and welcome the opportunity to further discuss our planned scope or work and schedule with you. qZ:kt 2121 S Towne Centre Place - Suite 130 I Anaheim CA 92806 I Off 714.634.3701 I F~ 714.634.3711