R2009-96 AUTHORIZING SECOND AMENDMENT TO AGREEMENT WITH HANSON PROFESSIONAL SERVICES, INC.

Home Browse Search

7. Apron Slab Void Detection Survey: Previous repair projects at the Lake Decatur Dam have included work to investigate the presence of voids under the apron slab and to fill the voids with flowable grout. In order to evaluate the presence of any additional voids under the slab, Hanson will engage the services of AECOM Technical Services, Inc. (ATS)to use Ground Penetrating Radar(GPR)to investigate the area under the slab for voids. Services to be provided by ATS for the Project are as follows: a. GROUND PENETRATING RADAR SURVEY ATS will provide 2 trained non-destructive testing specialists and suitable GPR equipment to achieve the project objectives. The project will be divided into two phases,a Trial Phase and a Production Phase. Trial Phase The Trial Phase includes a site mobilization/demobilization from ATS's Milwaukee office and adequate time to test various GPR antennae at the site. The purpose of the Trial Phase will be to calibrate the GPR equipment to site conditions and deternune the useful extent of radar energy penetration. Following initial data collection in the Trial Phase,the GPR crew will consult with Hanson Professional Services,Inc. staff on site to decide if the GPR data provides the information required. If insufficient value is derived from the GPR data,the project will terminate and ATS will demobilize and invoice for this phase only, without any equipment charges. Production Phase The Production Phase will include a GPR survey of selected transects (survey lines)parallel to the dam face. Full-length data lines will be conducted at about two(2)-foot intervals with exact locations to be deternuned on site. This will result in approximately twenty(20)500-foot passes. In areas where potential anomalies are located at the concrete/sub-base interface transects will be made perpendicular to the previous transects to deternune the extent of the anomaly. The Production Phase will begin immediately upon completion of the Trial Phase. ATS will return the GPR data to the office where it will be analyzed for anomalies and trends. Five copies of a final report will be prepared. The report will discuss the equipment and procedures used during the survey and will present the results in a plan view of the apron slab. The plan view will include the position along each transect of each anomaly imaged to the nearest foot. The size of each anomaly will be estimated and reported. ATS will mark selected locations on the apron slab for the purpose of ground truthing/calibrating the GPR data. A total of approximately 2-3 cores will be marked. b. SERVICES PROVIDED BY CONTRACTOR Provide a clean,unobstructed access to the apron slab for the data collection vehicle (van). Provide a dry and clean surface of the apron slab for the data collection. <�� HANSON PSA Amendment Rev.3 2 1:�08jobs\08L0198�Admin�05-Agreements�PSA Amendment 2.doc