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City of Arden Hills <br />Project B2502087 <br />June 13, 2025 <br />Page 17 <br />For recommendations on bituminous pavement materials, compaction, performance and maintenance, <br />and miscellaneous bituminous recommendations, please refer to sections C.3.c., C.3.d. and C.3.e, <br />respectively. <br />D.Procedures <br />D.1. Ground Penetrating Radar <br />D.1.a. Data Collection <br />GPR data was collected in May of 2025. GPR collection occurred at posted speed limits and data was <br />recorded continuously along the pavement to a depth of up to 2 feet. Analysis of this data provides a <br />continuous estimate of layer thickness for identifiable layers. <br />Scans of the pavement were collected according to GSSI, Inc. (manufacturer) SIR-30 processor settings at <br />a specified interval of approximately one scan per lineal foot in the outer wheel path. A calibration file, <br />required for data post-processing, was collected at the onset of testing. The RoadScan system from GSSI, <br />Inc. allows for the entry of user marks to note events. This capability was used to mark and tie in core <br />locations. Distance along the pavement is measured using a Distance Measuring Instrument (DMI). <br />D.1.b. GPR Analysis <br />Data collected by the GPR unit was returned to our office and analyzed to estimate the pavement <br />thickness. Pavement layer interpretation was accomplished using RADAN 7.0, a software package <br />included with the GSSI RoadScan system. The software includes tools to aid in delineating pavement <br />layer transitions and automatically calculates their depths from the pavement surface using the <br />calibration file(s) collected prior to or following testing. <br />Where “ground-truth” data (cores and hand augers) were performed, the interpreted layers from the <br />GPR scan were compared directly to the measured thicknesses from the borings to validate the accuracy <br />of the GPR analysis. <br />D.2. Pavement Coring and Hand Auger Borings <br />We performed pavement cores and hand auger borings in April of 2025. Exploration locations were <br />selected based on GPR results. The coring was performed with a 6-inch diameter diamond-toothed core <br />barrel fitted on a mechanically operated rotary drill. From the top of the apparent aggregate base layer, <br />we extended a manually operated hand auger through the base layer and into the subgrade layer. Upon <br />completion of the pavement cores and hand augers, we then performed our penetration test borings.