In the article, the authors describe the methodology for determining the length of piles according to ASTM D5882. The authors of the article describe the situation that arose at one of the sites in the city of Tyumen when, when digging a pit, a previously constructed pile field with a grillage was discovered. The authors examined the pile field in order to determine the length of the piles. The length of piles immersed in the ground was determined by the method of acoustic wave excited in a pile by impact in accordance with ASTM D5882 Standard Test Method for Low Strain Impact Integrity Testing of Deep Foundations. The measurement method is based on the property of an acoustic wave being reflected from the interfaces between media with different acoustic impedances. The article describes the methodology for determining the length of piles with further processing of the measurement results. The main conclusions are formulated based on the results of the work on measuring the length of piles by the method of an acoustic wave excited in a pile by impact.