 At the time of Wurster 's and Ganzert 's visit to the site , the entire bridge was buried by river sediments up to the springing line of the vaults . No efforts to dig them up were undertaken by Wurster and Ganzert . Only two of the 28 arches were exposed enough so that direct measurements of the clear span and the pier width could be undertaken . It was , however , possible to calculate the dimensions of the remaining bays from their exposed sections . 
