Improvements of naval harbour works at Den Helder according to the Dutch newspaper Middelburgsche Courant dated 19 February 1857

According to tidings will all ready in the begin of next month the pit tendered for the new naval dock at the Nieuwediep (Den Helder). The length of the pit at the bottom will be around 400 feet and her depth will be sufficient enough to dock a completely fitted out screw steam frigate. Just as with the newly built commercial lock was engineer Strootman supervisor during the building.