Del. Code tit. 23, § 1507

It shall not be lawful to fill in with earth, stone or other solid material in the tidewaters of the Delaware River between the points referred to in § 1505 of this title, beyond the bulkhead line or lines of solid filling by §§ 1505-1510 of this title adopted, fixed, established, laid down and exhibited on the map or maps, report or reports, except in the construction of duly authorized piers. No erection or structure of any kind shall hereafter be erected, allowed or maintained beyond or exterior to such bulkhead line or lines of solid filling, except duly authorized piers, which shall not be less than 150 feet distant one from the other, and which shall in no case extend beyond the lines indicated for piers on such map or maps, report or reports.