Specifications include, but are not limited to: a)Aluminum structural plate headwalls shall conform to the latest requirements of AASHTO M219 or ASTM B746 with a minimum thickness of 0.150”.b)Headwalls may incorporate the full variety of shapes and sizes available in corrugated metal pipe and structural plate culverts (pipe, arch pipe, arch, box culver, et al). Additionally, headwalls may be equipped with wingwalls of the same design and material. All headwalls will be designed by a duly licensed and registered Virginia Professional Engineer who will provide sealed drawings and calculations.c)The headwall manufacturer shall provide construction supervision for the assembly, installation, and backfill of the headwall. The supervisor shall have a minimum of 2 years’ onsite experience in aluminum headwall installations.d)A culvert stub shall be integral with the headwall by means of a full periphery weld on both the interior and exterior of their junction. The headwall is properly placed at the design elevation by ensuring the stub is placed at grade for the culvert crossing.e)All joints will have ¼” aluminum flanges fully welded to aluminum pipe and utilize 3/4” diameter bolts and neoprene gaskets.