Lake Lewisville, TX

This should help:

http://www.swf-wc.usace.army.mil/lewisville/faq.asp#metaldetectors



What is the policy on metal detectors?

A permit must be obtained from the Lake Office prior to use of metal detectors. Permits must be carried by the person it was granted at all times when using a metal detecting device on government property, otherwise, anyone found digging on the land may be subject to a citation and may be asked to leave the area. Metal detectors must be used in accordance with the lake policy. Permits are granted subject to the following:

Use of metal detectors will be confined to shoreline areas of the Corps parks, except the overnight camping areas, unless you have a camping permit. Shoreline areas are defined as those park areas periodically disturbed by wave action, approximately eight vertical feet above or below the lake's "normal" conservation level of elevation 522 MSL. Use of metal detectors is not permitted in non-park or upland areas. Non-identifiable items of nominal value (defined as less than $25.00), which are found, do not need to be deposited with the Corps of Engineers. Identifiable items (rings, watches, etc.) and items of greater than nominal value will be deposited with the Corps of Engineers for disposition in accordance with federal regulations.
Any item, which may contain historical, archaeological, or pale ontological significance, will be left in place if practical. The Corps of Engineers must be notified; if the item is or has been removed from the site, it will be deposited with the Corps of Engineers.
Any item pertaining to a criminal offense will be turned over to the local police or to the Corps of Engineers.
Digging shall be limited to small instruments, scoops, or other hand tools, which can be used by one hand only. Hand tools shall be limited to four inches wide, four inches deep, and twelve inches long.
No holes will be dug and left uncovered. All trash, litter, or other debris uncovered will be removed and placed in an approved trash receptacle. All disturbed or displaced soil will be returned to its original site. The areas will be left in as good or better condition than before hunting occurred.