Lake Pleasant AZ is a closed inland lake and all U.S inland lakes are NDZs. So yes indeed...you're most assuredly "fineable!" Some states have made it illegal even to have overboard discharge plumbing installed on a boat on an inland lake.
You have to be in open ocean at least 3 miles from nearest point on the whole US coastline to dump a tank legally...and you're just a wee bit too far from either coast to be able get 3 miles offshore without hauling the boat and putting it on a trailer or truck. So not only does the overboard lever have to be in the closed position, the system must be "secured." 33 CFR 159.7 (c) describes the acceptable means of doing that ("Type III" is a holding tank):
When operating a vessel on a body of water where the discharge of untreated sewage is prohibited by the Environmental Protection Agency under 40 CFR 140.3, the operator must secure each Type III device in a manner which prevents discharge of sewage. Acceptable methods of securing the device include -
(1) Closing each valve leading to an overboard discharge and removing the handle;
(2) Padlocking each valve leading to an overboard discharge in the closed position; or
(3) Using a non-releasable wire-tie to hold each valve leading to an overboard discharge in the closed position.
Btw...all this is in my book, available from the sbo.com online store (see link in my signature).
You have to be in open ocean at least 3 miles from nearest point on the whole US coastline to dump a tank legally...and you're just a wee bit too far from either coast to be able get 3 miles offshore without hauling the boat and putting it on a trailer or truck. So not only does the overboard lever have to be in the closed position, the system must be "secured." 33 CFR 159.7 (c) describes the acceptable means of doing that ("Type III" is a holding tank):
When operating a vessel on a body of water where the discharge of untreated sewage is prohibited by the Environmental Protection Agency under 40 CFR 140.3, the operator must secure each Type III device in a manner which prevents discharge of sewage. Acceptable methods of securing the device include -
(1) Closing each valve leading to an overboard discharge and removing the handle;
(2) Padlocking each valve leading to an overboard discharge in the closed position; or
(3) Using a non-releasable wire-tie to hold each valve leading to an overboard discharge in the closed position.
Btw...all this is in my book, available from the sbo.com online store (see link in my signature).