You have to trespass to swim here. The fence line surrounding the quarry has quite a few breaks which are easily passable. Be cautious of trash and broken glass around the lake, if you follow the map I added (park at red X, enter woodland across road, cross ditch at broken fence at yellow X, follow (approximate) path up and over ridge to head down a slope onto the pathway visible from Google maps, follow to the blue X - the beach you can swim from). Don't get caught and leave no trace