Just to add that as an early morning runner I often see people out walking/toileting their dogs on the beach. In winter it is often too dark for the owners to actually see what their dog is doing. Loads of so could responsible owners actually have only a limited knowledge of what their animal has been up to. And I have yet to see a dog owner clean up the urine from the beach. From another site:
Dog urine, like all animal urine, is usually sterile when it first leaves the body. That means it contains no pathogens that can cause infections in people--no bacteria, no viruses, and no fungi. However, the urine stream can pick up bacteria from the surrounding skin, and urine that is allowed to sit for any length of time becomes a breeding ground for bacteria (many of these are probably harmless, but it's inevitable that some harmful bacteria grow as well).
Whats wrong with a small patch of beach that is free from being a dog toilet.