Work by the state and an environmental group to lay an artificial oyster reef at a historic reef site in Sillery Bay has caused headaches for Pasadena residents, including debris washing onto shore and damaging boats passing over the site.

The $150,000 Mary Jo Garreis Memorial Reef northeast of Gibson Island is envisioned as the latest piece of a plan by the Magothy River Association to plant millions of oysters in the river in an effort to clean the water.

But problems with the reef began almost as soon as work began.

"It turned into a mariner's hazard," said Jerry Smith, the president of the Sillery Bay-Hunters Harbor...