When members of the group Single Volunteers of D.C. converged on Rock Creek Park two weekends ago armed with rakes and trash bags (and, we imagine, a hope they might finally meet that special someone), a uniformed National Park Service ranger demanded to see their permit. "I had no idea that you needed a permit to pick up trash," says Dana Kressierer, a leader of the group. Kressierer says that the ranger eventually allowed the group to continue its cleanup, but only after listening to a 10-minute lecture and a warning that it shouldn't commit random acts of kindness without the proper paperwork. Cindy Cox, assistant superintendent of Rock Creek Park, says the incident was something of a misunderstanding. The Park Service doesn't require permits, but is does ask do-gooders to complete a one-page form to protect the park against liability. "I wonder if the people who left all this trash to begin with were given such a hard time," remarked Kressierer.