No sooner than they were closed because of bacteria contamination, all 17 Quincy beaches have passed water quality tests and will be open in time for the first weekend of summer. One beach in Braintree and three in Hingham remain closed.

In nQuincy, bacteria levels at Merrymount, Avalon, Mound and Chickatabut beaches were 10 to 20 times the maximum considered safe.

The water was retested on Thursday and the posting was removed on Friday.

The news isn't as good in two other towns.

Smith Beach in Braintree has been closed since June 13. The bacteria level is almost nine times the limit. Also closed are Kimball, North and Seal Cove beaches in Hingham.

Bacteria levels frequently spike following heavy rains, and the South Shore has had a series of storms over the past 10 days.

See water quality test results for each community and for Cape Cod, the South Coast and North Shore.

For more on Quincy beaches, call 617-376-1288, or visit tinyurl.com/ledger-quincy-beaches. For more on Wollaston Beach, call 617-626-4972.

Seventy-five salt water beaches on the South Shore are tested for enterococci, intestinal bacteria found in humans and animals.

High levels of enterococci indicate the waters may also contain other disease-causing microbes that are present in sewage but are more difficult to detect. Bacterial colonies are filtered from three ounces of water and placed on a gel infused with nutrients and chemicals designed to promote growth.

The rest is here:

13 Quincy beaches reopen; four in Braintree, Hingham still closed