Prince George's County's chief health officer wants the County Council to prohibit the digging of shallow wells because such wells are likely to provide contaminated water.

Dr. Donald K. Wallace, health officer, said in a letter to Council Chairman William Arnonett that 109 wells of the 154 sampled by his department over the last year and a half produced water containing harmful bacteria.

According to census data, 6,617 of the county's approximately 200,000 households were served by wells in 1970. Most of the wells in the county are the shallow variety - dug 30 to 40 feet deep - that the health officials are complaining about.

Wallace said he sees a health hazard not only to those whose homes use wellwater but also to the county's public water system. He said it is possible for such contamination to occur where homes are served by both shallow wells and a public water line.

According to Wallace, Prince George's has more homes that depend on wellwater than any other Maryland county.

Shallow wells - in contrast to ones that are dug 300 to 400 feet deep - can easily become contaminated with bacteria that breed in the air, soil and surface water, Wallace said.

In his letter, Wallace noted that even after efforts were made to disinfect the 109 wells found to be contaminated in checks over the last 18 months, "only six . . . wells of the 109 produced a satisfactory sample at least two consecutive times."

The health department generally checks water quality when a well is installed or on request from a homeowner, who may want the quality certified when a house is sold. Before approving a new permit for well digging, the department takes two water samples on separate occasions. Both must be found to be satisfactory.

Both Wallace and Jeffrey Rein, environmental health officer, expressed concern about the hundreds of homes in the county that are hooked into the county water system supplied by the Washington Suburban Sanitary Commission, yet still have wells on the property.

According to Rein, homeowners through simple plumbing work can connect their shallow wells to the same pipes that carry public water into their homes, thus making it possible for contaminated wellwater to enter the public system.

"You might get some people who feel their water bill is sky high and who decide to connect their old well to the household plumbing," Rein said. The health department, he said, knows of no households where such a plumbing cross-connection has been made, but added, "the potential is there in hundreds of homes."

Wallace said he is certain that some county residents have become ill because of contaminated well water, but added that statistical data on such cases is difficult to compile.

"Unless a doctor is astute enough to think that the illness might be caused by contaminated water, he won't report the illness to us."

The Council has asked Wallace to recommend ways in which shallow wells might be made safe against contamination before they consider placing an immediate ban on future permits for the wells.

Many homes in Prince George's are equipped with deep wells, which generally produce safe water, Wallace said. Deep wells are less popular among county residents since they cost about $4,000 to install - some $2,000 more than a shallow well.