Faced with the tall, expensive task of replacing its overtaxed wastewater treatment system, the city of Ouray may soon be weighed down by another financial burden: spending millions of dollars to more rigorously treat its drinking water.

An initial test this spring on Weehawken Spring, which serves as the city’s sole source of drinking water, found the spring to be at high risk of being infiltrated by surface water.

City Public Works Director Joe Coleman said he plans to conduct a second test in...