New details have been released about what led to a 10-day boil water advisory in the community of St. Stephen.

The municipality said it received a high turbidity alarm for water coming from its primary well on March 15, which prompted Public Health to issue an advisory.

Officials said turbidity levels returned to normal until four days later, on March 19, when a second alarm occurred.

“At this time, a depression in the ground was observed outside of the primary well,” the municipality said in a statement.

Constructed around 1906, the well is about nine metres wide and nine metres deep, with the bottom open to the gravel aquifer. It has a stone foundation at the base with brick walls to the surface and is covered by a concrete roof.

In the late 1960s, a second smaller well was constructed about 60 metres away and connected to the primary well by a 450 mm diameter pipe that entered through the primary well foundation.

Officials believe the pipe collapsed outside the primary well on March 15, allowing gravel to enter through the foundation opening and leaving a void space over the collapsed pipe.

“The finer particles in the gravel were suspended in the well water for a period of time which triggered the alarm,” said the statement.

It is then believed that the material over the void space collapsed, causing more gravel to enter the well and triggering the second alarm, and leaving the depression outside the primary well to be seen at the surface.

“Multiple days of normal turbidity readings, combined with video observation of the inside of the well suggest that the migration of material into the well may have stabilized for the moment,” the municipality said.

The boil water advisory was finally lifted on March 24 after the community received clean test results from Public Health.

Officials also noted that while the material causing high turbidity levels — in this case, material from the gravel — may not be a health concern, elevated turbidity reduces the effectiveness of water disinfection.

“This is why a boil water advisory is important to protect public health,” said the statement.

Municipal officials said they will work with their engineers and the province to monitor for changes, and develop plans to enhance the resiliency of their water source.