LOWELL -- Catholic parishes in Littleton, Lowell, Westford and Wilmington are among those being grouped together as part of a plan by the Archdiocese of Boston to combine some parish operations to save resources.

In Lowell, a new group, or collaborative, will include Immaculate Conception, Holy Trinity and St. Anthony parishes. St. Dorothy and St. Thomas in Wilmington will be paired, as will St. Anne in Littleton and St. Catherine in Westford.

Those churches are part of 21 new collaboratives that include 44 parishes in the second phase introduced by the archdiocese. The new groups will be inaugurated next June, with the archdiocese planning to name new pastors for each collaborative by Christmas.

Each church will keep its name, building and financing, including assets and obligations. But they will have some combined staff, including a pastor, clergy, pastoral team and council, and pastoral plan, which the churches will jointly create once the collaborations are official.

Some Mass schedules may need to be adjusted as part of sharing resources, the archdiocese says in its question-and-answer guide.

St. Dorothy and St. Thomas in Wilmington have already combined their ministry and staff, said the Rev. Philip Earley, who has been the pastor of both churches for more than two and a half years.

"We've already built one pastoral staff to serve both parishes," Earley said. "We're pretty far down the road."

Combining finances in each collaborative will mean churches in better financial standing will have to support those in worse shape. Such in the case in each collaborative in greater Lowell.

St. Catherine in Westford, which is far larger than St. Anne in Littleton, had a $34,000 profit last fiscal year, according to the archdiocese. St. Anne had a $48,000 loss.

In the Lowell collaborative, the largest church, Immaculate Conception, had a $224,000 profit last year. But Holy Trinity had a $11,000 loss and St. Anthony had a $62,000 loss.

Once each collaborative is formed, parishes will spend two years drafting a pastoral plan to be presented to Cardinal Sean O'Malley for approval.

The first phase of grouping parishes together combined 28 churches into 12 collaborations and went into effect in June 2013. Three Billerica parishes -- Saint Mary, Saint Theresa and Saint Andrew -- were combined into a group in that phase. The archdiocese says it plans to ultimately do seven phases.

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