The "test pit" phase of utility work along Centre Street is over. Which means we can get ready for the real headaches to begin. Starting this week — and continuing for four to six months — work begins in earnest on replacing the neighborhood's ancient cast-iron gas mains with plastic ones. What this means is plenty of disruption along Centre Street through Hyde and Jackson squares. National Grid will replace 2,100 feet of natural gas pipe along the south side of Centre from Sheridan to Wise.