STAMFORD -- Metro-North Railroad is shuffling its New Haven Line schedule later this month to begin a $104 million project to modernize worn out overhead catenary lines that power trains between Fairfield and Bridgeport.

The work is the next phase in a 20-year project that began in 1998 to overhaul the New Haven Line's overhead power system from just south of the New York line to near Milford, according to Metro-North Railroad. Some sections of the wire system date back almost a century, according to the railroad. Another section of the project between Courtland Avenue in Stamford and South Norwalk is expected to be finished this fall.

Beginning Aug. 30, the railroad will close two of four tracks on the New Haven Line between the Southport station and Bridgeport impacting the arrival of peak New Haven Line trains, with trains leaving as much as six minutes earlier or up to 14 minutes later, with lesser effects on Harlem and Hudson line trains, according to the railroad.

The work will be complete in 2012, Metro North Railroad spokeswoman Marjorie Anders said.

"There aren't any fewer trains but they have been moved around," Anders said.

Other adjustments will include customers on previously direct runs will be required to change for connecting service at the Stamford station and passengers will have to board from temporary platforms at some stations, according to Anders.

In Stamford, 11 New York-bound trains between 6:40 a.m. and 9 a.m. will have slightly modified departures from between 2 and 7 minutes, under the new schedule.

In the afternoon, 15 return trains stopping at Stamford during the 4 p.m. and 8 p.m. peak period will have schedules altered less than five minutes.

While disruptive, Connecticut Rail Commuter Council Chairman Jim Cameron said that the replacement of wires is necessary and will benefit commuters with a dramatic reduction of wire breakages once work is complete. However, Cameron said riders should expect the reduced amount of track space to compound delays caused by breakdowns during the work.

"There is no doubt that the work is necessary," Cameron said. "It is a major challenge for them to run a four-track railroad with just two tracks. Commuters are creatures of habit so that's why it is so important to communicate to them what is happening with this."

The entire catenary project which is expected to end in 2018 with installation of a new overhead catenary system from Bridgeport to the Devon section of Milford will cost a total of $878 million, involving the stringing of 178 miles of overhead catenary wire and other infrastructure, and the replacement of 19 railroad bridges on the New Haven Line.

The Southport to Bridgeport stretch will include overhauls of five railroad bridges, Anders said.

During the work there will also be a new 4:43 p.m. direct train from Grand Central Terminal added to serve destinations on the New Canaan branch.

Additionally between Sept. 13 and November 19, the railroad will begin a 16 week-period of busing on the Danbury Branch on weekdays from 9 a.m. to 4 p.m., and on the weekends of Sept. 18, Sept. 25, Oct. 2, and Oct. 9, which will allow work on a $63 million project to install an automatic switching and signalization project on the single track line.

The line averages about 70,000 riders a month, according to the state Department of Transportation.

New timetables will be available in Grand Central and outlying ticket offices beginning next week, or can be viewed at www.mta.info/mnr.

Staff Writer Martin B. Cassidy can be reached at martin.cassidy@scni.com or (203) 964-2264.