Downtown Ventura may be rich in history, but it also has a wealth of near- historic pipes.

Antiquated cast-iron water and sewer pipelines have long needed to be replaced along stretches of Main, Oak and California streets — in the heart of downtown.

Construction crews are scheduled to begin replacement work in two weeks.

Merchants and restaurateurs, already seeing profits dip under a sluggish economy, will now get 100 days of jackhammers, orange cones and construction noise.

"It will be a blow," said Joe Beltran, a saddle maker and owner of Ventura Leather. He estimated his retail sales this year are already down 10 to 15 percent from last year.

It could be worse. City officials, sensitive to the intrusion, agreed to wait until after the holiday shopping season and vow to be done by the time summer crowds arrive.

"We know the merchants and others don't want us down there any more than we have to be," said Brad Starr, a principal city civil engineer.

To reduce traffic delays and disruptions, the city crafted a special contract with contractor Mge Underground Inc. of Paso Robles. The stipulations include:

- Most of the work along Main Street will be done between 7 p.m. and 7 a.m.

- Crews will work only Sunday through Thursday.

- All extremely noisy work — jackhammers, compressors, asphalt and concrete saws — must be silenced by 10 p.m.

- Crews will concentrate on a block at a time, and work on no more than two adjacent streets at any one time.

- Daytime work on portions of Oak and California streets near residences will be restricted to 8:30 a.m. to 4:30 p.m.

- Sidewalks and off-street parking will remain open throughout construction.

- The entire $1.75 million project must be completed in 100 days, or the contractor could face late penalties.

"This is the oldest part of the city," said Mark Quady, a construction engineer, who dated the existing pipes back to the 1920s and '30s.

Because much of the project is within blocks of the San Buenaventura Mission and historic mission plaza, an archaeologist and Chumash representative must monitor the underground work in case a cultural resource is unearthed. That could add delays, Starr said, although much of the work area has been dug up in the past.

"The biggest challenge is going to be keeping the businesses happy," said Burt Yanez, a construction inspector.

The city sent 2,000 mailers to downtown addresses this week. Some business owners complained they should have received more notice and expressed shock when asked about the coming work.

"I have been told absolutely nothing," said Carol Barcellos, owner of B. on Main, which sells eclectic gifts and decorative accessories in the 300 block of Main. Once told of the stipulations, however, Barcellos applauded the plan. Her biggest sales months are July and December.

"It's fantastic they are doing most of the work overnight," she said. "It sounds like they are doing everything they can to keep it from impacting us as much as possible."

The Downtown Ventura Organization will provide weekly updates on its Web site at http://www.downtownventura.org.

"No one likes the idea of the street being torn up, but this work has to be done," said Jerry Breiner, chairman of the organization's downtown operations team. "The important thing is that it is completed in a timely manner."

The replacement pipes will improve the reliability and capacity of both sewer and water pipelines. Larger, noncorrosive plastic pipes will be installed. About 4,800 feet of water pipes and 2,700 feet of sewer pipes will be replaced.

The streets will be repaved in September, after the Ventura County Fair, Starr said.