NORTH COUNTY -- The worse-than-usual traffic that has congested Interstate 5 this summer is the start of years of construction delays that ultimately are intended to deliver a 10-lane I-5 north to Cannon Road in Carlsbad.

Regional transportation planners say the $1 billion face-lift should unlock congestion that daily plagues the freeway through much of North County. Meanwhile, local officials and environmentalists hope that planners will keep their promise to pave the way for quieter neighborhoods along the freeway and better-protected coastal lagoons.

"We've got to gear up for it," said Encinitas Councilman Jerome Stocks last week. "We've got about 10 years of construction ahead of us."

The construction kicked off in the spring with a $10 million project that is adding a pair of "auxiliary lanes" -- traffic lanes that start at one exit and end at the next -- between Via de la Valle and Lomas Santa Fe Drive. Those lanes are set to open in October.

No sooner than the painted lines dry on the new pavement, the California Department of Transportation will begin extending the interstate's car-pool lanes, in several phases, from Via de la Valle to Cannon Road. That $1 billion car-pool campaign is expected to keep construction workers busy -- and roads more jammed than usual -- until at least 2015, transportation officials say.

Then, after a brief respite lasting several years, a second $2 billion round of construction is waiting in the wings for the 2020s, officials said.

The whole thing may seem like an awfully long string of traffic headaches to expect coastal commuters to endure, but Caltrans and San Diego Association of Governments officials maintain that ultimately it will make their lives easier. And they say improving the flow on I-5, California's primary north-south artery, is critical to the continued prosperity of San Diego County's $160 billion economy.

Voters are ready

Gary Gallegos, association executive director, said in an interview last week that the economy already is taking a hit because of the swelling gridlock. The huge number of Southern California tourists who love to spend weekends in San Diego -- and go to the beach, SeaWorld or Legoland California -- are choosing to wait until Saturday morning to drive down the coast.

"Because of the congestion on I-5, the tourist industry is losing one night," Gallegos said. "Instead of coming on Friday night, they're saying, 'Hey, we don't want to put up with the traffic.' "

On weekdays, traffic is locking up on the southbound side in the morning and on the northbound side in the afternoon. That, in turn, is creating huge backups on smaller city streets that weren't designed to handle freeway car volumes.

For example, Stocks said, rather than get on the freeway in the morning at La Costa Avenue, where traffic typically screeches to a halt, commuters fan out across his city, flooding Olivenhain Road, Leucadia Boulevard, El Camino Real and Encinitas Boulevard.

And, from La Costa south, traffic crawls for many miles.

Clearly, something needs to be done, said county Supervisor Pam Slater-Price, who represents coastal North County.

"It is a major California resource and asset, and we need to improve it," Slater-Price said.

The supervisor said the coming reconstruction has broad support in the North County community, something she suggests was underscored by voters' recent approval for extending a countywide sales tax and the big state transportation bond on the ballot last fall.

Even environmental groups appear to have resigned themselves to the inevitability of a major expansion. Rather than fighting the project, the Buena Vista Audubon Society, for example, is working with transportation agencies to make it an environmentally friendly project -- and to repair some of the damage that earlier work on I-5 caused to the lagoons.

The columns that support the I-5 bridges across those picturesque bodies of water are spaced so closely that they block much of the natural flow between the ocean and lagoons, said Andy Mauro, conservation chairman for Buena Vista Audubon Society. As part of the widening, Caltrans and the association are proposing to put in new support structures that are farther apart.

"This is an opportunity to fix it, to do it right, to make amends for some of the ills that we imposed on the natural ecosystem," Mauro said.

The Cannon connection

The $10 million auxiliary lane project under construction is scheduled to be completed around Oct. 1. Within days after that, Caltrans plans to launch a $54 million follow-up project that will extend the car-pool lanes that end at Via de la Valle for another two miles, to Manchester Avenue, said Allan Kosup, I-5 corridor director for Caltrans in San Diego.

The cost also will cover a reconstruction of the Lomas Santa Fe interchange, Kosup said.

Gallegos said the interchange will get new loops that allow everyone to turn right onto I-5. Now accessing the freeway from Lomas Santa Fe requires a left turn across traffic.

Kosup said the project should be completed by late 2009.

The $1 billion face-lift also entails extending the car-pool lanes from Manchester to Cannon Road in Carlsbad, as well as $500 million in improvements along Interstates 5 and 805 south of the merge.

The next round

As for the second, $2 billion stage expected to deliver the final I-5 footprint for the foreseeable future, that could get under way in 2020 and take five to 10 years, Kosup said.

The plan is to mimic Interstate 15, with its four so-called managed lanes in the middle geared not only to car pools, but to toll-paying solo drivers and buses with exclusive access to the lanes via ramps coming from transit stations.

The four exclusive lanes would run all the way to Highway 76 in Oceanside.

Unlike I-15, the 5 wouldn't have a movable barrier that enables transportation operators to daily adjust the number of lanes in each direction to reflect traffic flow.

There's a reason for that: I-5 flow tends to be almost even for each direction in the rush-hour, as well at other times, Gallegos said.

He said there is room within state property to build the managed lanes without tearing out the pink, red and white oleanders that color the center of I-5 and, for the most part, without intruding on residential properties.

Transportation officials say they also are considering adding one general-purpose lane in each direction from Del Mar to Oceanside. That would accommodate more cars, said Jack Boda, director of mobility management for the association.

"But that would take us into many backyards," Boda said.

Just how many will be determined by an environmental impact report under development and scheduled to be released late this year, he said.

The ultimate footprint

Coastal North County officials differ on whether the general-purpose lanes should be included.

Stocks, of Encinitas, said they should.

"In general, the more we can reduce the congestion the better the traffic problems will be within the city," Stocks said. "So, I would be inclined to support the 14-lane concept from Camp Pendleton down to the split."

Solana Beach Mayor Lesa Heebner said that she is more inclined to support the alternative that would just add four managed lanes to the eight existing general-purpose lanes.

"It is just too close to the homes," Heebner said.

Slater-Price, the county supervisor, said the bigger version is not only too close, it is too much.

"That is starting to not seem like San Diego," Slater-Price said. "It seems too urban -- too much cement."

Regardless of whether I-5 gets 12 lanes or 14, Kosup said Caltrans intends to pour a significant amount of cement into sound walls that shield nearby established neighborhoods from the ever-increasing freeway noise.

Solana Beach is hoping Caltrans goes one step further. Councilman Dave Roberts said his city wants those new car-pool lanes to be built out of a rubberized asphalt surface made from old tires.

"It is a lot quieter," Roberts said.

Contact staff writer Dave Downey at (760) 740-5442 or ddowney@nctimes.com.