San Diego International Airport officials are expected to get the green light this week to build an $80 million mega parking structure on North Harbor Drive – with a curious caveat. They must encourage the public not to use it.

Staff at the California Coastal Commission is recommending board approval for the three-story, 3,000-space garage that will service Terminal 2 if, and only if, the airport agrees to several conditions – many centered on encouraging people to take public transit to the airport, bypassing the need to park there.

The conditions mark a compromise between the two agencies, which have been wrangling over the garage for months. A flurry of letters between the airport and Coastal Commission staffers – whose job it is to enforce the state’s Coastal Act – show the commission pushed for a better explanation of why the garage was needed.

Commission staffers also wanted to know what had changed since 2009, when airport officials said they wouldn’t build the parking garage in order to encourage passengers to use public transit, rideshare and private parking lots away from the coast.

“This will be a major airport terminal expansion encouraging airport users to utilize existing public transportation rather than expand vehicle parking,” airport planning Manager Ted Anasis wrote March 27, 2009, during permit talks for the $1 billion Green Build project. “SDIA must consider this approach in order to reduce passenger and employee reliance on individual automobile use that requires vehicle parking.”

In a June 4, 2009, letter, Anasis added, “By not providing enough parking at the terminals currently, airport users have necessarily shifted to numerous options for ground access to the airport terminals, many if not all of which contribute to the advancement of the very Coastal Act policies in question here.”

Airport officials now say the garage is needed and will actually reduce traffic on North Harbor Drive. Someone who can park next to the terminal will take only two airport trips, one to arrive and one to depart, whereas someone using a rideshare service or catching a ride with a friend requires four trips, the thinking goes.

“In deference to the other agencies and the public, the airport was willing at that time to consider the possibility that limiting parking may increase transit use, and we agreed not to build the Terminal 2 parking structure at that time and study the matter further,” airport Spokesman Jon Heller said in a statement. “Fast-forward to today. Our passengers’ reaction to limited parking over the past six years strongly indicates that limiting parking does not increase transit use at San Diego International Airport and additional parking facilities are, in fact, needed.”

Heller said less than 2 percent of passengers use public transit to get to the airport, a level that remained consistent even when the parking inventory was drastically reduced in 2012 and 2013 with the closure of Terminal 2’s surface parking lot for construction.

“Clearly, limiting parking – or even eliminating parking – does not increase transit use at (the airport) and additional parking is warranted,” he said.

Parking is one of the airport’s three top moneymakers, and brought in nearly $39 million in fiscal year 2014. The parking and ground transportation cash makes up nearly 20 percent of all operating revenues at the airport, with other major revenue streams coming primarily from airlines and concessions.

Terminal lots, including the site of the planned parking garage, can demand a premium of $30 to $38 per day for the convenience, whereas airport lots further afield cost as little as $13 a day.

But the state is on a mission to reduce reliance on cars and thus, lower greenhouse gas emissions, and Coastal Commission staff wanted to know what the airport has done since it pledged to help increase public transit connections to the airport in 2008.

On this point, airport staffers have little to show for the last several years and lay some blame at the feet of the region’s transit agencies. It’s true, the airport’s funds are quite restricted due to federal aviation spending rules, limiting what transit projects can be funded off airport property. But airport officials put forth several initiatives they said would help encourage transit use. Just one is active today – and just barely.

An employee transit incentive program that covers half commuting costs is being used by 19 out of 393 employees, airport officials said. Another initiative – giving trolley passengers a shuttle ride from the Middletown Station to the terminals – is nearly up and running.

Three others are in a holding pattern or were piloted, then quickly canceled, like an employee shuttle that ran between Old Town Transit Center and the airport eight times a day for a year and a half before it was shut down in June 2010 “due to consistently low ridership.” Only six employees rode the shuttle daily, Heller said.

The Coastal Commission is requiring the airport to consider reviving and expanding that program to passengers as a condition of the parking garage approval.

Plans to put remote parking lots in North County with shuttle service to the airport are still being analyzed, with focus turning to spots along Interstate 5 and Interstate 15, such as the Escondido Transit Center, officials said.

The Coastal Commission is also requiring the airport:

• More prominently link transit options for passengers on the airport website, including bus service provided by MTS and planned airport shuttles

• Launch an in-airport advertising campaign, complete with posters, commercials, signs, etc.

• Work with MTS, NCTD and Amtrak to inform train and trolley passengers about the new Middletown trolley shuttle

• Collect and report data annually to the Coastal Commission about the number of people using public transit to get to the airport

• At least 90 days before construction, submit an updated Airport Transit Plan to the Coastal Commission “documenting the current status of efforts that have been made to improve existing and add new mass transit linkages to the airport for employees and users.” Annual progress reports to the commission are also required and will be used to evaluate future coastal development permit applications.

The airport will also need to provide a list of efforts made to collaborate with regional transit agencies toward getting the long-planned Intermodal Transit Center built on property just north of the airport in future permit applications.

The parking plaza will cost $80 million to build and is geared for passengers traveling for only a couple days, and for those picking up family and friends who need a parking spot for a couple hours or less.

The garage was initially scheduled for Coastal Commission approval in July, and an opening in June 2017. If the Coastal Commission board and airport both agree to the conditions this month, it should take two years to complete the project.

The commission meeting is scheduled to hear the parking garage item on Thursday at the Chula Vista City Council chambers.

Clarification: An earlier version of this post said the Coastal Commission would hear the airport item on Wednesday. The commission begins a three-day meeting Wednesday; the airport item is set to be heard Thursday.