By the end of the two-hour Costa Mesans for Responsible Government information fair Thursday night, attendees' opinions about high-density housing was clear.

Most of the 50 or more people in the room loudly expressed their dissatisfaction with the possibility of increased traffic and noise that they said would come with high-density developments in the city.

Housing density relates to the number of permanent residential dwellings on a particular area of land.

Costa Mesans for Responsible Government, also known as CM4RG, is a grass-roots, nonpartisan group that frequently disagrees with the City Council majority. Its goal in holding the event was to provide information about how the city plans to update its general plan, members said.

The city has held several community outreach sessions, nicknamed the Great Reach, in its effort to update the general plan, a state-mandated document that acts as a citywide blueprint for land use and safety through 2023.

CM4RG President Robin Leffler explained that the group doesn't necessarily want to sway opinions but rather "provide tools for people to get involved and make up their own mind" about Costa Mesa development.

"The changes I've seen are frightening to me," Eastside resident Jeff McConville said of development plans. "It's not an Eastside or a Westside thing … we're all in this together."

Perry Valentine, who formerly worked in the city's planning department, said Costa Mesa began with large farms in the Eastside, transitioned to residential tracts in the 1950s and 60s, and eventually built multifamily residences.

"We're just about built out now," he said.

Valentine said density of homes increases housing opportunities, common open space, recreational opportunities and walkability for residents.

However, the negative effects of increased housing gained more traction with attendees.

Some shouted in disbelief when speakers presented their calculations for how much proposed housing projects will increase traffic and parking problems in all areas of the city.

Anna Vrska, who serves on the Fairview Park Citizens Advisory Committee, called the situation "a recipe for disaster."

Along with the other presenters, Vrska emphasized the importance of voting in November's election.

"If we don't try to do anything about it, it can't get better," she said.