A housing plan designating sites along Highway 101 in Marin’s unincorporated areas for up to 419 dwellings was approved by county planners Monday.

The Planning Commission unanimously approved the program and passed it on to county supervisors after trimming a proposal calling for 502 units.

The plan specifies sites for 321 low- and moderate-income and 98 market-rate dwellings but does not change development potential already on the books.

Commissioners cut 40 low-income units envisioned for San Rafael’s Cal Park neighborhood off Woodland Avenue, and 43 market-rate units planned by the Martha Co. at Easton Point off Paradise Drive in Tiburon.

Proposals by Commission Chairman Don Dickenson to trim units planned at the Silveira-St Vincent’s ranch tract, and alter plans for Marinwood Plaza by making zoning less specific, failed to gain any support from colleagues.

But plans to wedge 40 low-income units on a 1.8-acre strip between the railroad tracks and the freeway off Woodland Avenue at Cal Park sparked a spirited discussion, with some commissioners worried that the county was giving the poor a raw deal.

“It’s so clear it’s a flood hazard,” Commissioner Ericka Erickson said of the Cal Park site, adding sea level rise was a big concern. “I don’t think it’s a responsible thing. … We should challenge ourselves to find better sites.” Commissioner Wade Holland agreed, noting “it looks like we’re squeezing the poor people between the railroad tracks and the flood zone.”

But several others disagreed. “Just because it’s a flood zone doesn’t mean it can’t be developed,” said Commissioner Katherine Crecelius. Colleague John Eller added that “there’s hardly a site in the county that doesn’t have environmental concerns.”

Commissioner Peter Theran lined up with Crecelius and Eller, saying, “It is buildable, and we have a serious responsibility to provide housing to people of all income levels.” But the three were on the short end of a 4-3 commission decision dropping plans for housing at the site.

Dickenson pressed several other issues, saying a “density bonus” the state gives developers of low-income housing could mean 298 units, rather than the 221 units county policies allow at Silveira-St. Vincent’s. His plan to cut development potential there to 164 units — which along with a density bonus would bring the total back to 221 — failed to gain traction. Likewise, his proposals to increase building potential at Marinwood Plaza from 82 units to up to 100, or up to 85 with a flexible mix of low- and market-rate housing, also fizzled. He later said that housing plans for the plaza may not succeed unless officials ease a specific call for 72 low-income and 10 market-rate units at the site.

More than three dozen residents and organization representatives rose to the podium during a four-hour public hearing. The crowd of about 80 dwindled to one by the time the session concluded after 5:30 p.m.

The commission session marked its third discusson of the program — and the 18th public airing of housing plans that are in most respects the same as plans approved last year.

State housing officials reviewed the 502-unit housing plan whittled down by the commission Monday, recommended minor changes, and indicated the proposal met statutory requirements of state housing element law. Changes made by commissioners were unlikely to change that view. In any event, a comprehensive report by principal planner Leelee Thomas and planner Alisa Stevenson indicated the state’s preliminary review did not prevent county officials from making changes.

The program calls for twice as many units as required by state policies, providing what officials call a “buffer” enabling planning flexibility. The state says Marin’s unincorporated areas need to provide for potential development of just 185 housing units — including 37 moderate- and 87 low-income units — through 2023.

Although several officials worried that extra or bonus incentive units provided to developers of low- and moderate-income housing could open the door for more than 600 dwellings, county staffers noted only a handful of such units have been built in Marin over the past decade.

Speakers, including many who had expressed their views at previous meetings, argued about the program pro and con, with housing advocates saying those who work in Marin deserve a place to live, and high-density foes saying the character of the local neighborhood was at stake.

“We don’t want to have a WinCup located there in the Marinwood area,” asserted Ray Day.

Larkspur Councilman Kevin Haroff warned the county had short-circuited environmental review in violation of state law — and the people’s right to be part of the decision-making process.

“We have thousands of people who work in Marin, who serve Marin, but who cannot afford to live here,” noted the Rev. Carol Hovis, head of the Marin Interfaith Council. “When some of our sisters and brothers are not settled, none of us are settled.”

Commissioner Holland concluded the session with remarks targeting traffic as the problem that has frustrated residents across the county. “We are just choking our streets to death,” said Holland, who last summer called for a building ban in Southern Marin.

Development, Holland added, must be focused along the Highway 101 corridor, as officials envisioned several decades ago in the Marin Countywide Plan, in order to keep West Marin a rural land of wide open spaces.