NAPA — A planned redevelopment project along the Soscol Avenue-Silverado Trail approach to downtown will be scrutinized by the Planning Commission Thursday night.

The city wants to use redevelopment financing to correct the area’s drainage and traffic problems. With these impediments gone, businesses and homeowners are expected to invest private dollars to revitalize what is considered an under-performing, blighted zone.

The Soscol Gateway Redevelopment Project has been under study for almost two years, with the city spending nearly $300,000 for a stack of studies.

A draft environmental impact report and a draft redevelopment plan covering 376 acres will be reviewed by the Planning Commission at 7 p.m. Thursday at City Hall, 955 School St.

Napa last attempted a redevelopment project some 40 years ago when it remade the downtown business district, clearing older buildings for new stores and installing brick sidewalks up First Street.

That was redevelopment at its most robust. The city took a leadership role in downtown’s commercial makeover, generating controversy that lingers today.

Soscol redevelopment would be significantly different, city officials say. Instead of buying land, sometimes through condemnation, for new commercial development as was done downtown, the city would focus on solving infrastructure problems, leaving it to the private sector to upgrade businesses and housing.

By creating a redevelopment project, the city would be able to tap most of the area’s growth in property tax revenue to pay for drainage and road improvements.

Under the latest estimate, some $37 million would be spent on siphoning off runoff from the eastern hills and street upgrades.

Soscol Avenue between Silverado Trail and Third Street would remain four lanes, with a landscaped median. A turn lane would be built on Silverado between Soscol and Third.

Another $8 million is targeted for three new roads, two of which would connect Silverado to Soscol; $3 million to underground utilities, and $30 million for other road work, riverfront enhancements and potential parking garages someday in the Oxbow District and near the planned transit village next to Napa Valley Exposition.

These are rough estimates. Additional studies will be needed in coming years to determine exactly what gets built, said Jennifer LaLiberté, the senior project coordinator for the city’s redevelopment department.

The five-way intersection at Silverado/Third/Coombsville is identified as desperately in need of re-engineering. It cannot handle today’s traffic, much less the traffic to come, a consultant said.

In the draft EIR, the city says it will work with Caltrans, which owns Silverado Trail, a state highway, on a solution. Elements of a solution include a second through lane on Silverado, both south and north of the intersection; conversion of East Avenue to one-way eastbound, and a second lane for Coombsville westbound at the intersection.

After the Planning Commission reviews the project Thursday, the City Council is scheduled to hold a workshop at 3:30 p.m. on Sept. 18. A hearing to adopt the plan is set for the evening of Oct. 16.

The city had hoped to set up the redevelopment project earlier this year, but paused when the county said the EIR didn’t fully address traffic issues.

After performing more traffic analysis, the city agreed that area traffic would get worse before it got better because funding for street improvements would lag new development.

To address concerns that private redevelopment could result in a loss of housing, the city wants to rezone both sides of Third Street between the Expo and the railroad tracks for multi-family housing.

Higher density housing is also planned around a proposed transit center on Burnell Street, opposite the Expo’s western boundary.

Air quality would suffer, with some “hot spots” near some high-traffic intersections, according to the draft EIR.

The city is considering mitigation measures to encourage bicycling and transit use.

Twenty percent of future increases in the area’s property tax revenue would go to promote affordable housing in the city.

The redevelopment project would have a 45-year life. The city would likely sell long-term bonds to finance infrastructure improvements.

If the city adopted the Soscol redevelopment project this fall, the first work — drainage — could occur in about five years, LaLiberté said.