A newly released report says that completing the embattled 10-mile Jefferson Parkway would give a $1.2 billion jolt to Jefferson County over a 20-year period, a nearly 17 percent premium over what the area would receive without the highway.

The report, conducted by Littleton-based Development Research Partners and shared with county officials last week, concludes that the proposed road would boost the amount of office and retail space in the parkway corridor from 2018 to 2037 to 7.6 million square feet from a projected 6.5 million square feet should the highway not be built.

Jefferson County government would also benefit from an additional $25.8 million injection in tax revenues over those two decades — a 23 percent improvement over a non-Jefferson Parkway scenario, according to the report.

“If we do nothing, it’s going to be horrific,” said Jefferson County Commissioner Don Rosier. “Development is continuing to occur and already traffic is getting worse and worse.”

He sees a new high-speed route across the northwest corner of the metro area as a matter of “health, safety and well-being” for those driving or living along roads that are overrun with regional traffic as rooftops continue to multiply in northern Jefferson County, including along Indiana Street, State Highway 93, McIntyre Street, State Highway 72 and Wadsworth Boulevard.

“I don’t want to see another deputy killed on 93,” Rosier said.

But those opposed to the parkway, which would connect Broomfield with Golden, say the real health risks to the public come from its completion. That’s because road construction, they say, could lead to the disturbance and spread of plutonium possibly buried in the soil, a grim legacy of the Rocky Flats nuclear weapons plant that operated just north of Arvada starting in 1952.

“If you move dirt for this highway, you have an even bigger problem,” said Elizabeth Panzer, a member of the Rocky Flats Downwinders. “(The report is) not anticipating the negative impacts from the parkway.”

Panzer said construction of the Jefferson Parkway will likely generate additional class-action lawsuits from those living downwind of the former plant, which was cleaned up more than 10 years ago but is still believed by many to harbor health hazards from the spills and fires that occurred over its 40 years of operation.

Parkway proponents contend that ongoing monitoring of the land surrounding the former weapons facility has yielded no dangerous readings of plutonium or any other contaminant.

The report, authored by economists Patricia Silverstein and David Hansen, focuses only on economic impacts in its analysis. It concludes that the parkway will not only bolster commercial and retail development along the corridor but appreciably speed it up.

“While it is expected that development will eventually occur with or without the completion of the Jefferson Parkway, the parkway will impact development patterns, especially related to the timing and types of uses along the corridor,” the report said.

The report assumes that the parkway will open in 2022. Project officials are still going through the environmental permitting process for the highway.

“The projected $1.2 billion impacts are significant, as they are only measuring the benefits to Jefferson County from three sites,” said Leigh Seeger, interim president of the Jefferson County Economic Development Corporation. “Completion of the beltway will have far-reaching economic benefits throughout the metropolitan region.”

The three areas along the parkway’s alignment that Silverstein and Hansen said would feel the greatest impacts are the Verve Innovation Park and Rocky Mountain Metropolitan Airport site to the east; Candelas in the middle; and a county-owned parcel southwest of State Highway 93 and 56th Avenue on the west.

Specifically, around the airport, the report found the Jefferson Parkway “will enable buildout of the siteʼs aviation, office, and industrial properties within a shorter 25-year timeframe” than would occur under a status quo scenario. Retail and hospitality uses at the site would also get a jump-start with the parkway.

At Candelas, the time to attract regional retail uses and an entertainment district would be halved by completion of the parkway — from 30 years buildout to 15 years, the report says.

Large swaths of land in the corridor — totaling 12,000 acres — will never be developed, according to the report, because they are either inside the 6,500-acre Rocky Flats National Wildlife Refuge or designated as open space.

That puts to rest one of the arguments that many parkway opponents over the years have cited for not building the road, Rosier said — that it will be nothing more than a magnet for suburban sprawl.

“When you take a look at the vacant land out there, most of it is already spoken for,” he said.

That doesn’t mollify Panzer, who lives in Arvada’s Five Parks neighborhood and whose son developed a rare heart-related cancer as a child. She is convinced that residual contamination from Rocky Flats is linked to her son’s health issues.

“Why are government officials so desperate to rewrite history for a cumulative gain over 20 years of $1.2 billion while dismissing whatever negative impacts their actions may cause?” she said.

A state health department study released at the beginning of the year found that some families living in the shadow of the former weapons plant have higher-than-expected incidence of certain cancers, but overall researchers uncovered no evidence to conclude that contamination from the plant has caused a cancer epidemic.

Rosier said if any hazards are detected during parkway construction, an order to halt work will be immediately given.

“We all agree that things will be stopped and corrected,” he said. “Nothing will be hidden; nothing will be covered up.”