Response from 4 Fire Departments and CalFire dropped Boron from the air..,..
SF Gate reported “cause unknown”, but we know. Report below:

A fire that started in a Vallejo park quickly spread Tuesday afternoon, forcing the evacuation of residents on a street adjacent to the park, Vallejo fire officials said.
Firefighters responded to reports of a fire at Hanns Park in Vallejo at 5:55 p.m. that spread north from the park and threatened a number of homes on Creekside Drive, said Vallejo Fire Public Information Officer Kevin Brown.
Residents along Creekside were asked to evacuate their homes, and the rear side of two houses suffered exterior damage from the flames, according to Brown.
Fire departments from Benicia, Crockett, American Canyon and Fairfield also responded, along with air support from CalFire, to help put out the fire.
No injuries were reported, and the cause is currently unknown.
The four-acre fire was contained and no active flames seen as of 7:25 p.m., Brown said, and residents are expected to return to their homes shortly.

Here is some additional information:

*The previous fire in Hanns Park occurred on Fri July 26, no structures were damaged but at least two acres burned on the South slope of Blue Rock Spring Creek.

*GVRD scouted the Park and posted the No Camping/Cleanup signs at camping sites on Mon July 29; I saw two camps posted but there may have been more.

*On Tue Aug 13 the second fire occurred. Here is a news clip from KPIX 5: https://sanfrancisco.cbslocal.com/2019/08/13/4-alarm-grass-fire-burning-in-vallejo-threatens-homes-near-hanns-park/

*Today Thur Aug 15 homeless camps tagged on Mon Jul 29 have not been visited/cleaned up. Previous camps posted on this site which CSS confirmed vacated have been reoccupied.

Net result is that no action may have possibly led to person property damage due to the second fire on Aug 13. I have scoured news sites for an official cause of the fire but no information is available as of yet.

Included is a photo from the paved trail taken this AM.

The City of Vallejo has to do something with these homeless encampments. Does the City want another "Paradise Fire" here in Vallejo? Enough is Enough.

Code Enforcement Division assigned this issue to Christina E., Community Services Section (CSS)

One word for the city of Vallejo, “liability”, as for the parties responsible for the fire, they will never be held accountable.

Agree Artsem, in this instance doing nothing could become very costly to the City. Not to mention that the average cost of each homeless person to the community is between $60-90K/year for:

*Hospital visits
*Police, fire, paramedic attention
*City services to clean up after them, repair damage, etc.

This "hands off" policy is going to continue to put pressure on city resources as they "react" to the issue and have lasting negative impacts on the community. Very sad.

Here’s what Justine wrote on the other post I entered about this fire and the homeless encampment in Hanns Park

Thanks for reporting this issue! The Police Department's Community Service Section (CSS) has opened a case for this issue. CSS has one part-time and three full-time employees who are responsible for addressing all quality of life concerns, supporting Neighborhood Watch groups, and working with the Neighborhood Law Program and Code Enforcement to address distressed and dangerous properties. We work hard to investigate each report in a timely manner, and will investigate this report as soon as we possibly can. Please keep in mind there is a lengthy process to remove illegal encampments. If you have any questions, please call our office at (707) 553-7218.

If you witness any suspicious or criminal activity that requires an immediate response, please call 9-1-1.