A new group is declaring war against an initiative that would torpedo the 3,200-home Napa Pipe proposal, and the battlefield is your mailbox.

A group called Keep Napa Napa — funded in part by the Napa Pipe developers — is mailing Napa County residents a letter announcing its intentions to help defeat the Responsible Growth Initiative. That initiative is modeled after 1980’s Measure A , which created a 1 percent cap on residential growth in Napa County, but also contains restrictions on the height of future buildings.

In the three-page letter, ex-Napa mayor Ed Henderson, Vallerga’s President Ray Sercu, vintner Elaine Honig and grapegrowers Francis and Kathleen Mahoney, among others, sign a missive that accuses the backers of the Responsible Growth Initiative of staying in the shadows and trying to threaten Measure J agricultural protections.

“It is clear the measure has unintended impacts, or worse, is driven by deliberate ulterior motives,” the letter states. “This measure could lead to dense development and crowding within the city of Napa’s quiet residential neighborhoods, where it would cause the biggest problems. It could generate countywide impacts that would increase traffic. And, it could endanger our county’s long-standing policies for protecting open space, scenic hillsides and agricultural lands.”

Napa attorney James Marshall stepped forward in late November, saying he and a small group of locals are behind the Responsible Growth Initiative. Marshall said the Napa County Board of Supervisors sparked the move when they voted, 3-2, to send the Napa Pipe proposal through a public process of environmental review.

Marshall was not immediately available for comment Wednesday.

In an interview last month, Marshall said he and his colleagues were galvanized by the county’s green light for the early stages of study for Napa Pipe.

“I’ve never participated in any election or someone’s campaign,” Marshall said Nov. 28. “The more people I talked to about this proposal (Napa Pipe), I couldn’t find anybody who was in favor of it.”

Napa Redevelopment Partners proposes 3,200 townhomes, as well as restaurants, a condo/hotel, light industrial uses and a park-like riverfront on the 152 acre property south of town that is the historic site of Kaiser Steel. The property is outside Napa city limits, and so has drawn fire both for the scope of the development proposal and for questions about whether it is an appropriate use of the land.

The backers of Keep Napa Napa charge the public has no clue who is really behind the initiative.

“All we know right now is that nobody with a history of working on behalf of local communities and the environment is involved in this initiative,” the letter reads.

Henderson, Sercu, Honig and the Mahoneys are joined as signatories to the letter by Napa Dr. Marko Boder, Laurie Gordon, Ira Lee, and Kathleen Migliavacca.

Marshall said backers of the Responsible Growth Initiative include retired attorney Frank Worthington, Napa Valley College swim instructor Kathy Hague, Dan Sullivan and Steve Morgan. Political strategist Victor Ajlouny, who worked on Supervisor Harold Moskwite’s 2004 campaign, is also involved.

Marshall said he hired Republican signature-gathering juggernaut Arno Political Consultants for the signature drive, and top-flight Sacramento election law firm Bell, McAndrews, Hiltachk and Davidian to write the initiative. Bell, McAndrews represented Moskowite in the case arising from his close 2004 election victory over then-Supervisor Mike Rippey.

Keep Napa Napa was unabashed in revealing Napa Redevelopment Partners, the Napa Pipe developers, as part of its funding source.

“To defeat this hatched-up, backroom scheme — a scheme that takes a meat cleaver approach to planning for our future — we are working with local leaders and citizens,” the letter reads.