Napa County is undertaking a sizable effort this year to tighten enforcement of limits on how much local wineries can grow. But with less than three months until a deadline to file for permit modifications, there’s growing concern among the small cadre of professionals usually tasked with such documentation about meeting the deadline.

Vintners concerned that their current county entitlements for such business aspects as gallons of wine produced and numbers of events held, visitors per day and workers employed aren’t in line with what’s actually happening have until March 29 to apply for fixes to their use permits.

And also key to the new county policy the Board of Supervisors unanimously adopted Dec. 4 is that local producers will have to start sharing with county officials as of July 1 their federal and state reports that detail wine and grape production volume.

“Most wineries don’t understand their federal report,” said Ann Reynolds of Wine Compliance Alliance.

But a regimen for reporting how many visitors show up at a winery, one of the key concerns that has driven this effort, was softened in the new policy. Mandatory reporting changed to a lengthening of the application period to 90 days before a temporary event. Repeat offenders of visitation limits are barred from permits.

“That may sway people toward going in for a modification,” said Joshua Devore, an attorney with Dickenson Peatman & Fogarty in Napa.

Part of the stated goal of the new policy is to encourage vintners to participate. One county planning official publicly estimated the number needing such permit adjustments could exceed 300.

“There are not enough consultants to handle all this work,” said Donna Oldford, who runs St. Helena-based land-use planning firm Plans 4 Wine.

Long-standing county policy has called for a major modification to a winery use permit when there is an increase in employees, visitors, events or production. Sometimes, Oldford’s bill for preparing an a modification application is more than for a new facility, because of the required site plans and technical reports on water use, traffic, wastewater treatment and site grading. Those can take four or five months to prepare.

“I won’t do one now, except for existing clients,” Oldford said. She estimated that three-quarters of her clientele need such help. “The day after the Board of Supervisors meeting, I had 41 calls on my voicemail, and I had to tell them no. It will be a major quagmire. ... You can’t do little or no code enforcement for 30 years and turn that ship around in a year.”

The new county policy does allow for up to five months after the March deadline to submit all documentation for a permit modification, but some professionals are concerned about what will be deem the applications substantially complete by the initial cutoff.

Wineries can also apply for a use-permit evaluation, to have county officials determine whether they are in compliance.

One of the penalties for not seeking a modification by the March deadline is locking in existing permits for one year before a vintner could seek modifications. But with approval times for permits at times stretching well beyond a year, some consultants wonder whether this penalty really has teeth.

Yet these provisions are part of a “good balance of carrots and sticks” county officials have tried to create with the new policy, according to Rex Stults, industry relations director for Napa Valley Vintners, a trade group with about 500 members.