A Northern California fire department says Verizon slowed its wireless data speeds to a crawl last month, rendering some of its high-tech tracking equipment almost useless as firefighters battled the largest wildfire in state history.

In an August 20 court filing, Santa Clara County Fire Chief Anthony Bowden said his department relies on internet services to keep track of fast-moving fires and coordinate resources and efforts among emergency personnel.

"The Internet has become an essential tool in providing fire and emergency response, particularly for events like large fires which require the rapid deployment and organization of thousands of personnel and hundreds of fuel engines, aircraft, and buIldozers," Bowden wrote.

This requires a lot of data. Bowden wrote that his department's OES 5262 mobile communication center sent and received five to 10 gigabytes of data through a wireless router each day while tracking the response to the Mendocino Complex Fire.

That fire has burned 406,532 acres in Northern California.

Service slowed to dial-up speed

The department had an unlimited government plan with Verizon, but the company would slow, or "throttle," data speed once the agency crossed a certain threshold, Bowden wrote.

"In the midst of our response to the Mendocino Complex Fire, County Fire discovered the data connection for OES 5262 was being throttled by Verizon, and data rates had been reduced to 1/200, or less, than the previous speeds. These reduced speeds severely interfered with the OES 5262's ability to function effectively," Bowden wrote.

Santa Clara County Fire Capt. Bill Murphy told CNN that the department's connection speed dropped to what you would expect from a dial-up service, making simple tasks like sending an email or updating a Google document almost impossible.

Verizon: 'We should have lifted speed restriction'

The document included an email chain that showed that the fire department had been working with Verizon to solve the throttling problem before the Mendocino Fires started and that Verizon did not lift the data caps until the fire department paid for a more expensive plan.

In a statement to CNN, Verizon spokeswoman Heidi Flato said the company made a mistake.

"Regardless of the plan emergency responders choose, we have a practice to remove data speed restrictions when contacted in emergency situations," she said in an email. "We have done that many times, including for emergency personnel responding to these tragic fires. In this situation, we should have lifted the speed restriction when our customer reached out to us."

She said Verizon is reviewing the situation and "will fix any issues going forward."

Bowden said that his firefighters had to use other agencies' internet connections or their own personal devices to keep their communication system running.

Bowden's statement is included in an addendum to a brief in a federal lawsuit to overturn the Federal Communications Commission's repeal of net neutrality rules.

Flato told CNN that this is a customer service issue. "This situation has nothing to do with net neutrality or the current proceeding in court," she said.

An FCC spokeswoman stressed the importance of cooperation.

"It's important for communications providers and public safety agencies to work together closely to ensure that agencies have communications services that meet their needs, especially in emergency situations. In addition, we strongly encourage communications providers to waive data allotments in situations involving emergency response," she said.

Firefighters found workaround

Murphy said that firefighters were able to work around the problem by using their own devices, but he is concerned about what will happen if others see their data throttled during an emergency.

"We're putting a lot of information out there for the public to receive and the expectation is that they will get it in a timely fashion," he said. "We believe it's very important that the public have unrestricted access so they can get the information we need them to get."

Murphy says the department still uses Verizon and has added a second provider to ensure redundancies in their system.