A sharp dispute is brewing in the Capitol over a plan pushed by the Los Angeles Department of Water and Power to ease new state rules over the way power plants use ocean water to cool their engines.

Three plants affected by the new rules – Harbor, Haynes and Scattergood – provide nearly 40 percent of Los Angeles’ available power generation and are critical to the stability of the grid, according to the DWP.

Environmentalists say a hastily amended proposal – it was written Friday – would unravel regulations that took the state water board five years to develop and would violate established state and federal policy. The debate is one of several related to environmental protections that are emerging in the Capitol as the final days of the legislative session get under way.

The issue is called “once-through cooling,” or OTC, which is the practice of power plants to suck in sea water to cool their machinery and expel it back into the ocean. Rules approved in May by the State Water Quality Control Board require restrictions on the practice to be in place within the next few years – by 2015 at Harbor, 2019 at Haynes and 2020 at Scattergood. The DWP proposal would push back the compliance date until 2031, according to DWP. A detailed description of the DWP’s position is available here.

Allowing DWP to extend the compliance until 2031 is “necessary and fair,” the utility said, citing the need to balance costs and the provide reliable power to ratepayers. “LADWP is in the process of building a cleaner, greener Los Angeles for the next 100 years. There are multiple environmental issues that LADWP faces.” The utility said some $2.2 billion in additional costs could be at stake if the new regulations go forward.

But environmentalists are angry, in part because the DWP bill was hijacked – known in the Capitol as a “gut and amend” – by removing the contents of an existing bill, AB 1552 by Assemblyman Steve Bradford, D-Gardena, the chair of the Utilities and Commerce Committee, and inserting completely new language.

The original bill dealt with the ability of non-profit charities to obtain electrical service. The new bill, which is viewed in the Capitol as a committee bill, is awaiting action in the Senate Appropriations Committee.

“They said they wanted to make minor changes (to the water board regulations), but sadly what they are doing is eviscerating the policy for LADWP’s interest, and they did it in a way that totally blindsided us,” said Jim Metropulos of Sierra Club California.

They also note that the confirmation of Charles Hoppin, the chair of the State Water Resources Control Board who played a significant role in the new regulations, is awaiting action on the Senate floor.

At least four other government offices – the State Lands Commission, the California Energy Commission, the Public Utilities Commission and the Independent System Operator, which supervises California’s electricity grid – worked with the water board as the regulations were being put together.

The U.S. Environmental Protection Agency also was consulted – indeed, the new rules were written at least in part to satisfy the EPA.