The City of Ione has adopted an updated General Plan that predicts population will more than quadruple by 2030.

The plan also encompasses a massive expanse of acreage in what is called a "planning area" for Ione, an area more encompassing than the city's "sphere of influence." The sphere itself is more encompassing than are the city's boundaries.

A related Environmental Impact Report is also certified by city council members to finish a planning process that began some 17 months ago.

Extensive public comment was heard on the two documents.

"The public's participation and contribution has been essential in preserving Ione's history and creating a viable and flourishing community," said Sarah Arvidson, city public-affairs consultant.

The EIR analyzes more than 100 effects that could be caused by Ione's following the new General Plan. It finds that of those, nearly one in five would be "significant and unavoidable" impacts.

Some overlap exists among the specified impacts. For example, several would occur in the related areas of auto traffic and air quality and predict Ione's non-compliance - or contributions by the city to area non-compliance - with state and regional air-quality mandates and requirements by the state and by Amador County in level of service for auto traffic.

"Buildout anticipated under the proposed project would exceed growth protections used in attainment plan development as well as result in substantial increase in (greenhouse-gas) emissions," the EIR states. "There are no feasible mitigation measures to offset the proposed project's increase in emissions. Thus, this impact is cumulatively considerable and significant and unavoidable."

Elevated greenhouse-gas emissions are predicted to stem from substantial population growth.

Current population in Ione is estimated to be around 7,819. That figure includes the 3, 832 inmates at the Mule Creek State Prison and the 440 or so wards at the Preston Youth Correctional Facility.

The 2009 General Plan estimates that the population in Ione will reach 17,258 by the year 2030. But in contrast, that figure excludes populations at state facilities.

Current city boundaries contain 2,904 acres of land. Previously, additional sphere-of-influence acreage was 856. That nearly doubles under the new General Plan, to 1,534 acres. The Planning Area boundary will contain some 31,770 acres, city documents show.

The City of Ione General Plan was originally adopted in 1963. It was last fully updated in 1982. Revisions of individual elements have come between 1982 and the present, including an update of the Housing Element in 2005.