by KYW's David Madden

FOLSOM, NJ (CBS) -- Customers of South Jersey Gas could soon see their monthly bills go up.

In a filing with the New Jersey Board of Public Utilities, South Jersey Gas notes it hasn't raised rates in more than three years.

The company contends it has made $462 million worth of capital improvements since then with another $305 million in the pipeline over the next year.

If approved, the average monthly residential bill would go up a little more than $20, or about 16.5%.

Public hearings would be held before any decision.

The Sierra Club has come out against the proposal, contending some $75 million would go toward a controversial 23 mile natural gas pipeline that could be built through the Pinelands.