Regulated transmission and storage gross profit increased $3.9 million to $60.7 million for the quarter ended December 31, 2012, compared with $56.8 million in the prior-year quarter. This increase is primarily the result of increased revenue from the Gas Reliability Infrastructure Program (GRIP) filing that became effective in April 2012.
Nonregulated gross profit increased $7.1 million to $22.5 million for the first quarter of fiscal 2013, compared with $15.4 million for the prior-year quarter. Realized margins for gas delivery, storage and transportation services and other services decreased $0.7 million quarter-over-quarter, primarily due to a seven percent decrease in consolidated sales volumes, which was largely attributable to warmer weather. Asset optimization margins increased $6.5 million from the prior-year quarter, primarily due to smaller losses incurred from the settlement of financial positions, partially offset by higher storage demand fees. Additionally, realized asset optimization margins in the prior-year quarter included a $1.7 million charge to write down to market certain natural gas inventory that no longer qualified for fair value hedge accounting.
Consolidated operation and maintenance expense, excluding discontinued operations, for the first quarter of fiscal 2013, was $106.5 million, compared with $114.6 million for the prior-year quarter. The $8.1 million quarter-over-quarter decrease resulted primarily from the establishment of regulatory assets for $3.0 million of certain current-quarter costs, a $2.9 million decrease in legal costs and a $1.1 million decrease due to increased capital spending in the current quarter.
Interest charges for the first quarter of fiscal 2013 were $30.5 million, compared with $35.7 million for the prior-year quarter. The $5.2 million quarter-over-quarter decrease resulted primarily from interest capitalized related to Rule 8.209 spending in the current quarter and the early redemption of the 5.125% $250 million senior notes due January 2013, with funds borrowed under a $260 million short-term debt facility in August 2012.