Shares of Parkland Corporation (PKI.TO)(PKIUF) fell as much as 13 per cent on Wednesday as the Calgary-based fuel and retail company forecast weaker third-quarter financial results.

Parkland says it expects to book $325 million in adjusted earnings before interest, taxes, depreciation and amortization (EBITDA), a more than 10 per cent decrease from the $364 million reported in the same period last year.

Speaking on a conference call with analysts, CEO Bob Espey blamed an "isolated incident" where the company's U.S. business held fuel inventory in excess of the company's retail and commercial needs. Parkland says it held this wholesale supply amid falling pump prices, resulting in a $65 million non-recurring loss.

"We saw product prices decline significantly, and in some markets, the declines were greater than the underlying benchmarks," chief financial officer Marcel Teunissen said on Wednesday's call. "It was a black swan event."

"Where we overestimated was in the growing of the wholesale business as large as we did," Espey added.

Parkland says falling gasoline and diesel prices in Canada weakened fuel margins for the company, despite steady demand. At the same time, the company noted its B.C.-based refining business was impacted by higher operating, natural gas, and compliance costs, as well as higher trailing crude prices in a declining market.

Toronto-listed shares fell 10.35 per cent to $26.50 as at 11:53 a.m. ET.

Parkland is known for its On the Run convenience store brand in Canada, as well as its network of service stations under various banners across the country, the northern United States, and the Caribbean. The company also delivers bulk fuels, including heating oil and propane.

Despite expectations for a weaker Q3, Parkland is maintaining its full-year guidance. The company says seasonal heating demand in Canada and a strong start to tourist season in Florida and other international markets bolster its fourth-quarter expectations.

Parkland expects to deliver 2022 adjusted EBITDA within its guidance range of between $1.6 billion and $1.7 billion.

Espey says Parkland is set to report third-quarter financial results in early November.

Jeff Lagerquist is a senior reporter at Yahoo Finance Canada. Follow him on Twitter @jefflagerquist.

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