Import cargo volume at the nation’s major retail container ports has returned to normal levels following ratification of a new West Coast labor agreement, according to the monthly Global Port Tracker joint report released Tuesday by the nation’s retailers and maritime industry researcher Hackett Associates.

“Despite some lingering labor issues, the volume of cargo and the rate of growth have both largely settled down,” said National Retail Federation Vice President for Supply Chain and Customs Policy Jonathan Gold. “There are still congestion issues to be dealt with, but we’re hoping to see reasonably normal back-to-school and holiday seasons this year now that the tensions of contract negotiations are behind us.”

The Pacific Maritime Association and the International Longshore and Warehouse Union both voted in May to ratify a new five-year contract agreed to in February. The lack of a contract and operational issues led to crisis-level congestion at West Coast ports after the previous agreement expired last July, resulting in longer than usual times for trucks to deliver and pickup cargo containers.

The slowdowns at West Coast ports in the first quarter of the year also were blamed for the nation's gross domestic product shrinking at the annual rate of 0.7%.

Ports covered by Global Port Tracker handled 1.52 million 20-foot equivalent units in April, the latest month for which after-the-fact numbers are available. That is down 12.4% from March, when numbers were driven up by a surge of backlogged cargo after the labor dispute ended, but up 6.1% from April 2014. (One TEU is one 20-foot-long cargo container or its equivalent.)

Estimates for May are for 1.56 million TEUs, up 5% from 2014. June is forecast to end up at 1.52 million TEUs, up 2.6% year over year. TEU movements for July through October are also expected to be more than last year.

The first half of 2015 is forecast at 8.8 million TEUs, an increase of 5.4% over the same period last year.

Hackett Associates Founder Ben Hackett said a “stubbornly high” inventory-to-sales ratio after last year’s rush to bring in adequate stocks of merchandise will couple with other economic factors to affect cargo volumes through the summer.

“The West Coast recovery remains sluggish and the East Coast is not managing to hold on to the growth levels it has experienced over the past few months,” he said. “June is going to be a mixed month for the West Coast with volatility between the ports, but July and August are projected to see growth across the board. On the East Coast, we are projecting growth for most ports.”

Global Port Tracker covers the U.S. ports of Los Angeles/Long Beach, Oakland, Seattle and Tacoma on the West Coast; New York/New Jersey, Hampton Roads, Charleston, Savannah, Port Everglades and Miami on the East Coast, and Houston on the Gulf Coast.