Ocean imports from China to U.S. East and Gulf Coast ports soared in the first half of the year, while imports to U.S. West Coast ports declined, according to report from Zepol Corp., a Minneapolis-based consultancy. Zepol says this trend is a possible sign that U.S. importers are continuing to divert cargoes from the West Coast long after the end of the labor-management strife that plagued ports there earlier in the year.

The report found that Chinese imports to East Coast ports through July 8 rose 20 percent from the same period in 2014, while imports to Gulf Coast ports jumped 43 percent. By contrast, Chinese imports into West Coast ports declined 3 percent year-over-year.

Total import traffic, which covers other regions besides Asia, into the East Coast rose by 15 percent year-over-year, while import traffic into the West Coast dipped 4 percent, Zepol said. The firm generates its data through bills of lading from U.S. Customs and Border Protection (CBP). The percentages are based on 20-foot equivalent unit (TEU) container traffic.

The ports of Houston; Savannah, Ga., and New York and New Jersey showed strong gains, with Savannah reporting a 32-percent gain in total imports, Houston posting a 26-percent increase, and New York/New Jersey reporting a 12-percent increase. Chinese imports into Houston soared 53 percent year-over-year, Zepol said.

Zepol said upgrades to the Suez Canal and more sailings with larger vessels to the East Coast have been key factors in luring Asian imports to the East and Gulf coasts. The firm said it could not determine how much additional traffic bound for East and Gulf Coast ports were composed of goods that would have normally called at West Coast facilities but were diverted because of the labor problems there.

An 11-month contract standoff between the International Longshore & Warehouse Union (ILWU) and ship management represented by the Pacific Maritime Association (PMA) led to massive vessel delays and shipment backlogs until a new 5-year contract was agreed to in February and ratified by both sides in May. However, many importers before and during the impasse had diverted cargo away from the West Coast to ports in the East and Gulf regions.

While some of that diverted freight returned to the West Coast, much has not. For example, through the end of May, Savannah had reported three consecutive months of all-time record monthly volumes. The port experienced meaningful gains in diverted traffic from the West Coast, but couldn't quantify the increases.