The developer of the Dakota Access oil pipeline missed a year-end deadline to plant thousands of trees along the pipeline corridor in North Dakota. The company said it was still complying with a settlement of allegations it violated state rules during construction.

Texas-based Energy Transfer Partners (ETP), which built the $3.8bn pipeline that is now moving North Dakota oil to Illinois, is falling back on a provision of the September 2017 agreement that provides more time should the company run into problems. The company must provide 20,000 trees to county soil conservation districts along the pipeline’s 359-mile route in North Dakota.

The deal with North Dakota’s public service commission settled allegations that ETP removed too many trees in some areas and that it improperly handled a pipeline route change after discovering Native American artifacts.

The agreement required the company to replant trees and shrubs at a higher ratio in the disputed areas, along with an additional 20,000 trees along the entire route. ETP filed documents in October detailing efforts by a contractor to plant 141,000 trees and shrubs, but the PSC asked the company a month later to provide more documentation that it had complied with all settlement terms.

Company attorney Lawrence Bender recently submitted a report from contractor KC Harvey Environmental further detailing the replanting efforts in the disputed areas. He noted that in some areas where landowners refused trees, the trees were reallocated to other landowners “who had the space and desire to accommodate more plantings”.

Only about 8,800 of the required 20,000 additional trees were planted in 2018. There were several factors, including equipment and staffing issues, difficulties finding willing landowners and poor planting conditions, according to Perennial Environmental Services, which ETP hired to handle the work.

A soil conservation district in one of the seven counties refused to participate at all because it didn’t feel any of the 15 tree species identified in the settlement agreement were suitable.

The agreement allows for the work to continue into 2019 if there are problems with the tree supply “or other market conditions”.