Two polyethylene (PE) units, a key part of a $6 billion petrochemical expansion on the Texas Gulf Coast, have achieved mechanical completion, considered a major milestone, Chevron Phillips Chemical Co. LP (CPChem) said Monday.

The PE units sited near Old Ocean in Brazoria County are undergoing a series of rigorous commissioning activities, system checks and final certifications before start-up. Once operational, each unit would be capable of producing at least 500,000 metric tons/year.

“These new units allow us to utilize the abundant natural gas liquid feedstocks provided by the development of shale resources in the United States to meet the growing demand for polyethylene from our global customers producing performance films, high-pressure pipe and packaging,” said CPChem CEO Peter Cella.

Ethylene feedstock for the PE units would be supplied via the company’s ethylene pipeline and storage system that also was expanded as part of the CPChem’s U.S. Gulf Coast Petrochemicals Project. Along with the PE units, the company purchased nearly 3,000 rail cars and constructed a state-of-the-art rail facility with capacity to store 1,500 rail cars able to ship PE pellets to global customers.

The final element of the CPChem’s project entails constructing an ethane cracker in Baytown, which should be completed by the end of the year. CPChem is a 50-50 partnership between Chevron Corp.’s Chevron U.S.A. Inc. and subsidiaries of Phillips 66. The world-scale ethane cracker and ethylene derivatives facilities initially were announced in late 2011, with the project given a green light in 2013.

A plethora of petrochemical newbuilds and expansions are underway along the Gulf Coast.

ExxonMobil Corp. and Saudi Basic Industries Corp. agreed in April to develop a world-class ethane steam cracker in South Texas near Corpus Christi, a facility that with final approval would be able to produce 1.8 million metric tons/year of ethylene. The proposed project would feed a monoethylene glycol unit and two polyethylene units, one of 11 projects ExxonMobil has announced as part of its 10-year, $20 billion Growing the Gulf initiative.

In a $1.7 billion venture between Total SA, Borealis and Nova Chemicals, plans are to build a 1 million ton/year ethane steam cracker and polyethylene unit in Port Arthur, which is in the heart of the Texas Gulf Coast petrochemical industry.

Dow Chemical Co. now is commissioning a 400,000 metric ton enhanced polyethylene production facility in Freeport, TX, the first of four derivative investments at sites in Texas and Louisiana, which are part of its planned $6 billion expansion on the Gulf Coast. In May Dow also launched a five-year, $4 billion petrochemical buildout, mostly for U.S. projects, that includes adding a 600,000 metric ton polyethylene unit on the Gulf Coast and expanding a Texas ethylene cracker.

Among the other big projects, Sasol Ltd. and Ineos Europe AG units in 2014 issued a final investment decision to build a high-density polyethylene (HDPE) plant in the La Porte, TX, petrochemical complex southeast of Houston. The partnership plans to produce 470 kilotons/year of bimodal HDPE. Ethylene required to produce HDPE would be supplied by each partner for the La Porte plant, which is to be built at the Battleground Manufacturing Complex operated by Ineos.