The Marathon Petroleum-sponsored midstream partnership is starting Harmon Creek III, commissioning Blackcomb and advancing Permian-to-Gulf Coast pipeline, processing and LPG export projects.

Published by Allstream Insiders.

Allstream Insiders Summary

MPLX has increased its 2026 growth-capital outlook by $500 million to $2.9 billion, primarily to accelerate construction of two Gulf Coast fractionators planned near Marathon Petroleum’s Galveston Bay refinery.

The company plans to direct more than 90% of its organic growth capital toward natural gas and natural gas liquids infrastructure, with projects concentrated in the Permian and Marcellus basins and along the Texas Gulf Coast.

Several projects are moving into service or commissioning during the second half of 2026:

• Harmon Creek III is beginning operations in August 2026, adding a 300 MMcf/d gas processing plant and 40,000-bpd de-ethanizer in the Marcellus.
• The Blackcomb Pipeline began commissioning in July 2026 and is expected in service in the fourth quarter of 2026 with 2.5 Bcf/d of Permian-to-Agua Dulce capacity.
• The Bay Runner Pipeline is expected in service in the third quarter of 2026, forming part of a system designed for up to 5.3 Bcf/d between Agua Dulce and Brownsville, Texas.
• The BANGL Pipeline expansion is expected in the fourth quarter of 2026, increasing NGL capacity from 250,000 to 300,000 barrels per day.
• The Titan Complex is expected in the fourth quarter of 2026, increasing MPLX’s Delaware Basin sour gas treating capacity from 150 MMcf/d to more than 400 MMcf/d.

Longer-dated projects include the Traverse and Eiger Express natural gas pipelines, a second Bay Runner corridor, a second Delaware Basin processing plant, two 150,000-bpd Gulf Coast fractionators, and a 400,000-bpd LPG export terminal at the Port of Texas City.

MPLX Is Marathon Petroleum’s Primary Midstream Provider

MPLX is a separately traded master limited partnership formed by Marathon Petroleum Corporation (MPC) in 2012. MPLX describes itself as MPC’s primary midstream provider, operating natural gas, NGL, crude oil, refined-product, terminal, marine and refinery-logistics infrastructure.

The relationship is particularly important to the Gulf Coast fractionation program. MPLX plans to construct the two fractionators near MPC’s Galveston Bay refinery, and MPC is expected to purchase the facilities’ offtake for global marketing.

Marathon Petroleum’s connection to MPLX therefore extends beyond sponsorship. MPC is a customer for midstream and refinery-logistics services, while several of MPLX’s current growth projects are designed to extend the integrated movement of Permian natural gas and NGLs toward the Gulf Coast.

MPLX Project and Capital Tracker

MPLX’s August update identifies projects at operating, commissioning, construction and development stages. Ownership percentages below represent MPLX’s reported interest in each asset or project.

Harmon Creek III Begins Marcellus Operations in August

The Harmon Creek III complex is beginning operations in August 2026, establishing the most immediate new processing milestone in MPLX’s current project schedule.

The project consists of a 300 MMcf/d natural gas processing plant and a 40,000-barrel-per-day de-ethanizer in the Marcellus. MPLX owns 100% of the project.

Harmon Creek III expands two related portions of the Northeast value chain. The processing plant separates NGLs and other components from the raw gas stream, while the de-ethanizer adds fractionation capability downstream of processing.

For contractors and suppliers, the transition into operations could involve final mechanical completion, electrical and instrumentation closeout, testing, commissioning, controls integration and operating-support work. Those categories are Allstream analysis of a processing and de-ethanizer startup; they do not represent announced contract awards.

Blackcomb Enters Commissioning as Bay Runner Nears Service

The Blackcomb Pipeline began commissioning in July 2026 and is expected to enter service in the fourth quarter of 2026. The pipeline is designed to transport 2.5 Bcf/d of natural gas from the Permian Basin to Agua Dulce, Texas.

MPLX reports a 34% ownership interest in Blackcomb. Its connection to Agua Dulce places Permian supply at a major South Texas hub with access to domestic and Gulf Coast markets.

The Bay Runner Pipeline is expected in service in the third quarter of 2026. Bay Runner and the planned Bay Runner Twin are designed for up to 5.3 Bcf/d of natural gas transportation capacity between Agua Dulce and Brownsville, Texas. MPLX holds a 30% interest in the corridor.

The second Bay Runner pipeline carries a 2029 expected service date. This separates the near-term startup of the first pipeline from the longer-dated expansion and prevents the combined design capacity from being interpreted as immediately available.

BANGL and Titan Extend the Permian NGL Value Chain

MPLX expects the BANGL Pipeline expansion to enter service in the fourth quarter of 2026. The project increases NGL transportation capacity from 250,000 to 300,000 barrels per day between the Permian Basin and the Texas Gulf Coast.

MPLX acquired the remaining interest in BANGL during 2025 and now reports 100% ownership. The expanded pipeline is designed to support the company’s Gulf Coast fractionation facilities by moving additional NGL supply toward the coast.

The Titan Complex is also expected in the fourth quarter of 2026. MPLX is expanding Delaware Basin sour gas treating capacity at the acquired Northwind Midstream system from 150 MMcf/d to more than 400 MMcf/d.

MPLX completed its Northwind acquisition in August 2025. The platform includes sour gas gathering, treating and acid-gas injection infrastructure in Lea County, New Mexico. The Titan expansion increases the treating capability of that system and supports the company’s broader Permian processing and pipeline position.

Two Gulf Coast Fractionators Lead the Capital Increase

MPLX attributed the $500 million increase in its 2026 growth-capital outlook primarily to accelerated execution of the Gulf Coast fractionation project.

The program includes two fractionators rated at 150,000 barrels per day each, planned near Marathon Petroleum’s Galveston Bay refinery. MPLX owns 100% of the fractionation facilities and expects the first unit in service in 2028 and the second in 2029.

The $500 million capital increase should not be treated as a disclosed construction cost for the two fractionators. MPLX described the increase as primarily reflecting accelerated execution, but it did not assign the full amount exclusively to either unit.

The facilities form the central processing step in MPLX’s planned Permian-to-Gulf Coast NGL chain:

1. Permian gas processing and sour gas treating, including Secretariat and Titan.
2. NGL transportation through the expanded BANGL Pipeline.
3. Fractionation near the Galveston Bay refinery.
4. Pipeline movement toward the planned LPG export terminal at Texas City.
5. Marine export of finished LPG products.

Texas City LPG Export Terminal Targets 2028

MPLX reports a 50% interest in a planned 400,000-barrel-per-day LPG export terminal at the Port of Texas City. The joint-venture project is being developed with ONEOK and is expected in service in 2028.

The export terminal and an associated pipeline are designed to provide a marine outlet for LPG production from the Gulf Coast fractionation system. The location also places the terminal near MPLX and Marathon Petroleum infrastructure around Galveston Bay.

The terminal could create industrial work across refrigeration, product storage, marine loading, pumps, pipeline connections, electrical systems, automation, inspection and commissioning. These work categories are based on the announced LPG export scope and do not establish procurement packages or contractor selections.

Traverse and Eiger Express Add Permian-to-Katy Capacity

MPLX holds interests in two additional natural gas pipelines planned between the Permian Basin, South Texas and the Katy market area.

The Traverse Pipeline is designed for 2.5 Bcf/d of bidirectional transportation between Agua Dulce and Katy. MPLX reports a 34% interest and expects the project in service during the second half of 2027.

The Eiger Express Pipeline is designed to transport 3.7 Bcf/d of natural gas from the Permian Basin to Katy. MPLX reports a 22% interest, with service expected in mid-2028.

Together with Blackcomb and Bay Runner, the projects are designed to create multiple routes between Permian supply, Agua Dulce, Katy and Brownsville. Each pipeline remains a separate project with its own ownership structure, capacity and schedule.

Secretariat II and Marcellus Gathering Support 2028 Growth

MPLX placed the 200 MMcf/d Secretariat I plant into service in April 2026 and is planning a second Delaware Basin facility.

Secretariat II is designed as a 300 MMcf/d gas processing plant, with expected service in the second half of 2028. MPLX reports 100% ownership.

In the Marcellus, MPLX is also advancing a gathering-system expansion near its Majorsville gas processing complex. The program includes gathering, compression and debottlenecking work supporting producer activity, with service expected in the first half of 2028.

These projects extend the processing and gathering program beyond the immediate Harmon Creek III startup and establish additional work scheduled through 2028.

MPLX Sets a $2.9 Billion Growth-Capital Outlook

MPLX now expects $2.9 billion of growth-capital spending in 2026, an increase of $500 million from its previous outlook. More than 90% of organic growth capital is planned for natural gas and NGL infrastructure.

The company recorded $874 million of growth capital expenditures during the second quarter and $1.665 billion during the first half of 2026. MPLX also recorded $67 million of total maintenance capital expenditures during the quarter and $119 million during the first half.

These amounts are companywide capital figures. They should not be allocated to a specific pipeline, processing plant, fractionator or terminal without a project-level disclosure from MPLX.

Allstream Perspective

MPLX’s second-quarter update moves several projects from a long-range portfolio into near-term execution. Harmon Creek III is beginning operations, Blackcomb is in commissioning, Bay Runner is approaching its expected service window, and both BANGL and Titan are targeted for the fourth quarter.

The larger capital signal is the acceleration of the Gulf Coast fractionators. Those facilities connect MPLX’s Permian processing and NGL transportation assets with Marathon Petroleum’s Galveston Bay position and the planned Texas City LPG export terminal.

For the industrial supply chain, the combined program could support work across gas processing, sour gas treating, fractionation, process module fabrication, large-diameter pipeline construction, compression, metering, terminal refrigeration, marine loading, controls, inspection and commissioning. The next evidence to monitor is confirmed startup of Harmon Creek III and Bay Runner, completion of Blackcomb commissioning, fourth-quarter service milestones for BANGL and Titan, and construction progress on the fractionators and Texas City export terminal.