Data Center Campus Master Planning: Pads, Substation, Roads and Phasing

A master plan is the drawing set and narrative that turns a parcel into a campus. It sets the total program (how many buildings, how many megawatts, how much floor area), then locates every major element: the utility substation or switchyard, building pads, generator and cooling yards, internal roads, utility corridors, stormwater ponds, security perimeter and landscaped buffers. It also fixes the order in which those pieces get built.

Planning authorities increasingly expect that level of structure. A draft design code for a data center campus in the London Borough of Havering, for example, requires all buildings, external plant and plot infrastructure to sit within defined build zones, developed in line with a phasing plan, with full details of each zone submitted as it comes forward.¹ U.S. counties use different tools (rezoning with proffers, planned development districts, development agreements), but the idea is the same: approve the frame once, then fill it in.

The master plan is different from the land question that comes before it. Our guide to how much land a data center needs covers acreage per megawatt, including how much remains after floodplain, wetlands and easements. Master planning starts with that buildable envelope and decides how to fill it.

On a large campus the substation is the anchor. It has to sit where incoming transmission lines can reach it without crossing future building pads, and it has to leave room for added transformers and line terminals as load grows. In an Arizona siting case for a utility substation serving a data center, the proposed 230 kV substation was located within the data center’s own planned area development, so the substation footprint was planned as part of the campus parcel rather than as a separate site.⁶

Two practical rules follow. First, keep the high-voltage corridor at the edge of the site closest to the source, so lines do not slice the buildable area. Second, run the medium-voltage feeders from the substation to each pad along a planned duct bank route that can be extended phase by phase. The Abilene, Texas, campus developed for Oracle and OpenAI shows how central this is: Lancium assembled the roughly 1,100-acre site and its electrical infrastructure, and Crusoe designed and built the data center buildings on it.¹¹

Bus layouts and expansion bays are covered in our guide to substation configurations, along with whether the utility or the customer should own it. For the master plan, the key point is to reserve the land for the ultimate substation, not the first phase of it.

Once the power entry is fixed, the plan lays out pads: flat, compacted platforms for each data hall building and its equipment yard. Pad size follows the building program. Microsoft’s second Mount Pleasant site, for example, was reported with six data center buildings of just over 568,000 square feet each, and the expanded campus with nine buildings of nearly 580,000 square feet east of Interstate 94.⁴

Grading ties the pads together. A contractor’s scope for a 190-acre, 240 MW campus included mass grading, the substation, access roadways, curb and gutter, wet and dry utility infrastructure, irrigation and stormwater management, plus equipment pads and precast building shells.² An engineering firm’s master plan for a 300-acre campus called for 3D models of wet and dry utilities, a drainage report, a 3D grading plan, roadway design and a spill mitigation plan.⁷ Designing these together lets the engineer balance cut and fill across phases, set pad elevations above flood levels and size ponds for full build-out. Our guide to stormwater management goes deeper on ponds and permits.

Building height is a master plan choice too. Multi-story data centers fit more floor area on each acre, but they make heat and water distribution harder, require lifting heavy equipment to upper floors and reduce roof space for cooling equipment.¹² Where land is cheap and plentiful, single-story buildings with ground-level yards remain simpler; where land is scarce, stacking can be the only way to reach the target megawatts. Space for chillers, dry coolers and generators is covered in cooling plant and equipment yard space.

Setbacks determine how much of the parcel the core campus can actually use, and the rules increasingly treat buildings, equipment and substations differently. Fairfax County, Virginia, adopted a data center zoning amendment on September 10, 2024, that requires data center buildings to be at least 200 feet from the lot line of adjacent residential property, and equipment such as backup generators to be 300 feet away or screened by the building itself, with lesser distances possible by special exception.⁸ The same amendment requires data centers to be at least one mile from a Metro station and calls for noise studies before and after construction.⁸

Substations got their own rules. On December 9, 2025, Fairfax approved a substation amendment requiring new substations to be at least 100 feet from residential property lines, with a visually solid fence or wall at least 12 feet high facing streets or homes, a 50-foot landscaped buffer next to residential areas and a noise study showing compliance with a 55 dBA nighttime limit at the residential property line.¹³

The planning consequence is that the noisiest elements, generators, cooling yards and the substation, should sit on the side of the site farthest from homes, with the buildings themselves acting as a sound wall where possible. Our guide to noise, setbacks and buffers explains how local noise limits are written and measured.

A campus usually needs three kinds of circulation: fire apparatus access around every building, heavy truck routes for transformers, generators and construction deliveries, and employee and visitor traffic that stops at a secured entrance. Keeping these separate reduces conflicts during the years when one phase is operating and the next is under construction.

Fire access is the hard constraint. The International Fire Code requires fire apparatus access roads at least 20 feet wide with 13 feet 6 inches of vertical clearance, and requires the road to reach within 150 feet of all portions of a building’s first-story exterior walls, measured along an approved route.⁹ Dead-end access roads longer than 150 feet need an approved turnaround.⁹ Local amendments vary: Seattle’s draft fire code allows the 150-foot distance to grow to 375 feet for fully sprinklered buildings.¹⁰ For campus planning this usually means a ring road around each building or pair of buildings, with gates the fire department can open.

• Confirm the adopted fire code edition and local amendments with the fire marshal early.⁹
• Size gates, turning radii and pavement for the heaviest delivery, often a large power transformer; see heavy-haul access.
• Plan construction entrances that stay separate from the secured operating entrance once phase one is live.
• Check public road capacity and driveway permits with the road authority, often through a traffic impact study.

Phasing is where master plans prove their worth. The pattern on recent AI campuses is a small first phase followed by much larger additions on the same or adjacent land, often faster than the original plan expected.

• Abilene, Texas. The first two buildings totaled about 980,000 square feet and more than 200 MW of IT load; a second phase added six more, for roughly four million square feet and 1.2 GW, and Crusoe topped out the eighth and final building of those phases in 2025.³ Local reporting said construction on the campus would continue into early 2027.¹¹
• Mount Pleasant, Wisconsin. Microsoft’s campus was first planned as 315 acres with three buildings totaling 1.2 million square feet, then grew after approvals for another 1,000 acres; in January 2026 the village approved 15 more data center buildings.⁴ Microsoft said construction of the first facility was complete in June 2026.¹⁴
• Richland Parish, Louisiana. Meta’s Hyperion campus began on about 2,250 acres with roughly four million square feet across nine buildings phased through 2030, and Meta bought about 1,400 adjacent acres at the end of 2025.¹⁵ In 2026 Meta said it plans to more than double the campus to 5 GW.¹⁶
• New Carlisle, Indiana. Amazon’s Project Rainier campus sits on about 1,200 acres with about 30 buildings planned; seven buildings were built in under a year, and AWS activated the campus in October 2025.⁵

Each case shows the same lesson: repeated, near-identical building pads served by a substation and road system sized for the end state. Our guide to phased vs. full build-out covers the business case for staging, and load ramp schedules covers how utilities deliver power to match.

A useful first master plan does not need full engineering. It needs enough accuracy to show that the target program fits and that the power, roads and drainage work for every phase.

1. 01Build a constraints map from a survey and public data: floodplain, wetlands, easements, slopes and every applicable setback.
2. 02Ask the utility where a substation and line corridor could go, and how large the ultimate yard would be.
3. 03Test two or three pad layouts against the buildable envelope, including generator and cooling yards.
4. 04Check fire access, truck routes and the public road connection with the fire marshal and road authority.⁹
5. 05Draft a phasing plan that shows what is built in phase one and what land stays open, then confirm it against the zoning path.¹

Landowners can do a light version of this before marketing a parcel, since buyers read a credible concept plan as evidence the site works. If you want an outside view of whether a parcel can hold a campus, you can get a site reviewed.