SOUTH MERCER
Substation-AdjacentKing County, Washington · WECC
At a glance
SOUTH MERCER is a substation-adjacent datacenter candidate site in King County, Washington, scoring 59.7/100 DC Readiness — 64th of 344 scored sites in the county. Its nearest substation is SOUTH MERCER (0 mi, 115 kV). It sits in the WECC grid region and the PUGET SOUND ENERGY INC service territory, where interconnection has averaged 3.5 years from request to operation. GridCensus catalogs 100 MW of candidate capacity here.
Power & interconnection
Speed to power
Deep queue and long historical waits — plan for a multi-year interconnection timeline and engage the utility early.
Connectivity
Site characteristics
Risk & environment
Location context
Regulatory climate
No notable statewide DC restriction on record; confirm local zoning and utility tariffs.
Incentive detail: Sales tax exemption on DC equipment and construction for eligible facilities; no state income tax.
Site location
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How does SOUTH MERCER compare with other sites in King County?
SOUTH MERCER ranks 64th of 344 scored candidate sites in King County. Its 59.7/100 is roughly in line with the county average of 56.1. It is about 15% above the Washington average of 51.7 and about 12% above the national average of 53.2.
Against the Washington average, its strongest sub-score is fiber connectivity (84 vs 63) and its weakest is speed to power (50 vs 50). Power and speed to power each carry 20% of the composite score, fiber 12%, water 7% and hazard 6%.
How close is SOUTH MERCER to power, fiber and other datacenters?
The nearest mapped substation, SOUTH MERCER, is about 0 miles away and operates at 115 kV. For connectivity, the nearest internet exchange facility is EdgeConneX Seattle (EDCSEA01) at 4.3 miles. 16 fiber providers report service at the location in FCC broadband data. The closest operating datacenter on record is Intergate Seattle East Building 1, 4.4 miles away.
What are the flood, water and hazard risks at SOUTH MERCER?
The site is in FEMA flood zone X, outside the Special Flood Hazard Area (minimal or moderate flood risk). At the county level, FEMA's National Risk Index rates King County "Relatively Moderate".
Full DC Readiness breakdown
All 13 weighted sub-scores (0–100) behind the composite DC Readiness score.
Nearby comparable sites
Other scored datacenter candidate sites in King County, ranked by DC Readiness.
| Site | Type | Voltage | Capacity | Queue wait | Score |
|---|---|---|---|---|---|
| MAPLE VALLEY | Substation-Adjacent | 500 kV | 1,000 MW | 3.5 yrs | 68.4 |
| COVINGTON | Substation-Adjacent | 500 kV | 1,000 MW | 3.5 yrs | 68.2 |
| ECHO LAKE | Substation-Adjacent | 500 kV | 1,000 MW | 3.5 yrs | 67.4 |
| RAVER | Substation-Adjacent | 500 kV | 1,000 MW | 3.5 yrs | 66.6 |
| TAP206230 | Substation-Adjacent | 500 kV | 1,000 MW | 3.5 yrs | 66.3 |
| OBRIEN | Substation-Adjacent | 230 kV | 300 MW | 3.5 yrs | 65.2 |
| OZ King | Greenfield | — | — | 3.5 yrs | 64.6 |
| SAMMAMISH | Substation-Adjacent | 230 kV | 300 MW | 3.5 yrs | 64.2 |
SOUTH MERCER: common questions
What is the DC Readiness score of SOUTH MERCER?
SOUTH MERCER scores 59.7/100 on the GridCensus DC Readiness scale, rated good. It ranks 64th of 344 scored sites in King County. The King County average is 56.1 and the Washington average is 51.7.
What is the nearest substation to SOUTH MERCER?
The nearest mapped substation is SOUTH MERCER, about 0 miles away, at 115 kV. GridCensus catalogs 100 MW of candidate capacity for the site.
Which electric utility serves SOUTH MERCER?
PUGET SOUND ENERGY INC (investor owned) holds the retail service territory that contains the site; its holding company is MACQUARIE GROUP.
What grid region is SOUTH MERCER in?
SOUTH MERCER is in the WECC region. Projects interconnecting there have averaged a 3.5-year wait from queue request to operation.
Is SOUTH MERCER in a flood zone?
The site is in FEMA flood zone X, outside the Special Flood Hazard Area (minimal or moderate flood risk).
How far is SOUTH MERCER from an internet exchange?
The nearest internet exchange facility is EdgeConneX Seattle (EDCSEA01), about 4.3 miles away; 16 fiber providers report service at the location.
Related pages
About this data
Source: GridCensus composite of HIFLD transmission and substation data, EIA, FEMA National Risk Index, FCC broadband data, PeeringDB and ISO interconnection queues, as published October 10, 2026 — GridCensus refreshes it monthly. See the methodology for how records are matched, cleaned and scored.
Cite as: GridCensus, “SOUTH MERCER, King County, WA”, https://gridcensus.com/datacenter-sites/washington/king-county/south-mercer-110b932e (data as of October 10, 2026).
Dataset updated . Screening estimates derived from public data sources.
Figures are screening estimates derived from public infrastructure data. Catalogued capacity reflects theoretical candidate capacity, not deliverable or committed interconnection. Confirm all values with the utility, ISO, and on-the-ground due diligence.
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