Like exploratory tentacles of the Borg — or devilish underground shoots of bamboo — it’s coming right across the Rt 15 Point of Rocks bridge, just north of Dickerson proposed Datacenter Complex. Intention seems most like interconnect to Dickerson Datacenter Complex.
Recent heavy maintenance on Rt 15 Point of Rocks bridge suits this interconnection. Dozens of underground conduits; potentially thousands of fibers. This is a major, carrier-grade infrastructure project.
A kempt, curated growing series deeply exploring the already numerous and not yet fully known real, possible, suspected, feared, alternative and even “fringe” / paranormal aspects inescapably miring datacenters.
A 2026 power-engineering study found that hyperscale data centers behave not merely as electrical loads, but as vast power-electronics systems whose rapidly fluctuating server demands can excite grid oscillations and propagate disturbances across interconnected networks. Far from a fringe “dirty electricity” claim, the research suggests data centers may interact with the power grid in ways fundamentally different from traditional industrial facilities, raising serious new concerns about resonance, stability, reliability.
Part of a kempt, curated, growing Series deeply exploring the already numerous but not yet fully known documented real, possible, suspected, feared, alternative and even “fringe” / paranormal aspects inescapably miring Datacenters. — Index
Per VDOT’s Land Use Permit System. It is not VDOT laying state fiber; it is private carrier work in VDOT right-of-way, mainly by Zayo Group, LLC.
What is being installed
The big Route 15 work north of Leesburg appears to be:
Zayo Group, LLC — 864-count fiber optic cable
- Method: mostly aerial overlash — attaching new fiber to an existing strand on an existing pole line.
- Location: US 15 / James Monroe Highway / Catoctin Mountain Highway north of Leesburg toward Point of Rocks.
- Scale: roughly 7+ miles in the active permit segments.
- Fiber count: 864 fibers, which is backbone / high-capacity carrier-scale, not ordinary residential drop fiber.
VDOT permit language repeatedly says things like:
- “overlash … placing (1) 864 fibers to existing strand on existing pole line”
- multiple aerial road crossings
- some “pull thru” existing conduit
Source base:
VDOT Land Use Permit map/service: https://vdotgisportal.vdot.virginia.gov/env/rest/services/LUPS_LU_PROD/LUPS_Permit_View/MapServer
VDOT land-use permit purpose: https://www.vdot.virginia.gov/doing-business/technical-guidance-and-support/land-use-and-development/land-use-permits/
Active Zayo permit segments
VDOT active/approved line permits on Route 15 in Loudoun:
1. Permit 949-61885
- Customer: Zayo Group, LLC
- Work: overlash 10,481 ft of 864-fiber cable
- Aerial road crossings: 5, totaling 616 ft
- Approx. geography: starts around Little Spring Road / north Leesburg, runs north toward Lucketts.
2. Permit 949-61895
- Customer: Zayo Group, LLC
- Work: overlash 10,215 ft of 864-fiber cable
- Aerial road crossings: 4, totaling 412 ft
- Approx. geography: central Route 15 / Lucketts corridor.
3. Permit 949-61894
- Customer: Zayo Group, LLC
- Work: overlash 10,256 ft of 864-fiber cable
- Approx. geography: Lucketts northward.
4. Permit 949-61896
- Customer: Zayo Group, LLC
- Work: overlash 6,765 ft of 864-fiber cable
- Road crossings: 6, totaling 873 ft
- Also: pull through 468 ft of 864-fiber within VDOT right-of-way
- Approx. geography: north end approaching Point of Rocks bridge / Potomac crossing.
There was also an earlier/bundled Zayo permit, 949-61736, marked RETURNED TO PERMITTEE, that described a larger combined job:
38,872 ft of 864-fiber overlash
12 aerial road crossings
468 ft pull-through in existing conduit That looks like the same overall route later split/refined into the approved segments above.
Where is it coming from / going?
What the permits prove
The VDOT permit geometry runs approximately:
South end: just north of Leesburg, around Little Spring Road / Route 15 / Battlefield Parkway area
North end: Point of Rocks / Catoctin Mountain Highway, at or near the Virginia side of the Potomac crossing.
So the permitted Virginia-side construction is essentially:
Leesburg/north Leesburg → Lucketts → Point of Rocks bridge
What is likely, but not explicitly stated
The permits do not disclose the commercial endpoint, customer, circuit purpose. But given that the permittee is Zayo, and Zayo markets major Northern Virginia/Ashburn data-center connectivity, the most likely network purpose is: Northern Virginia / Ashburn-Leesburg data-center fiber fabric ↔ Maryland / Frederick-side route via Point of Rocks
Zayo publicly says it has a large Northern Virginia/D.C. fiber footprint serving data centers and cloud providers. Source:
https://www.zayo.com/newsroom/northern-virginia-data-center-providers-select-zayo-for-dark-fiber/
Zayo’s own network page describes broad dark-fiber / long-haul / data-center connectivity. Source: https://www.zayo.com/network/
Other fiber work nearby
There is also a Lumos Incorporated permit on Route 15:
- Permit 949-61570
- Directional bore 471 ft
- Places three 1.5-inch HDPE conduits with one 432-count fiber optic cable
- Includes a handhole
- Much smaller localized bore than the Zayo route
So if you saw trenching/boring/handholes, that could be Lumos or localized utility work. If you saw crews on pole lines for miles, that is likely Zayo.
Bottom line The “massive fiber backbone” north along Route 15 is most likely Zayo installing/overlashing an 864-count fiber route from north Leesburg up to Point of Rocks, probably to connect the Northern Virginia data-center network with Maryland/Frederick/northbound routes.
Public VDOT records confirm the route and fiber count, but do not reveal the final commercial endpoints or customer traffic purpose.
Capacity Analysis
One 432-count or 864-count fiber cable does not require dozens of 2-inch plastic pipes. It normally requires one duct/conduit. Practical answer For typical backbone cable: Fiber cable Typical outside diameter Duct needed
━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
432-count OSP ribbon fiber ~0.74–0.86 in 1 duct is enough
──────────────────────────── ─────────────────────────────── ──────────────────────────────────
864-count OSP ribbon fiber ~0.86–1.04 in 1 duct is enough
──────────────────────────── ─────────────────────────────── ──────────────────────────────────
2-inch SDR-11 HDPE duct ~1.91–1.94 in inside diameter easily fits one 432 or 864 cable
So if you are seeing dozens of orange/blue/black plastic pipes, those are almost certainly multiple empty conduits / spare ducts / segmented pathway capacity, not one pipe per 432 or 864 fiber cable. How many fibers can fit in one 2-inch pipe? Depends on cable type, but roughly:
- A standard 2-inch SDR-11 HDPE conduit has about 1.9-inch inside diameter.
- A modern 864-count cable can be about 0.86–1.04 inch OD.
- A modern 432-count cable can be about 0.74–0.86 inch OD. Therefore:
- One 2-inch duct can comfortably carry one 864-count fiber cable.
- It can also carry one 432-count cable very comfortably.
Physically, it may fit multiple cables, but carriers usually avoid that for long backbone pulls because of friction, bend radius, future maintenance, and replacement issues. Why bury dozens of pipes? Because each pipe is a future pathway. A carrier or utility may install a duct bank now with:
- one duct for today’s cable,
- one or more ducts for spare backbone expansion,
- separate ducts for different owners/carriers,
- separate colors for identification,
- spare conduits for later leasing/sale,
- redundancy/diverse circuits,
- future microduct bundles.
A 2-inch duct can even carry very high-density cables. Prysmian lists 6912-fiber FlexRibbon cable as fitting in a 2-inch duct in one product family, so 432/864 is not pushing the physical limit. Source: Prysmian FlexRibbon brochure. Applied to the Route 15 permits The VDOT Lumos permit said three 1.5-inch conduits with one 432-count fiber cable. That means likely:
1 conduit occupied now
2 spare conduits for future use The Zayo Route 15 permits I found were mostly aerial overlash of one 864-count cable, not buried duct, except for short pull-through segments. Sources:
Corning 432-count cable: nominal OD 0.83 in:
https://ecatalog.corning.com/optical-communications/US/en/Fiber-Optic-Cables/Outdoor/Outdoor-Duct-Cables/SST-UltraRibbon-Single-Tube%2C-Gel-Free-Cable/p/432EV4-14100D53
Prysmian FlexRibbon OSP examples: 432 around 0.74–0.78 in, 864 around 0.86–1.00 in, 6912 in 2-inch duct:
https://na.prysmian.com/sites/na.prysmian.com/files/media/documents/TLS-0012B-0423_FlexRibbon%20NA%20Brochure.pdf
2-inch SDR-11 HDPE conduit dimensions around 2.375 in OD / ~1.917–1.943 in ID: https://www.buyawg.com/item/hdpe-conduit/hdpe-sdr-11-conduit/sdr-11-2
How much data speed / capacity?
A lot. The glass fiber is mostly just the path; capacity depends on the electronics at each end.
Rule of thumb for one single-mode fiber
Simple lit service
One fiber strand can carry:
- 1 Gbps
- 10 Gbps
- 25 Gbps
- 100 Gbps
- 400 Gbps
- 800 Gbps
- sometimes 1.6 Tbps with newest optics
That is for one optical channel/wavelength. With DWDM / wavelength multiplexing Carriers can put many “colors” of light on the same fiber. Example:
- 80 wavelengths × 100 Gbps = 8 Tbps
- 80 wavelengths × 400 Gbps = 32 Tbps
- 80 wavelengths × 800 Gbps = 64 Tbps So one fiber can carry tens of terabits per second in real carrier networks. For a pair of fibers Many long-haul systems use a fiber pair:
- one fiber transmits east/north,
- the other transmits west/south. So a “single circuit” may consume 2 strands. But modern bidirectional optics can also send both ways on one fiber using different wavelengths. Applied to 432 / 864 fiber cables If each strand were conservatively lit at 100 Gbps:
- 432 fibers × 100 Gbps = 43.2 Tbps
- 864 fibers × 100 Gbps = 86.4 Tbps
If each strand/fiber pair uses dense wavelength multiplexing, the theoretical route capacity becomes enormous — petabits per second scale across the whole cable. Human-scale comparison 1 Tbps = 1,000 Gbps. A single modern fiber can carry enough capacity for:
- hundreds of thousands to millions of video streams,
- many data centers’ worth of traffic if using DWDM,
- far more than ordinary town/residential broadband demand. So: one fiber strand can carry from 1 Gbps to 100+ Tbps depending on optics; tens of Tbps is normal for modern backbone use.
› so an 864-fiber optic bundle can carry absurd capacity?
Yes — absurd capacity is the right intuition. An 864-fiber cable is carrier/data-center backbone scale. Even modestly lit, it is enormous:
- At 10 Gbps per fiber: 8.64 Tbps
- At 100 Gbps per fiber: 86.4 Tbps
- At 400 Gbps per fiber: 345.6 Tbps
- At 800 Gbps per fiber: 691.2 Tbps
And that is without counting dense wavelength multiplexing. With DWDM, one fiber can carry many separate optical channels, so the total theoretical capacity of an 864-strand route can reach petabit-per-second scale. Important caveat: not all strands are necessarily lit. Carriers often install huge fiber counts because:
- most strands remain dark/spare,
- strands are leased to different customers,
- some are reserved for redundancy,
- some are used for future expansion,
- electronics are upgraded over time without replacing the cable.
So the cable itself is a massive long-term asset. The actual traffic depends on how many fibers are lit and what optics are installed. But yes: 864 fibers is not neighborhood broadband scale; it is regional backbone / hyperscale data-center scale.