Stormwater & the built surface
The runoff a campus-scale impervious surface adds to the design storm.
A campus-scale impervious surface changes what a design storm does downstream. A real impact study routes that change down the reach. This site has a committed reach table of 6 navigated reaches. That table is the real river geometry this chapter's screen would route down. The routed design storm is not computed yet, because no cited runoff parameters are on the record for this basin. Those parameters are the contributing areas, the curve numbers, and the times of concentration. The study does not fabricate them. Committing that cited set is what lights the routed model.
Reach-network river centerlines (NHDPlus via USGS NLDI)
- Centerline geometry is real NHDPlus, display-only — no reprojection/simplification.
- Mainstem/tributary reach boundaries are a proportional cut by reaches.yaml lengths.
- Tier-0 screening geometry for the FlowLayer viz; not a calibrated hydraulic network.
The flow annex — the reach network →
A data center drinks electricity and sheds water. This campus sits in the Maumee headwaters (HUC 04100005), and to build it Google had to move a stream — which required a permit it had to fight for.
A contested certification
IDEM issued the §401 water-quality certification
on 2026-06-05, over organized oppositionrec — a 90-page public-hearing transcript and ~295
pages of compiled comments, including from the Hoosier Environmental Council. [verified] That a
routine certification drew a contested hearing is itself the friction this platform exists to
document.
What it permits, in numbers, for Phase 3 alone:
- Permanently relocates 3,415 linear feet of Adams Ditch (0.78 ac, 3,794 cubic yards of fill)
to clear the DC06 and DC07 footprints.
[verified] - Fills 0.84 acre of forested Wetland 56, to be restored as herbaceous wetland.
[verified] - Mitigates off-site: 160 lf of stream credits plus 2.52 acres of forested-wetland credits at
the Openings mitigation bank, and 3,255 lf of new on-site channel.
[verified]
The receiving water is Adams Ditch → Doctor Ditch → the Maumee, and it is distinct from where
the Fort Wayne sewage plant discharges (IN0032191 → Baldwin Ditch). The campus sheds stormwater,
not sanitary effluent — commenters flagged the lost wetland’s stormwater-filtering function
specifically. [verified]
Reading the runoff off a drawing
A §401 covers the stream and wetland — the §404 nexus. It does not cover the runoff off the roofs
and the parking. For that you measure the plan. The §401’s Exhibit 7 is a scaled site plan
(1″ = 200′, “Alternative B”), and it can be measured: by colour-segmenting and scale-calibrating
the drawing, ~46 acres of building footprint (seven data halls, ~290k sf each) plus ~180
acres of pavement = ~226 acres impervious on the 858-acre permit area, about 26%.
[inference] Method uncertainty is roughly ±15–20%, and the firm regulatory figure awaits the
SWPPP / Rule 5 construction stormwater permit, still [open].
Why it matters: the soils are hydrologic group C drained, D undrained — Pewamo and
Blount–Glynwood lake-plain clays that shed water fast. [verified] Two hundred-plus acres of new
impervious surface on high-runoff clay, draining to a relocated headwaters ditch, is a measurable
change to a small stream.
Lima’s campus runs ~34% impervious against Fort Wayne’s ~26% — the difference is wetland buffer
the parcel keeps. Both figures are derived from a drawing rather than stated by a permit, which
is why both carry [inference] and why the Rule 5 filing stays this chapter’s ask.
The record behind this chapter
What this chapter stands on: the records it reads, the inputs its modeled figures rest
on, and the reference data behind its baselines — the same pages the record screens
serve, not a second copy. A figure the record does not support stays [open] and links nothing.
- Permits1 record