Heat
The discharge's heat against the reach's temperature criterion at design low flow.
Cooling water leaves a plant warm. A real impact study states how much heat the discharge adds to the reach that receives it. That reach holds 5.4 °C of headroom against the state's numeric temperature criterion at its design low flow, which is the frame Clean Water Act §316(a) uses. This screen reads the modeled campus load and the corridor's own reported effluent temperatures against the same water.
Screened cohort: 1 modeled data-center load [inference] · 6 permitted dischargers (3 reporting an
effluent temperature [verified]) — screened identically, never conflated.
2 permits already report an effluent temperature over the criterion. 1 modeled load resolves NO mixed temperature at the chronic flow — the reach cannot physically carry that heat as liquid water; the magnitude lives in the exceedance factor, not a fabricated ΔT. 3 more rows contribute no comparable temperature (no cited chronic flow, or no screen at all) — counted, not hidden.
- A MODELLED (data-center) row's heat load is the CONDENSER heat rejection (IT x cooling overhead) — an inference about a facility that is not yet discharging. An INDUSTRIAL row's is the permittee's own reported effluent temperature x reported flow — a measurement. They are screened identically from there on but never conflated; read `kind` before quoting a number.
- Fully-mixed, design-low-flow, order-of-magnitude: no CORMIX plume model, no mixing-zone credit, no decay. T_mixed above the daily-max criterion flags the need for a permit-level thermal / CWA §316(a) analysis, NOT an automatic violation.
- The thermal assimilative capacity is rho*cp*Q*(daily_max - ambient). At a 0 cfs design flow (the Ottawa 1Q10) or an ambient already at the criterion the capacity is 0 — any heat load exceeds by construction (no Inf ΔT, mirroring the toxics screen).
- The design ambient is a live NWIS 00010 reading where the gage carries one, else the reach's own reported in-stream (upstream/downstream) DMR monitoring, else the zone's seasonal-average temperature criterion as a stated design ambient. An in-stream station sits downstream of that plant's own outfall, so it is a measured in-stream temperature, not an undisturbed upstream background.
- Cooling scenarios span the heat PARTITION, not uncertainty in the load: `once_through` sends the whole rejection to the stream by definition, `evaporative_blowdown` sends only the blowdown's sensible heat (the rest leaves as latent heat to the air) at a temperature CALIBRATED to an observed corridor analog — an [inference] by analogy, never this facility's own figure. `conservative_bound` is the Phase-2 ceiling.
- Reported DMR values are verbatim from the permittee's submissions via ECHO and reduced to degC by their REPORTED unit (00011 is Fahrenheit, 00010 Celsius); an exceedance count is ECHO's own determination, never computed here by comparing a value to a limit. A permit with no numeric thermal limit is recorded as monitor-only — a cited absence, not a clean bill of health.
- The OAC 3745-1-06 (O)(5) closed-cycle-blowdown exemption (blowdown < 5% of the 7Q10) is evaluated and surfaced whether or not it applies. RIS tolerances are the Great Lakes biological limits for a §316(a) balanced-indigenous-community read, [reference] (federal guidance, not law).
The full per-discharger comparison — every mixed temperature, the heat-partition scenarios, and the derived-vs-observed calibration — is in the thermal annex.
Thermal capacity is a product of three things: how much water the stream carries, how warm that water already is, and how warm the rule lets it get. On the Ottawa River in late June all three run against any new heat load.
Ohio’s rule for this zone, OAC 3745-1-35 Table 35-11 (G), sets a daily maximum of 29.4 °C for the June 16–30 window. The river’s measured ambientrec in that window is 24.0 °C. That leaves 5.4 °C of headroom. Multiply that headroom by the design low flow of 0.2 cubic feet per second (cfs). The whole reach can then absorb about 0.1 megawatts (MW) of heat.
The screen above is fully mixed and order-of-magnitude. It gives no mixing-zone credit and runs no plume model. It flags where a permit-level thermal analysis would be required. It does not find a violation.
What the corridor already reports
The corridor carries six permitted dischargersref , and three of them report an effluent temperature at all. The Lima refinery reports 32.22 °C at outfall 001, which is above the 29.4 °C daily maximum the zone sets for the receiving water.
Three of those permits are monitor-only. They require the permittee to report a temperature and set no numeric limit against it. So the corridor’s heat is measured but not bounded.
The exemption that does not reach
Ohio EPA exempts closed-cycle blowdown from the thermal mixing-zone rule when the blowdown is under 5 % of the 7Q10. That test is written for plants on rivers. Here 5 % of a 0.2 cfs 7Q10 is 0.010 cfs, and the modeled blowdown is 3.868 cfs. The exemption misses by more than two orders of magnitude, so it does not apply.
What a real thermal study would produce
Clean Water Act §316(a) lets a permittee argue for an alternative thermal limit. It grants that only on a demonstration that the receiving water still supports a balanced indigenous community. No thermal characterization for this campus exists, and nothing on the Ottawa corridor currently holds a thermal limit. Both facts are tracked on the leads board.
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.
- Permits22 records
- Maumee NPDES inventory (EPA ECHO)Reference dataset