THRESHOLD COMPLEX EXPLORATION LOG

Designation / Log ID: 30-A27

Apparent Date/Time: 02 September 2026 / 09:22 (local) — secondary stamp reads 14:51 17 March 1979

Entry Method: Steel hatch marked “S-18 SPILL CONTAINMENT – SECONDARY CONTAINMENT”. Hatch diameter measures 0.92 m on exterior. Interior clearance measures 1.05 m on entry and 0.81 m on exit.

Environmental Baseline

Lighting: industrial LED strips, color temperature measured at 4120 K. Intensity constant at 118 lux.

Ambient temperature: 19.7 °C. Humidity: 48 %.

Background sound: low-frequency hum at 47 Hz. Baseline reading 28 dB.

Air movement: intermittent. Barometric pressure 1013.6 hPa on entry; 1021.9 hPa after 11 m of travel.

Spatial Observations

Gallery estimated 22 m long by 7.4 m wide by 3.8 m high. Laser measurement returns 16.3 m long by 9.1 m wide by 2.9 m high.

Floor: continuous epoxy coating with yellow containment lines. Line width measures 0.15 m. Pattern remains fixed after four traversals.

Walls: painted concrete block. Block joints measure 0.8 mm. Joint width remains constant under repeated measurement.

Ceiling: exposed steel deck with six circular drain ports. Port diameter measures 0.18 m. Visual inventory returns six ports. Physical count remains six after five passes.

Repeating motif: every 2.4 m a secondary containment sump is recessed into the floor. Sump depth measures 0.35 m. Liquid level is identical across all units.

Anomalies

Visual inventory of containment berms returns 8. Physical inventory returns 8. Berm height measures 0.22 m while calculated containment volume across the same berm equals 0 L.

Floor remains level under spirit level. Measured liquid film on the lower wall panels slopes 1.8° toward the south wall. Slope reverses after 7 minutes of continuous observation without change in physical orientation.

Gallery pressure measures 1013 hPa while the external hatch indicator reads 1004 hPa. Seal integrity lights remain green.

Sound of footfall arrives 1.9 seconds after the corresponding floor vibration is detected. Delay increases by 0.27 s for every additional 2.1 m of distance from the entry hatch.

Humidity at mid-gallery remains 48 % while condensation forms on the sump rims after 5 minutes of observation. Condensation evaporates without measurable change in local humidity.

Local magnetic field strength measures 0.6 gauss at floor level and 2.1 gauss at 1.5 m height. Field direction reverses after 13 minutes without change in gallery state.

Drain port flow rate measures 0 L/min while residual liquid volume in the sumps decreases by 1.4 L over 9 minutes.

Entity Notes

None observed.

At the 7.2 m mark a localized temperature rise of 3.8 °C occurs across a 1.9 m radius. Rise persists for 11 seconds then collapses. No visible source or airflow change accompanies the event.

Exit / Continuity Status

Exit achieved by retracing path through the steel hatch. Exterior release required moderate force.

Exterior time on exit: 10:04 local. Elapsed interior time: 42 minutes.