From the operating records that already exist: logbooks, monitoring sheets, maintenance schedules, incident reports and internal memos in which she proposed or revised settings. A technical statement from a senior officer explaining the system and her role, citing those records, ties the file together.
Logbooks and revision histories are the evidence
Most resorts never wrote their pool procedures as a manual, and an L-1B petition built on an assertion that the specialist knows the system tends to draw a request for evidence. Start with the daily monitoring sheets and chemistry logs, which show dates, readings, adjustments and who made them. Add the maintenance schedule for the heat exchangers and mineral-scaling work, the memos or emails in which the specialist proposed changes to blending ratios or monitoring frequency, any incident reports she resolved, and the training material she prepared for other staff.
From those, a senior officer of the Harrison Hot Springs company can write a technical statement describing the system, explaining how it differs from ordinary pool operation, and tracing her role in developing it, with each claim pointing to an exhibit. Include the U.S. property's engineering drawings or specifications showing the same system will be installed.
Documents not in English require certified translations, and photographs need captions that connect them to the procedure they illustrate.