Water & wastewater | Modelled case study
Rotate certificates on remote water PLC gateways
Can trust be replaced across unmanned sites without losing telemetry or control?
The modelled organisation
A recognisable problem reaches the operating agenda
This composite scenario follows the SCADA Operations · Field Maintenance · PKI functions. It is grounded in the cited problem context but does not identify a real customer.
Operating environment
A water utility operates treatment plants, pumping stations, reservoirs, remote PLC gateways, engineering workstations, telemetry, and vendor maintenance links.
What is at stake
Control and recovery must remain available during facility loss, communications degradation, or supplier intervention without leaving permanent shared access behind.
Situation
Intermittent communications, seasonal access, shared gateway images, and limited staff make certificate expiry a physical operations problem.
Event that forces action
Issuer migration, certificate expiry, gateway replacement, or a vendor credential incident.
Concrete system boundary
Systems this case study puts in scope
The model is specific about the operational surfaces that must be discovered, changed, or independently checked.
remote PLC gateways
certificate issuer
telemetry and control sessions
field fallback and rollback
Modelled case study walkthrough
How this organisation would use QNSI
The walkthrough connects the real-world problem to a bounded QNSI contribution and an independently reviewable result.
Recognise the operating condition
Intermittent communications, seasonal access, shared gateway images, and limited staff make certificate expiry a physical operations problem.
Frame the decision the owners must make
Can trust be replaced across unmanned sites without losing telemetry or control?
Apply QNSI to the controlled boundary
Group gateway certificates by site access, issuer, firmware, connectivity, redundancy, and rollback readiness in QNSI.
Leave the team with a concrete result
A site-by-site rotation route with preloaded trust, outage coordination, validation call, and deferred-risk register.
Prove the result in the organisation's environment
Operators test local control, telemetry continuity, alarm delivery, remote recovery, and water-quality safeguards.
What useful success looks like
A decision artifact plus proof from the real environment
The model stops at a target result. It becomes an actual case study only when a customer produces and independently validates this evidence in production.
Decision artifact
A site-by-site rotation route with preloaded trust, outage coordination, validation call, and deferred-risk register.
Independent validation boundary
Operators test local control, telemetry continuity, alarm delivery, remote recovery, and water-quality safeguards.
Real-world problem grounding
Primary sources behind the model
These sources establish the external requirement, failure mode, or risk context used to model this case. They do not endorse HEOSSI or prove that QNSI completed the scenario.
Customer evidence status
This is modelled, not a customer claim
The organisation is a composite and the result is a target state. This page does not prove a deployment, customer outcome, certification, legal conclusion, regulator endorsement, or completed control.