Sewer Inflow and Infiltration Event Monitoring

Define the investigation area and question

Map the sewer area, relevant branches, pump stations and downstream conditions. Identify the operating problem: wet-weather loading, recurring high level, changed pump duty or another observed concern. The selected boundary should make it possible to compare the relevant events and choose a useful next field check.

Record known connections, temporary arrangements and recent network work. A catchment map needs an effective version because changes can alter the relationship between rainfall and the monitored point. The responsible utility team should identify gaps in the current mapping before the project assumes a complete boundary.

Select observations for the actual hydraulic condition

The network and instrumentation specialists determine appropriate flow or level methods for the selected locations. Record pipe or channel geometry, access, surcharge, sediment and other conditions that matter to the measurement. A method suitable for one operating range may need qualification under another.

Where level is used as an observation, retain it as level unless an accepted relationship supports a derived flow. Backwater, obstruction and changing downstream conditions can alter that relationship. The report should preserve the actual quantity and quality rather than force every point into an unsupported flow total.

Establish the rainfall source and its limits

Identify the rain gauge or other accepted source, its location, time basis and quality. A rainfall record outside the relevant catchment may not represent the event at every network branch. The responsible analyst should approve how the source can support the selected comparison.

Keep missing observations and any estimated rainfall visible. Align the event windows with the network records using acquisition times. A delayed upload should not shift the apparent rainfall response into a later operating period.

Build a representative dry-weather reference

Select periods that the utility considers suitable for the intended baseline. Record day type, legitimate discharge patterns, pump operation and known maintenance. A single quiet night may not represent the ordinary variation of the area.

Preserve the reason each period was included or excluded. The baseline should remain reproducible when the report is reviewed later. If a source was suspect or a route changed, keep that qualification rather than treating the period as an ordinary reference merely because its values look plausible.

Compare wet-weather events by their actual conditions

Record rainfall timing and the network response, including relevant delay and recovery. Events can differ in intensity, duration, antecedent conditions and operating arrangements. The analyst should determine which comparisons support the intended investigation.

A coincident increase in level or flow can guide further work, but it does not by itself identify the exact inflow or infiltration location. Keep the observed relationship separate from the proposed explanation. The field programme supplies the evidence needed to confirm a specific route or defect.

Distinguish surcharge and blockage from additional inflow

Retain downstream level, pump status or other relevant operating context where available. A high upstream level can reflect restricted discharge as well as an increased incoming quantity. The network specialist needs the actual hydraulic evidence before assigning the cause.

Keep inspection and maintenance findings with the event. A cleared obstruction, changed pump arrangement or altered downstream condition can change the next comparison. The report should show those interventions so a lower subsequent level is not automatically attributed to reduced infiltration.

Plan safe installation and recurring access

The utility determines confined-space, access, isolation and site-specific working requirements. Include qualified local personnel and the approved work method in the installation plan. Remote records should help target field visits, while physical checks remain under the relevant site's procedures.

Select protection and maintenance arrangements for the actual wastewater environment. Fouling, sediment, debris and changed mounting can affect measurement quality. The quotation should identify cleaning, reference checks, consumables and responsibility for restoring an instrument after work.

Turn the event review into a prioritised work list

A useful output identifies the area, relevant event, observed pattern and next evidence needed. The action may be a local inspection, mapping update, additional measurement or a review of downstream conditions. Give each task an owner and retain the resulting finding.

Keep priorities tied to the utility's operating requirements and available evidence. A strong correlation can justify investigation without proving a particular defect. The work list should remain explicit about that distinction so later teams do not inherit a hypothesis as an established network fact.

Accept one complete event record

Agree the expected measurement, reference and reporting outputs before commissioning. Verify point identities, units, time alignment and quality through the exported record. Include an unavailable source and show how the comparison is qualified when rainfall or network evidence is incomplete.

Where a suitable natural wet-weather event is not available during commissioning, distinguish initial instrument and data-path acceptance from later event-analysis verification. The delivery schedule should identify the remaining observation and responsible review rather than imply that the complete seasonal behaviour has already been tested.

Prepare the sewer-monitoring scope

Send the catchment map, recurring event history, available rainfall data, existing instruments and known network changes. Identify the utility's network engineer, local maintenance lead, data owner and installer. State the question the first monitored area should help resolve.

The proposal should separate field instrumentation, temporary or permanent installation, data integration, analytical review and follow-up investigation. A bounded first area gives the utility a practical basis for comparing evidence, assigning work and deciding where additional measurement would be useful.

Plan installation, continuity and operating handover

The installation proposal should identify the field equipment, available interfaces, local power, mounting conditions and communication path for the accepted point list. Suitable LoRaWAN points with 4G backhaul are selected against the actual site survey and reporting requirement. The local team supplies access and the relevant specialist participation for the physical work and reference checks.

Before commissioning, agree what evidence each test should produce. Include point identity, unit conversion, an appropriate independent comparison and the handling of unavailable observations. Where the supplied architecture retains records during an interruption, verify recovery with original acquisition times. A recovered historical record and a live notification are separate functions in the acceptance schedule.

Handover includes installed photographs, the accepted configuration, operating instructions, an export demonstration and a list of open actions with owners. Assign routine instrument checks, user administration, communication service and the replacement process. A later change to equipment, operating conditions or reporting rules should have an effective date and a review of the affected acceptance evidence.

Compare the complete quoted scope

Request separate lines for equipment, configuration, installation, specialist verification and recurring services. Identify work supplied by the customer or an existing contractor, together with the access and information needed to complete it. The quotation should make the proposed result and each dependency understandable before procurement.

Use current quotations for the selected equipment and actual site arrangement. The project estimate should account for practical maintenance and replacement as well as first installation. Agree the initial acceptance boundary and the evidence required before extending the same configuration to additional assets or locations.

Connect the decision to the project

Use Water management, Sewer network monitoring, Water utilities to place this task within the wider installation. Bring a recent operating record and identify the decision that the proposed measurement should support. A focused discussion should establish the first boundary, the responsible site participants and the evidence needed before expanding the scope.

Agree who maintains the point register and who can change interpretation rules. Preserve the previous version when a device, product, reporting period or responsibility changes. During handover, demonstrate an export that another authorised person can reconcile without relying on the dashboard operator to explain missing fields.

Discuss the scope with addanode using the actual site information, available interfaces and proposed acceptance record.

Sources and method

The IFC General EHS Guidelines, 2007, provide wastewater-management context. Site hydraulics, instrument methods and interpretation are established by the responsible utility specialists; no universal rainfall-response threshold or defect location is assumed.

Frequently asked questions