Shared CO₂ Transport & Infrastructure

This Module describes requirements for Projects that use shared infrastructure for the transport and intermediate storage of CO₂. Using a mass-balance approach anchored at the point of capture, it allocates transit losses along each segment of the shared chain and returns the quantity attributable to the Project, at the point of entry to durable storage. It also contains guidance on other key aspects of shared infrastructure usage including emissions allocation, chain of custody tracking, and measurement and reporting requirements.

This Module applies to Carbon Dioxide Removal (CDR) or Reduction Projects that capture biogenic or atmospheric CO₂ and store it within durable storage reservoirs, where all or part of CO₂ transportation occurs within shared infrastructure. 

In this instance, ‘shared infrastructure’ refers to any infrastructure for CO₂ transport or intermediate storage that is simultaneously or sequentially used by other entities (including other CDR projects, industrial users, or CO₂ utilisation chains). 

Examples of shared CO₂ transport infrastructure include the following components of a CO₂ transportation system, where any such components are shared with other users:

• Transportation methods such as CO₂ pipelines, ships, trains, and trucks;
• Intermediate storage vessels, such as tanks and buffer vessels; 
• Associated processes between the boundaries of the capture plant and storage facility, such as liquefaction, regasification, and gas treatment; and 
• Other equipment, such as compressors, pumps, and heat exchangers.

Shared infrastructure may be owned and operated by the Project Proponent, or by a third party. A third-party operator may account for the CO₂ it transports and stores using its own methods, reflecting how its infrastructure is instrumented and operated. This Module does not prescribe a single such method, but outlines a number of principles on creating a verifiable mass-balance across complex systems, supported by measurements of reasonable accuracy. Where a Project relies on an operator's accounting to establish its stored quantity, that accounting must be consistent with the principles set out in this Module, so that the quantity attributed to the Project is determined on the same mass-balance basis and is not overstated.

The scope of this Module is limited to the transport of CO₂  between the boundaries of a Project’s CO₂ capture location and its durable storage reservoir. Within this boundary, the Module quantifies the mass of the Project's CO₂ delivered to the point of entry to durable storage, net of losses within the transport system (Section 6).

From the point of entry to the storage reservoir, the applicable Storage Module governs the quantification of the durably stored quantity, together with durability, risk of reversal, and monitoring of the stored CO₂. 

For guidance on broader aspects of carbon removal and reduction pathways involving CO₂ capture and storage, refer to the relevant Protocol.

Projects using shared CO₂ transport infrastructure must follow the Environmental & Social Impacts requirements of the Isometric Standard, including any pathway-specific environmental and social risks addressed in the applicable Protocol.

A Project using shared CO₂ transport infrastructure typically spans multiple segments and locations, some operated by parties other than the Project Proponent. For any segment that the Project Proponent owns, operates, or controls, the Project Proponent must demonstrate that the requirements of the Standard are met directly.

For each Transport Infrastructure Segment operated by a third party and shared with other users, the Project Proponent must show two things:

• that the segment is permitted under applicable law and operating in compliance with those permits.
• an evaluation to demonstrate that the Project's use of the segment causes no material additional environmental or social harm.

The Project Proponent is not required to obtain the operator's internal documentation, or to independently re-assess the operation of infrastructure it does not own or control, unless the available evidence indicates a risk of non-compliance or harm, in which case the Project Proponent must obtain further evidence sufficient for the VVB to assess that risk.

Transport and intermediate storage of CO₂ through shared infrastructure typically involves multiple parties, for example distinct operators for capture facilities, transport and intermediate storage, and storage sites. To avoid double-counting, a single Project Proponent must be specified contractually as the sole owner of the Credits, in accordance with the Ownership Section of the Isometric Standard.

For each Project evaluated under this Module, the Project Proponent must document the project's characteristics in a Project Design Document (PDD), as set out in the Documentation Section of the Isometric Standard. The PDD forms the basis for Project Validation and Verification, and must include the requirements outlined in the Standard and the applicable Protocol.

For a Project using shared CO₂ transport infrastructure, the PDD must in addition include:

• a description of the shared transport system, including the transport methods, intermediate storage, and associated processes and equipment used, the durable storage destination(s), and the components that are shared with other users; and
• the division of the transport pathway into transport infrastructure segments (Section 5), including the boundaries of each segment and the points at which segments are designated.
• the determination of the Project's share of each shared transport infrastructure segment (FSₛ), including the basis on which each share is derived from the segment measurements (Section 5.2);

Further documentation that must be included in the PDD is specified in the Section to which it relates, namely: 

• the approach to quantifying CO₂ losses, including the treatment of retained heel and line-pack (Section 6);
• the approach to allocating embodied, transport, and energy-use emissions across segments (Section 7);
• the chain of custody for each segment (Section 8); 
• a description of measurement points along the chain of custody, to be included in the Project’s monitoring plan (Section 9);
• the approach to reconciling the start- and end-point measurements (Section 9.2);
• the approach to temporal delays, where used (Section 9.3); and
• the arrangements for securing access to data for segments operated by third parties, and an assessment of data-gap risk and the conservative gap-handling procedure (Section 9.4).

Where a Project uses shared CO₂ transport infrastructure, its CO₂ is conveyed to durable storage through a chain of transport and intermediate storage assets. These assets may be operated by different parties, and along the chain the Project's CO₂ may be combined with, or separated from, CO₂ belonging to other users.

To make the attribution of CO₂ consistent and auditable, the transport pathway between the boundary of the Project's capture facility and the entry to its durable storage reservoir is divided into a series of transport infrastructure segments. A transport infrastructure segment is a portion of the transport pathway across which the CO₂ streams present, the Project's share of them, the mode of transport, and the operator all remain unchanged.

The transport infrastructure segment, designated according to Section 5.1, is the common unit of accounting for this Module. The Project's share of each segment (Section 5.2) is used to quantify the Project's CO₂ losses, segment by segment (Section 6), and to allocate embodied, transport, and energy-use emissions to the Project (Section 7), so that losses and emissions are apportioned on a single, consistent basis. The chain of custody to a given storage reservoir is the continuous, unbroken sequence of transport infrastructure segments connecting the capture facility to that reservoir (Section 8).

The Project Proponent must divide the transport pathway, from the boundary of the capture facility to the entry point of the durable storage reservoir, into transport infrastructure segments. A new transport infrastructure segment must be designated:

• each time two or more CO₂ streams are merged;
• each time a CO₂ stream is separated into two or more streams;
• at each change in the mode of transport (for example, from pipeline to ship, or from ship to truck);
• at each change of operator, or handover of custody, between parties responsible for the infrastructure; and
• at additional points determined by the Project Proponent for operational or system-boundary clarity, in agreement with Isometric.

The division of the transport pathway into segments, including the boundaries of each segment and the points at which segments are designated, must be documented in the Project Design Document (Section 4.3).

Where a transport infrastructure segment is shared with other users, the Project's losses and emissions attributable to that segment must be determined from its share of the CO₂ conveyed through the segment:

$$FS_s = \frac{CO_{2,Project,s}}{CO_{2,Total,s}}$$

(Equation 1)

Where:

• $FS_s$ is the Project's share of the CO₂ conveyed through segment s; equal to 1 for a segment used exclusively by the Project.
• $CO_{2,Project,s}$ is the is the mass of the Project's CO₂ conveyed through segment s over the Reporting Period, in tonnes CO₂.
• $CO_{2,SegmentTotal,s}$ is the total mass of CO₂, from all users, conveyed through segment s over the Reporting Period, in tonnes CO₂.

$FS_s$ is carried from segment to segment along the custody chain: the Project's CO₂ entering a segment is its CO₂ leaving the preceding segment, net of that segment's losses; and where a stream is separated at a node, the Project's CO₂ is allocated across the segments leaving the node.

$FS_s$ must be determined from the segment measurements required under Section 9.1.

Protocols for CCS determine the net Removal or Reduction for a Reporting Period based on a quantity stored in each durable storage reservoir, $CO_{2,Storage,i}$. 

Where a Project is the sole user of dedicated transport infrastructure, $CO_{2,Storage,i}$  is measured directly at the point of entry to durable storage and attributed in full to the Project.

Where the Project's CO₂ is commingled with that of other users in shared CO₂ transport infrastructure, it cannot be measured at the point of entry to durable storage as a quantity attributable solely to the Project. In this case, the quantity of the Project's CO₂ delivered to durable storage at each destination i is determined from the quantity it captures and the CO₂ lost in transit to that destination:

$$CO_{2e,\text{Delivered},i} = p_i \times CO_{2e,\text{Captured},RP} - CO_{2e,\text{TransitLosses},i}$$

(Equation 2)

$$\sum_{i}^{N} p_i = 1$$

(Equation 3)

Where:

• $CO_{2e,\text{Delivered},i}$ is the gross mass of the Project's CO₂ delivered to the point of entry to durable storage i over the Reporting Period, net of transit losses, in tonnes. 
• $CO_{2e,\text{Captured,RP}}$ is the gross mass of the Project's CO₂ captured over the Reporting Period, as determined by the applicable Protocol, in tonnes. 
• $CO_{2e,\text{TransitLosses},i}$ is the Project's attributable CO₂ losses within the transport system along the custody chain to reservoir i, quantified in accordance withSection 6.1, in tonnes.
• $p_i$ = the proportion of the Project's captured CO₂ routed to durable storage reservoir i; equal to 1 where all of the Project's CO₂ is routed to a single reservoir.
• $N$= the number of durable storage reservoirs receiving the Project's CO₂ in the Reporting Period.

Equation 2 is stated in gross (all-origin) CO₂ mass, consistent with the definition of $CO_{2,Storage,i}$  in the applicable Storage Module. Where a Protocol applies a biogenic or eligibility fraction (for example, $F_B$ in the Bio-CCS Protocol), that fraction is applied by the Protocol to $CO_{2,Storage,i}$ and is unaffected by this Module.

All quantities in Equation 2 and in Section 6.1 are masses of CO₂, determined as the mass of the conveyed fluid multiplied by its CO₂ concentration in accordance with Section 9.1.1, so that variation in CO₂ concentration or purity along the transport chain is accounted for.

The transit losses quantified under this Module (Section 6.1) and any losses quantified beyond the point of entry to durable storage by the applicable Module or Protocol are separate and must not be double-counted. 

The quantity determined under Equation 2 is reconciled, for each Reporting Period, against the quantity confirmed as durably stored, and is treated conservatively where the two do not reconcile, in accordance with Section 9.2.

The Project's transit losses to the point of entry to durable storage are the sum, over the segments forming the custody chain to that reservoir, of the Project's attributable share of the CO₂ lost from each segment:

$$CO_{2e,\text{TransitLosses},i} = \sum_{s} FS_s \times L_s$$

(Equation 4)

Where:

• $FS_s$ is the Project's share of the CO₂ conveyed through segment s, determined in accordance with Section 5.2 (equal to 1 for a segment used exclusively by the Project).
• $L_s$ is the total mass of CO₂ lost from segment s over the Reporting Period, in tonnes CO₂e, determined in accordance with Section 6.1.1.
• the summation is taken over all transport infrastructure segments forming the custody chain to reservoir i.

Lₛ must be determined from the mass and CO₂ concentration measured at the segment's measurement points, in accordance with the measurement requirements of Section 9.

The loss from each transport infrastructure segment, Lₛ, must be determined by one of the two methods below. The Project Proponent must state the method selected for each segment in The Project Design Document (Section 4.3).

Method A — direct mass balance. The segment loss is the difference between the CO₂ measured entering and leaving the segment, adjusted for any change in the CO₂ held within the segment over the Reporting Period:

$$L_s = CO_{2,\text{in},s} - CO_{2,\text{out},s} - \Delta I_s$$

(Equation 5)

• $CO_{2,\text{in},s}$ is the mass of CO₂ measured entering segment s over the Reporting Period, in tonnes CO₂e, determined in accordance with the measurement requirements of Section 9.1.
• $CO_{2,\text{out},s}$ is the mass of CO₂ measured leaving segment s over the Reporting Period, in tonnes CO₂e, , determined in accordance with the measurement requirements of Section 9.1.
• $\Delta I_s$ is the change in the mass of CO₂ held within segment s between the start and end of the Reporting Period (Section 6.1.2), in tonnes CO₂e; equal to zero for a segment that holds no CO₂ inventory.

Method B — source-level. The segment loss is the sum of the CO₂ released from the segment by each loss mechanism:

$$L_s = CO_{2,\text{fugitive},s} + CO_{2,\text{vented},s} + CO_{2,\text{leaked},s}$$

(Equation 6)

Where each term is the mass of CO₂ lost from segment s over the Reporting Period through fugitive emissions, venting, and leakage respectively, in tonnes CO₂e. Each term must be determined from direct measurement in accordance with the measurement requirements of Section 9.1 or, where direct measurement is not feasible, from certified or published emission or loss factors specific to the infrastructure, equipment, or operating conditions of the segment.

Where a loss factor is used in place of direct measurement, it must be representative of the segment to which it is applied. The Project Proponent may use:

• Infrastructure- or equipment-specific factors: a loss factor specific to the infrastructure or equipment type used in the segment, for example manufacturer-certified fugitive emission rates for the pipeline material or vessel type in use, results from independent system-wide pressure-decay or leak testing of the segment, or values published in a recognised industry standard for that equipment or operating condition.
• Regional factors: a loss factor determined for the geographic area in which the segment operates, produced by a reputable source such as a pipeline or utility operator, a governmental body, or an independent research organisation. The segment must lie within the area for which the factor was determined.

When using Method B, the Project Proponent must justify in the Project Design Document (Section 4.3) that the factor is applicable to the segment, and must propagate the associated uncertainty into the conservative estimate of net Removals or Reductions in accordance with the Uncertainty section of the Isometric Standard.

CO₂ may be retained within the transport system at the start or end of a Reporting Period, for example as line-pack within a pipeline, or as heel retained in a transit vessel or intermediate storage tank after offloading. This retained CO₂ is within the transport system but has not been lost, and has not yet been delivered to the reservoir.

The change in the mass of CO₂ held within each segment over the Reporting Period, $\Delta I_s$ , must be accounted for in the segment mass balance (Equation 5), so that retained CO₂ is not misclassified as a loss. The mass of CO₂ held within a segment at the close of a Reporting Period must be carried forward as the mass held at the start of the following Reporting Period, so that no CO₂ is double-counted or omitted across the period boundary. This treatment must be consistent with the provisions for temporal delays in Section 9.3.

$\Delta I_s$ may be taken as zero for a segment that operates at materially the same pressure, temperature, and composition at the start and end of the Reporting Period, where this is justified in the monitoring plan. Where a segment is shared, the CO₂ held within it, and any change in that inventory, is allocated to the Project on the same basis as the segment's losses ($FS_s$, Section 5.2).

The Project Proponent must state the approach taken to quantifying retained CO₂, including the treatment of heel and line-pack, in the PDD (Section 4.3).

GHG emissions accounting for CO₂ transport infrastructure should be carried out in accordance with the GHG Accounting Module v1.1 and Energy Use Accounting Module v1.3.  The following sections provide guidance on specific considerations for shared CO₂ transport infrastructure.

Embodied emissions associated with shared CO₂ transport infrastructure must be accounted for and amortized in accordance with the GHG Accounting Module v1.1, which provides for proportional allocation where infrastructure is shared among multiple users. Where a Project's CO₂ is transported through more than one transport infrastructure segment (as defined in Section 5), this allocation must be applied to each segment in turn.

For each shared segment, the allocation basis must use the sum of:

• the capacity it used, i.e. the mass of the Project's CO₂ conveyed through the segment; and
• the capacity it reserved but did not use (not less than 0), counted only where no other user conveyed CO₂ through it.

This share is measured against the segment's total design capacity. The principle is that a Project bears the embodied emissions of the capacity it used, plus any capacity it reserved and left idle, but never capacity left idle by the operator or filled by another user.

This allocation and its amortization schedule must be reviewed and updated as the Project's use, its reserved capacity, and the segment's total design capacity become known, in accordance with the GHG Accounting Module v1.1.

Where CO₂ is transported by non-pipeline modes (such as truck, rail, or ship), the emissions from that transport must be accounted for in accordance with the requirements in Section 4.2 of the GHG Accounting Module v1.1. Energy use associated with pipeline transport and functionally connected infrastructure is accounted for under Section 7.3.

Where a transport movement is used exclusively by the Project, its transport emissions are attributed directly to the Project. Where a movement is shared, such as in a shipment in which the Project's CO₂ is one part of a larger total volume, the transport emissions must be allocated to the the Project at the level of each transport infrastructure segment (Section 5), on the same capacity-based allocation basis as described in Section 7.1.

This allocation must be reviewed and updated as the Project's use and its booked capacity become known.

Shared CO₂ transport infrastructure consumes energy, including the electricity, fuel, and heat used by compressors and booster stations, liquefaction and regasification, heaters, pumps, and intermediate storage. This energy use must be accounted for in accordance with the Energy Use Accounting Module v1.3. Direct emissions from non-pipeline transport (truck, rail, or ship) are accounted for under Section 7.2.

Where energy-consuming infrastructure is shared among multiple users, the associated energy emissions must be allocated to the Project at the level of each transport infrastructure segment (Section 5), based on the mass of the Project's CO₂ handled within the segment relative to the total mass of CO₂ handled within it, or by another justifiable allocation basis that more accurately reflects the Project's energy use, subject to verification and consistent with the Energy Use Accounting Module.

The Project Proponent must maintain an unbroken and auditable chain of custody for the Project's CO₂, from the point at which the Project assumes custody at the boundary of the capture facility through to the point at which the CO₂ enters the durable storage reservoir. 

Within shared infrastructure, the Project's CO₂ may be kept physically separate from, or commingled with, CO₂ from other sources, including where residual CO₂ from a prior user is retained in a sequentially-used asset. The Project Proponent must identify, for each transport infrastructure segment, which of the following applies:

Where a segment is operated by a third party, the Project Proponent must obtain the custody and transfer records for that segment, or arrange for the operator to provide them, in accordance with Section 9.4.

The chain of custody terminates where the Project's CO₂ enters the durable storage reservoir. A storage confirmation from a third party storage provider evidences that the Project's CO₂ was durably stored and closes the custody chain. The mass certified as stored is reconciled according to Section 9.2.

At Validation, the Project Proponent must document in the Project Design Document, for each transport infrastructure segment:

1. whether the segment's custody form is Segregated or Non-segregated, and the evidence supporting that determination; and

2. the procedure for recording and reconciling CO₂ mass and concentration at each point of transfer, consistent with the transfer-mode requirements above.

At Verification, the Project Proponent must provide the custody and transfer records for the Reporting Period.

At each transport infrastructure segment, the Project Proponent must measure the mass of and concentration of CO₂, to determine the segment's CO₂ losses (Section 6.1) and to allocate project emissions between the users of that segment (Section 7). The required measurement approach depends on whether the segment uses continuous or batch transfer.

At each transport infrastructure segment, the Project Proponent must measure the mass and CO₂ concentration of the Project's CO₂. The required measurement approach depends on whether the segment uses continuous or batch transfer.

For segments with continuous flow (pipeline and other continuously-metered segments), the Project Proponent must confirm that there is continuous metering of CO₂ mass flow and CO₂ concentration at the entry and exit of each segment, and at each point where streams merge or separate.

For each consignment into a batch system (such as road, rail, or water), the Project Proponent must record the measured mass and CO₂ concentration at loading and at receipt, reconciled against the preceding record. Mass of each consignment must be determined by one of: a legal-for-trade weighbridge or platform scale; calibrated static tank gauging using level, temperature and pressure together with a validated equation of state; or a calibrated mass or volumetric flow meter on the transfer line.

CO₂ concentration of each consignment must be determined by either a continuous inline analyser meeting the requirements below, or, where inline analysis is impractical for discrete consignments, laboratory analysis of a representative sample drawn in accordance with a recognised sampling standard.

Metering instruments and analysis methods used under either transfer mode must meet the following requirements, consistent with the requirements applied at the capture facility and the storage reservoir under the applicable Protocol and Storage Module:

• have an accuracy of 2% of the measured value, or better;
• be calibrated at a frequency that meets or exceeds manufacturer requirements, and in any case at least annually; and
• be traceable to national standards.

Where a segment is operated by a third party whose metering is installed to a different recognised specification, such as a custody-transfer or fiscal-metering standard, that specification may be accepted, in agreement with Isometric.

The loading and receipt records for a consignment are treated as reconciled where they agree to within their combined measurement uncertainty and the change in in-system inventory over the transfer (including heel and line-pack). A consignment whose records diverge beyond this tolerance must be handled as a measurement discrepancy under Section 9.1.3.

Where a consignment passes through intermediate storage, the Project Proponent must reconcile inventory before and after (tank level, pressure and temperature), stating the minimum heel and line-pack assumptions applied.

A Project's transport chain may involve many measurement points across several segments, operated by different parties and built to different measurement specifications. The requirements below allow measurement rigour to be matched to what is material, while keeping the overall quantification conservative.

Measurement rigour must be proportionate to the materiality of the segment. Where the losses across a segment is demonstrably immaterial, or a pre-existing measurement point operated by a third party cannot meet the applicable requirement of Section 9.1.1, the Project Proponent must instead document that point's measurement uncertainty and propagate it into the conservative estimate of net removals in accordance with the Uncertainty section of the Isometric Standard.

At Verification, for each Reporting Period, the Project Proponent must provide a record of any discrepancy between the start-point and end-point measurements for each segment that exceeds their combined measurement uncertainty and the change in in-system inventory, together with the investigation of its cause, and evidence of any notification made to Isometric where the discrepancy was material.

For each Reporting Period, the quantity of $CO_{2e,\text{Delivered},i}$ determined under Section 6 must be reconciled against the quantity confirmed as durably stored by the storage operator (for example, through a storage certificate). This reconciliation operates over the Reporting Period across the whole transport chain, in addition to the per-transfer reconciliation under Section 9.1.1.

The two quantities are treated as reconciled where the difference between them falls within their combined measurement uncertainty and any change in the CO₂ held within the transport system (in transit, as line-pack, or as retained heel) between the start and end of the Reporting Period. 

Where the difference exceeds what measurement uncertainty and the change in in-system inventory can account for, the Project Proponent must investigate and document the cause, and the quantity credited for the Reporting Period (Section 6, Equation 2) must be reduced to the lower of the capture-derived quantity and the quantity confirmed as durably stored.

At Validation, the Project Proponent must document in the PDD the capture-side and storage-side measurement locations and the approach to reconciling them, including how the combined measurement uncertainty and the change in in-system inventory are determined, and the form and source of the storage confirmation.

At Verification, for each Reporting Period, the Project Proponent must provide the reconciliation of the capture-derived quantity against the storage confirmation and the quantified transit losses, together with, for any difference exceeding the combined measurement uncertainty and in-system inventory change, the investigation of its cause, the conservative quantity applied, and evidence of any notification made to Isometric where the difference was material.

Where CO₂ is transported and intermediately stored through shared infrastructure, there may be a delay between the point at which CO₂ is captured within a Reporting Period and the point at which it enters durable storage.

Where it is not possible to identify the specific time at which CO₂ captured during a Reporting Period enters durable storage, the following may each be estimated on the basis of the average per tonne of CO₂ handled during the Reporting Period, rather than by matching a specific quantity of captured CO₂ to the time it enters storage:

• CO₂ losses within the transport system (as quantified under Section 6); and
• Emissions associated with transport and intermediate storage (as accounted for under Section 7).

This must be applied consistently with the conservatism and Materiality principles of the GHG Accounting Module.

At Validation, where the Project intends to estimate CO₂ losses or transport and intermediate-storage emissions on a per-tonne average basis as described above, the Project Proponent must document the approach in the PDD, including the basis on which the per-tonne average is derived. 

The Project Proponent remains responsible for providing all data required to quantify and verify the Project's Removals or Reductions, CO₂ losses, and emissions across every transport infrastructure segment, including segments operated by third parties. 

The Project Proponent must secure the provision of the necessary segment data through the contractual arrangements outlined the Ownership section of the Isometric Standard, or by other binding means, and must make that data available to the VVB at verification.

Where a third-party operator reports the mass of CO₂ handled on a periodic basis, for example a monthly certificate of the quantity of the Project's CO₂ received into the operator's transport or storage system, such a certificate may be used as the segment-boundary measurement for the custody-transfer point to which it relates. The documentation must state the Reporting Period, the mass and the CO₂ concentration or purity basis of the quantity certified, and the metering standard on which it is based. 

Data underlying the quantification is published in accordance with the Data Sharing requirements of the Isometric Standard.

Because shared transport relies on third-party operators, there is a risk of gaps arising in the data needed for quantification. Where a data gap occurs, the following requirements apply:

• The Project Proponent must apply a documented and conservative procedure to substitute or estimate the affected parameter such that the credited quantity of stored CO₂ is not overstated; 
• the substitute value must be derived from validated support data,  for example a mass-balance reconciliation across the segment, custody-transfer or billing records, or measurement at an adjacent metering point;
• the resulting uncertainty must be carried through in accordance with the Uncertainty Accounting Section of the Isometric Standard. Each gap, its duration, and the substitution method used must be logged and disclosed.

As soon as it becomes apparent to the Project Proponent that a data gap has arisen or is likely to arise, the Project Proponent must notify Isometric without undue delay, so that the approach to handling it can be agreed ahead of Verification.

At Validation, the Project Proponent must assess in the PDD the risk of data gaps arising in shared transport, and document the conservative gap-handling procedure to address them.

At Verification, for each Reporting Period, the Project Proponent must provide a log of any data gaps and the substitution or reconstruction applied, and evidence of any advance notification made to Isometric.