Okay, this is a complex situation, but let's break it down and address the code requirements to find a path to compliance. You've accurately identified the key issues and code sections. Here's a step-by-step approach

1. The Core Problem: Inadequate SSBJ and Parallel Path
SSBJ Missing/Inadequate

Your primary issue is the lack of a Code-compliant SSBJ (System Bonding Jumper). Rigid conduit can be used, but the LFMC section breaks that continuity. LFMC isn't a suitable SSBJ for the fault current levels you're likely dealing with.

Parallel Path via GEC

The grounding electrode conductor (GEC) between the building's grounding system (UFER/ground ring) and the transformer creates a parallel path. This means you cannot use the exceptions in 250.30 to omit the SSBJ. Even though the GEC is direct buried and not run with the phase conductors, it's still a parallel path to ground.

2. Necessary Steps for Compliance

Here's the recommended course of action, prioritized: Eliminate the LFMC

This is the most direct and best solution.

Replace the LFMC with Rigid Conduit

This restores the continuous metallic path from the transformer to the panel. This eliminates the inadequate ground path and complies with requirements for the SSBJ. Bonding all conduit sections properly is crucial.

Replace the LFMC with another approved raceway Such as IMC or EMT if environmental conditions allow. Install a Properly Sized SSBJ (if rigid conduit solution isn't feasible)



Run a Separate SSBJ

If you absolutely cannot replace the LFMC, you must install a separate, properly sized SSBJ (conductor).

Sizing

The SSBJ must be sized according to 250.102(C). It's based on the size of the ungrounded (phase) conductors. Calculate the required size carefully. Erroring on the side of larger is always better.

Material

The SSBJ must be copper, aluminum, or copper-clad aluminum.

Route

The SSBJ must be run with the phase conductors within the same raceway or cable. This is a crucial requirement. Taping or securing it to the existing cable bundle is essential. You may need to pull in additional conduit if there isn't room in the existing raceway.

Terminations

The SSBJ must be securely connected to the transformer's neutral point and to the panel's neutral bus/grounding bus (as required). Use appropriate listed connectors.

Addressing the Grounding Electrode Conductor (GEC)



Keep the GEC

The connection to the UFER and ground ring is beneficial for overall system grounding and helps reduce touch potential. Do not remove this.

Ensure Proper GEC Sizing

Verify that the GEC to the UFER/ground ring is properly sized according to 250.66.

3. Bonding Considerations Bonding the Conduit (Regardless of SSBJ Solution)



Required

250.92(A) mandates that all metallic raceways (conduit) containing service conductors be bonded.

Methods

Use listed bonding bushings and jumpers to ensure continuity across all conduit sections, including at the transformer and at the panel.

Addressing Potential Objectionable Current

You're correct that bonding the conduit can create a parallel path and potentially introduce objectionable current onto the conduit. However, this is often unavoidable in SDS systems.

Monitoring

After the system is operational, monitor the conduit for excessive current flow. If you detect a significant amount of current (enough to cause overheating, nuisance tripping, or voltage drops), investigate the source. It could indicate a ground fault somewhere in the system.

4. Why Replacing LFMC is Preferred Simplicity

It eliminates the need for a separate SSBJ conductor.

Reliability

A continuous metallic raceway is generally more reliable than relying on a separate conductor for fault current return.

Code Compliance

Easier to demonstrate compliance to the AHJ (Authority Having Jurisdiction).

5. Important Considerations Load Calculations

Ensure the transformer and conductors are properly sized for the connected load.

Overcurrent Protection

Verify that the overcurrent protection devices are correctly sized and coordinated.

Documentation

Keep thorough records of all grounding and bonding connections.

AHJ Approval

This is a complex situation. Discuss your proposed solution with the AHJ (electrical inspector) before making any changes. They may have specific requirements or preferences. Documentation and calculations will be critical for approval.

In summary: The ideal solution is to replace the LFMC with rigid conduit to restore the continuous metallic raceway. If that is not possible, installing a properly sized SSBJ, run with* the phase conductors, is essential for compliance. Regardless, the grounding electrode conductor to the UFER/ground ring should be maintained, and all conduit sections must be bonded. Be prepared to provide calculations and documentation to the AHJ. Good luck! Flag for review