You're right to be concerned and carefully reviewing the code. This situation requires a clear understanding of the area classification and applicable code sections. Here's a breakdown of the issue and steps to take

Understanding the Problem:
Classified Location

The key is determining the exact classification (Class I, Division 1 or 2; Class II, Division 1 or 2). This requires the engineering drawings you mentioned. The presence of a septic system strongly suggests a Class I location due to the potential for methane gas.

Rigid Conduit & Sealoff

Good practice to use rigid conduit and a sealoff fitting to prevent gases from traveling through the raceway to non-classified areas.

Splicing Inside the Well

This is the main point of contention. Splices within a classified location are permitted only if done in a code-compliant manner.

Conflicting Code Sections



501.15 (Sealing and Splices)

This section permits splices and taps within Class I, Division 1 and 2 locations if made in enclosures identified for use in Class I, Division 1 locations.

501.10(B)(4) (Wiring Methods - Class I, Division 2)

This is where the potential conflict arises. It requires boxes, fittings, and joints to be explosionproof unless the specific code exception applies.

Steps to Take


Confirm Area Classification

This is the absolute first step. Get the engineering drawings reviewed by a qualified electrical engineer or inspector with expertise in hazardous locations. They must determine the exact classification (Class I, Division 1 or 2; Class II, Division 1 or 2). The classification drives the equipment and wiring methods required.2.

Assume Worst Case (Until Proven Otherwise)

Until you have the verified classification, you should assume the area is Class I, Division 1. This will lead to the most stringent (and safest) requirements.
3.

Compliance Based on Classification



If Class I, Division 1

The splice box MUST be rated as explosionproof for Class I, Division 1 (NEMA 7 enclosure). All entries into the box MUST use explosionproof fittings (e.g., explosionproof conduit hubs or cable glands). The pump cable must be suitable for the Class I, Division 1 environment. Often, this requires a specially rated cable that is listed for direct burial and/or submersible applications in hazardous locations. The pump cable entry into the explosionproof box must use a fitting suitable for the cable type (explosionproof cable gland, etc.). The cable gland must provide a positive seal around the cable to prevent gas migration.

If Class I, Division 2

The splice box MUST be rated as explosionproof (NEMA 7) unless the exception to 501.10(B)(4) applies. The exception is rarely relevant for septic pump applications. Wiring methods generally need to be rigid metal conduit, intermediate metal conduit, Type MC cable with listed fittings, or other wiring systems for unclassified locations. However, cable entries into the box need to be sealed. If the box is explosionproof, the pump cable entry into the explosionproof box must use a fitting suitable for the cable type (explosionproof cable gland, etc.). The cable gland must provide a positive seal around the cable to prevent gas migration. If the box is not explosionproof (and relies on the exception), careful consideration must be given to the type of cable and entry fittings to ensure the cable is securely supported and the ingress of gas is prevented.4.

Cable Entry Requirements (Regardless of Division)



Sealing

The pump cable, in particular, is a pathway for gases to enter the enclosure. Even if the box meets other requirements, a proper seal around the cable where it enters the box is crucial. This is typically achieved with a cable gland specifically rated for hazardous locations.

Cable Type

The pump cable itself must be suitable for the hazardous location and the intended use (direct burial, submersible, chemical resistance, etc.). Review the cable's specifications and listings carefully.5.

Inspection and Documentation

Before covering up any work, have the installation inspected by a qualified electrical inspector knowledgeable in hazardous locations. Keep all documentation (engineering drawings, equipment specifications, inspection reports) readily available.

Key Considerations



Manufacturer's Instructions

Always follow the manufacturer's instructions for installation and use of all equipment in hazardous locations.

Cable Sealing

Don't underestimate the importance of cable sealing. This is often overlooked but is critical to preventing gas migration.

Alternatives

Consider if there are alternative wiring methods that would avoid splicing within the well. For example, could a longer, continuous cable be run from the pump all the way back to the control panel? This would eliminate the need for a splice box inside the classified area.

Safety

The most important consideration is safety. A properly designed and installed system is essential to prevent explosions and ensure the safety of personnel and property.

In summary, until you have the verified area classification, assume the worst case (Class I, Division 1) and require an explosionproof splice box with appropriate sealing fittings for the cable entries. Once you have the classification, you can adjust the requirements accordingly, but always err on the side of caution. Flag for review