This is a really interesting and practical question! The answer is almost always yes, you absolutely try to "clear" the foundation wall whenever possible. Here's why and some nuances

Why You Clear the Foundation Wall (and run underneath):
Avoid Penetrations

Penetrations through foundation walls are a significant source of potential problems:

Waterproofing Issues

Foundation walls are designed to keep water out. Any penetration is a weak point and requires careful sealing.

Structural Integrity

Drilling or coring through a foundation wall can potentially compromise its structural integrity, especially if not done properly.

Differential Settlement

If the underground utility is somehow physically linked to the foundation, differential settlement (where one part of the foundation settles more than another) can create tremendous stress on the utility line, potentially leading to leaks or breaks.

Cost

Properly engineered and installed sleeves, link seals, and waterproofing details for foundation penetrations are expensive.

Code Requirements

Building codes often have strict requirements for foundation penetrations, requiring inspections and specialized materials.

Easier Installation and Maintenance

Running beneath the foundation often simplifies the installation process. It avoids the need for precise alignment with pre-existing openings or careful drilling. It also often makes future maintenance or repairs easier, as the utility line is more accessible (assuming proper backfilling and compaction).

Reduced Risk of Damage

When utilities run under the foundation wall, there is less chance of accidentally damaging the foundation during installation or future work.

Important Considerations & Caveats



Depth of Burial

You need to ensure that you have sufficient depth of burial for the utility under the foundation to prevent frost heave, damage from surface loads, or interference with future excavation. Local codes and the type of utility will dictate the minimum burial depth.

Soil Conditions

The type of soil is a huge factor. Unstable soil (like soft clay or peat) could cause settling and potentially stress the utility even if it's not directly linked to the foundation. Proper soil compaction and possibly engineered backfill are essential.

Existing Underground Utilities

Before digging, you always must locate existing underground utilities. Hitting one could be catastrophic. "Call Before You Dig" is mandatory in most places (811 in the USA).

Proximity to Footings

Be extremely careful when excavating near footings. You don't want to undermine the foundation. You may need to consult a structural engineer to ensure your excavation won't affect the stability of the footings.

Slab Thickness and Underslab Drainage

You mentioned going through the slab. Consider the thickness of the slab and any underslab drainage systems. You don't want to disrupt drainage pathways.

Existing Buildings / Retrofits

If you are retrofitting an existing building and there is not enough depth, running beneath the footing is not an option. In this instance, you will likely have to penetrate the footing.

Regulations

Your local building codes and utility regulations should be consulted to determine what the standards are in your area.

In Summary:

The standard practice is to run utilities under* the foundation wall, provided it's feasible given depth requirements, soil conditions, and other underground infrastructure. Avoiding penetrations simplifies the installation, reduces costs, minimizes the risk of water intrusion and structural problems, and makes future maintenance easier. However, careful planning, proper excavation techniques, and adherence to local codes are crucial. Consulting with a qualified engineer or contractor is always recommended. Flag for review