We have used the garden for 4 years and make our own compost. We have not noticed it in the grass. It seemed like the worms were in the soil and not in the overlying compost. Is there a non chemical solution? 

Good Morning, 

Thanks for your question. 

It is good for your garden that you make your own compost and add it to your garden. 

From viewing your photos, I do not think your worms are white grubs. Please click on the following link about white grubs: https://extension.umn.edu/corn-pest-management/white-grubs

The worm in your photo has many legs and antennae. Please click on the following link: https://www.bugguide.net/node/view/1781649

Please click on the following link about healthy soil in your garden: https://extension.umn.edu/managing-soil-and-nutrients/living-soil-healthy-garden

This information states: 

Every teaspoon of soil is home to billions of microorganisms—bacteria, fungi, nematodes, insects, and earthworms that play important roles.

• Bacteria and fungi break down dead plant and animal tissue which become nutrients for plants.
• Nematodes eat plant material and other soil organisms, releasing plant nutrients in their waste.
• Specialized mycorrhizal fungi form symbiotic (mutually beneficial) relationships with plants. The fungi bring hard-to-reach nutrients and water directly to plant roots, and the plants provide the fungi with carbohydrates.
• Worms and insects shred and chew organic material into smaller bits bacteria and fungi can easily access.
• Garden earthworms burrow and create pathways in soil that fill with air and water for plant roots.

I don't think these worms are a problem in your garden. They are probably helping to break down the organic material in your compost. No need to use chemicals to eliminate them. 

Good Luck!