Hi Kevin,

Wild violets are tenacious and require repeated efforts when trying to eliminate them using non-chemical methods. The violets form underground rhizomes and also spread by seed. 

To pull them by hand or using a gardening tool requires digging down to get a hold of the rhizome. Then you will need to be vigilant and pull any that you see when you survey your yard. 

Even chemical means may require multiple applications depending on the density and spread of the violets in your yard. This Penn State University article tells you all about wild violets and their removal. https://extension.psu.edu/lawn-and-turfgrass-weeds-wild-violet  The next link talks about the save use of pesticides such as reading labels carefully and wearing the appropriate personal protective equipment. https://ohioline.osu.edu/factsheet/anr-67

If you don't want to pull the violets by hand because the area is too large and chemical intervention is out of the question, you could consider smothering the affected area with thick layers of newspaper, cardboard, old carpet, etc. Of course this will also kill anything else growing under the cover and, it is not guaranteed to work. 

I hope this helps and good luck,

Sabine