Atrazine is a well known pollutor of our drinking water and is suspected as a Carcinogen and Endocrine disruptor, why would someone want to use it?
If you do not care that you are polluting the water yuou drink you could respray, but there are other, less expensive, less polluting, more environmentally friendly products out there to use.

I agree with you , kimmsr. Big problem here in KS. However, you might offer Gardendummie some alternatives. I'd be interested in seeing what those might be.
hortster

Rather than treating the symptom of a problem, the "weeds", find out why they are growing there, correct the conditions that promote or allow them to grow, soil pH and nutrient availability, and do what is necessary to grow a strong and healthy turf that will discourage "weed" growth.
Spraying poisons around is making the world our grandchildren will be living in hazardous to their health.

There are other products much less offensive than atrazine. I know that you likely will not go into the detail that kimmsr suggests. I suggest that you go online and research the options. My only thought is that you should use the minimum to maintain your goals. I believe that "less is more" but that "less" doesn't mean "nothing."
hortster