rainwater for greenhouse food production

We are designing an 150,000 sf industrial production facility in Chicago with a greenhouse on the roof for food production. A cistern is proposed to collect rainwater from the roof, have it treated and used to meet >50% water demands of the greenhouse production. Does this qualify for WEc2 at all? Greenhouse water is considered a process load, but it certainly reduces potable water usage. Additionally there's a state moratorium on using rainwater for toilets and urinals in Illinois. Also, we have reached the maximum 5 points on ID through other sustainable features and exemplary points, so ID option is out.