I have contributed to several EISs and have cleaned up afterward too. I've been involved with more cleanup than the other. I think it best to develop a preliminary EIS and then revise it if necessary as the design progresses. Things will change and additional risks may be revealed. I have seen more than one very expensive blunder result from failing to consider impacts before the detailed design and also from failing to inform and update the EIS after the detailed design. I appreciate that contractors want to minimize cost, but that also means avoiding potentially larger costs when a project isn't done right. In this age of litigation, simply filing an EIS and having a regulator accept it doesn't protect you from staggering lawsuits.

Well,

Environmental, Air, Soil, Surface water, and Groundwater vulnerability studies should be achieved and taken into account in basic or detailed design.

Regards

Usually from my experience, there are 2-5 reasonable alternatives to be assessed and weighed in an ,EIS, before deciding by decision maker. Alternatives on location, capacity, avoiding sensitive sites, cost, impacts to resources, etc. No point in conducting detailed design until there is decision on the desired or best option, then conduct detailed designs and adjust final effects, mitigation’s, etc. if necessary. Often there would be some degree of public involvement, review, comment, etc. before final decision. We used a process that was less detailed (Environmental Analysis) for more routine projects, but still used alternatives, effects analysis, etc. The decision maker (responsible official) would review EA or EIS and decide which alternative best meets objectives, avoids or limits undesired effects, before detailed design, etc. And when needed, adjustments in environmental analysis or decision could be made with justification, documentation, notification, etc. Legal and environmental standards were incorporated.