The state and federal standards are the minimum requirements needed to operate an ICF/IID program and those standards are often low in all areas including disaster plans. In Texas, a disaster plan has a good deal of items and information required. You must have food, clothing, medications, etc. as a norm. There is one important issue that the state requirements overlook when it comes to disasters.
Consider the potential for a disaster at your facility. You have made preparations. You have all your required supplies, you have a disaster plan, and you have staff willing to work during the disaster. The day comes and disaster strikes. You are not required to evacuate, but your facility is without power, without water, and without phone service. You expect it is going to be three to four days before these items are restored. Your staff use flashlights at night, all the medications you need are on-site, you have water, you have food, and things are going along just fine. You can not see any potential problems, until someone has to go to the restroom. Because your facility is in the middle of town, it's not like you can go out into the woods. No, you are stuck with two options. You could use your three day supply of toilet paper, because you know you have those standards supplies on hand as all ICF/IID programs should. Once you use your bathroom though you are faced with a major problem. You could use some of your drinking water to flush the toilet, and hope that the sewer lines are not part of the services that have been cut, or you could have everyone use the toilet and simply leave it until the utilities are back. The problem with leaving it is that it becomes smelly, it promotes a potential health hazard, and depending on how long the crisis last, it could be a major issue to flush the toilet once utilities do come back. That's your first option in a nutshell, or you could be prepared.
The second option that you could have in place is to purchase five gallon buckets - the kind you find at hardware stores - and go to a sporting goods store and purchase a toilet seat made for the five gallon buckets - yes, they make a special seat to attach. Now the people you serve can use the toilet with dignity and still within the bathroom. Once finished, the bucket can be emptied into a trash bag or cleaned through another approved method. Between bathroom usage, the bucket can be put outside. This will help avoid the smell, the health hazard, and the potential for a really bad clogged toilet once the power and utilities do come back. You may want to consider a few of these buckets so that rotations can be maintained.
The bottom line is the state's directives for a disaster plan and supplies is good, but it does not cover everything. Consider bathroom needs and the preparation that can go into getting ready for a disaster to ensure you face no problems.
I am not trying to promote anyone's website, but here is a link to a potential toilet bucket - just remember, you can get your own going easily through places like Lowes and Home Depot, and there are several other organizations selling complete kits as well: Bucket Toilet Example