Hello Brian,
I don't believe there is a specific feature class to house stormwater sampling points. I have listed below two locations that would work to house the data but are not meant for it.
LGIM(LGDM) > Infrastructure Operations > Tap Points - This feature class doesn't have many fields to hold data but could be used to hold your points until you find a better location or if an appropriate feature class is added to the LGIM.
LGIM(LGDM) > Water Distribution > Water Sampling Stations - This feature class may already be used if you have sampling stations for the Water Department but if not it has more of the fields you would want to track the sampling data.
One other option if you don't mind adding feature classes to the LGIM(LGDM) would be to create a feature class, in LGIM(LGDM) > Stormwater for example, to house the points with the ability to create fields for any attributes you would want to maintain. Generally when migrating data to the LGIM(LGDM) this has to be done as every city has their own important data sets that they would like to maintain and they do not match up with any feature class within the LGIM(LGDM) currently.
Hope this gave you some ideas,
Jesse
