The project I am working on is in a campus setting and the neighboring site's excess runoff is discharged into a storm drain pipe that runs through our project's site. To save costs, we would like to utilize this existing pipe to help collect our runoff. Downstream we plan to connect this storm drain line into a new underground infiltration basin on site. This basin would be sized to infiltrate the correct amount of runoff from our project site. So in a black box scenario the volume infiltrated on site would be according to the LEED standards. However in reality, the infiltration basin would be filled initially with some of the neighboring site's runoff because of the shared line and eventually some of our site's runoff would flow freely off site if the basin gets filled. With LEED's emphasis on managing storm water on site, would this type of system disqualify it? The same amount of water will be infiltrated on site, just some of it will technically be from a neighboring site. Or will we need to run parallel pipes to keep the systems separate?