I am trying to add up the total contributing drainage area of multiple stormwater BMP's that are located on the same parcel for a layer that contains tens of thousands of parcels. I performed a one-to-many spatial join to join the BMP points to the parcel polygon layer. Now I have a layer that contains multiple polygons for each parcel, one for each BMP present on that parcel. I would like to add together the drainage area attribute from the BMP layer for each parcel, so that I have a layer that lists each parcel only one time, but has the sum of all the drainage areas as an attribute.
I was able to figure out a solution using the summary statistics tool using the drainage area as the statistic field and the JOIN_FID as the case field. After I came back here and saw this comment, I tried using the dissolve tool, dissolving on the JOIN_FID and taking the sum of the drainage area field. Both seemed to result in an acceptable product.