ZIP codes from E911 may be incorrect

[adamfranco]

I noticed that in Middlebury, the E911 database has ZIP=05740 for many addresses near the village of East Middlebury, while the USPS's ZIP code lookup service returns the main 05753 ZIP code for these addresses.

I called the Postmaster of the East Middlebury post office and he gave me the history:

05740 is the ZIP code that only applies to the PO boxes in the East Middlebury post office building. The East Middlebury area used to not have street delivery and all residents in that part of town had free PO boxes in the East Middlebury post office. Their mailing addresses used to have the 05740 ZIP code so that the would get routed to the post office if the street address was on the envelope instead of the PO BOX number. At some point (I forgot to ask when) the residents petitioned to get street delivery and all street delivery in the Town of Middlebury uses the 05753 ZIP code. At this point 05740 should only be used for mail going directly to PO Boxes and not to houses.

This indicates that the E911 database does not have ZIP correct in at least this case. I've found other addresses near the New Have Town line that E911 gives as 05742 (New Haven's ZIP code), but which usps.com lists as Middlebury's 05753.

At this point I do not have confidence importing ZIP codes from E911 as there may be other subtle errors like these that would be hard to tease out. Leaving addr:postcode blank would at least give a list of items to do follow-up work on.

[adamfranco]

If we wanted to sometimes include addr:postcode with this import it may be worth trying to source that from another location, such as independent research with each local postmaster unless there is only one ZIP code in E911 for the town and that ZIP code is confirmed checks against USPS.com. If E911 reports more than 1 ZIP for a town and that isn't confirmed by usps.com then I don't think we can have any confidence that the ZIP in E911 is correct.

[JaredOSM]

I agree, it probably makes sense to leave the Zip code off the import, and deal with it in a separate project in the future.