Stormwater Open Curb Manhole Survey Considerations

Review Information Needed on Manhole/Curb Dimensions and Recording it on the Survey Form

All Fabco Industries Water Quality Inserts (WQIs) are manufactured to properly fit inlets by using specific information compiled in a survey of the “as-built” inlet. The Fabco open curb manhole survey form serves as the tool to provide that information.

Fabco Industries highly recommends that this web-page be reviewed by the actual inlet surveyors prior to getting to the survey site. Friendly Reminder: The actual survey form has the QR code incorporated onto it. Scanning the code at the job-site will take the user to this survey support web-page.

Recording Manhole Measurements

The critical aspect of the manhole measurement is that you are measuring for the “Clear Space/Opening” (Box A) through which the Fabco Insert body may be placed into the inlet.

open curb manhole survey manhole measurements boxes
open curb manhole survey inlet and manhole measurements diagram
open curb inlet survey unit fit in manhole

Reminder: The body of the Fabco Inlet Insert may need to be placed into the inlet through the manhole opening.

open curb inlet survey manhole clear space diagram

That being the case, it is critical to get the clear space diameter (above left), not the outer diameter of the cover frame (above right).

Distance Measurements

Open Curb Manholes come in a wide variety of configurations. Regardless of configuration, it is important for Fabco to understand the lengths of the interior and exterior ends of the curb throat  (Boxes B and C) and the distance from the center of the manhole to the curb line (Box D). Note that the measurements for the interior and exterior ends of the curb throat are made from the inlet’s interior wall, which is represented by the dashed green line in the image below:

open curb manhole measurements photo example

The next set of measurements to record are for the curb throat height opening, depth from the curb throat opening, and the diameter of the manhole inlet itself. For the height of the curb throat opening (Box E) be sure to measure from the ceiling of the curb throat to the floor of the curb throat. For the depth of the curb throat inlet opening (Box F) be sure to measure from the floor of the curb throat opening to the very bottom of the manhole inlet. For the interior manhole diameter (Box G) be sure to measure the diameter from the interior walls of the inlet structure.

open curb manhole survey manhole exterior measurements boxes
open curb manhole survey inlet and manhole exterior measurements diagram

After filling out boxes E, F and G, check the curb throat opening for bars or grating.

See photo below for an example:

open curb inlet example stormwater inlet survey assistance