I have never seen this before, in someone's field notes they measured inverts of inlets whereby they noted the invert down from the top of grate and had a second number indicating "G=0.58'" with the invert to bottom of box. Anyone able to translate this? Likely it is something simple, but for the moment I am drawing a blank.
Oh, and we cannot contact the original note keeper as they have left the profession.
Thanks in advance ...
7" diameter inlet ?
They climbed into the inlet (shhhh don??t tell OSHA)) and measured up from the invert to the inside top of the box, which is 0.58 ??thick? to the rim, maybe?
Is that a sump depth measurement? We sometimes have to report bottom of structure and/or sump depth.
Not sure I have seen the notation G for that, but it could be regional or even specific to that office - I have seen a lot of field note "conventions" that are not so much conventions as they are the individual's decision to write the notes the way they wanted to.
Something to do with a slope measurement? Although I don't know what the G would stand for...
They measured to a grate, "G", that was 0.58ft or 7in in size.
I'll render an engineering opinion on "G=0.58' ". It is a measure up to the top of the inlet curb piece. Typical curb height was 6" exposed or 0.50'. Inlet grates were typically depressed 1" (0.08') below the gutter line to assist in catching water. One field shot thus resulting in 3 existing elevations. The shot was midpoint of grate against the curb face. The invert was to the middle of the invert line with the upstream invert being higher and the downstream being lower, usually a 0.10'.
If the pipe size jumped from 15" to 18" it was typical to match the crowns, so there was an 0.25' difference in pipe inverts. Sometimes there were more than 1 pipe in, so multiple inverts were recorded; Inv In 2.75', Invert In 3.00', Inv Out 3.25'. Pipe slope was generally calculated from inlet invert to inlet invert over center to center distances, not the exact pipe inverts and pipe lengths. The capacity of the pipe was dependent on the hydraulic slope not the physical slope.?ÿ?ÿ
Inlet top frames could be either precast concrete with included curb section or cast iron with included curb section. Municipalities usually used state DOT standards, NJ = cast iron, PA = concrete.
Paul in PA, PE, PLS
After reading Paul's post; does G=Gutter? Meaning the measure up from invert of the pipe was to the inside of the top of the structure and you should ad 0.58' to get to the shot taken at the gutter.
Have you opened up the structure and checked?
Dougie
Girth of the pipe??ÿ?ÿ
Grade??ÿ Ground?
Hmmm, if that G is really gutter, is it possible that the original surveyor simply measured the top of curb with a total station and then taped the gutter and invert measurements, i.e. everything is referenced to top of curb?
I have always measured gutters with the total station. Taping it, and the inverts, from the top of curb would be unusual, but I have seen it before, with one crew member holding a lath as horizontal as possible on top of the curb as the reference point.
