Appeal 34986

707.11 PRESSURE DRAINAGE SYSTEMS

707.11 PRESSURE DRAINAGE SYSTEMS: "Cleanouts shall be provided for pressure drainage systems as classified under Section 710.7."
710.7 DRAINAGE AND VENTING SYSTEMS: "The drainage and venting systems, in connection with fixtures, sumps, receiving tanks, and mechanical waste-lifting devices shall be installed under the same requirements as provided for in this code for gravity systems."

The intent of the appeal is to allow construction of our sanitary force main per the approved plans (attached), without cleanouts.

ORIGINAL APPEAL TEXT:
The approved plans call for the 1-1/2" force main to be installed from the fuel facility lift station to a private Port of Portland manhole without cleanouts. The total length of the force main is approximately 1250 LF. This is how the pipe was installed in the field. Please see the attached plan sheets.

RECONSIDERATION TEXT:
Per phone conversation with City of Portland Appeals, cleanouts would be installed every 300LF along the force main.

ORIGINAL APPEAL TEXT:
Installing cleanouts every 100LF on the force main will create over one dozen potential failure points in the line. If someone does maintenance on the line in the future and does not seal every cleanout cap properly, there will be a path for the release of sewage to the surface. For this reason, Burns & McDonnell does not typically add cleanouts to sanitary force mains in our designs. Another way these cleanouts could create releases of sewage is by inadvertent damage done to the cleanouts from Port of Portland vehicles which frequently drive in the area. The Port of Portland maintenance team frequently mows the field in which this line is installed. The Port of Portland wildlife control team is also frequently driving their trucks in this field whenever wildlife is present and needs to be removed/chased away from airport grounds.

The OPSC calls for the same cleanout fittings used for gravity applications to be used on pressure systems (710.7). I understand from the OPSC that these fittings "...shall be designed to be watertight and gastight" (707.3), but I am unfamiliar with cleanout fittings which are pressure rated for a force main application. Our concern here is that gravity cleanouts may be unable to withstand the pressures generated by the force main. The grinder pumps to be installed within the lift station are designed to generate over 50psi of pressure under normal operating conditions.

OPSC 707.4(2) allows for omission of cleanouts on gravity sewers "...on a horizontal drainage pipe installed on a slope of 72 degrees or less from the vertical angle." The intent of this exception appears to consider sanitary lines which achieve scouring velocity solely with gravity. During pump operation, the force main will continuously achieve scouring velocity.

Another issue with installing cleanouts is that two separate parts of this force main, totaling approximately 350LF, were installed via HDD methods due to existing obstructions. Because of the obstructions and because the exact depth of the line in these areas is unknown, accessing the force main to install cleanouts may be unachievable with conventional excavation methods.

RECONSIDERATION TEXT:
Installing cleanouts every 300LF will provide fewer failure points to the line than installing cleanouts every 100LF while still allowing the line to be serviced.