HomeMy WebLinkAboutPermit Correspondence 1983-10-21
.
.
\'1
I
Registered Professional
Civil and Mechanical Engineering
Land Surveying
325 South Sixth Street
Cottage Grove, Oregon 97424
503/942-0126
Sinclair Engineering, Inc.
October 21, 1983
Loren . ,Pleger
Building Official
RE: Monta Loma Mobile Home Park
Springfield, OR
Dear Loren:
This letter is to reiterate our telephone conversation on Friday
October 21, 1983; addressing the" external loading on the 2" class 200 PVC
pipe installed in the Manta Loma Mobile Home Park.
The pipe was laid in a 3-4 inch wide trench at a depth of 24-30
inches;,whereas the State Plumbing Code permits Schedule 40 pipe to be
laid at a minimum depth of l8-inches.
It is my professional opinion that the "additional depth in the
narrow trench will provide the equivalent protection from surface loading
as the Schedule 40 pipe would sustain from the "18-inch trench depth.
I
I
'I
I
,
I'
I
I
I base my opinion on approximately 20 years of experience of using
2-inch.PVC Class 160 in similar circumstances; and have witnessed concrete
trucks backing over" trenches" where" the water" main had recently been
installed,
Normally, trench external:loading is ,not a concern for pipelines
less than 4-inches.in diameter~ As an,example, Johns-Mansville has pub-
lished an Installation. Guide "Manual for PVC pipe. 1 1/2" - 12" diameter and
the published deflection charts start at 4-inches, A 4-inch Class~lOO pipe
will sustain an H-20:load in poor soil"conditions (70% Standard Procter "
Density) with a..3% deflection at' 36~inches depth,' The H-20 load is the
maximum truck axle load used for highway design,
I would strongly recommend,- however; that the mobile home park owner
should protect his pipeline during "the" wet" months by planking over the
trench whenever a mobile home is "backed" into place in the park. After the
first winter, this requirement should not be necessary.
I would also recommend that no mobile. home foundations be permitted to
be constructed over the Class 200 pipeline, 1
RLS/sr
CC: Olson & Thompson
c:/lY, (' 1
~,~k-~L
Roger L,Sinclair
Professional Engineer
~ 15'D Lu,,",-v-o.... st.
~