CF-Allen Rd Park-CS031209Dec..tuber 9~ 2003
Mike Satrtplcs
Aflbrdable Enterpris~
Re: Allen Lakes (~ Coppell Pond Wall Repairs
Glenn W. Campbell, P. E.
4201 Spring Valley Road
Dallas, TX 75244
45§-374-0810
F~x: 4S9-374-081 ~
Dear Mr Samples:
The pnrpose of his letter b to document the findings of our field inspection and proposed repairs to the
stone masonry facade fcr the referenced project. The inspection was authorized tD' Mr. Matt Rooney, md
was conducted on December $~' and 8~, 2003.
The wall surround the pond c~>~siat~ cfa concrete wall of unknown v¢idth and eotlfigurafion and a
separate stone ntasom'5 facillg, tn s~varal Iocatious a leos horizontal crack has opened in this atone
facade and the stone below the crock has dropped several inches up to one f~ot. This condition occurs
primarily in t~,o locations on the downstream end of thc pond Along the remainder of the wall, a narrow
void has been creatgd underneath the stone far. de. The stone facade has not yet failed in lhe lmter case -
however it will eventually fail ii1 the same rammer as the thgade that has already failed.
The cause of both conditions is tile same -- the shale foundation beneath the stone lit9ade has softened and
e;nxled away from beneath the stone, leaxing a void space. As the void widcm and deepens, the sWne is
left mlsupported and eventually tails. The concrete wall is likely keyed into the shale and does nof appear
to have ~ affected b) the failures in fl~e stone caqade.
Two s~lutions ~e available, Ihe first ~oktfion ~s to corian-act a new wall in front of the existing walt
using drilled piers and suspended concrete footin8 beam fi~r a foundation. Thi~ solution would
permanently remedy the situation, but would be very e×pensive ~ implement.
The second solution would be to e×cavate the shale at the toe of the stone fa¢ade and construct a
reinfm'ced contra'to footing wall. Thi~ solution, like the original c~)nsm~cfion, uses a "shallow"
tbtmd~fion in the shale and is therefore susceptible to the same degradation of lb0 shale over a period of
ton to fifteen years.
For estimafing ptutvoscs, the proposed concrete foOting wall should be keyed approximately 6 to 8 inches
deep into the hard shale, have a width of 12 inches, and extend upward ~ least three courses of stone.
The concrete mix should tkse a course aggregate of less tha~ 'a inch, and should be vibrated into the void.
D~e footing wail where the misting failm'es ate should be approximately 24 inches wide, 6 to 8 inches
into the hard shale, and have ~n overall height of 24 inches. Reinforcing should consist of two #4 b~rs
top and bonom with #3 ties at i8 inch spacing.
We appreciate the opporlunity to consult with )ou on this interesting prt,ject, We would be pleased to
develop construction drawings if the Owner elects to proceed with lhe tecommendatinns herein Plea.se
call if >ou have an>' questions or need any additional information.
'"" ..... '""'"
Brtan Carapbell, P.E,
J