Frank, Give me a call later today to discuss. Call my cell. Harry >>> "Jenkinson, Joel" 07/19/10 16:11 PM >>> Frank, To be honest, I'm really not certain what I have in regards to soil borings or geotech logs (probably not much) but I will look into it. Odds are that the only borings we have are through pavements, but I will also check with Public Works to see what if anything they may have. I believe this is certainly a valid concern. Just this afternoon after lunch, Dave Foster and I were doing a routine mid-month inspection of the airfield, and Dave was pointing out areas where he has encountered additional buried concrete (which I acknowledge is not the same as rock, but it is something you need to be aware of for this work). As shown in the attached pictures (taken in an area about 300 feet west of the Rwy 15 - Twy Juliet intersection) Dave has found concrete buried in numerous locations around the airfield, including in some of the areas you shaded in the graphic that came with your e-mail. Our maintenance guys are digging up and removing the waste concrete as they have time when they find it - mostly to protect our mowing equipment, but also because we know it needs to come out and it will help the RSA grading if we get rid of as much of it as we can now - but there is no way we will get it all. I think our predecessors (AATI) didn't do us any favors, as it appears they allowed debris from roadway demolition (and who knows what other projects) just to be buried on site. Dave also advises that he assisted when new power and control cables were being run between the VASIs a few years ago (maybe 5 or 6 years back) and the reason he had to help is because the ditch-witch the contractors had was literally not cutting it, so he went in with the backhoe to trench. He says the rock - probably Austin Chalk? - was pretty shallow near the south VASI box in particular, about 18 inches below grade. Also, when the electrical was put in for the AWOS in 2007, the rock was even more shallow, just a few inches below grade in places, and the trenching was almost totally in rock. The rock is relatively soft in most places and can be removed with an excavator, but once it's dug out, you will most likely need to haul it off and bring in topsoil to replace it. We saw a little of this already with the north RSA project. I think it might be prudent to go ahead and plan for a geotech / soil survey. I really doubt we have the data you would need to make good estimates. Alternatively, you might just assume that the grading and trenching is going to hit an awful lot of rock, especially (I suspect) in the area of the storm drain improvements near the big "drain hole" west of the Rwy 15 - Twy Hotel intersection, south of the 15-GS. Regards, Joel Joel Jenkinson Director, Addison Airport main: (972) 392-4850 fax: (972) 788-9334 ________________________________ From: McIllwain, Frank O. [mailto:FOMcIllwain@GarverUSA.com] Sent: Monday, July 19, 2010 3:26 PM To: Jenkinson, Joel Cc: McAnally, Mitchell, R; Bible, Colin M.; Harry Lorton Subject: ADS Grading and Drainage - Past Soil Borings Joel: As we refine our RSA grading and drainage design, especially on the west side, I am becoming concerned that ditch excavation may encounter rock. Without soil borings, we can't estimate the rock excavation. Do you have old geotechnical reports and/or soil boring logs for the areas shown on the attached exhibit? Frank McIllwain, PE Senior Project Manager Aviation Team Leader Office: 972-377-7480 Ext: 222 Mobile: 214-250-3967 E-mail: FOMcIllwain@GarverUSA.com ===================== TxDOT is going Green to keep our air clean. Find out how at www.drivecleanacrosstexas.org