Case History 4 === Liz: [00:00:00] Welcome back to the GBA Case history series brought to you by the GBA podcast. My name is Elizabeth Brown and I'm a principal geotechnical engineer at JLT Consultants. Abi: And I am Abi Corbett, a project consultant at SME. So today we're gonna dig into case history number four, and this is one of those stories that at least to me, really reminds you how. A good idea to save some money can really just turn into a very expensive lesson. Liz: Oh yeah, this one hits on value engineering, construction observation, and the dangers of relying on what looks right in the field. Abi: And fair warning, this one is gonna have all those classic ingredients, groundwater, drilled shaft, a cost saving idea problems that no one saw coming, and then it all gets buried in concrete. Liz: Oh yeah. Great fun.[00:01:00] Abi: All right. Let me get it set up for you though. This was a large structure that's gonna get supported by drilled shafts. The owner retained a constructor and architect, a structural engineer, and of course our GBA member firm for geotechnical engineering. The member firm was assigned to perform subsurface exploration, prepare a geotechnical engineering report with foundation design recommendations, and observe the drilled shaft construction. Liz: So, I mean, it seems like, from a high level everything is covered there. Pretty, pretty standard. But really, I think the question is what did they actually find during their subsurface investigation Abi: Right. It wouldn't be a case history without a little bit of spice. So their subsurface exploration showed hard pan overlaying by water bearing silt, which. I mean, it's already a red flag for a drilled shaft construction. The [00:02:00] report clearly stated that if water bearing silt was encountered, steel casing was needed to be sealed into the hard pan with a bell form below the casing. Liz: So, that seems pretty standard, right? Like still, still not seeing anything too, too crazy here, right? They're gonna have some permanent casings, you know, it's gonna be. Maybe some conservativeness there, but you know, they're taking it safe. Abi: Yes, and importantly, the project was designed with that permanent casing for what they're so-called the wet holes. Liz: Okay, so we're, I mean, we're still heading in the right direction here. Abi: Exactly some good solid conservative recommendations, but that's where our story's gonna really take off. The drilled shaft contractor got that report and then proposed a value engineered alternative. Liz: See now this is the thing, like there are times [00:03:00] when value engineered alternatives are great and fantastic. Like sometimes I think that they kind of get a little bit of a bad rap 'cause things go wrong. But I just wanted to take a moment to like, Hey, there are times when. Value engineered alternative can be, can be very cost effective and a really good solution for the project. They just sometimes don't always end up that way. So can you kind of like, lay out for us and kind of summarize like, so what, what was proposed? What was the value engineered alternative? Abi: Absolutely. And before I do, it's important to note it's not like the owner asked for valued engineering this. Was truly from the drill shaft contractor, but basically they suggested pulling the casing after placing concrete something they said that they've successfully done on other projects too. They recommended some techniques and those are outlined in the case history if any of our listeners wanna check 'em out. [00:04:00] But according to the contractor, it would save the owner a significant amount of money. Liz: Oh, isn't it always quote, a significant amount of money we're talking about here. Abi: It seems like it. Liz: To their credit, everyone acknowledged this wasn't risk free. Like everyone was on board. They said, we know, we acknowledge there is risk. So I mean, that's a plus. Abi: Yeah. And it's inherent in that value engineering. I don't think that anyone would be surprised if it wasn't. And really, you're right. Everyone acknowledged it. The representatives from the owner, architect, structural engineer, the geotechnical firm, and the construction manager all met up to discuss this proposal. Everyone understood that pulling casing and wet conditions risk contaminating the concrete, especially near the top. Liz: So, I mean, at least here, like they actually met and talked about it. So, I mean, in a lot of [00:05:00] the case histories that we discussed, that's not the case. Right? There's a lack of communication. That's a good thing. So their approach for managing the risk was in essence, Hey, we will watch closely and we'll fix anything that we see that happens. Abi: Exactly. Might sound a little bit scary, but the construction manager believed any contaminated concrete could be removed by the drilled shaft contractor with a bucket, and that simple visual observation by the contractor and the geotechnical firm could be enough to just confirm that the sound concrete remained. And like you said, they did have a meeting and everyone agreed to proceed with the recommendations. Liz: Okay, so now what, what, what actually happened, Abi? Abi: Okay, so set in the scene. We're 24 shafts in and some things start to not feel so. Right. Liz: It always has to happen, right? [00:06:00] So I'm guessing this has to do with maybe some test results that start coming back. Abi: You are spot on. So a seven day compressive strength test from one shaft showed only 2,740 PSI, which unfortunately was only about 55% of the 5,000 PSI design strength. Liz: Ooh, that's not a small miss. Like this could be a big issue here. Abi: Yeah, and it gets more complicated because some of those earlier shafts, they had seven day tests averaging over 3,200 PSI, but we're still in a phase where no 28 day tests were available. But some good news kind of, I guess the team was concerned enough to go ahead and act. Liz: Okay. Well that, that's good, right? That's the right instinct there. Abi: They immediately started coring that [00:07:00] shaft that had the low strength test. But that's kind of where we find our, our real issue. And it's, it's an issue. Liz: Well, let me guess. It's maybe not so much a strength issue as a contamination issue. Abi: the coring revealed a zone of soil contaminated concrete near the bottom of the corrugated liner. Liz: Ooh. So this raises the worst possible question. Is this happening everywhere? Because remember earlier we talked about they thought that if it happened, it's gonna be up at the top, right where it's easy to fix. So this isn't what they were thinking. Abi: Yeah, and honestly because they were so far in, they wanted those answers quickly. The construction manager just decided to have all of the 32 drilled shafts cored. Liz: Oh, that's, that's a lot. And expensive. So really, it sounds like, the scope and the cost then started to balloon at this point in time.[00:08:00] Abi: A hundred percent and isn't the whole point of value engineering so that the scope and the cost are efficient and don't balloon. Liz: Exactly. Abi: So in total, 11 of those 32 shafts ended up showing soil contamination. Interestingly enough, though, the compressive strength of the concrete was still acceptable, Liz: Oh, that's interesting. So the strength is okay, but flawed per the original design. Abi: right? And it always is gonna go back to that original design. So the root cause gets traced back to an insufficient head of concrete during the final casing pull, which then allowed the water in the mud to intrude. Liz: Oh, yeah. See, and no one saw that coming, that that wasn't the concern that they were thinking was gonna happen. Abi: Right. And also literally no one saw it happening. The lighting was inadequate on site. So while we're [00:09:00] relying on these visual observations, what's looking like sound concrete was actually soil coated with gray cement paste. So it's, I mean, impossible to distinguish visually. Liz: Oh yeah, that's not good. Abi: Yeah, you really like as far as being able to see visually, you probably need some good lighting, but hey, what do I know? Liz: Right? Abi: So each defective shaft had to be repaired, and they decided to do that by drilling a two foot diameter core through the contaminated zones, and then install, additionally reinforce concrete to restore that capacity. Liz: I mean, that's an effective solution, but it's kind of painful to the schedule and to the pocketbook. Abi: Talk about painful, so including investigation, testing, redesign, and repairs. That cost came to nearly $1 million, [00:10:00] and Liz, this case is in 2017, so I went ahead and looked it up and it's probably closer to like $1.3 million today. Liz: Ouch. Ouch. Abi: I don't know if that really counts as value engineering at that point. Liz: Right. Well, so now you know what happens next. Right now comes the finger pointing. Right? And everyone seemed to have a reason why, Hey, this isn't our fault Abi: Right. As soon as something goes wrong, always we see the finger pointing. So the owner, they're saying, we hired competent professionals and we were even prepared to pay for the permanent casing. The structural engineer said we weren't involved with the execution and didn't even observe construction. The construction manager was running with the drilled shaft constructor was responsible to meet their contract, which fair, and the geotechnical firm said something along [00:11:00] the same lines, I mean. It wasn't their procedure and their observation didn't relieve the contractor of meeting the contract, and of course the contractor said, but everyone agreed to this at the beginning. Liz: Of course, shared risk with unclear ownership. Abi: Yeah, it sounds familiar to a lot of the cases we chat about. What's cool though in this one is ultimately the parties realized that litigation would make this even worse. They got together and negotiated a reduction of extra charges and decided to resolve the issue without ever going to court. Liz: Now that's pretty cool. I mean, that doesn't happen all that often, so that's a pretty unique way to solve this. Abi: Absolutely. I think honestly, it helps. Highlight a lot of the lessons that GBA is trying to show here. And let's go ahead and let's try and break it down into just three. Liz: All right, so let's, [00:12:00] let's summarize those for our listeners. Abi: What I really wanna start with is, looks can be deceiving. Those visual observations alone, especially in the poor conditions like the lighting in this case, it's risky. In no case should a geo professional firm compromise the quality of its services just to accommodate some poor planning by maybe the client designer or constructor Liz: Yeah, exactly. If you're relying that much on visual observation, you gotta make sure that you're doing everything you can and limiting your risk. Abi: uhhuh. Liz: lesson learned here is that high risk procedures often go awry. So saving money upfront doesn't always mean saving money overall. Plus, in this case, the major project participants seemed to have put themselves in harm's way to save money for a client that realistically didn't seem to care all that much about the savings. Abi: Yeah, that was something that really hit me hard when I was reading [00:13:00] this case. And third compromise can often be our smartest solution. While everyone in the parties felt that the constructor should be the one absorbing all of the extra costs, they realized that that cost would be so big. It would motivate the constructor to sue everyone. So at that point, everyone has to spend money on legal fees. Everyone has to take time away from billable work, and it's just better walking away if lawyers don't have to get involved in all this. Liz: Right. A lot less money spent that way. Abi: No doubt. This case is truly a powerful reminder that value engineering doesn't eliminate risk. It just redistributes it Liz: And if you can't clearly define who owns that risk, you may end up owning a very expensive surprise. Abi: to say the least. So that wraps up case history number four. Thanks for joining us for this episode of the Case History Series, brought to you by the GBA [00:14:00] podcast. I hope you were able to take away some useful information that'll help you and some others at your firm make good risk-based decisions in the future. If this specific episode was helpful, subscribe, leave us a review or share it on LinkedIn.