Report of Existing Sheet Pile Length Probe Testing
The board rejected the riprap high price bid, went a new direction with an Design build Fixed Firm price RFP, so hopefully we get better quality at a lessor cost, then shortly after Langan resigned. I have not said much since then as we are all moving in what I felt was a good direction for Mira Bay. Cardno stepped up, put together a great RFP, residents with procurement knowledge helped out, all seemed good.
Hurricane Irma changed all that, showed us how vulnerable we are. We now have a resident at 5606 Seagrass in danger of losing their back yard or more, and they are rightly concerned. I am glad to report that Cardno once again stepped up, came out yesterday (Sep 12th) and inspected this and other properties. On inspection of the many lots we saw the many gullies created in the berm when the water was pulled out by the Hurricane, in which it is a possible piping indication. I was able to give Cardno some photo evidence of that occurring at one property as well, Cardno said they would monitor this for verification. We also found another property where the cap has cracked nearly in halve and the concrete is crumbling off and their upland holes are many and massive at 5622 Skimmer.
There is much conjecture on Next Door about the cause of the 5606 Seagrass seawall failure. Well Cardno was there inspected and told me the toe kicked out, they pointed it out and we could easily see where that happened and the soil that went underneath the wall.
Piping concerns:
We all know it was said this was not happening, then it happened, then we were told it was an isolated incident, well that statement has now gone into the waste bucket, so looking at the seawall failure at 5606 Seagrass and its physical makeup of that seawall , we should go to one of the last Langan reports;
2017-07-11 – Harbor Bay CDD Original Sheet Pile Probing Study
The proper calculation is take the embedded length on this report then minus the negative berm and you get the true embedded length, this was explained to me by the Bolves Attorney directly from the engineering documentation he gave to me concerning the short sheeting and negative berms studies done back in the 2011 or earlier.
The Langan Report clearly shows 5606 Seagrass as short sheeted, we also know Langan had said the mangroves there helped the berm to be stabilized. However you will see on this report 5606 Seagrass has a 10 foot sheet (the original design called for 12 feet) with 4 feet buried at a 0 (zero) berm elevation. So the true embedded length for this report is 4 feet, yet that seawall toe blew out, which also proved the mangroves had no effect.
What is more alarming is you can use this simple formula and see there are other areas in their limited testing where the embedded length minus the negative berm is less than 4 feet.
Even though Langan did not extrapolate their own numbers, it is easily done; it is more frightening that their own report puts these lots they tested in worse scenario than 5606 Seagrass, which was at 4 feet
Probe test # 9 5618 Seagrass 3.96
Probe test # 10 5618 Seagrass 3.4
Probe test # 12 5621 Skimmer 3.2
Probe test # 19 5634 Skimmer 3.5
Probe test # 20 5632 Skimmer 3.7
But is 4 feet enough? Well since 5606 blew out at the 4 foot level we know we should be at a much higher number, you can read the report and do the math for yourselves for the remaining lots.
Also attached is the short sheet probe done by HSA Engineering back in or around 2011, you will see on this document they report the exposed height no the depth of the wall, so you need to make that calculation as well.
I suspect the uplands damages and the seawall repair at 5606 is going to be 3 to 4 times higher if we had just fixed it in the first place. However these 2 reports give us much needed info as to where we we most likely see the next seawall failures, (including those walls with massive cap rotation we know of already) ,we can direct our attention to getting those new seawalls in ASAP in which the upland damages can be mitigated, or we may face numerous failures like 5606 Seagrass, driving the cost higher yet.
TN