Last Updated - 08/27/2005 12:01 PM

County surveyors have set up a number of stakes in and around the slide area. Several times each day, they take accurate GPS readings of the location of the stakes. They tell me the readings are accurate to within hundredths of a foot. We certainly appreciate assistance from Utah County and having their surveyors climb the hill over and over to help us deal with the slide.

They compare the location of the stakes at each reading to determine where any movement might be occurring. Here is the latest status of those readings and the slide:

The good weather has meant things haven't really changed this week. No appreciable movement has been reported on the slide. I'll let you know if something happens.

The reports from the weekend through today show little to no movement. The sunshine and dry weather brought the slide to a virtual standstill. Francis Ashland from UGS had this to say:

Utah County's GPS survey measurements yesterday (5/14) indicated that movement of the main slide may have suspended or slowed to a very slow rate. About 2 cm of movement was detected in the lower part of the slide.
 

Visually, it appears that the slide has moved some again last night. Not much has changed though. the mud and debris has pretty much filled the storage rooms at the back of the garages of two of the townhomes, and is now pressuring the back of the inside garage wall on both units. The damage is clearly visible from outside as well.

Sadly, the mud finally broke through the back wall of the townhomes this evening. While the slide continues to move by piling up more against the back of the one building, it still is no immediate threat to any other buildings. The lower slide moved 67cm (that's around 30 inches) since this morning.

The sequence above shows what happned over the course of the day..

Francis Ashland, from the Utah Geological Survey (UGS) has this to say:

Utah County's GPS survey measurements on Wednesday (5/11) showed a dramatic increase in the rate of landslide movement. The 24-hour increase in the movement rate ranged from 4.5 to 12.5 times the previous rate.

The plots show the movement through Wednesday at the three stations on the landslide (stations 2-4). About 1.2 meters of movement occurred between Tuesday and Wednesday in the upper part of the slide (station 4). About 44 cm of movement occurred in lower part of the slide directly above the townhouse.

Measurements of the GPS survey points below the toe of the slide (station 1) and in the crown of the major scarp (station 5) indicate no movement.

The National Weather Service's Pleasant Grove weather station received about 0.86 in. of precipitation in the 24 hours ending at 6:00 AM this morning. Doppler imagery currently shows no rain showers in the Cedar Hills area, but rain showers are currently moving into northwestern Utah (Box Elder County).
 

From my own assessment:

The back of the townhomes are being pushed in by the tremendous weight of the mud. The townhomes are sustaining significant damage at this point. The steep bank above continues to erode. The dirt near the top of the path I use to walk up to the upper stake area is shifted down (vertically) some two feet in some areas.

There is still no immediate danger to other buildings, but the building that is already empty is already sustaining, and in danger of continued significant structural damage.

 The picture at left shows the inside of the back wall of one of the townhomes. The concrete foundation wall is being pushed in and appears to be on the verge of collapse.

The rain just keeps coming. The saturated soil is now moving significantly more than it has since the original slide. The steep bank above is sloughing off a lot of material as the rain continues to come down. Watching the bank, you can see dirt and rocks breaking off and rolling down bit by bit every few seconds.

A significant amount of water is streaming down through the drainage opening the excavators opened up a couple days ago. It would appear that was a great strategy.

The slide movement increased dramatically. Overnight, the slide moved 2.7 feet at the top, and 0.6 feet at the bottom just behind the townhomes. Other surrounding areas showed some movement as well. This is no surprise given the amount of precipitation we've seen.

Risk of additional damage to the townhomes directly against the slide is very high at this point.

As expected, we've seen continued slight movement in response to the rain we've had the last couple days. The engineering firm working on the slide has drilled in another area of the slide today. The reports from the UGS that are based on the survey information collected by the county surveyors show movement consistent with what we've seen on other rainy days - still on the order of just a few centimeters.

The boulder that was threatening to fall from the steep bank finally came down this morning. It came to rest in the mud immediately below where it fell. I guess gravity is still working predictably in the slide area! Some additional material sloughed off the bank as well.

The developer's geotechnical engineering firm was able to get some core drilling equipment and some earth-moving equipment onto the slide area today. They reshaped the slide area just a bit to allow for water to drain away from the slide area rather than puddle in it. Once the cores are drilled, they will begin the process of analyzing the slide area to determine next steps.

We continue to be blessed by having little rainfall in our area despite the forecast. We are certainly hoping this continues.

Francis Ashland, from the Utah Geological Survey, took measurements again and reviewed the slide site yesterday and today. He plotted the data collected by the county surveyors with their GPS surveying equipment. The plots show very slight movement at a few of the stakes. This doesn't seem like much, but it does indicate the surrounding area is unstable. Also, the fissures (cracks) higher up on the mountain, above the slide, have widened from around two inches to around four inches. This also indicates the hill above the slide is still moving.

We had significant rain on Friday and Saturday. After the rains, it appears the toe (the bottom end) of the slide has moved around .1 feet. Some parts of the steep bank above the slide have sloughed off as the rain poured down. The top of the slide turned to a very wet mud that slushed around and required the stake to be reset. This recent rain unfortunately sets up the possibility of some real movement if we get significantly more rain. The forecast calls for significant rain during the Mon-Wed timeframe, so that indicates we are again at high risk at this point.

The surveyors continue checking, but the slide shows no movement at all. Even with the minor rains we had, there has been no movement. If this relatively dry weather holds up, we are in good shape!

We've had a few sprinkles of rain this morning, and at 3:30 PM it began raining fairly hard. Luckily, it only lasted about 15 minutes. The slide had two days of dry, breezy weather to dry out prior to this rain.

County surveyors have taken measurements a few times today, and the data continues to show no current movement in the slide material. Because there has been no movement, they will not take readings again until 7 PM. We will then be able to tell if the rain has had any immediate effect on the slide.

The evening readings indicate that the stake at the top of the slide moved again, but only about 3cm (0.1 ft) both vertically and laterally this time.  No other stakes moved at all.

The slide has indeed virtually stopped moving. Hopefully we won't get any rain and things will remain stable.

The recent readings indicate that the stake at the top of the slide moved again, but only 10cm this time. This continues to indicate stability of the material in the slide. No other stakes moved at all.

Based on this information, we are no longer recommending evacuation for the twin unit across the street from the slide. Obviously, the one townhouse unit that the slide has reached is still at the greatest risk, and we are still recommending evacuation for those residents.