I am writing with concern for residents of Lakeside Heights.
I went online to research what possibly caused the conditions that created the undermining and sinkholes in the subdivision.
One of the tools I used was Google Earth satellite imagery. In my opinion the following points that may be contributing to the infusion of water need to be ruled out.
It appears that since the sewage treatment pounds are located directly uphill from the subdivision. The sewage ponds or holding tanks are kept at a constant water level by a float system, so they need to be inspected to rule out that the holding pond are not leaking.
From what I can see the reservoir adjacent to the sewage treatment pounds appears to be without a membrane to prevent permeation into the soil.
The soils directly downstream of the reservoir should be ruled out as a constant influx of moisture as a slow leak in either the sewage treatment pounds or from the reservoir maybe a factor in water saturation, possibly contributing to conditions know as liquifaction of the soil.
Liquifaction occurs when water surrounds the soil particles.
Water can travel down fractures in rocks for miles.
I would rule out infusion of water from a geothermal source. A volcanologist should be consulted as there are active vents within Clear Lake and throughout this volcanic region.
In the satellite imagery there are possibly two underground vents immediately between the subdivision and the main highway.
One appears to be used as a dump site used to fill in the sink hole and the other is next to it, due south and appears darker in color and looks more like an active thermal vent.
A major water or sewer line break may have been the catalyst that set the earth in motion creating the initial sinkhole, however, the extensive erosion within Lakeside Heights leads a reasonable person to believe that there may be other factors that need to be thoroughly investigated.
Susan Anthony
Resident of Vallejo and Clearlake
