There are many beautiful examples of sunken gardens to be found, but our own sunken garden, directly in front of the house, was not a consequence of intentional garden design.

When we were first considering purchasing this property, the most evident features of the property, other than the house itself, were the surrounding woodland, and the terrain.  Where most buyers are usually concerned with the condition of the house, we were most concerned about the composition of the soils.

We were primarily drawn to the natural woodlands on this property

The woodland on the property was beautiful, but some parts of the property have very steep slopes, greater than 2:1 in some areas, and the soils are somewhat friable.

This is not an area to purchase property blindly.  This region along California’s central coast has a history of significant mudslides, some of which, like the notorious Love Creek landslide in Ben Lomond on January 5, 1982, have resulted in significant loss of life and personal injury over the years.

We’d lived in the Santa Cruz Mountains once before, so we knew what the possibilities were with properties that have this sort of terrain.  However, we wanted to be truly informed buyers, so we made our purchase of this property contingent on the results of a thorough geologic, and hazard assessment, which was performed by our own Geotechnical Engineer prior to the close of escrow.

This may sound overly cautious to some, but our own previous experiences living in this part of coastal California had taught us that the forces of nature in this area demand a certain level of respect.  Earlier this spring there was a spectacular reminder of what Nature is capable of in this region, after saturating rains triggered this large rock slide.

While our engineer was busily compiling his report, our own inspections during escrow uncovered an area underneath the front deck, which was attached to the house, where it was clear the owners of the property had been adding large amounts of gravel and river rock over a period of time surrounding one of the deck’s support posts.  Something seemed amiss.

There was no disclosure in the sale agreements regarding this finding, so the owners were questioned at length.  They had already lost a previous potential buyer, and we threatened to halt the sale as a result of these findings.

The owners eventually admitted that this area had been sinking previously, but contended this had been in the past, and that they’d resolved the issue prior to listing the house for sale.  Concerned they were telling us what we wanted to hear, as no potential buyer wants to hear that a property has a sink hole of unknown origin, we were wary of their response.

Our Engineer was independently asked for his assessment as to what might be going on under the deck.  The problem was that there are many potential causes of sink holes.  Subterranean geologic fissures, erosion due to underground springs, poorly packed fill, just to name a few, and the range of potential costs to repair the problem is just as varied, and often not covered by insurance.

After a number of sleepless nights, and digesting the evaluation by the engineer, we proceeded with the purchase, primarily because it was shown that the settling soil would not impact the house directly as the foundation was supported with numerous piers that were anchored to the bedrock below.

Even if the perimeter foundation wall was completely exposed (blue arrow), support piers, anchored 16 feet down in bedrock, are what actually support the house (red arrow)

At the end of the first year here it was becoming apparent that the ‘stable’ sink hole was anything but stable.  Eventually the soils collapsed enough that the deck railings attached to the corner of the house separated, and there was a significant shift in the surface soil.

The first real evidence the ground was still sinking...the deck railing was pulling away from the house

By the second year the soils had moved so much, an entire section of driveway began to collapse.

This section of driveway began to collapse

This section of driveway was almost floating.

There was a large void under the section of driveway that had collapsed. The question was, why?

Holding the camera under the deck, and shooting toward the house, we also discovered the foundation wall was now fully exposed to the point that you could have put your entire arm underneath it.

The base of the foundation wall was exposed

As the area of soil collapse appeared to be rapidly expanding, we started by doing some more extensive surveying ourselves.

When the driveway tried to swallow an entire yard stick, we knew this situation had to be addressed, immediately.

Pushing a yard stick through the gap in the driveway showed the void was almost three feet deep

We began by removing the broken concrete to see if there was anything immediately obvious.  It was apparent however that with our own equipment we wouldn’t be able to excavate the area enough.  It was time to call the experts, so we hired a team of excavators.

Our own equipment wasn't sufficient to excavate very far below the surface

Before the excavators arrived, the deck was completely removed so they could dig down and find the source of the problem, unencumbered.

Our excavation contractor has many years of experience exploring the soils in this part of the Santa Cruz Mountains, and has many stories to tell of the things he’s seen over the years.  He had his own suspicions as to what might be going on as soon as he saw the damage.

We don't usually have heavy equipment on this scale driving around the farm!

The first six feet of excavation revealed various strata composed of differing sizes and colors of rock, and gravel, even huge poured cement slabs.  Having studied archaeology in college for a time, I was initially somewhat bemused by the various man made layers of materials that were exposed by the excavator.

However, my bemusement quickly turned to anger and frustration when it became evident the sellers of the property hadn’t been completely honest regarding the severity of the collapse in this area, nor were they honest about the extent of their own efforts to fix it.

As much as we're willing and able to do projects around here, sometimes it's simply more efficient to call the experts

Half a day of digging, and we had an enormous hole in the front yard, but it wasn’t long thereafter, 10 feet below grade in front of the house, that we had our answer.  Our excavator’s prediction was correct.

The lazy, unscrupulous builder of this house, rather than hauling the trees removed to make way for the house, had buried the enormous trunks and stumps 10-12 feet underneath the fill soil, and then poured the driveway over the top.

Excavating the area revealed large buried stumps and tree trunks

As angry and frustrated as we were at this builder though, we were actually relieved that we now had a better understanding of the cause of this sink hole, and could now address the problem, and fix it properly.  Not knowing why the ground was opening up caused much more anxiety than formulating a plan to fix it.

The trouble was our wet winter last year, became a wet spring this year, and until the soils were thoroughly dried out, excavating the tree trunks and stumps would have to wait.  Although we could pull the offending material out, the soils would not compact properly until they were dry.  The exploration area was temporarily filled back in, for safety sake, and then yesterday, the excavators were able to return to clean up the mess left behind a quarter century ago by the the lazy builder.

The crew returned, and began to re-excavate the area yesterday

Our crew really did a fabulous job, setting straight to the task of re-excavating this area.  It was as if they’d done it a hundred times before, and apparently it seems they may have, as in this area at least, burying woody debris on the job site used to be very common.

The first piece of tree trunk removed of many

It wasn’t long before the first substantial remnant tree roots were uncovered.  Even though we’d seen evidence of some of this debris during the excavation in March, some of these stumps were even larger than the excavators had anticipated!

Multiple large stumps were buried in the soil

They struggled for some time to drag this massive root ball up and out of the hole…

This was not the only stump that had to be removed

…eventually, with team work, they succeeded.

Fir Stump

That was just the beginning.

Using a chain they were able to drag the stump away from the excavation area so work could continue

As the hole widened and deepened, three tires and an old inner tube were pulled out, and we half expected we’d find the vehicle they’d been attached to…thankfully though, there wasn’t one.

We dredged up three old discarded tires and an inner tube during the excavation

Sadly we didn’t find any buried treasure either…none worth keeping anyway.

One of the old tires unearthed during the excavation

All of the offending debris, with the exception of the tires, was old fir stumps, and decaying logs.

This stump had a hole where the roots had once grown back on themselves

The trouble with fir, unlike the redwood here, is it rots much more quickly.  As the wood decays, voids in the soil are created above the stump, and the ground collapses.

Considering their age, the stumps were quite well preserved due to the lack of oxygen below ground

Deprived of oxygen underground, decay was slowed initially, but some 25 years later the rate of decay was significant enough to translate into a three foot drop in surface soil in just a couple of years.

A full day of excavating yesterday yielded more than 7 tons of smaller woody debris.  That however doesn’t include the FOUR enormous rotting Douglas Fir root balls that were hauled out.

These stumps, removed from the front garden area yesterday, will need to be sectioned before they are loaded on the truck and removed

These were so large, that the contractors have had to return today so they can partition these root balls with chainsaws so they will fit in the dump truck to be hauled away. None of the heavy equipment they brought was capable of lifting the stumps intact into the back of the truck.

Not counting the four huge fir stumps, more than 7 tons of wood was hauled away yesterday

Although this has taken a substantial amount of resources to remove this material, it would be far more expensive to landscape the front area of the house, and repair the driveway, without fixing the source of the problem.  The previous owners had tried that to no avail.

Not quite the look we're going for in front of the house, but without this equipment we'd never have been able to resolve this problem

We were somewhat thwarted on regrading some of this area last night due to the first substantial rainfall of the season, which has temporarily turned the front of the house into a mud pit after 0.66 inches of rain fell.  There’s more rain on the way tomorrow, but as the garden needed the water, we can’t complain.

Once the soil dries out from last night's rain, this compactor will finish grading and compacting the area that was excavated

However, by early next week our contractors will return to finish the grading in this area.

Grading is halted on the project now until the soils dry again

Before they return we have some irrigation repairs to do, as one casualty of yesterday’s excavation was the main irrigation line that leads out to the orchard was severed.  Compared to the sink hole, that’s a minor repair.

With the offending woodland debris now removed, we’ll be able to finally move forward with re-landscaping the front garden area, and replacing the damaged driveway, with the knowledge that this sink hole is finally repaired.

In the meantime it’s time to brainstorm ideas for the new design for the approach to the house.  This time though, I can say with unwavering confidence, we are not planning to install another sunken garden.