Hydrologics

Chaos Central, home to the Unix Curmudgeon, the Nice Person, their respective business ventures, and one teen-aged cat, is conveniently situated on the military crest of a bluff overlooking one of the southernmost bays of Puget Sound.  Convenient because, 80 years ago, when the house was built, it had a commanding view of the city below and the bay beyond, now obscured by the dense forest that has regrown on the lower slopes of the bluff in the last half-century.  The steep bluffs and deep ravines that characterize the terrain around Puget Sound enforce a lot of green space in the towns and shorelines, one of the attractions of the region.  Like many houses built on hillsides early in the automobile age, the garage is incorporated into the basement, where the opening provides both a convenient exit point for unwanted water, but also no protection against flooding.  Also typical of the Puget Sound bluffs, the hill behind the crest extends upward at a lower grade for nearly a kilometer, collecting more water than this layer cake of glacial till and gravel can contain.

A few weeks ago, while the Unix Curmudgeon was plying his trade in the icy Bitterroot Valley of Montana–a region geologically similar to Puget Sound, but some 1000 meters higher elevation and a much drier 1000km inland–the Nice Person, back at Chaos Central, woke on a Sunday morning to a disturbing and painful lesson in hydrological science, and the ensuing chaos generated thereby.   During the night, the torrential rains that routinely dump more than two meters of water on our fair city between late fall and early spring had deposited nearly 15 cm of water on the hillside.  Some of which, of course runs off through steep ravines cut into the bluff, or down the streets and into storm drains, which, by now, were miniature geysers at the base of the bluff, unable to accept any more input.  The rest of the water soaks into the hilltop, to feed the majestic fir, cedar, and maple for which our region is justly famous.  The excess percolates through the ground, to seep out the sides of the bluff in springs and feed the cascades of moss, ferns, and invasive ivy that grow on nearly vertical surfaces.

Of course, water being water, it flows in the path of least resistance.  The bluffs of Puget Sound consist mainly of glacial till, in the form of nearly impermeable clay.  Excess ground water, therefore, flows near the surface downhill until it encounters a place to escape, which, in the case of human habitation, is generally driveways and basements cut into the hillside. Thus, even though Chaos Central is poised at the edge of a steep drop, the water pressure on the uphill side of the house becomes considerable.

During the night, water that could no longer seep into the graveled drive began to pool, meeting with underground water flowing from further uphill, which was already bubbling up along the base of the uphill wall in the garage.  When the pool in the driveway rose above the garage floor, water crept in under the wall into the Nice Person’s fabric arts studio.

An emergency call to our son, now moved 40 km away, brought muscle into the damage control plan, while the Unix Curmudgeon listened helplessly from 1000km away (where the warm, wet air mass pushing water into Chaos Central was now just warm, clearing away the icy coating on Montana valley roads) and offered suggestions over the phone.  The obvious solution to the problem of getting water to flow out of the basement was to lower the level standing on the driveway, so son Mark, the civil engineer, expert on all things hydrologic and seismic, started chipping away at the concrete-like till beneath the thin layer of crushed rock just in front of the garage door.  Fortunately, the Nice Person managed to obtain one of the last available sump pumps in the city, which, when placed in a leaky bucket in the shallow hole carved in the driveway, removed enough water to lower the local water table below the basement floor.

The damage was slight–confined to a corner of the carpet in the fabric arts studio and a strip of sheetrock in the corner of the room.  After a night or two of waking every few hours to activate the pump, the Nice Person located an automatic unit, which continued to pump intermittently for the next week as the winter rains continued, until a sharp freeze at year’s end arrested the flow of groundwater.  By this time, the Unix Curmudgeon had found his way home, having been stranded carless in Montana in not very suitable bicycling conditions, and began planning a more permanent solution to the problem of flooding at the top of a bluff, a phenomenon that, though sounding implausible, is very logical given the geology of the region.

The city frowns highly on the concept of pumping errant groundwater into the storm sewers, which are intended to handle surface runoff only, so the permanent solution will most likely be to install the outdoor sump pump permanently at the side of the driveway, with a collector along the front of the garage, and pumping it into the roof gutter drain system to carry it far enough from the house to resume its normal course toward the tree roots and creek below.  This seems to be a cheaper and more [hydro]logical solution, as opposed to digging up the uphill foundation or breaking through the basement floor to install drains and sumps internally, since the water is right there, on and just under the surface of the driveway.  The saga continues.  Once again, we prove that you shouldn’t buy old houses just because you know how to fix them.  Because you do have to, frequently and often, in inventive ways.