A settlement of hunter/gatherers, once abandoned, would simply melt away as grass, bushes and trees replaced shelters, plazas, latrines, whatever. Everything was organic.
Today, unless you're backpacking or homeless, your residential footprint is not as amenable to nature's gentle ways. The green lifestyle is gathering momentum, but most modern homes are still non-biodegradable and rely on a centralized infrastructure to bring in light, heat and water, and to send out waste for treatment.
On that last point, waste treatment, a trend toward living more lightly appears to be taking shape in Portola Valley and Woodside.
Andrew Brownstone, the president of BioSphere Consulting in Santa Cruz, spoke recently at a Woodside Town Council meeting in support of two properties for which the owners were requesting deviations from local wastewater regulations so they could install alternative on-site waste treatment, but using systems that are not septic tanks.
Whereas a typical septic system consists of a gravity-operated tank and pipes, the alternative being advocated by Mr. Brownstone has a tank and pipes, but includes a pump, a microbial filter, a control panel and online monitoring. The biggest difference is in the treatment of the waste.
As in a septic tank, bacteria do the work. But instead of minimally treated effluent soaking into a dedicated leach field, Mr. Brownstone told The Almanac, the effluent makes several cleansing trips through a microbial filter and the resulting clear, odorless water is injected or dripped into the soil beneath ordinary landscaping.
Basically, it's subsurface irrigation using water that is significantly cleaner than the discharge from a sewage treatment plant, he said. Soccer fields and lawns are ideal locations, and there are whole golf courses that use these systems, he said.
Since this effluent is on its way to becoming local, fresh groundwater, its successful operation depends on the presence of healthy, water-permeable soil imbued with indigenous microbes to complete the cleansing action.
"Let the critters finish the job," Mr. Brownstone noted, "and we can actually close the loop on this whole water cycle." The water quality is "very, very safe," he added. "You save water by protecting water."
Alternative systems must adhere to the same soil percolation tests and residential setbacks as septic systems, but the discharge from a septic tank occurs deep underground where, lacking oxygen, the useful microbes do not live, Mr. Brownstone said. Cleansing action may come from filtration through rocks, but the liquid's ultimate quality is unknown if it reaches groundwater, he said.
In sewer treatment, the resulting discharge is typically of a higher quality but is pumped into the ocean and thus becomes unavailable for re-use as groundwater.
"A good idea can be well executed or poorly executed, which will ruin a good idea," Mr. Brownstone said. "We want to set the example of what this industry can be."
Mr. Brownstone is also a geologist, which is handy because his services include soil analysis, which usually takes about an hour per residential property, he said.
There are sites that are unsuitable: too much clay makes the soil impenetrable and the water can bubble up, which can be seen as a public health concern if there is a creek nearby or the site has a high water table.
On the other hand, if the soil contains too much sand, it won't retain the water long enough to fulfill its irrigation function, he said.
"I'm very convinced that it's critical that you have someone who can really evaluate soil," Mr. Brownstone said. "Basically, our challenge is to treat the wastewater and keep it underground. We know when to say, 'Gosh, we just can't do that.' Every site has a finite capacity to hold water."
Behind the curve
After Mr. Brownstone's remarks to the Woodside council on the sewage-connection deviations, the council voted to approve them as staff had recommended. Such a system is also planned for Woodside Town Hall, and there are already three residential systems in Woodside and four in Portola Valley, Mr. Brownstone said.
While California is often thought of as a trend leader on environmental issues, waste treatment without traditional septic tanks and sewers is old news in other parts of the country, including Alabama and Arkansas.
In Bethel Heights, Arkansas, for example, 700 homes are using a large-scale alternative system, as is a rural community of 2,000 households in Mobile County, Alabama, according to Eric Lanning of Oregon-based wastewater system manufacturer Orenco Systems — a manufacturer that Mr. Brownstone frequently recommends.
This alternative, with no changes to existing pipes, leapfrogs gray-water systems, which require two sets of pipes: one for potable water and the other for used water.
But it may also require a few changes of habit. Water softening agents, for example, will "completely disrupt" the system, Mr. Brownstone said. Also problem-inducing are bleach, drugs and more human residents than originally planned for.
"There are people who do the wrong thing," he said. "That's where the biggest expense is."
A typical alternative system such as Orenco for a single-family, four-bedroom home runs around $70,000, Mr. Brownstone said. Regular maintenance from a local technician is important and runs about $50 per month, he said.
The system includes an Internet connection. "You really want to have close management," he said.
A typical septic system costs around $20,000, said Jack Shane, president of A-1 Septic Tank of Hayward.
Asked to comment on alternative systems versus an apparently commonly held view that residents must choose between a traditional septic tank and a sewer connection, Mr. Shane replied: "Septic tanks are, if you will, a dying breed. This generation we're in now, they don't know anything but sewers."