Seattle Sun Newspaper - Vol. 8, Issue 1, January 2004

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Shifting ground in Greenwood

gets City's attention

By JAMES BUSH

There was no earthquake this summer, but Greenwood homeowner Cal Rooks twice felt his home shudder and fall.

Janet Rayor couldn't help but notice that the portion of North 87th Street in front of her home dropped several inches during warm weather. "I don't need a study to tell me that two water mains have broken in my street this summer," she said.

The continuing movement of the earth under the Greenwood business district and surrounding residential blocks was bad before, but got far worse during this year's dry summer, neighbors agree.

"We have a crisis," said John McSweeney. "We had a situation in February we have a crisis now."

Officials of several City departments addressed about 30 Greenwood residents at a Nov. 18 meeting of the Greenwood Community Council. The briefing addressed several measures the City has taken in hopes of explaining (and finding ways to stop) the ground movement.

A year ago, homeowner Diann Knezovich was the first to hypothesize a link between the shifting soil beneath her Palatine Avenue North home and the constant pumping of water from the excavation for the new Safeway store at North 87th Street and Greenwood Avenue North ("Is Greenwood sinking?" Seattle Sun, January 2003 issue).

Other Greenwood residents say constant pumping of ground water continues at several major commercial structures, as has the sagging of the soft ground.

The results have been dramatic enough to get several City departments involved. Seattle Public Utilities took a close look at inspection tapes for its storm sewer and sanitary sewer lines in the area. It also hired geotechnical consulting firm Shannon & Wilson Inc. to study soil test records from past building projects in the area in order to locate major peat deposits and determine approximate ground water levels.

The results make one thing clear: Greenwood is a swamp. The area bordered by North 85th Street, 8th Avenue Northwest, North 97th Street, and Greenwood Avenue North forms a bowl which drains to the north. An 1894 map of Seattle shows that the upper reaches of Piper's Creek formerly extended all the way to North 85th Street. Peat deposits up to 16 feet deep can be found throughout the neighborhood.

Peat, formed by vegetation and other organic debris accumulating in a low, wet area over many years, acts almost as a sponge, retaining water most of the year and releasing it during the driest times of year. But, when peat loses too much water, it starts to compress, causing subsidence (sinking of the ground surface). And, as many of the area's homes and streets are built directly on top of peat deposits, the result can be costly.

Bob Mirenzi, Knezovich's husband, says they had no choice but to spend $25,000 to put their home on pilings, in order to counter the effects of several sinkholes.

"We could literally crawl under our house," Mirenzi said.

The couple's home, which is located directly behind a Walgreen's drugstore and half a block from Safeway, was the first neighborhood residence to be hit hard by the earth movement, but many of their neighbors found themselves in the same situation by late summer.

"Now, every couple of weeks people are coming to me with problems I had a year ago," says Mirenzi.

While the City has acknowledged that there is a problem, officials aren't so sure there's any immediate solution. Currently, there are no regulations governing the pumping of ground water by property owners. The City routinely allows contractors to de-water construction sites.

When the Greenwood area was originally developed, many of the structures included a shallow basement or no basement at all and the building process involved minimal excavation. Now, it's common design practice to install two or three levels of underground parking below major residential or commercial buildings, resulting in deeper excavations and far more water removal.

Alan Justad of the City's Department of Planning and Development , says he isn't sure it's been proven that groundwater removal from construction sites is responsible for the earth movement. Without such proof, development rules are unlikely to change, he said. "Do we have enough of a connection to tell everyone in this area: 'You've got to change how you develop'?"

But constant pumping of water from built structures means that this isn't just a construction issue, noted Dave Garland, watershed unit supervisor for the state Department of Ecology's water quality program. "This isn't just construction de-watering," he said. "It's perpetual de-watering."

Garland has been working to address water quality issues in Piper's Creek for the past several months. The stream already has high bacteria counts, and any loss of stream flow could exacerbate the existing water quality problems, he says. "In watersheds where peat is present, it's a valuable contributor to late summer stream flows." Also, ground movement caused by the de-watering of peat could cause leaks in sewer lines, leading to additional contamination.

To this point, however, investigation by Seattle Public Utilities has found no evidence of leaks in either the storm or sanitary sewer systems.

Terry Kakida, SPU's drainage and wastewater planning manager, says the Shannon & Wilson study will continue with some field testing to confirm the preliminary results. There will also be a test to gauge the effectiveness of reintroducing water into a dry portion of the peat layer. A final report is due by early February.

Michael McGinn, Greenwood Community Council president, says he's a little disappointed by the slow pace of City regulators. "It just strikes me that this is a time when an agency should be taking more of an aggressive look at how to protect the common good, rather than saying we don't know what to do," he said.

"We're in Seattle," said McGinn. "We should be leaders in this type of thing."