Agency hopes to complete its monitoring of methane in Sexton Mountain neighborhood
by: Christina Lent, State officials want input on the completed methane mitigation measures at the Sexton Crest development in Sexton Mountain.

Oregon's Department of Environmental Quality is looking for public comments on the completion of a methane mitigation project in the Sexton Crest residential development.

DEQ officials propose to sign off on mitigation measures that have been completed and issue a conditional 'no further action' determination for the Beaverton neighborhood.

Comments are due by May 2.

'This is the last piece for us,' said Tom Roick, a DEQ project manager.

The presence of methane gas from fill materials beneath the Sexton Crest area have been mitigated as part of site development, Roick said.

The development is between Southwest Murray Boulevard, 148th Terrace and Maverick Terrace in Sexton Mountain on what used to be the site of the Cobb's Quarry Landfill.

The former unpermitted landfill at the location was filled with material like sod and other organics that produced methane gas when decomposing, Roick said.

To ensure that the site was redeveloped safely, concerned Sexton Mountain neighbors encouraged DEQ officials to work with the developer to oversee the project.

Under a July 2003 voluntary agreement with Sexton Crest Homes LLC and Sexton Crest Townhomes LLC, DEQ provided oversight of the design and implementation of methane mitigation measures.

As part of site development that broke ground in August 2003, more than 110,000 cubic yards of soil and other fill materials like roots, twigs, asphalt and concrete were excavated and hauled off-site for reuse or disposal at a DEQ-approved location.

That amount of soil and materials would fill an estimated 6,875 dump truck loads.

Engineering controls, including two passive methane venting systems and a low-permeability membrane, were also installed in the new building foundations during development.

Safely developed

As part of an ongoing partnership, GeoDesign submitted inspection documentation for each residence to DEQ between September 2004 and April 2006.

After reviewing the reports, DEQ approved occupancy for each home and townhouse with respect to methane mitigation.

No methane was detected during final monitoring of each structure, Roick said.

The last home was granted occupancy approval in June 2006.

'We're pleased to have the development there, and know that it was developed safely,' said Elise Smith, a longtime Sexton Mountain resident who took action with other neighbors to make sure methane issues at the site were tackled properly.

'Families have moved in, and there is a little community there. It's fun to see kids riding their bikes and out playing basketball. It's good to see families make this their home.'

Smith and other neighbors who watched the site's development took comfort in knowing that future homeowners would be protected.

'The DEQ had the machine to be able to make sure the site was monitored and the oversight to make sure construction was taking place with safety in mind,' Smith said.

'Our whole guide for our involvement was to make sure people were safe,' said Susan Cook, another active Sexton Mountain neighbor. 'We want them to continue to be safe.'

A Jan. 29 project completion report prepared by GeoDesign summarizes the installation of the methane mitigation controls and completion of pre-occupancy methane monitoring.

The selected methane mitigation components have been implemented for the site and each residential unit, according to the report.

To ensure the future safety of homeowners, an easement and declarations of restrictions have also been attached to the deed of each home that will be transferred with the title to the buyer as part of the process anytime a home is sold.

The restrictions and easement require that the engineering controls not be disturbed and that any modifications or new construction must be reviewed through the city of Beaverton's permit process, Roick said.

'The city has identified that area as a methane hazard area, and within that designation, construction activities are subject to specific requirements for methane mitigation,' he added.

Some unknowns

The DEQ will continue to monitor compliance with the easement and declarations of restrictions.

'Hopefully the homeowners read the information and are aware of their responsibility,' Smith said. 'We're beginning a new chapter now, where we hope the people living there begin to take interest in their neighborhood.'

Cook agreed.

'Ideally, we want them to be aware that any change or modification to their home has the potential to cause harm because of the unique situation of the site,' Cook said. 'They need to be aware that the city has a process in place to make sure the engineering controls are not disturbed.

'I still want to protect them from those unknowns.'

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