This photo supplied by the state Department of Environment Quality shows the fugitive emissions on Aug. 24 during an inspection of an asphalt mixing plant between Corvallis and Philomath. 

State environmental officials say a Salem construction firm has violated state emissions laws and must take corrective action at a controversial asphalt mixing site it has been operating between Corvallis and Philomath.

The Department of Environment Quality issued an Aug. 29 “warning letter with opportunity to correct” to Houck Construction, which has been providing asphalt for a Highway 20 paving project between Philomath and the Oregon Coast.

The asphalt mixing work has led to complaints since late July from residents about late-night odors and noise from the mixing, which occurs in the evening hours to match the 7 p.m. to 6 a.m. construction time slot the Oregon Department of Transportation has been using to limit the inconvenience to motorists.

DEQ officials inspected the plant at the end of Clemens Mill Road on Aug. 24 and “documented excessive fugitive emissions generating blue haze escaping from the top of the asphalt silo,” wrote Karen White-Fallon, air quality officer in her letter to Houck. “These fugitive emissions are likely contributing to some of the odor from the facility.”

White-Fallon was accompanied on the unannounced plant tour by inspector Michael Eisele and Claudia Davis, air quality manager for the DEQ’s Western Region office in Salem.

The Houck plant passed the inspection in five other air quality metrics: emissions opacity, particulate emissions, the size of particulate matter, burner tuning and recordkeeping and reporting requirements.

The violation is a Class II or mid-level issue. Class I violations are the most serious, with Class III the least serious. No formal enforcement action follows, although Houck was required to provide a plan for corrective action by 5 p.m. Tuesday.

Houck officials emailed their response to DEQ officials, while noting that the original was in the mail postmarked Tuesday. In the letter from Roy L. Houck, the company asserted that the fugitive emissions most likely were steam, but that they are “researching methods of reducing silo emissions in order to develop and implement a corrective action plan.”

The DEQ violations letter calls for corrective action to be completed by Oct. 29, although ODOT officials said the Highway 20 project that is using the 84,500 tons of asphalt supplied by Houck will conclude the paving portion of the work this month. DEQ officials said the plant was producing 270 tons per hour, although the site has a capacity for 400.

The Clemens Mill site, which Houck has been using on a temporary basis for the duration of the paving contract, is on Benton County land zoned urban industrial. The asphalt work is outright permitted in the zone.

Rollie Baxter, the most vocal of the residents who raised concerns about the odor and noise, said in an email to state Sen. Sara Gelser “in the end, I think Benton County will have to change the zone code to prevent this from happening again.”

Greg Verret, county community development director, has said he will be “reviewing our priorities for code amendment projects with the Board of Commissioners” in October and that it remains unclear what changes might be made.

Contact reporter James Day at jim.day@gazettetimes.com or 541-758-9542. Follow at Twitter.com/jameshday or gazettetimes.com/blogs/jim-day.