Preliminary South Portland Fence Line Study: EPA Method 325

Citizen Science in Environmental Monitoring
Oral Presentation

Prepared by T. Mikulka Ph.D.,CIH
Retired, 6 Arrow Point Road, Cape Elizabeth, Maine, 04107, United States

Contact Information:; 207-899-4123


Authors: Tom Mikulka, Ph.D., CIH (ret). and David Falatko, PE

Abstract: This study was initiated in September 2020 to get fence line data on benzene emissions that might influence the positioning of Maine DEP permanent monitors in the future. It also would provide an alternative way for citizens of South Portland to monitor emission sources of benzene such as gasoline storage tanks and heated tanks of # 6 oil and asphalt. EPA Method 325 is currently the preferred method by the EPA for fence line monitoring of refineries and industrial facilities. The advantage of the method is that the sampling period is for 14-28 days as compared to current Maine DEP method (TO-15) which includes sampling for 24 hours every six days. It is a low cost method that can easily be implemented by facility management and monitored with duplicate samples by local government or other interested parties. The other advantage is that the sampling can be done by trained citizens. The disadvantage is that it only quantitates benzene. Beacon Environmental Labs was selected as the laboratory to supply the preconditioned sample tubes and analysis (5).

Initially, 12 sites were selected with a sampling period of 28 consecutive days. A 13th site (25 Ballard St.) was added for the last 14 days. Two of the sites were located in Portland across the Fore River from 4 tank farms. A control site was located in Cape Elizabeth. Sample tubes were hung in protective covers at heights of approximately 10 ft with the exception of one hung on a roof top at approximately 30 ft above ground (Site 3). Each day, wind direction and average temperature were recorded. One site, Maine St. and Lincoln Ave., was started one day before the other sites. The results of the 28 days of sampling showed that only one site had average levels above the Maine ambient air guideline (AAG) of 0.4 ppb at 0.88 ppb. Two other sites had average values of 0.38 ppb while the remaining seven fence line sites ranged from 0.28 to 0.34 ppb. The two Portland sites had benzene levels comparable to the control site.