08.18.2008 - DEQ O F O yy��
re �11 Department of Environmental Quality
Northwest Region Portland Office
of 2 2020 SW 4`h Avenue,Suite 400
Theodore Kulongoski,Gmemor Portland,OR 97201-4987
.l859. (503)229-5263
FAX(503)229-6945
TTY(503)229-5471
August 18, 2008
Chris Breemer
GeoEngineers
15055 SW Sequoia Parkway, Suite 140
Portland,OR 97224
Re: Review of Human Health and Level I and Level II Ecological Risk Assessments
Tigard Library, ECSI#4063
Dear Chris:
The Department of Environmental Quality(DEQ) has reviewed the Human Health Risk
Assessment and Level I and Level HEcological Risk Assessments dated July 11, 2008 for the
Tigard Library Site in Tigard, Oregon.
The risk assessments are accepted as written,with the following comments to be considered
during the feasibility study:
1. Page 2, fourth paragraph: In discussing high water events, it should be noted that the
pond and Pinebrook Stream are both overtopped by Fanno Creek during flood events,
such as last December. There is also piping-type flow between the Pinebrook Stream and
the pond during lower-water times, as observed in the sink holes at the pond edge.
2. Page 6, Section 3.5.2.3: The material that"calves"off of the outlet of the pond is eroded
by the flow and carried into Fanno Creek. At 16 mg/kg arsenic, this is a concern that will
require source control for erosion into Fanno Creek, as we discussed during site visits.
The outlet of the Pinebrook Stream also needs to have erosion protection added. We
encourage an aggressive schedule for these outfall improvements to prevent further
arsenic migration into Fanno Creek,preferably before this winter.
3. Page 7, Section 3.5.2.6: The sediment quality in the Pinebrook Stream needs to be
considered during the feasibility study for possible source control measures to prevent
erosion. The significant erosion event from the upper stretch last December resulted in
appreciable sediment transport into the lower wetland and Fanno Creek.
4. Page 9, Section 4.4.2.3: One of the questions about future land use was the likelihood of
direct contact by the public to the field area north of the Library, for events such as
picnics or concerts. Based on the general statement of no anticipated change of use, the
feasibility study needs to consider that direct contact uses of the field area are intended.
The area between the walkway and Fanno Creek would appear to be intended for habitat
with less likelihood of direct contact,but potential uses of this area should also be
considered during the feasibility study.
5. Page 15, Section 5.3.2: Because arsenic is identified as an aquatic OPEC, further
evaluation will be required and may include toxicity bioassays.
We recommend meeting in the near future to discuss these comments and the next steps and
schedule toward the focused Feasibility Study for the site. Please contact me directly at (503)
229-6900 if you have questions.
Sincerely,
Loren G. Garner, Project Manager
Northwest Region Cleanup Section
:1 Cc: Keith Johnson,DEQ
Dennis Koellermeier
City of Tigard
13125 SW Hall Blvd.
Tigard, OR 97223