Construction Management for a Transportation Facility

Client: Transportation Facility

Location: Portland, Oregon

Contamination History

In the past, steel mills in the Portland area and elsewhere gave away waste slag material for reuse. The DEQ approved the reuse conditionally for embankment construction (where it would be encapsulated), but commonly the slag was used for other purposes, such as parking lots. This resulted in contamination in surface waste and sediment. In these instances, the DEQ requires that the slag be removed or capped.

Remediation

Our clients, who inherited an industrial property with a slag/gravel lot, hired MFA to resolve this issue. Because the property was located in the floodplain, any fill (asphalt required to construct the environmental cap) had to be “balanced” by an equivalent volume of excavation. MFA designed an asphalt cap and balanced it with excavation of stormwater treatment ponds and vegetated swales. This met the balanced cut/fill requirements, as well as providing stormwater treatment consistent with City of Portland requirements.

Design, Permitting, and Construction Oversight

MFA managed the design, permitting, and construction of the green stormwater infrastructure facilities and remedial asphalt cap. The cap required minor grading and compaction of the slag surface by a qualified environmental contractor and placement of an asphalt surface. The stormwater treatment system involved excavation of two settling ponds and two swales, transport and disposal of the excavated soil, placement of soil, planting, and construction of a stormwater management system for the newly asphalted area.

MFA provided construction oversight and coordinated the work with several contractors, inspectors, and regulatory agencies. The result benefited the owner, who ended up with a more marketable property, as well as the tenant, a transportation facility that preferred an asphalt parking lot for its truck fleet. The tenant’s stormwater discharges have achieved the permit benchmarks since construction was completed.