Pacific Lumber Stormwater Conveyance and Treatment

Herrera designed conveyance improvements and a new stormwater treatment system to help Pacific Lumber and Shipping achieve compliance with their Industrial Stormwater General Permit (ISGP) at their Longview log yard site. Due to the abundant quantities of fine materials generated by log yard activity and because log yard debris has a very high chemical oxygen demand (COD), the ISGP has stringent benchmarks that apply to log yards. During initial concept development a variety of treatment techniques were evaluated based on their potential to meet the industrial stormwater permit requirements as well as other considerations such as; capital costs, long term operations and maintenance costs, footprint, and reliability. The selected system involves optimizing the conveyance system to maximize infiltration and improve settling and treatment within the conveyance system. This is followed by treatment through a sandfilter and then discharge to an infiltration basin.

Herrera designed conveyance improvements that included ditch restoration; new storm drainage conveyance including piping and precast structures; lining of existing storm drainage piping; a pump station; sand filters; retrofit of an existing building to serve as an electrical room; a mud tank; a decant facility; and an infiltration pond. In addition to typical engineering design details the project required modeling, geotechnical and soils analysis, and materials handling. Herrera also coordinated with Ecology to facilitate the design approval process.

Herrera also provided construction support services, including responding to requests for information, reviewing submittals, site review(s) to confirm that project elements had been designed in accordance with contract documents, participating in weekly construction meetings, preparing daily inspection reports, and preparing a final punch list. Herrera also provided special inspections of storm drainage conveyance installation; pond liner; treatment facility pumps, valves, pipes; and infiltration pond.