Design Project

Once the grant agreement was signed, the work began in earnest on the project. City staff had several opportunities to give presentions to various agencies and groups of people explaining the project and its importance to this valley. The City developed a Request for Proposal (RFP) and hired MKN and Associates to produce drawings and specifications for construction of the biofilter. During the design phase of the project, the design team needed to determine exactly what the project is intended to achieve in order to ensure the design of the facility would be consistent with the desired overall function. The design drawings went through several revisions before the final design was chosen. Extensive design reviews were conducted at 60%, 90%, and 100% completion. Once the design was complete, the project went out to bid for construction in May 2016. 

In addition to the design, significant effort went in to ensuring the woodchips to be used in the biofilter would be the most effective and provide the desired results. A pilot project was conducted testing readily available local types of woodchips. The pilot involved placing the various types of chips in a container and replicating the residence time suggested in literature. Staff then tested ammonia, nitrate, flow, alkalinity, and temperature of the water both entering and leaving the filter. The chips that performed the best resulted in the lowest total nitrogen in the effluent. Types of chips tested were overs (a byproduct of composting), blonde (from construction demolition), and pine (from local trees that died due to the drought). As a result of the pilot, it was found the overs performed the most consistently over time, and they will be used in this biofilter project. They are being provided at a tremendous discount to the project by Engel and Gray.