Progressive Design-Build Delivery Model Yields Innovative Design of AWPF

Presentation Description: Alternative delivery models are becoming more popular in the water industry for implementation of large and complex projects. Alternative delivery approaches such as progressive design-build (PDB) can foster collaborative teamwork while producing innovative solutions that are cost-effective and schedule-conscious. In addition, access to construction staff yields important constructability input, while also allowing construction of testing infrastructure to assist with design development.

The City of Los Angeles is currently implementing the LAGWR Project using a PDB approach. The project will purify up to 25 mgd of tertiary effluent from the Donald C. Tillman Water Reclamation Plant (DCT WRP) for replenishment of the San Fernando Groundwater Basin via the Hansen Spreading Grounds. The advanced water purification facility (AWPF) will include ultrafiltration, reverse osmosis, and UV advanced oxidation.
Design and construction of a AWPF is very complex and includes a myriad of analyses and decisions. Input from utility and construction staff during design of the DCT AWPF was solicited , however several specific issues were unique and addressed with innovative solutions using the PDB delivery model.

First, to maximize the amount of groundwater recharge, a detailed evaluation (including field verification) was conducted to assess opportunities to reduce select waste flows from the DCT WRP (e.g. grit, scum, filter backwash), thereby increasing flow to the AWPF.

Second, 1,2,3-trichloroproane was identified as a potential chemical of concern that might pass through RO and UVAOP treatment and exceed California notification limits. A single element RO testing unit was constructed and operated at DCT to test 1,2,3-TCP removal by RO given that limited literature was available on 1,2,3-TCP removal..

Third, water quality sampling suggested elevated inorganics during wet weather events that could accelerate scaling of RO. Installation of an on-line orthophosphate analyzer in the existing tertiary effluent channel was used to quantify daily and seasonal trends to inform the chemical pretreatment design upstream of RO.

Finally, construction staff provided invaluable input on sub-surface construction and excavation approaches to maximize available footprint and AWPF treatment capacity.

This presentation will review the benefits of the PDB approach for LAGWR as demonstrated by the resolution of the issues described herein.

.1 SWRCB Education Units
1 SWRCB Drinking Water Contact Hour