As a subconsultant, NV5 installed, monitored, and reported flow measurements for the City of Newport Beach’s Arches Drain Diversions Project for use in the design and permitting of the diversions. NV5 supported the development of the Monitoring Plan and Quality Assurance Project Plan (QAPP), collected flow measurements, and conducted water quality sampling for fecal indicator bacteria.
To obtain the required flow measurements for the two low-flow diversions that collect dry and wet weather flows from the Arches Drain, NV5 installed low flow monitoring equipment within the storm drain of the proposed two diversions. The dry weather flow monitoring consisted of measuring non-storm flows to capture diurnal changes in flow due to irrigation. NV5 prepared flow volume calculations and provided a deliverable with a summary of the flow data as a daily average, minimum and maximum flows. The baseline flow measurements over the full range of expected flows were used for the design, discharge permitting, and project effectiveness assessment. The flow data was used to verify the expected flows for the design of the two diversions and to assess the effectiveness of the two low flow diversions in reducing the anthropogenic sources of fecal indicator bacteria exceedances at the Arches Drainage outfalls and postings at the closest AB411 sampling location. The results from the baseline dry weather flow measurement and water quality sampling allowed determining the baseline fecal indicator bacteria loads from dry weather flows from the two largest drainage areas within the Arches Drainage for comparison to the post-construction conditions after the two diversions have been implemented and in operation. The results of the flow measurements and additional chemical analysis of the baseline conditions were also used for the discharge permit for Orange County Sanitation District.
