Grading Stormwater Quality Infrastructure: An Integrated, Quantitative, Regional Approach

Date / Time:
Tuesday, Sep 13 10:20am to 10:50am
Sunset III
Track / Session:
Effectiveness Assessment / Quality Improvement
Short Description: 
As part of the 2016 ASCE Orange County Infrastructure Report Card, a quantitative approach of grading stormwater quality infrastructure through integration of geospatial and monitoring data was used.

Orange County ASCE infrastructure report cards were prepared in 2002, 2005, and 2010, and were instrumental in raising awareness of elected officials, decision makers, and the general public as to the need to maintain and improve public infrastructure as well as identify sustainable funding sources for doing so. A surface water quality infrastructure category was added to the report card in 2010 and was included in the 2016 effort as well.
A surface water quality infrastructure working committee (committee) was formed to assess the ability of existing and near future planned surface water quality infrastructure in Orange County to meet the following three goals:
1. Support healthy resilient watersheds;
2. Ensure safe and healthy aquatic resources; and,
3. Promote use of stormwater as a resource.
Surface water quality infrastructure that was evaluated as part of this effort included devices, systems, structures, facilities, and areas which filter, treat, divert, infiltrate, or capture/harvest stormwater and non-stormwater runoff. The committee, for the purposes of the report card, defined surface water as near beach ocean water, streams, flood control channels and lakes, with the exception of water detention facilities and recreational waterbodies which do not receive flow directly from or discharge directly to the storm drain system. Surface water also included Urban Runoff, both stormwater and dry weather runoff; Non‐Urban Runoff, runoff from undeveloped areas; and pumped groundwater and springs.
Experts were recruited to participate on the committee, and included representatives from the County of Orange, local municipalities, academic institutions, non-governmental organizations, and the surface water quality consulting community. Early meetings identified the desire to approach the evaluation of surface water quality infrastructure in more of a quantitative manner than in previous report cards. With the availability of a significant amount of land use, geophysical, surface water, and other environmental data, a decision was made to implement an integrated, quantitative assessment approach. Each working committee for the 2016 report card was tasked with formulating an overall infrastructure grade on the evaluation of four main categories:
1. Condition;
2. Capacity;
3. Operation & Maintenance; and,
4. Resiliency.

The committee took the following approach for each category –

The working committee used data on the condition (health) of watersheds, receiving waters, and stormwater runoff in Orange County to calculate an overall score for this category. The methodology utilized a combination of GIS and environmental monitoring/water quality data, with the help of an aggregate water quality index for analysis. California Stream Condition Index data was also integrated into the assessment.

The methodology for scoring the capacity of surface water quality infrastructure relied on GIS analysis of the percentage of both wet and dry weather runoff from developed areas treated, infiltrated, diverted, or captured for harvest/reuse.

Operation & Maintenance:
The methodology used for scoring operation & maintenance of surface water quality infrastructure was based on an online survey of municipalities.

Defined as the ability of a water body to return to its natural state after undergoing a temporary change, resiliency was scored primarily based on the analysis of the number of beach mile day postings by the Orange County Health Care Agency, as well as GIS analysis of the percentage of developed land area tributary to a basin, diversion or other surface water quality feature capable of mitigating a spill or chemical release.

This integrated, quantitative approach is easily repeatable, and will improve as the amount and accuracy of data improves. It is also hoped that this could become a model approach used where other report cards are prepared.

Primary Speaker:
Grant Sharp, County of Orange
Supporting Speaker 1:
Daniel Apt, Olaunu