Stormwater Management Options and Decision-Making in Urbanized Watersheds of Los Angeles, California

Biochar-augmented biofilters to improve pollutant removal from stormwater – can they improve receiving water quality?

“…Water quality is impacted and often regulated at the watershed scale, so understanding and planning for management decisions within the entire watershed is more impactful than responding to water quality issues at a single site. Wolfand et al 104,105 and Gallo et al 111 concluded that the end watershed management goal greatly impacts the optimal spatial distribution, size, infiltrative properties, and performance needs of biofilters (Table 1). For example, concentration-based versus load-based standards should be approached differently; biochar-augmented non-infiltrating filters are recommended to meet concentration-based standards whereas load-based standards are best met with infiltrating conventional biofilters (Table 1).…”

“…Similarly, Gallo et al 110 studied urbanized watersheds in Los Angeles and investigated the extent of implementation of SCMs (including biofilters) required to reduce metal loads and meet concentration-based water quality requirements. Computational modeling results show that when SCMs are simulated to capture the 85th percentile storm volume, pollutant loads are greatly reduced (up to 75%, 85%, and 84% in the Ballona Creek, Dominguez Channel, and Los Angeles River watersheds, respectively).…”

“…For example, in the Dominguez Channel watershed (184 km 2 , 71% impervious), despite treating 90% of the watershed runoff with biofilters, Cu only reached 12.5% and Zn only reached 25% compliance. 111,112 Given the challenges in meeting water quality requirements with conventional SCMs, Wolfand et al 104 investigated how improving biofilter performance with the addition of biochar may impact water quality at the watershed scale. Implementation of biochar-augmented biofilters was examined using the Ballona Creek watershed as a case study.…”

“…If biochar-augmented biofilters are installed, however, only approximately 20 000 biofilters would be required. Given the median capital cost of a biofilter in Los Angeles is $14.60 per unit, 111 this could represent significant cost savings to a municipality; in this case, approximate capital cost would decrease four-fold from $1.2m to $290 000.…”

Investigating Tradeoffs of Green to Grey Stormwater Infrastructure Using a Planning-Level Decision Support Tool

“…Additionally, there is a lack of studies that evaluate the hydrologic impacts of green versus grey SCMs on hydrology. This is important to consider as Gallo et al (2020) and Wolfand et al (2018) demonstrated the importance in considering multiple SCM types to determine which types most effectively achieve the primary goal of a watershed [37,38]. Additionally, Spahr et al (2020) demonstrated in a cross-city public survey that the consideration of multiple benefits is important to the general public.…”