ECONOMIC APPROACHES TO MANAGING STORMWATER RUNOFF IN THE SEATTLE AREA

Abstract

This thesis evaluates the use of best management practices (BMPs) as cost effective tools for reducing the incidence of combined sewer overflows (CSOs) in the Ballard CSO basin. I estimated the cost of detaining stormwater runoff in the Ballard CSO basin through BMPs. This study also evaluated three separate stormwater management programs that incentivized the adoption of BMPs. A full stormwater capture program, a tradable allowance program, and a BMP credit program were simulated to estimate total cost. The full stormwater capture program used a quantity instrument to require all parcels to detain stormwater on-site. The tradable allowance program also used a quantity instrument, but gave parcel owners the option to detain runoff on-site or to purchase stormwater allowances. The BMP credit program utilized a price instrument to charge parcel owners for runoff. Parcel owners were given the option to waive the fee if they allowed the city to build BMPs on their property. The findings indicate BMPs have a lower average cost of managing stormwater runoff than traditional centralized infrastructure. All three scenarios also generated lower total costs than a centralized infrastructure approach. The simulation determined a tradable allowance program generated the lowest total costs, however difficulties in implementation of the program limited the viability of the program. The analysis determined the BMP credit program to be a more viable option. This program provided relatively low total costs and promoted BMP adoption in the Ballard CSO basin. The thesis also identified how Seattle's current drainage fee may be unfairly charging parcels for runoff. I recommend a stormwater management program that offers a BMP credit to parcels utilizing stormwater runoff technologies and increased drainage fee transparency.