In 2013, AMWA and the National Association of Clean Water Agencies (NACWA) released a report, The Impacts of Altering Tax-Exempt Municipal Bond Financing on Public Drinking Water & Wastewater Systems, to estimate the cost implications to water and wastewater systems of limiting or abolishing tax-exempt municipal bonds. The report found that more than $39 billion worth of state and local tax-exempt debt was issued in 2012 to finance water and sewer projects. If municipal bonds had been fully taxable that year, the report says, municipalities' water and wastewater financing costs would have increased by roughly $9 billion.
In 2017 AMWA and NACWA created a supplement to this report that estimated the value of the municipal bond tax exemption for drinking water and wastewaer projects during the previous year. The organizations found that communities issued $38 billion in 2016 municipal bonds to pay for water, sewer, and sanitation infrastructure projects, and that fully taxing municipal bond interest would have increased total debt service on these bonds by 25 percent, or $16 billion over their expected repayment periods. The full results of the 2017 supplement, which includes a breakdown of interest savings by state, are available here.