EPA LEAF Testing of Ultra-Lightweight Foamed Glass Aggregate to Support Vapor Barrier Applications on Ponds and Lagoons

Abstract

Foamed glass aggregate (FGA) was characterized to evaluate its potential to serve as a vapor barrier on various water bodies [water supply reservoirs, industrial lagoons, acid mine drainage (AMD) ponds, etc.] Specifically, the FGA was tested for its total metal content for the target analyte list (TAL) metals and the leaching of the same by Environmental Protection Agency (EPA) Methods 1311 [Toxicity Characteristic Leaching Procedure (TCLP], 1312 [Synthetic Precipitation Leaching Procedure (SPLP)], 1313 (Leaching as a function of pH), and 1316 [Leaching as a function of the liquid-to-solid (L/S)] ratio. The commercially available FGA ranges from 25 to 38 mm in diameter and is oversized (OS) compared to the maximum particle size allowed by the TCLP/SPLP test (9.5 mm) and EPA 1313/1316 (5 mm). As such, each leaching test was run on a particle size-reduced FGA (<9.5 mm), and the contact period during EPA 1313/1316 tests was extended from the method maximum of 3 to 7 days to promote equilibration. Additionally, a secondary EPA 1313 test was performed with sulfuric acid to evaluate conditions relevant to mining/industry conditions, and higher L/S ratios of 20, 50, and 100 were added to EPA 1316 to simulate pond/lagoon-type conditions. The FGA was found to be nonhazardous and passed the most stringent regional clean-fill requirements where it was produced. Leaching by EPA 1316 with L/S ≥ 20 satisfied the EPA drinking water standards except for arsenic; however, this was attributed to the increased FGA surface area created by self-abrasion during the end-over-end tumbling extraction, which produced 17 wt% fines. Two additional 7-day EPA 1316 extractions performed using the OS FGA at L/S 10 and 100 in a modified extractor with a magnetic stirrer (no self-abrasion) leached no heavy metals above the method detection limits, only common soil elements. For an EPA 1313 test (L/S 10) on the OS FGA under strongly sulfuric acid conditions (pH < 1.5), 9 of 15 heavy metal (Sb, As, Ag, Be, Cd, Mo, Se, Tl, V) concentrations were all below their reporting limits for drinking water, and all other TAL metals (including common soil elements) were substantially below representative AMD conditions.