Evaluation of Road Base Material Derived from Tank Bottom Sludges - Final Report

Period Covered by the Report: 7-23-99 to 12-22-00
Date of Report: 2-20-01
EPA Grant Number: R827015-01-0
Title: Evaluation of Road Base Material Derived from Tank Bottom Sludges
Investigators: John N. Veenstra, Dee Ann Sanders, Donald R. Snethen
Institutions: Oklahoma State University
EPA Project Officer: Bala Krishnan
Project Period: July 23, 1999 to June 22, 2000 (N/C Ext. to December, 22, 2000)
Project Amount: $70,556
Research Category: Beneficial use of waste products

Description:

Objective(s) of the Research Project:

The purpose of this research project was to evaluate the suitability of crude oil tank-bottom sludges for use in roadbase mixtures for light-duty roads. Disposal of tank sludges is a significant item of tank maintenance for producers, refiners and transporters of petroleum materials. All tanks eventually accumulate sludge, but the worst problems occur in crude tanks at production locations. Beneficial reuse from small production sites requires that the sludge material be reused without treatment. The amendment of asphalt road base material using tank bottom sludges to create an "asphalt-like" material should prove very economical.

To determine the suitability of sludges for this purpose, a research project was designed to:

• Sample representative tank batteries over a wide geographical area and over a number of producing strata;
• Determine physical and chemical properties of the sludges and compare them to properties of asphalt emulsions used for roadbase mixtures on light-duty roads;
• Form roadbase samples using different soil aggregates and a range of sludge samples;
• Test the samples for properties appropriate to roadbase material for light-duty roads;
• Subject the samples to multiple freeze/thaw cycles;
• Analyze the samples for leaching of toxic organics and metals using TCLP protocols;
• Analyze leachate for acute toxicity using Ceriodaphnia dubia;
• Analyze samples for content of normally-occurring radioactive material (NORM); and
• Make recommendations on the suitability of tank-bottom sludges for roadbase material.

• Sludge samples were obtained from ten tank batteries;
• Samples were analyzed for specific gravity, loss due to evaporation at 60 and 100 C, metals by ICP spectrometry, n-Hexane extractable material (HEM), characterization of C₆ to C₃₅ petroleum hydrocarbons, fractionation into saturates, aromatics, and asphaltenes;
• Four sludges were selected from the ten and were used to form roadbase samples using two different soil aggregates. These samples were subjected to physical testing to establish material suitability for use in roadbases: AASHTO - T166-83 Bulk Specific Gravity of Compacted Bituminous Mixtures; AASHTO - T209-82 Maximum Specific Gravity of Bituminous Paving Mixtures; and AASHTO - T246-82 Resistance to Deformation and Cohesion of Bituminous Mixtures by Means of Hveem Apparatus.
• The four samples were subjected to multiple freeze/thaw cycles, then were analyzed for hazardous materials as follows:
• TCLP characterization of toxic metals and toxic organics (not including pesticides);
• 48hr acute toxicity testing of leachate (using Ceriodaphnia dubia);
• Content of normally-occurring radioactive material (NORM).

The findings of the project were:

• None of the sludges made roadbase material that met the minimum specifications for light-duty roads.
• None of the roadbase samples was hazardous according to the TCLP analyses.
• Leachates from all the samples were toxic according to the 48-hour acute toxicity test.
• None of the samples had unacceptable levels of NORM.

The recommendation that can be made from the results of this project is to dispose of or reuse the tank-bottom sludges under existing state rules. In Oklahoma, the sludges can be used as a topcoat for lease or county roads, in accordance with a permit granted by the Oklahoma Corporation Commission. As long as the leachate is prevented from entering ambient waters (which is prohibited under Federal law and the state permit requirements), the environmental harm appears minimal.

Sanders, D., Snethen, D., and Veenstra, J. (2000) Evaluation of Roadbase Material Derived from Crude Tank-Bottom Sludges," Proceedings of the 7^th Annual International Petroleum Environmental Conference, Albuquerque, NM.

Sanders, D., Snethen, D., and Veenstra, J. (2001) "Suitability of Crude Oil Tank-Bottom Sludge as a Binder for Roadbase Material," (in preparation for submission to peer-reviewed engineering journal).

No further activities are planned.

Supplemental Keywords: tank-bottom sludge, crude oil sludge, recycled construction material, sludge landfarming.