APPENDIX A

APPENDIX C

MEMO

Date: September 9, 1999

To: RTDF Working Group for Phytoremediation at Petroleum Contaminated Sites

From: Jim Brown, Lockheed Martin/REAC & Royal Nadeau, U.S. EPA Environmental Response Team Center (ERTC), Edison, NJ

Re: Basis for Plant Materials Selection in Plant-Mediated Bioremediation¹ at Petroleum Contaminated Sites

Selection of Suitable Plant Species

Plant Selection Criteria:²
Well adapted to soil and site conditions
Easy to establish & maintain
Rapid growth & well-developed fibrous root system (enhanced rhizosphere effect)
Provide good soil cover to prevent soil erosion by wind and water
Low maintenance
Suitability for livestock feeding (some cost recovery possible)
Suitable as site restoration species (long term stability)
Value for wildlife cover and forage
Aesthetic benefit

No single plant species can fulfill all these criteria; a mixture of cool and warm season grasses and legumes can. The advantage is a low-cost, low-maintenance, stable plant/soil system that also facilitates bioremediation of hydrocarbon contaminants.

Use of cool season grasses and agronomic crops requires continuous maintenance; use of a cool and warm season grass mixture requires little maintenance. The following is a summary of typical cool and warm season grass characteristics:

Cool Season Grasses - quickly established, rapid top growth, growth during spring/fall (dormant in summer without water and nutrients), high nutrient requirement & root zone density within active treatment zone (0-6/12 inches), vigorous competitors under ideal conditions. Cool season grasses require high maintenance (i.e. regular additions of water and fertilizer).

Warm Season Grasses³ - slowly established (2 years), very deep rooted, bunchgrass characteristic, not vigorous competitors when soil moisture and nutrients are optimal; tolerant of drought and low nutrient availability. Once established, warm season grasses require little or no maintenance and tolerate marginal soil conditions.

EPA's Current Approach to Superfund Site Revegetation/Restoration

Considers final land use.

Focuses on site revegetation/restoration following remediation; native plants preferred, beneficial to wildlife.

Compatible with goals for plant-mediated bioremediation at petroleum- contaminated sites.

Technical Approach

Select a compatible mixture of cool and warm season grasses and legumes; permit natural succession of cool to warm season grasses, including shrubs and trees. After succession, little or no maintenance required.

Technical Support

EPA has an interagency agreement with the Natural Resource Conservation Service (NRCS) of the U.S. Department of Agriculture for revegetation/restoration of Superfund sites. Support is provided through regional plant materials centers. Contact local NRCS office for locations.

^{1 The term 'plant-mediated bioremediation' is suggested rather than 'phytoremediation'; the latter term requires evidence of an active plant role in detoxification.
^{2 Assumes insufficient research data currently available to select plant species based on demonstrated plant-mediated bioremediation effectiveness.
^{3 Most drought-tolerant warm season grasses are deep-rooted, and require deep, well-drained soil. In arid and semi-arid regions, saline soils will develop under irrigation if soil drainage is impaired. Under these conditions, improvements such as tile drainage or deep ripping of compacted subsoils may be required. If soil drainage cannot be improved, salt-tolerant native grasses and shrubs may be most appropriate.

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