PVC plastic is also toxic if it burns. Fertilizer application is another maintenance practice that needs to be considered for a healthy residential site. Water-based paints are recommended replacements and often have similar durability over time. Other landscape construction materials have varied degrees of toxicity. Asphalt also needs regular recoating to maintain its seal and structural integrity. Principle: The sustainable residential site should be a nurturing and safe
environment for all life. Another material that has questionable use on a sustainable residential site is polyvinyl chloride (PVC), frequently found in plastic pipes and tubing. Two other commonly used materials that ideally should not be used in the sustainable landscape are asphalt and oil-based paint. Integrate Healthy Maintenance Practices
Common maintenance procedures on many residential sites utilize relatively large volumes of toxic chemicals as a means of making them appear “healthy.” These chemicals are often hazardous to people, plants, and wildlife while giving the false impression of a wholesome environment. They are ideally made without poisonous chemicals, heavy metals, or oil. The added fertilizer loads in waterways contribute to algae growth that in turn depletes the water of oxygen, as previously discussed (see “Select Plants for Regional Precipitation” in “Natural Events and Cycles” in this chapter). Although many materials fulfill these criteria to different degrees, some materials should ideally be avoided because they do not. These primarily involve the use of materials and maintenance practices that are pollutant and toxin free. Background research should be conducted on each material by carefully reading manufacturers’ specifications and product labels before it is adopted for use in a sustainable landscape. In general, safe materials are toxin and pollutant free with relatively little embodied energy. Other wood, such as railroad ties or old utility poles, that contains creosote or pen – tachlorophenol is not recommended either because these chemicals are potentially harmful to touch or breathe. Asphalt produces fumes when hot
A compost area should collect and recycle vegetative material from the house and site. Some organic fertilizers have an added advantage because they use recycled material such as sewage sludge. Fertilizers also possess among the largest quantities of embodied energy of all landscape materials. Fertilizers applied to the residential landscape are in fact one of the major contributors of pollution in streams, rivers, and lakes. Use Toxin-Free Materials
Much has already been said about appropriate materials for a sustainable residential site. Other forms of plastic, clay, or metal pipes should be considered as alternatives to PVC pipes. Nevertheless, there are additional tactics that can be employed to ensure that the residential landscape is indeed a healthy place. Although this is a popular and commonly used material in the landscape, the chlorine is a potentially harmful chemical when it leaches into ground water or outgases into the air. Pressure-treated lumber manufactured with chromated copper arsenate (CCA) before 2003 is one such material and has already been discussed (see “Discard Toxic Materials” in “Site Restoration” in this chapter). The chemicals are applied in low volumes to specific locations at the appropriate time to affect the insect or pest when it is most vulnerable. There are numerous substitutes for asphalt, especially on a residential site where it is frequently limited to driveways. Integrated pest management uses biological controls such as predator insects and scent traps in combination with nontoxic chemicals. All of the previously discussed sustainable principles and strategies contribute to such an environment. An “integrated pest management” program should be used if additional support is required for plant materials to flourish. Even new pressure-treated wood manufactured with amine copper quat (ACQ) or copper azone (CA) remains controversial because of the associated history with chromated copper arsenate. Perhaps the most effective means of reducing this chemical dependency is to create a landscape that is vigorous enough on its own to resist pests and diseases.