Ecological goals for an urban garden:
Identify and remediate contaminants.
Reuse suitable exiting site elements to make landscape features such as retaining walls and rubble to shape constructed landscapes or planting beds.
Keep water on site through means of planting, permeable surfaces and proper drainage. This minimizes the use of the already over-taxed municipal sewer system. Use collected site water for irrigation by collecting and storing it in an underground cistern located on the site.