Shoreline Techniques Implemented at the Garden
Stable shorelines were created under the Section 319 Project using permutations of six basic techniques:
- Treatment 1: Clay soil shelf with emergent and aquatic wetland habitats
- Treatment 2: Underwater stone berm with emergent and aquatic communities on created shelf
- Treatment 3: Submerged sheet piling with emergent and aquatic communities on created shelf
- Treatment 4: Exposed sheet piling
- Treatment 5: Interplanted boulders with small stones interspersed
- Treatment 6: Coir roll
Much of the construction work under the Section 319 Project was accomplished "in the dry" with the lake area under construction completely drained. Three existing cofferdams and a sandbag dam/causeway were utilized and the water was pumped from the lakes to the Garden's outflow weir at the south end of the lakes. The ability to draw the lakes down allowed the Garden to simplify the construction process and allow placement of aquatic planting bed soils in areas that, once refilled, would be below the lakes' normal water levels. Most of these techniques can be employed in situations where lake levels cannot be completely drawn down -- the primary limiting factor is that aquatic planting bed soils cannot be compacted properly if placed directly into water, and so lake drawdown of at least 2 feet is necessary for most of the treatments described here.
