Construction and Establishment

There are many important aspects of a wetland that must be considered after all of the planning is complete. Wetland construction and establishment consist of the following steps from the wetland checklist.

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Step Five: Construction

constructionA knowledgeable contractor and skilled equipment operators will be required for this phase of the project. All plans should be reviewed and discussed with the designer and the contractors during a pre-bid meeting. This meeting will provide an opportunity to explain the nature of the project. Many experienced contractors have never worked with constructed wetlands.

After a contractor is selected, a conference should be held with operators, the contractor, the plan designer, and any other experts you might need. This will provide an opportunity for all questions to be answered before work begins. Planning and preconstruction activities should be similar in scale to the size and complexity of the wetland project itself.

There are several different activities which must be considered during wetland construction. They include:

  • Building access roads
  • Clearing wooded areas
  • Constructing dikes
  • Digging basins
  • Installing pipes and valves
  • Mulching all disturbed areas.
Note: Proper equipment selection is critical. Equipment size and type are important elements because a poor equipent choice can result in significant cost increases. Also, ensure that construction is following the plan, and address concerns as quickly as possible.

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Step Six: Plant Establishment

After grading and all other soil moving efforts are complete, the bottom of the wetland should be planted. Plants must be chosen based on the characteristics of the water to be cleaned, the type of soil, and the location of the wetland. Many types of wetland species are available for your use, and the diversity is sufficient to enable selection of effective, well-suited plants for most situations.

Planting is typically done by hand and seeds, seedlings, or storage organs may be used. Seedlings are probably the easiest and quickest to utilize. Immediately following seedling planting, small amounts of water should be added to the wetland to aid establishment and prevent plants from drying out. After these rooted plants are established, the water level may be slowly raised. When depth is sufficient, floating plant species may be added to compliment the rooted species. Other plants will infiltrate over the life of the wetland - adding species diversity and increasing wetland effectiveness.

Do not plant willows in a constructed wetland, and remove any willows that begin to grow in the wetland as quickly as possible. Willow roots can break through the liner or compacted clay layer at the bottom of the wetland. This results in water loss, environmental damage, and wetland inefficacy.

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Step Seven: Filling the Wetland

This step may occur to some degree before or during plant establishment. Now that the construction and plant establishment is complete, it is time to add water to the wetland. This should be done slowly to ensure that all of the runoff water lines and pumps are functioning properly. Immediately following wetland filling, treatment will not be optimal. Exposure to large amounts of heavily nutrified or polluted water should be avoided. Flow should be maintained to avoid stagnation, and nitrogen in this water is beneficial at this stage. This period of partial use will allow time for microbial communities to develop. Additionally, plant establishment will continue.

After nine months, the wetland should be ready for normal use. Over the next few years, efficacy will likely increase as species diversity provides more opportunities for removal of nutrients and pollutants released into the wetland.

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