Development of lower cost drainage systems for heavy soils

Abstract

Four potential ways were identified and investigated for reducing drainage costs on heavy soils without reducing drainage efficiency. All involved the extension and development of mole drainage and related practices. The four methods were:

1. Improving the effectiveness of narrow bands of permeable backfill in discharging water from mole drains.

2. Installing model main systems instead of permeable backfill systems on suitable moling soils.

3. Increasing mole channel stability to extend mole channel life and collector spacings.

4. Replacing standard pipe and permeable backfill systems with lower cost mole drain liners in non-moling soils.

The use of mole channel liners (method 4) offers considerable potential for reducing drainage costs on very marginal and non-moling soils. Development work was continuing after completion of the project to reduce pipe wall thickness and installation costs.