Alleviating Compaction & Liners for Stormwater

Question 1

What are the causes and effects of compaction at construction sites?

Answer 1

Excavation, mixing, stockpiling, equipment storage, equipment traffic, and exposed subsoil are all causes to compaction. The effects of compaction include porosity decreases and bulk density increases. As a result permeability of air and water in soil decreases, soil water-holding capacity is reduced, and root growth is impeded. Also can lead to increased runoff and erosion.

Question 2

How is soil compaction determined?

Answer 2

Field observations, including presence of ponded water, discolored or poor plant growth, and eroded soil can show evidence of compaction. It can be determined through filed measurements that include taking bulk density samples, using commercially available cone penetrometers, and using surface nuclear gauges.

Question 3

What are methods for alleviating compaction?

Answer 3

soil ripping - fracture compacted soil without adversely disturbing plant life, topsoil, and surface residue
compost - organic matter resource that has the ability to improve the chemical, physical, and biological characteristics of the soil
selective grading, time, and reforestration are other methods.

Question 4

What are liners used for?

Answer 4

To limit infiltration of water from a stormwater BMPs into underlying and adjacent soil.

Question 5

Which sectors are required to have liners for ponds?

Answer 5

Automobile salvage yards, air transportation facilities that conduct deicing activities, hazardous waste treatment/storage/disposal facilities, timber product facilities operating under an SIC code of 2491, scrap recycling and waste recycling facilities.

Question 6

When are liners recommended?

Answer 6

• circumstances where a permanent pool is needed but difficult to maintain due to site conditions
• permeable pavement designs in compacted fill soils
• areas where seepage from a BMP into the groundwater would otherwise occur but should be avoided due to risk of contamination (confirmed stormwater hotspots and active karst terrain)
• locations where recommended horizontal or vertical separation distances cannot be achieved
• use impermeable liner as needed to separate tree BMPs from road, parking lot, sidewalk, or building foundation