Geology and properties of limestone
Geology and hydrogeology
Limestone geologies can be heavily fractured and include almost impermeable chert layers and nodules. Flow predominantly occurs in the fractures due to a much higher hydraulic conductivity as in the limestone matrix. The limestone found at the Akacievej site is a carbonated sand limestone (Copenhagen chalk) and a bryozoan limestone, both with a strongly varying hardness. Due to glacial activity, the uppermost 1-5 meters of the limestone are crushed. A good description of the geologic stratification is given in the Report [1] (in Danish). The figure on the right shows the typical krono-, bio- and lithostratigraphy in eastern Zealand (Denmark) and Øresundsregion.
Properties of limestone
The sorption behavior for chlorinated solvents on limestone was examined in Salzer (2013). For chlorinated solvents like PCE, sorption to limestone can be strong (kd values of 0.5-1 L/kg were observed).
Typical values of the hydraulic properties and the transport properties at the Akacievej field site
The following table gives an overview of values that were determined for the Akacievej site:
| Parameter | Value | Comment |
|---|---|---|
| K_crushed | 5x10^-4 m/s | crushed limestone conductivity |
| n_matrix | 0.10 - 0.20 | matrix porosity |
| ap | 2 mm | typical fracture aperture |
| K_matrix | 1x10^-7 m/s | limestone conductivity |
| B | 20 - 25 m | aquifer thickness |
| D_m | 7.5x10^-7 m^2/s | effective diffusivity |
| k_d | 0.5-1.0 L/kg | sorption coefficient for PCE on limestone |
- ↑ Geo/Geus, Geologi, (Copenhagen, 2014)
