Environmental Enlightenment #143

By Ami Adini - Reissued February 11, 2016

This is a SHORT, LIGHT and SIMPLE newsletter. Its purpose is to rekindle in the initiated terminology they have once learned, and enlighten the uninitiated on terms they may have heard but never known the meaning of.

“Permeable” Is “Porous,” but “Porous” May Not Be “Permeable”

Outside of math, A = B may not necessarily mean B = A.

A pore is a space in rock, soil, or unconsolidated sediment that is not occupied by mineral matter and that allows the passage or absorption of fluids.

The word comes from Latin porus, Greek poros,where it means “passage.” A thing that is porous is having pores, and porosity is the condition or situation of being porous.

There are several properties of aquifers that determine how much water can be drawn from them. Porosity is the percentage of rock or soil that is void of material and thus can be filled with water. The larger the pore space or the greater their number, the higher the porosity.


Porosity in Percentage


Primary Openings

Equal-size spheres (marbles)
Loosest packing
Tightest packing












Sandstone (semiconsolidated)


Basalt (young)


When a fluid permeates a medium, it spreads, penetrates or flows throughout that medium. In Latin, per means through and meare means to pass. A permeable substance is one than is able to be permeated.

If pore spaces in sediment or bedrock are interconnected, then water can travel through those easily. This material is said to be permeable. Permeable rock units make good aquifers.

The property of permeability is related to porosity.

In qualitative terms, permeability is expressed as the capacity of a porous rock or soil to transmit a fluid.

Large interconnected pore openings are associated with high permeability, while very small unconnected pore openings are associated with low permeability. Sand and gravel with large interconnected pore openings have high porosity and permeability.

Clay tends to have high porosity, but the very small openings tend to inhibit the passage of water. Therefore, clay displays low permeability.

You can find past issues of our "Environmental Enlightenment" at amiadini.com Wealth of information about environmental site assessments in the real estate transactions and issues concerning assessment and cleanup of contamination in the subsurface soil and groundwater.

Call me if you have any questions. There are no obligations.

Ami Adini Environmental Services, Inc.
Environmental Consultants & General Engineering Contractors
California Lic. #1009513 A B HAZ ASB
818-824-8102; mail@amiadini.com

Ami Adini is a veteran environmental practitioner with over 40 years of experience. He carries a Bachelor of Science degree (B.Sc.) in Mechanical Engineering including academic credits in Nuclear and Chemical Engineering and postgraduate education in these fields. His career includes design and construction of nuclear plant facilities, chemical processing plants and hazardous wastewater treatment systems. He is a former California Registered Environmental Assessor Levels I & II in the 1988-2012 registry that certified environmental professionals in the assessment and remediation of environmentally impacted land, and a Registered Environmental Professional (REP) since 1989 with the National Registry of Environmental Professionals (NREP). He is a California Business & Professions Code Qualifying Responsible Managing Officer (RMO) in the General Engineering Contractor classification with Hazardous Substance Removal and Asbestos certifications, and president of AMI ADINI ENVIRONMENTAL SERVICES, INC. (AAES), a general engineering contractor and consulting firm specializing in environmental site assessments, rehabilitation of contaminated sites and removal of environmental risks from real-estate transactions. (Contact Ami for a complete resume.) AAES provides practical solutions to environmental concerns using the highest standards of ethics and integrity while providing its clients with maximum return on their investments.