Effect of Manure Ponding

on

Soil Hydraulic Properties

A Thesis

Submitted to the Faculty of Graduate Studies

in Partial Fulfillment of the Requirements

for the Degree of Masters of Science

in the Department of

Agricultural and Bioresource Engineering

University of Saskatchewan

Saskatoon

By

Terrance Alden Fonstad

Fall1996

© Copyright Terrance A. Fonstad, 1996. All rights reserved

PERMISSION TO USE

In presenting this thesis in partial fulfillment of the requirements for a Postgraduate degree

from the University of Saskatchewan, I agree that the Libraries of this University may

make it freely available for inspection. I further agree that permission for copying of this

thesis in any manner, in whole or in part, for scholarly purposes may be granted by the

professor or professors who supervised my thesis work or, in their absence, by the Head

of the Department or the Dean of the College in which my thesis work was done. It is

understood that any copying or publication or use of this thesis or parts thereof for

fmancial gain shall not be allowed without my written permission. It is also understood

that due recognition shall be given to me and to the University of Saskatchewan in any

scholarly use which may be made of any material in my thesis.

Request for permission to copy or to make other use of material in this thesis in

whole or in part should be addressed to:

Head of the Department of Agricultural and Bioresource Engineering

University of Saskatchewan

Saskatoon, Saskatchewan S7N OWO

ABSTRACT

The purpose of this study was to extend previous studies investigating the clogging of soil

by ponded hog manure and to clarify the meaning and the magnitude of the "manure seal".

Specific objectives are related to the effect of clogging upon soil hydraulic conductivity:

1) to measure the effect of clogging with time,

2) to measure the effect of clogging with depth, and

3) to determine the effect of soil texture upon clogging.

Seven soils were studied in column tests in a controlled environment. Hog manure was

ponded on the soils for a period of 185 days and the soils were monitored for changes in

apparent hydraulic conductivity, hydraulic conductivity with depth and visual alterations.

The soil-manure interface was found to govern infiltration into the soil and the apparent

hydraulic conductivity of the soil column. This layer was 5 mm to 7 mm thick and was a

result of particulate matter in the manure clogging the surface soil pores which increased

in thickness with time. Soils below this layer retained their ability to conduct flow with

the exception of some reduction in hydraulic conductivity caused by small particulate

matter passing through the clogged layer and air entrapment caused by fermentation.

The clogging of the soil reduced the apparent hydraulic conductivity of the soil columns to

less than 10-6 cm/s within 5 to 25 days and to less than 10-7 cm/s within 20 to 30 days.

The time required to reduce the apparent hydraulic conductivity of the soil column was

dependent on soil texture and was less for soils with less than 25 % clay content and more

for soils with more than 25% clay content.

ii

ACKNOWLEDGEMENTS

I wish to acknowledge the assistance and guidance from my supervisor, Professor C.P.

Maule of the Department of Agricultural and Bioresource Engineering, my committee

members and my fellow students. Funding for this project was provided by the Canada­

Saskatchewan Green Plan Agreement on Agriculture and SPI Marketing Group.

iii

TABLE OF CONTENTS

PERMISSION TO USE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

ABSRACT ................................................................................... ii

ACKNOWLEDGEMENTS ................................................................ iii

TABLE OF CONTENTS .................................................................. iv

LIST OF TABLES ......................................................................... vi

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... vii

LSIT OF SYMBOLS AND ABRIVIATIONS ........................................ tx

1. INTRODUCTION ................................................................. 1

2. LITERATURE REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

2.2 Investigation of the Mechanism of Soil Clogging . . . . . . . . . . . . . . . . . .. 7

2.3 Time and Hydraulic Conductivity Reduction . . . . . . . . . . . . . . . . . . . . . . . . 11

2.4 Thickness of the Clogged or Sealed Layer .. . . . . .. . . . . . . .. . . . . . . . . . .. 16

2.5 Summary and Need for Further Studies . . . . . .. . . . . . . .. .. . .. . . . . . . .. . . 19

3. DIFFERENCES IN LABORATORY AND FIELD SITUATIONS ON

APPARENT HYDRAULIC CONDUCTIVITY AND FLUX............ 21

4 METHODOLOGY .............................................................. 31

4.1 Soil Collection and Analysis ................................. ~. . . . . . . . . 31

4.2 Column Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.2.1 Column Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.2.2 Column Soil Packing .. . . .. . . .. . . . . .. . . . .. . .. .. . .. .. . . . .. . . . . .. . 35

4.3 Hydraulic Conductivity Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36

4.3.1 Initial Hydraulic Conductivity Determination With Water . 36

4.3.2 Hydraulic Conductivity Measurement With Ponded Manure. 37

iv

5.0 RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 42

5.1 Soil Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5 .1.1 Physical Soil Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5 .1. 2 Chemical Soil Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5.1.3 Soil Column Properties . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

5.2 Construction Criteria and Soil Properties . . . . . .. . .. . .. . .. . .. . .. . ... .. .. 45

5.3 Hydraulic Conductivity With Water ..................................... 45

5.4 Manure Ponding Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 46

5.4.1 Column Apparent Hydraulic Conductivities . . . . . . . . . . . . . . . . . .. 46

5.4.2 Soil Manure Interface ............................................. 51

5.4.3 Measured Apparent Hydraulic Conductivity ................... 52

5.4.4 Effect of Clogging With Depth ................................... 55

5.4.5 Effect of Texture and CEC on Clogging . . . . . . . . . . . . . . . . . . . . . . . . 56

5.5 Sources of Error ............................................................. 66

6.0 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

v

LIST OF TABLES

TABLE DESCRIPTION PAGE

3.1 Sensitivity Analysis .................... 0 ........... 0 ........... 0..................... 23

4.1 Origin of Soils Used in Column Study .. 0. 0 ......... 0 ....... 0 ......... 0. 0 ......... 0 31

4.2 Testing Methods for Soil Physical Analysis .. .. . . . . . . . . . . . . .. . . .. . . . . .. . . .. . . . . .. . 32

4.3 Chemical Analysis of Hog Manure Used in Column Test .. . .. . . . . .. . . . . . . . . . ... 38

404 Schedule of Events ............ 0 .......... 0 ........ 0 0. 0............................... 40

5.1 Physical Properties of Soils Used in Columns . . . . . .. . .. .. . . . . . . . . . . .. . . . . . . .. . . . . 43

5.2 Soil Chemical Properties of Soils Used in Columns............................. 44

5.3 Soil Physical Properties Following Compaction into the Columns . . . . . . . . . . . . 44

504 Summary of Hydraulic Conductivities............................................. 47

vi

FIGURE

LIST OF FIGURES

DESCRIPTION PAGE

3.1 Laboratory vs. Field Situation (soil-manure interface defined as 5 mm thick and

hydraulic conductivity of 5 x10-9 cm/s) .............................................. 21

3.2 Apparent Hydraulic Conductivity vs. Depth of the Wetting Front (for a laboratory

column with varying thickness of the soil-manure interface (ds1) assuming Ks2 =

10-5 cm/s) ............................................................................... 26

3.3 Flux vs. Depth of the Wetting Front (for a laboratory column with varying

thickness of the soil-manure interface layer (ds1) assuming Ks2 = 10-5 crn/s) .. 26

3.4 Apparent Hydraulic Conductivity vs. Depth of the Wetting Front (for a laboratory

column with varying hydraulic conductivities of the subsoil (Ks2)) ............. 27

3.5 Flux vs. Depth of the Wetting Front (for a laboratory column with varying

hydraulic conductivities of the subsoil (Ks2)) . . .. ... . .. . .. . .. . ... .. . .. .... .. . .. . .. 27

3.6 Typical Field Situation for a Earthen Line Manure Storage..................... 28

3.7 Apparent Hydraulic Conductivity vs. Depth of the Wetting Front (for a lined

earthen manure storage with varying hydraulic conductivities of the subsoil) .. 30

3.8 Flux vs. Depth of the Wetting Front (for a lined earthen manure storage with

varying hydraulic conductivities of the subsoil (Ks2)) .............. _.. ... . .. ... . . 30

4.1 Initial Soil Column Setup for Manure Seepage Study . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.2 Final Soil Column Setup for Manure Seepage Study . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34

5.1 Hydraulic Conductivity of Soils in Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 48

5.2 Change of Apparent Hydraulic Conductivity With Time . . . . . . . . . . . . . . . . . . . . . . . . 49

vii

5.3 Apparent Hydraulic Conductivity Change With Time . . . . . . . . .. . . . . . . . . . . . . . . . . . 50

5.4 Measured and Calculated Apparent Hydraulic Conductivity vs. Time........ 54

5.5 Change in Hydraulic Conductivity With Time and Depth....................... 56

5.6 Hydraulic Conductivity vs. Time for Soil No.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 58

5.7a Hydraulic Conductivity With Depth at Tl and T2 vs.% Clay Content........ 60

5.7b Hydraulic Conductivity With Depth at Tl and T2 vs.% of Fines............... 61

5.7c Hydraulic Conductivity With Depth at Tl and T2 vs. Plasticity Index......... 62

5.7d Hydraulic Conductivity With Depth at Tl and T2 vs. Effective Pore Diameter 63

5.7e Hydraulic Conductivity With Depth at Tl and T2 vs. CEC. . . . . . ........ .. . . . . ... 64

viii

Cl,C2,etc. de dl d2 d3 K,k Kapp

Kcal Kw,Kmo

Kl K2

K3

Pl P2 t Tl

T2

CEC EC ID PI TS USDASCS

LSIT OF SYMBOLS AND ABRIVIA TIONS

-Column No.1, Column No.2, etc. - effective pore or void diameter -thickness to the soil-manure interface -distance between the top and middle manometer (25 mm) -distance between the middle and bottom manometer (75 mm) -hydraulic conductivity -"apparent" or "effective" hydraulic conductivity, hydraulic conductivity of the column as measured as a whole - calculated apparent hydraulic conductivity - hydraulic conductivity of soil columns as tested with water prior to manure application - hydraulic conductivity of the soil-manure interface layer in the columns - hydraulic conductivity of the top 25 mm of soil in the columns between the top and middle manometer - hydraulic conductivity of the top 25 mm to 100 mm between the middle and bottom manometer - time from manure ponding (Day 0) to Day 38 - Day 38 of testing to Day 185 -time - time period from Day 38 to Day 73 representing five sets of readings and measurements - time period from Day 157 to Day 185 representing five sets of readings

and measurements

- Cation Exchange Capacity - electrical conductivity - inside diameter - Plasticity Index - total solids -United States Department f Agriculture Soil Conservation Service

ix

1.0 INTRODUCTION

Since 1990, the Prairie Provinces have seen a dramatic increase in large scale hog

production facilities. These facilities prefer to use earthen manure storages of sufficient

volume to accommodate 200 or 400 days of storage. Typical storage volumes range from

10,000 m3

to 35,000 m3• These storages are constructed using conventional earth moving

equipment and the insitu soil materials. In comparison to concrete and steel storages,

earthen storages are cost effective and an environmentally feasible way of holding the

manure until field application, as long as proper design consideration is given to control of

seepage. Hog manure has very high levels of ions important for plant growth contained

both in solution and in the particulate matter in the manure. Ions in solution have the

potential to move due to advection, dispersion, and diffusion while manure particulate

matter is credited with clogging soil pores inhibiting fluid movement into soil (Davis et al.

1973; Chang et al. 1974; Culley and Phillips 1982; Rowsell et al. 1985; Barrington et al.

1987).

Seepage reduction due to the sealing of soils by manure has been investigated in North

America for many years. Davis et al. (1973), Culley and Phillips (1982), Miller et al.

(1985), and Rowsell et al. (1985) also investigated the sealing of soil by liquid dairy cattle

manure. All concluded that the manure was able to form an effective seal and reduce

infiltration rates to an acceptable rate which was defined as lx1o-6crnJs. Final infiltration

rates approached 10-7 crn/s. Barrington et al. (1987) conducted column tests to study the

infiltration of

1

liquid hog manure into soils of varying textures. It was confirmed that, regardless of soil

texture, the final hydraulic conductivity of the test columns (100 mm of soil height)

approached 1 x 1o-7 cm/s.

Even though there is extensive evidence to show that animal manure has the ability to

reduce infiltration rates in storage ponds to 1o-7 cm/s, many studies have indicated

increased solute levels near manure storages to varying degrees and at varying distances

depending on soil type, site characteristics, manure type and operating conditions (Miller

et al. 1976; Ciravolo et al. 1979; Phillips et al. 1983; Barrington and Broughton 1988;

Gangbazo et al. 1989; Culley and Phillips, 1989; Westerman et al. 1993) .

The use of the word "seal" in the literature has caused some confusion as to the actual

performance of the reduction in hydraulic conductivity due to the particulate matter in the

manure clogging the soil surface pores. Barrington and Madramootoo (1989) showed

that the ability of a soil to clog or seal by manure is a function of the average or effective

pore diameter of the soil. They also demonstrated that the apparent hydraulic

conductivity of the soil beneath an earthen manure storage was a function of each of the

saturated media in the system (i.e. the organic mat, the manure soil interface and the soil).

Research prior to the early 1990s was used to develop many of the guidelines used today

for the siting, design and construction of earthen manure storages. Several of these

guidelines appear to place a reliance on the sealing of the soil by manure. The United

States Department of Agriculture Soil Conservation Service has published a supplement

2

called "Waste Storage Ponds No. 425". The supplement varies somewhat between US

States. Some versions of this supplement (Iowa 1988 and 1992) state that "there must

be a minimum of 5 feet of "sealable" soil beneath earthen manure storages. This appears

to be a misinterpretation of the mechanisms involved in the reduction of hydraulic

conductivity of soil due to manure. Other versions of the supplement use the benchmark

of at least 15% clay content for manure sealing to be effective. In Canada; Quebec,

Ontario, Manitoba, Saskatchewan, and British Columbia use a requirement of a minimum

of 15% clay content and a liner of 10-7 crnls hydraulic conductivity for the establishment of

earthen manure storages. These regulation appear to be based on the laboratory work of

Barrington et al. (1985, 1987 and 1989). The use of these laboratory test findings for

field situations has caused some concern within the geotechnical engineering community

as the hydraulic conductivities reported are based on a 100 mm soil column and are the

"apparent" hydraulic conductivities (Barrington et al. 1987).

In the case of soils "clogged" or "sealed" by manure, the governing factor determining

infiltration rate is the ratio of the thickness to the saturated hydraulic conductivity (d/K)

of the layer with the lowest saturated hydraulic conductivity (Barrington et al. 1987). A

thin layer at the manure-soil interface (e.g. 5mm) of extremely low hydraulic conductivity

(e.g. 10-9 crnls) can produce a "apparent" hydraulic conductivity near 10-7 cm/s for a soil

thickness (e.g. 0.1 m) of soil with a high initial hydraulic conductivity. If the hydraulic

gradient is over a larger distance (e.g. 1.0 m or 10.0 m) then the "apparent" hydraulic

conductivity will be proportionately higher.

3

As shown in the discussed literature there is an inadequate understanding of both the

effect of soil clogging from ponded manure in cold climates and the role it plays the in

determination of the average or apparent hydraulic conductivity. The purpose of this

study is to extend previous studies to further investigate the clogging of soil by ponded

hog manure. Specific objectives are related to the effect of clogging upon hydraulic

conductivity:

1) to measure the effect of clogging with time

2) to measure the effect of clogging with depth, and

3) to determine the effect of soil texture upon clogging.

Effort will be placed on the use of common geotechnical engineering terminology and

relating the results to terminology used in previous studies. The results of this study will

help to clarify the meaning and the magnitude of the "manure seal" mentioned by previous

researchers such as Chang et al. (1974), DeTar (1979), Rowsell et al. (1985) and

Barrington et al. (1987).

4

2.0 LITERATURE REVIEW

2.1 Introduction

The purpose of this study is to extend previously pubHshed research to investigate the

clogging of soil by ponded hog manure. Studies into the sealing or clogging of soils were

prevalent in the late 1940s and early 1950s when groundwater recharge by surface

infiltration ponds was being used to replenish depleted· surficial aquifers. These projects

were hampered by an unexpected reduction of hydraulic conductivity under prolonged

submergence (Allison, 1947; McCalla, 1950). The ponds were found to be experiencing

clogging at the surface of the soil. Studies were then initiated to determine the

mechanisms causing the clogging (Gupta and Swartzendruber, 1962; Mitchell and Nevo,

1963; Avenimelech and Nevo, 1963). It was found that the clogging was a function of

microbial activity and polysaccharide accumulation in the reduction of flow through soil

(Allison, 1947; McCalla, 1950; Avnimelech and Nevo, 1963; Mitchell and Nevo, 1963;

Chang et al. 1974; Nicholaichuk, 1978; McConkey et al. 1990). Further studies were

conducted to investigate sealing or clogging of waste water treatment infiltration beds and

to try to find ways of lengthening the life of these treatment facilities by better

understanding the mechanisms causing the clogging (Laak, 1970; DeVries, 1972). The

results of these and other studies led researchers to speculate that earthen manure storages

may be good candidates for infiltration rate reduction due to soil clogging. Research on

clogging by manure was completed both in the field and in the laboratory and under

differing environmental conditions (Hart and Turner, 1965; Davis et al. 1973; Chang et al.

5

1974; Lo, 1977; DeTar, 1977; Culley and Phillips, 1982; Rowsell et al. 1985; Barrington

et al. 1987; Barrington and Madramootoo, 1989; Gangbazo et al. 1989). Based on this

research, Barrington and Jutras (1985) and Barrington and Broughton (1988) published

guidelines for selecting site for earthen manure reservoirs. They recommended a minimum

soil clay content of 15% based on the resulting effective void diameter (Barrington and

Jutras, 1985) and that a manure mat on this soil will result in a final infiltration rate of 10-7

cm/s or 0.1 Um2/day. Barrington and Jutras (1985) went on to give grain size distribution

curves showing the bands in which the soil would "seal" but qualified their

recommendations by saying that the minimum infiltration of 0.1 L/m2/day would still result

in hog manure liquids saturating 300 mm of clay soil over a period of 9 years and 300 mm

of a sandy soil in 11 months. As a result of this research, regulatory agencies have

adopted the use of a minimum of 15% clay content (British Columbia, 1991; Manitoba,

1993; Ontario, 1994; USDA SCS, 1993), and a "final" hydraulic conductivity of 10-7 cm/s

(British Columbia, 1991; Manitoba, 1993; Ontario, 1994). This "final" hydraulic

conductivity is apparently a result of the effect of manure clogging. Rugulations of the

state of Iowa (1988 and 1992) appear to count on the 'sealing' of soil by manure and

require 1.5 meters of "sealable" soil around a newly constructed storage. This appears to

be a interpretation of the sealing mechanisms and the thickness of the sealed or clogged

layer(s).

Although researchers agree that all soils tested will clog and most agree that sandy soils

still allow large quantities of high strength effluent and organic matter to pass through

(Hart and Turner, 1965; Barrington and Jutras, 1987a). Due to the prevalence of

6

research into whether or not a soil will clog and not into whether it will impeaded the

transport of solutes, there is a lack of definition as to which soils are suitable and safe for

the construction of earthen manure storages. The USDA Soil Conservation Service

(1993) gives the most complete guide to what soil types and profiles are recommended for

construction of manure storages. In addition to a minimum clay content they recommend

a plasticity index of> 10 (USDA SCS, 1993).

This study will attempt to determine the effect of manure on soil hydraulic properties as

affected by time, depth, and texture. This literature review will establish the current state

of knowledge and aid in the interpretation of the results. Complimenting studies by others

will attempt to determine the penetration of organic matter with depth and the effect of

soil physical and chemical properties on the soils ability to prevent transport of solutes.

2.2 Investigation of the Mechanism of Soil Clogging

The clogging of soils is defined as the "resistance to flow caused by a change in friction

coefficients or in reduced size or volume of pore spaces" (Davis et al. 1973). The

clogging will occur as long as there is particulate matter or microbial activity present

(Gupta and Swartzendruber, 1962; Barrington and Jutras, 1983). Allison (1947) reported

a reduction in infiltration rate of two orders of magnitude (10-3 cm/s decreased to 10-5

cmls) in ponds subjected to prolonged submergence of natural surface water. Avnimelech

and Nevo (1963), Laak (1970) and DeVries (1972) were concerned with elin1inating this

7

clogging effect in order to lengthen the life of waste water filtration beds. Avnimelech

and Nevo (1963) reported that:

• decreasing the C:N ratio in the organic matter or adding inorganic nitrogen was found

to minimize the amount of polyuronide found in the sand and to be accompanied by a

decline in the extent of clogging,

• polysaccharide production increases with an increase in the C:N ratio,

• the decomposition rate of the organic amendments in the sand seemed to affect the

synthesis of polyuronides and the development of clogging,

• organic substances with very low decomposition rates, such as sawdust or sewage,

would not promote polyuronide production, and

• organic amendments which initially contain a high percentage of polyuronides, such as

barley meal, would induce clogging more than can be expected from the above

statements.

Livestock waste or manure fits this criteria as an organic amendment with a high

concentration of nitrogen and often contains waste barley. Hart and Turner (1965) and

Davis et al. (1973) conducted experiments in California to determine if soil clogging

reduced the infiltration losses from earthen dairy waste ponds. Hart and Turner (1965)

concluded that after two years the infiltration was still considerable and that biological

sealing of the lagoons did not appear to be very effective. They reported that the

digestion of the particulate matter within the lagoon may have reduced the clogging effect.

Davis et al. (1973), however, reported a reduction in water infiltration rate of two orders

of magnitude within four months of manure ponding. These researchers suggested that

the suspended settleable solids in the liquid dairy manure should provide a matrix that

8

would commence sealing or clogging even in coarse sand. They further concluded that

because the manure gives rise to a bottom slime and rapid decomposition of biological

sludge, that the cells of living and dead bacteria adjacent to the soil surface are forced into

the soil pores by hydraulic pressure blocking infiltration. In addition to the biological and

physical clogging of soils, various researchers have shown that chemical clogging can

occur through the exchange of ions causing defloculation or through the products of

oxidation-reduction reactions clogging the soil (Laak, 1970).

Chang et al. (1974), working in California with soil columns placed in the bottom of a new

storage pond; Lo (1977), working in Nova Scotia with laboratory columns; and

Barrington and Jutras (1983), working in Quebec with small scale earthen field storages

and laboratory columns; investigated the extent of the sealing or clogging mechanisms.

All the researchers agree that the initial clogging is a result of the physical entrapment of

particulate matter at the soil surface which, over time, will penetrate into the soil surface.

Chang et al. (1974) reported that biological clogging virtually sealed off the soil for further

water movement within 64 days and to depths of at least 250 mm. Lo (1977) determined

the organic matter distribution in the soil profile after the infiltration tests were completed.

The results indicated that starting from the soil surface, the organic matter decreased

gradually with increasing soil depth in all soil types except sand. In the case of sand, the

concentrations were fairly uniform. The distribution of organic matter in the soil profile

gives a certain indication of soil pore clogging. This researcher felt that the reduction of

organic matter in the soil profile indicated that the sealing process was not a surface

9

phenomenon only. The degree of soil pore clogging was more intense near the soil

surface and became less intense as the depth increased.

Lo (1977) concluded that the sealing of anaerobic lagoons occured in the following way.

The rapid reduction of infiltration rate immediately after the commencement of testing

indicated that physical clogging, i.e. the physical trapping or filtering of solids by the soil

matrix, was predominant in the initial stage of sealing. The continued gradual reduction of

infiltration rate was probably a combined result of physical, chemical and biological sealing

processes. Lo ( 1977) agreed with Chang et al ( 197 4) and suggested that final sealing was

caused by clogging as a result of excretions from anaerobic microorganisms. Lo (1977)

also concluded that the final hydraulic conductivities varied inversely with hydraulic

gradient which seemed to suggest that the physical sealing process was still important.

Barrington and Jutras (1983) concluded that:

• physical clogging factors played a major role as long as soil effective void diameter

was small enough to retain all manure solids,

• swine manure, because of its granular and easily biodegradable character, required a

finer soil than the fibrous, fermentation-resistant dairy manure solids,

• biological factors contributed by transforming the manure seal accumulated at the soil

surface; their effect was about 1/10,000th and 1/60th of that of physical factors for

dairy and swine slurries respectively, and

• chemical factors, acting at the soil level, were insignificant.

10

2.3 Time and Hydraulic Conductivity Reduction

Hart and Turner (1965), Davis et al. (1973), and Chang et al. (1974) all worked with

manure storages in the California dairy industry. Both Davis et al. (1973) and Chang et al.

(1974) reported reductions in hydraulic conductivity to below 1 x10-6 cm/s while Hart and

Turner (1965) reported considerable infiltration loss (1.5 x 10-5 cm/s after two years) from

constructed storages in California in sandy loam soils. The average infiltration rate with

water for three storages was 2 x10-5 cm/s and the final infiltration rate was only 20% to

40% less at the end of two years. The expected biological sealing of the lagoons did not

appear to be very effective. The lagoon bottoms had been compacted thoroughly before

the initial filling, but the sandy loam soil was too permeable.

Davis et al. (1973), while studying the performance of dairy waste ponds in San Diego

County, reported that a manure storage pond constructed in sandy loam soils had a

infiltration rate with water of 1.4 x10-3 cm/s which reduced to 7 x10-5 cm/s after two

weeks and to 6 x10-6 cm/s after four months. Evaporation from the surface of the pond

was not measured but the authors felt that the infiltration rate would have become

insignificant if evaporation was considered.

Chang et al. (1974) determined the hydraulic conductivity of soil columns and the sections

of soil columns retrieved from the bottom of a newly constructed manure storage pond at

intervals from Day 0 (day of manure application) to Day 64. The authors found that the

hydraulic conductivity, as measured by their apparatus, reduced from 3.9x10-3 cm/s at Day

11

0 to 4x 10-5 crnls by Day 64 in the sand soil and from 7x 10-5 cm/s to less than 1.7x10-6

cm/s in the clay soil. It should be noted that with the. methods used~ these researchers

could not measure hydraulic conductivities less than 1.7x10-6 cm/s. These authors

concluded that the initial seal was caused by the physical entrapment of suspended

particles in soil, followed by a secondary mechanism of microbial growth that , they claim,

completely sealed off the soil from water movement. These "sealed" columns were dried

and when retested exhibited hydraulic conductivities similar to the initial hydraulic

conductivities. The researchers felt that this indicated that the inhibition of water

movement in the soils was not caused by the deflocculation of soil particles due to cation

exchange.

The following researchers in Canada reported similar results of a reduction in hydraulic

conductivity reaching 10-6 cm/s within a short period of time and 2 x 10-7 cm/s to 5 x 10-7

cm/s after more than a year of manure ponding:

• Lo (1977), working in November weather conditions in Nova Scotia and using twelve

200 mm diameter soils columns fliled with liquid dairy manure,

• Culley and Phillips (1982), using undisturbed soil columns to determine the rate of

sealing with Ontario soils,

• Barrington and Jutras (1983), using four constructed ponds to study manure sealing in

Quebec,

• Rowsell et al. (1985), using soil cores to determine the effect of ponded manure head

on the infiltration rate of Ontario soils,

• Barrington et al. (1987a), using experimental reservoirs and 100 mm diameter by 100

mm cores of Quebec soils and,

• Barrington and Madramootoo (1989) using soil cores of sand and clay loam to

measure the extent of seal formation as swine manure infiltrates soil.

12

Lo (1977) reported that for all the columns except the clay, the infiltration rate decreased

exponentially within the first 30 minutes of operation. This reduction in hydraulic

conductivity continued for the first few weeks and with a continued gradual reduction

thereafter. Mter three months of operation, the infiltration rate for all of the columns

remained relatively stable at similar lower levels until the end of the study (one year). This

low infiltration rate is approximately 5 x10-7 cm/s.

Culley and Phillips (1982), Rowsell et al. (1985), and Barrington and Madramootoo

(1989) reported that all soils tested exhibited an exponential decrease in conductivity.

Culley and Phillips (1982) reported all soils reached conductivities of 3.5 x10-6 cm/s within

5 days and which further reduced to 1 x10-6 cm/s within 10 days. Rates of sealing

increased in the order of clay<loam<sand, the same order as bulk densities and coarseness

of texture.

Culley and Phillips (1982) used the following equation to determine the hydraulic

conductivity as a function of time from application of the manure:

Ink= -a- (bIn t) Eq. 2.1

where:

k = hydraulic conductivity,

t = time since manure application,

a= coefficient related to the intercept (In A), and

b = coefficient which is a measure of the rate at which the soil,

sealed

Values of a and b for each soil were determined by least squares

regression.

13

Rowsell et al. ( 1985) reported the infiltration rate was found to decrease for all the soils

tested and reached a value of 1 o-6 cm/s or less within 30 days for the soils with 1 m

hydraulic head; at 5 m head the infiltration rate reached a value of 1 o-6 cm/s within 10 days

for clay soil but required > 30 days for the loam and sand soils. Rowsell et al. ( 1985)

used the Kostiakov infiltration equation q = atb , where a and b are constants, to relate

infiltration rate to time.

Barrington and Jutras (1983) and Barrington et al. (1987a) reported that soils with initial

infiltration rates as high as 2.3 to 3 x10-3 cm/s demonstrated a reduction in hydraulic

conductivity to 10-6 cm/s within 2 weeks for their reservoirs and 2 days for their soils

columns. The hydraulic conductivity for both the reservoirs and the soil columns further

reduced to near 5 x10-7 cm/s after one year. It is interesting to note that the hydraulic

conductivity of the clay soil columns increased from 1x10-8 cm/s at 48 hours to 2.4 x10-7

cm/s at 840 days. Barrington and Madramootoo (1989) found the infiltration rate for all

columns was related to infiltration time through linear regression using the logarithmic

form of the exponential equation:

where:

I=Wtx

I= infiltration rate (rnls),

t =infiltration time (hours), and

W and X = constants

Eq. 2.2

14

Culley and Philips (1982) found that the difference in sealing rate between sandy and clay

soils was possibly due to the more rapid blockage of the large but less numerous sand

pores than the smaller more porous clay. They suggested that their similarity in

conductivities for all materials between 5 and 10 days could be explained if the layer of

manure solids which formed on the top of the soil columns controlled the flow rate of

liquid through the columns. Barrington and Madramootoo (1989) agreed with this last

statement, and went on to conclude that for sandy soils the reduction in hydraulic

conductivity was governed by the soil-manure interface clogging and that there was no

significant difference in hydraulic conductivity with depth. They also reported that clay

soils experienced some reduction in hydraulic conductivity which was thought to be a

result of the ability of the clay loam soils to accumulate manure solids with depth and their

stronger adsorption properties which help to retain solids along the walls of the flow

channels.

DeTar (1977), working in Pennsylvania using infiltration rings in the base of a dairy

manure storage pond, found that for manure slurries with > 0.3% total solids (TS), the

infiltration rate became relatively constant after four days near 3 x10-6 cm/s. He

considered the soil "sealed" if the infiltration rate dropped below 1 x 1 o-6_ cm/s and

reported that, for longer time periods, the infiltration rate appeared to reach a minimum

steady value of 6 x10-7 cm/s. Given that these values of infiltration rate reduction with

15

time match those of other researchers, it is safe to conclude that physical clogging should

occur in effluents with> 0.3% total solids (TS). Barrington et al. (1987b) tested the

performance of slurries down to 3 % TS and found no significant difference from higher

TS contents.

2.4 Thickness of the Clogged or Sealed Layer

To answer the objective of the effect of clogging with depth, to make use of the reviewed

research in designing earthen manure storages, and in estimating the risks associated with

the construction of these storages in different soils, it is important to know the relative

thickness of the layers of different hydraulic conductivity.

The soil layer that becomes clogging with manure particles ranges between 3 mm for clay

to 5 mm to 15 mm for sandy soils (Laak, 1970; Barrington and Jutras, 1983; Rowsell et al.

1985). The layer experiencing further reduction in hydraulic conductivity due to

biological and chemical clogging is variable, depending upon soil texture and chemistry

but is thought to be restricted to the top 300 mm of soil (Allison, 1947; Chang et al.

1974).

Barrington and Jutras (1985) and Barrington and Broughton (1988) recommend the use of

the soil effective void (or pore) diameter to determine a soil's suitability to allow clogging

16

by manure. They used the following equation which describes the effective soil pore or

void diameter by transforming a given soil into one of a single particle size of equivalent

fluid permeability:

where:

where:

de= 4N X De

( 1 - N)

de= effective soil pore or void diameter (Jlm).

N = soil porosity (fraction).

De= equivalent soil particle size diameter (Jlm)

De was calculated from the particle size distribution of the soil using:

i = denotes specific soil particle size classes,

Eq. 2.3

Eq. 2.4

<li =is the shape coefficient of the ith particle size class: 50 for clay, 15 for silt and

10-20 for sand,

si = is the weight fraction of the ith particle size class, and

Di = is the average soil particle diameter for the ith particle size class.

Barrington and Jutras (1985) and Barrington and Broughton (1988) recommended a

maximum de of 0.45 Jlm and 2.0 Jlm for hog manure and dairy manure storages

repectively. To achieve a de of 0.45 Jlm and 2.0 Jlm Barrington and Broughton (1988)

recommend a soil with a clay content of 15% and 5% respectivley.

17

In Canada; Quebec (Gangbazo, 1989), Ontario (1994), Manitoba (1993), Saskatchewan

(1992), and British Columbia (1991, 1992) use a requirement of a minimum of 15% clay

content and a liner of 10-7 cm/s hydraulic conductivity for the establishment of earthen

manure storages. These regulation appear to be based on the laboratory work of

Barrington et al. (1987 and 1989). The use of these laboratory test findings for field

situations has caused some concern within the geotechnical engineering community as the

apparent hydraulic conductivity is based on a 100 mm soil column and apparent hydraulic

conductivity is calculated from the following equation (Barrington et al. 1987):

K =

where:

dm + di + ds Eq .2 .5

( d m /k m + d i/k i + d s/k s)

K = the system's apparent hydraulic conductivity,

km, ki, ks = the saturated hydraulic conductivity of the organic mat,

manure soil interface, and soil respectively as measured

with piezometers, and

dm, di, ds = the depth of the organic mat, manure soil interface,

and soil respectively.

18

2.5 Summary

All researchers agree that the initial clogging occurred at the soil manure interface and that

this clogging was not dependent on soil texture but was on total solids content of the

manure (Davis et al. 1973). Even though all soils tested clogged to demonstrate similar

long term infiltration rates, the time required to achieve these lower steady infiltration was

dependent on soil texture (Lo, 1977; Rowsell et al. 1985). These researchers reported that

sand clogged faster than clay and hydraulic head lengthened the time required for clogging

of the coarser textured soils. This surface clogged interface layer was reported to range

in thickness form 3 mm to 15 mm (Laak, 1970; Barrington and Jutras, 1983; Rowsell et al.

1985). Sealing with depth was reported to be a result of both particulate matter migration

with depth and time and the production of polysaccharides from the anaerobic digestion of

the organic wastes (Chang et al. 1974; Barrington and Madramootoo, 1989). The major

polysaccharide contributing to the clogging of soil beneath manure storage ponds, even at

low temperatures, is thought to be polyuronide which would be especially prominent in

effluents with high C:N ratios, such as manure, and an initially high percent of

polyuronides, such as barley meal (Avinmelech and Nevo, 1963). This biological clogging

was reported to affect soils to a depth of at least 250 mm after 64 days in areas of warm

ground temperatures(> 15°C) (Chang et al. 1974), but was reported to ~e much less

effective in areas of cooler ground temperatures ( < 10 °C) even after 840 days of manure

ponding (Lo, 1977; Barrington et al. 1987a). Hart and Turner (1965) reported very poor

soil clogging and biological sealing in sandy loam soils in California. Barrington and

Madramootoo (1989) reported that this clogging was limited to the surface and any

19

reduction in hydraulic conductivity with depth was not consistent and very secondary to

the surface clogging.

Using Equation 2.5, if we assume that km is very large compared with ki and ks, that di is

very small compared with ds, and that di and ki are very small, 5 mm and 10-9 crn/s

respectivley (Rowsell et al. 1985) and (Barrington et al. 1989) then for a 100 mm soil

column for values of ks > 10-6 cm/s, K approaches 1 x 10-7 cm/s even for very large

values of ks. Further, as ds becomes larger, K becomes proportionately larger. Therefore

in field conditions, if we consider the 10 meters below the storage, the apparent saturated

hydraulic conductivity would be 1 x 10-5 cm/s instead of 1 x 10-7 cm/s according to

Equation 2.5. This raises a concern with the use of a "final" hydraulic conductivity of an

earthen manure storage based on an assumption that manure clogging will reduce the

initial hydraulic conductivity to near 10-7 cm/s. It is therefore important to clarify the

extent and depth of manure clogging so that the recommendations put forward by these

reviewed researchers can be applied to design and regulatory guidelines with an

understanding of the risk associated with use of marginal soils in construction of earthen

manure storages.

Researchers have hypothesized that the clogging of soil was by particulate matter of the

soil surface but none of the researchers reviewed had proven this. Even if the reduction in

hydraulic conductivity of soils is a result of clogging of the surface soil pores, there still

remains the questions of the depth of soil affected by the clogging, the change in the

clogged layer with time, and the extent of soil texture on the ability of soils to assist in

clogging and reduction in hydraulic conductivity.

20

3.0 Differences in Laboratory and Field Situations on Apparent Hydraulic Conductivity and Flux

As previously discussed in Section 2.5, the use of laboratory findings in field situations

must be done with the knowledge of the consequences of changing of variables on the

resulting apparent hydraulic conductivity and flux. To say that the "final" hydraulic

conductivity (Iowa, 1991; USDA SCS, 1993) of a constructed earthen manure storage

must be less than 1x1 o-7 cm/s, one must understand how the laboratory situation compares

with the field situation. Figure 3.1 illustrates the variables within each situation that will

be used in Eq. 3.1 and 3.2 (Freeze and Cherry, 1979).

Manure Interface

(Ks1= 5x10·9 cm/s)

10m (ds2) Situation (K s2= 1 o-4 to 1 o-7 cm/s)

5 mm (ds 1) Laboratory

100 mm (ds2) Situation

Figure 3.1 Laboratory vs. Field Situation (soil-manure interface defined as 5 mm thick and hydraulic conductivity of 5 xt0·9 cm/s)

21

ds1 + ds2 Kapp=----------------------- 3.1

(ds1/Ks1 + ds2/Ks2

where: Kapp =apparent hydraulic conductivity (cm/s),

dsl =thickness of the soil-manure interface (em),

ds2 =depth to the wetting front below the storage (em),

Ks1 =hydraulic conductivity of the soil-manure interface layer (cm/s), and

Ks2 =hydraulic conductivity of the sub-surface soils (cm/s).

q = Kapp x grad 3.2

where: q =flux (cm/s) or (q x 86 400 s/day = (L/ m2/day)),

grad =gradient (em/em)

Table 3.1 shows the result of a sensitivity analysis of Figure 3.1 using Eq. 3.1 and 3.2.

The baseline values are after Barrington et al. (1987) using a 100 mm soil column with 1

m of ponded manure head. The thickness of the soil-manure interface was assumed to be

5 mm (Rowsell et al. 1985) with a hydraulic conductivity of 5x10-9 cm/s. The soil column

hydraulic conductivity was assumed to be 10-5 cm/s and all assumptions for the application

of Darcy's Law apply. In addition, the assumption that the suspended s~lids are filtered

out at the soil-manure interface and fluid flow resembles that of water was applied

(Barrington et al. 1987a).

22

Table 3.1 Sensitivity Analysis (baseline values are Ha=lOO em, ds1=0.5 em, Ks1=5x10-9

em/s, ds2=10 em, and Ks2= 10-5 em/s)

Table 3.1a Changing Applied Hydraulic Head

Ha (em)

100 200 300 400

Kapp (em/s)

1.0E-07 1.0E-07 1.0E-07 1.0E-07

q (em/s)

1.1 E-06 2.1E-06 3.1E-06 4.1E-06

Table 3.1b Changing the Soil-Manure Interface Hydraulic Conductivity

Ks1 Kapp q (cm/s) (em/s) (em/s)

1.0E-07 1.8E-06 1.8E-05 1.0E..OS 2.1E-07 2.2E-06 S.OE-09 1.0E-07 1.1 E-06 1.0E-09 2.1E-08 2.2E-07

Table 3.1c Changing Soil-Manure Interface Thickness

ds1 Kapp q (em) (cm/s) (cm/s)

0.3 1.7E-07 1.8E-06 0.5 1.0E-07 1.1 E-06 0.7 7.6E-08 7.9E-07 1.5 3.8E-08 3.7E-07

Table 3.1d Changing the Subsoil Hydraulic Conductivity

Ks2 Kapp q (em/s) (cm/s) (em/s)

1.0E..04 1.0E-07 1.1 E-06 1.0E-05 1.0E-07 1.1E-06 1.0E...06 9.5E-08 1.0E-06 1.0E..07 5.3E-08 5.5E-07

Table 3.1e Changing the Depth to the Wetting Front

ds2 Kapp q grad. (em) (em/s) (cm/s) (em/em)

10 1.0E-07 1.1 E-06 10.5 100 9.1 E-07 1.8E-06 2.0 500 3.3E-06 4.0E-06 1.2

1000 S.OE-06 5.5E-06 1.1

23

This analysis shows that, for the range of values tested: • Kapp is unaffected by hydraulic head,

• flux varies directly with head,

• Kapp and flux vary almost directly with the hydraulic conductivity of the

soil-manure interface layer,

• Kapp and flux vary almost directly with the thickness of the soil-manure

interface layer,

• Kapp and flux are remain virtually unaffected for values of Ks2 > 10-6 cm/s,

• there is an exponential decrease in the effect of the depth to the wetting

front (ds2) as the wetting front moves down, and that

• Kapp for a 1 meter layer below the storage would be approximately 1 o-6

cm/s rather than 10-7 cm/s.

Figures 3.2 to 3.5 illustrates the effects of the thickness of the soil-manure interface layer

(ds1) and the hydraulic conductivity of the subsoil (Ks2) for the field situation illustrated

in Figure 3.1. Even for thickness of ds1 of 15 mm the depth to the wetting front governs

Kapp and Kapp approaches the value of the soil hydraulic conductivity as the wetting

front moves down (Figure 3.2). The change in flux (q) is almost directly proportional to

the change in thickness of the soil-manure interface (ds1) and increases approaching 1

Um2/day as the wetting front moves down (Figure 3.3). This is an order of magnitude

higher than the 0.1Um2/day mention by Barrington and Broughton (1988) as resulting

from a earthen storage which "seals" to a hydraulic conductivity of 10-7 cm/s.

Figure 3.4 and 3.5 illustrate the effect of the change of the subsoil hydraulic conductivity

on Kapp and q. Figure 3.4 illustrates that Kapp approaches 10-5 cm/s for all values of Ks2

> 10-4 cm/s while the soil-manure interface layer has virtually no effect on Kapp for values

of Ks2 < 10-6 cm/s below 1m below the storage. Figure 3.5 illustrates that the flux

approaches 1 Um2/day for values of Ks2 > 10-5 cm/s and is directly proportional to Ks2

24

for values of Ks2 < 10-6 cm/s with q approaching 0.1Um2/day for Ks2 = 10-6 cm/s, .01

Um2/day for Ks2 = 10-7 cm/s and so on. A value of Ks2 of 10 cm/s is plotted on Figures

3.4 and 3.5 to illustrate the limitations of Eq. 3.1. The selection of soils by effective pore

diameter and clay content (Barrington and Broughton, 1988) and Plasticity Index (USDA

SCS, 1993) would eliminate these high conductivity soils in a true field situation. Figure

3.5 would appear to suggest that only soils with an in-situ hydraulic conductivity of less

than 10-6 cm/s should be considered for unlined earthen manure storages if the criteria of

0.1L/m2/day (Barrington and Broughton, 1988) is to be met.

25

Apparent Hydraulic Conductivity vs. Depth of Wetting Front (for varying thicknesses of the soil-manure interface layer (ds1))

........................... r············r············r·············r··············r·············-r·············· ··························· 1.0E-04

~ J subsoil hydraulic conductivity I -u 1.0E-05 ..._ _ _..~iiiillllll ..... __ .__ .... ....., ....... 1--_,_1 ,....-~_....,_...,._--! .,.. -+- Kapp (ds1=3 mm)

! _,,...----.1~==-·==-~gl~ds~1~3~m~m~~ ~~~~~~~~~-~---fi······:':········Kapp (ds1=5 mm)

g 1.0E-06 /-;-::.::.:1~:_-=-t--·t--- . ·-----Kapp (ds1=7 mm) ~._:~ /;:'1./'/A;~._- 1 ds1=15mm 1

L.fi/ -+- Kapp (ds1=10 mm)

~ 1.0E-07 -teliV.~'f"". '--+---+---+--+---+---+--+---+---+---! -g. ~/ '-. -+- Kapp (ds1=15 mm)

::t: ~. I value used by regulators I 1.0E-08

J 1 2 3 4 5 6 7 8 1 100mm

son Column Depth of Wetting Front Below the Storage (m)

9 10

Figure 3.2 Apparent Hydraulic Conductivity vs. Depth of the Wetting Front (for a laboratory column with varying thickness of the soil-manure

interface (dsl) assuming Ks2 = 10-5 cm/s)

Flux vs. Depth of Wetting Front (for varying thicknesses of the soil-manure interface layer (ds1))

1.0E+01 ··-·········· ·······-····· ··········-·· ·-··········· ····-········ .......•..•... ·······-····· ..........•.....•..•....•... ··············~ r-_._--q-(ds_1_=_3_m_m_) -,

1.0E+00 ...;.

~ L~~~~~.~~-~-~~--~-.. ~.:jJ~~=~·=~=~~~=~=-:=:=:1~~=~=~=-~~J~~=~~=~·=:~~~~~~~~~~~~;~~::~:~~ -•-q~s1=5mm) ~ ::-~:·=~:;.-t:=~·::::;-:.:::~~~:::~~J~::~~.... . .. ,,: .... q(ds1= 7 mm)

~ 1.0E-01 :- _ _. ... ;.~ .. ·q(ds1= 10 mm)

----q(ds1= 15 mm)

1.0E-02 +---+----t--+---+---+-----<1------t---r---t------;

1.0E-03 +---+---1--+---+--~--+---r--+---+---; 0 2 3 4 5 6 7 8 9 10

Depth of Wetting Front (m)

Figure 3.3 Flux vs. Depth of the Wetting Front (for a laboratory column with varying thickness of the soil­

manure interface layer ( dsl) assuming Ks2 = 1 o-5 cm/s)

26

Apparent Hydraulic Conductivity vs. Depth of Wetting Front (for varying values of K2(cm/s})

1.0E-04 ,.--....,...--.--..----,--"""""-r---,--,....---r-----r-

1-~..-----------.

,_._ Kapp(Ks2= 1 0)

,......_ _ __.__--;I

~ l Ks2 = 10 cm/s ,! 1.0E-05 t--~-~-~-~--t==:t:::::t~~~~~~1···•···Kapp(Ks2= 10-4) ~ __,;r--·· Ks2 10-4 ·:;: ~r- -··::·.

~1.0E-06 /~,~~.~, ...... :: ... u •• ,·:N ,, ............ ,, ............. ~.:::-~.;[ ........ , ... ,,, ..... Kap~Ks2= 1~) o // I -·-·-:~::-···-· Kapp(Ks2= 1 0-6)

t I l ~1~~A~~~~-~-~-~-~~-~-~-~=~~=~~·~-~~~1~ ... .,; 1 Ks2 = 10-7

1.0E-08 -tt'--t----t---+---+--+---+---+----1--+'---1 ( 1 2

100mm 3 4 5 6 7 8 9 10

Soil Column Depth to the Wetting Front (m)

Figure 3.4 Apparent Hydraulic Conductivity vs. Depth of the Wetting Front (for a laboratory column with varying hydraulic conductivities

of the subsoil (Ks2))

Flux vs. Depth of Wetting Front {for varying values of Ks2{crnls))

-.-q(Ks2=10)

-··:::.--·- q(Ks2=10-5)

... iX; .... q(Ks2= 1 0-6)

1.0E-03 I Q 1 2 3 4 5 6 7 8 9 10

100mm Soil Column

Depth of Wetting Front (m)

Figure 3.5 Flux vs. Depth of the Wetting Front (for a laboratory column with varying hydraulic conductivities

of the subsoil (Ks2))

27

Now consider a typical earthen manure storage constructed to a typical design of a 600

mm compacted soil liner with a hydraulic conductivity of less than 10-7 cm/s (Figure 3.6).

Eq. 3.1 can be expanded to include three layers (Eq. 3.3) and the equation for flux will

remain the same.

Manure Interface

Typic a I Current

Construction

0.6 m (ds2) Recompacted

Soil Liner

( K s 1 = 5 x 1 0-9 c m Is) (Ks2=1x10-7 cmls)

9.4 m (ds3)

( K s 3 = 1 0- 4 to 1 0 -? c m Is)

Wettin Front

Figure 3.6 Typical Field Situation for a Earthen Line Manure Storage

dsl + ds2 + ds3 K app~-------------------------- 3.3

where:

(dsl/Ksl + ds2/Ks2 + ds3/Ks3)

ds2 and Ks2 become the thickness and hydraulic conductivity of the liner

respectively and ds3 and Ks3 are the distance to the wetting front below the

storage and the subsoil hydraulic conductivity.

28

Figure 3.7 illustrates that, for all values of Ks2, Kapp approaches a value slightly greater

than 10-6 crn/s but almost a full order of magnitude less than illistrated in Figure 3.4.

Figure 3.8 illustrates that for all values of Ks2, q approaches a value slightly greater than

0.1L/m2/day which is almost a full order of magnitude lower than illustrated in Figure 3.5.

These figures would suggest that an earthen manure storage should not exceed a seepage

of more than approximately 0.2 Um2/day if lined with a 600 mm soil liner with a hydraulic

conductivity of less than 10-7 crn/s.

As mentioned previously, this study will attempt to clarify the extent of the reduction

caused by manure ponding on soil hydraulic conductivity with depth and time on various

soil textures. This information, along with other studies on the ion concentrations in

exfiltrate from the column tests, will assist designers and regulators to define which soils

are suitable for construction of earthen manure storages and how much effort should be

placed on lining of these storages.

29

>; ar

Apparent Hydraulic Conductivity vs. Depth of Wetting Front

1.oE-04 ,..--.....--.........,--,......;<!..-fo_r_v,a_!.ry~in.....::g~va_l.:...:...ue_s .. o..::...:f_K_s3--+(c.....:.rn/:..:.:...::_s!.!...)).,.........._-,--_......, .----------.

-+- Kapp(Ks3= 1 0)

1.0E-08 +---+-----1--+---+--t----+----+--+------+----1 0 2 3 4 5 6 7 8 9 10

Depth of Wetting Front (m)

Figure 3.7 Apparent Hydraulic Conductivity vs. Depth of the Wetting Front (for a lined earthen manure storage with varying hydraulic

conductivities of the subsoil (Ks3))

1.0E+01

1.0E+00

Flux vs. Depth of Wetting Front (for varying values of Ks3(cmls))

................................................................................................................................... ··············· -+-q(Ks3= 10)

···~·~···· q(Ks3= 10-5) ~ ..... _e 1.0E-01 +---+--l---+-----*=:;;:;;;;o ............. ~-~=-..n .•.. =···=···..d.-'~·--····=·······==l .... :;;;, .... ··::=~ .......... ;· ........... ::-.-.~\ ~ ~~·~··--~·~'~"'~~-~~w:~-~~~~·-""~~~--~~r-~--~~ >< ·~ .......... .. ---- q(Ks3= 10-6) :I

u:: ~~ 1.0E-02 L-L-L=t==t==±::==i===b==b~bd _._ q(Ks3= 10-7)

1.0E-03 +---+--1---+---+--+---+----t~-+---+----i 0 2 3 4 5 6 7 8 9 10

Depth of Wetting Front (m)

Figure 3.8 Flux vs. Depth of the Wetting Front (for a lined earthen manure storage with varying hydraulic

conductivities of the subsoil (Ks2))

30

4.0 METHODOLOGY

4.1 Soil Collection and Analysis

Thirteen subsoil materials were collected from various locations near Saskatoon,

Saskatchewan. Soils were collected from trench excavations, cuttings from test drilling or

from soil stockpiles. The soils are referred to by numbers 1 through 7. These were

chosen as they represent some of the "typical" soils found in Saskatchewan.

In preparation for physical and chemical analysis these subsoil samples were air dried,

ground and sieved through a 2mm sieve to remove larger stones and aggregates. The

Modified Pipette Method (lndorante et al., 1990) was used to determine soil sand, silt, and

clay content for selection of the final seven soils for use in column testing (Table 4.1).

These soil materials were selected on the basis of having a representative range of textures

that may be commonly used in construction of earthen manure storages, ranging from that

of medium clay content (30-40%) to low clay (less than 10%) and high sand content.

SOIL

1 2 3 4 5 6 7

Table 4.1 - Origin of Soils Used in Column Study

Sample Description and Site lndentification

Sample #3, Boychuck Drive Samples #1 & 2, C of S #1 & 2 Sample #6, Site #3 Sample #5, Site #2, TH2 Sample #11, CPIG Sample #13, Cominco Potash Mine Sample #12, Site #1, TH2

31

Method of Retrieval

Taken from excavation (5 m deep) spoil pile Taken from soil stock pile Cuttings from drilling (1 m to 4 m depth) Cuttings from drilling (2 m to 4 m depth) Cuttings from drilling (2 m to 4 m depth) Taken from excavation (5 m deep) spoil pile Cuttings from drilling (2 m to 4 m depth)

The seven soils were then analyzed for physical properties within the laboratories of the

Engineering College (Table 4.2) and for chemical properties by Enviro-Test Laboratories

in Saskatoon, Saskatchewan. pH and EC (electrical conductivity) of the soils were

obtained from saturated paste extracts; cation exchange capacity was by lN BaCh, and

Sodium Adsorption Ratio from N a, Ca, and Mg ions from the saturated paste extract.

Table 4.2 - Testing Methods for Soil Physical Analysis

Physical Property Method Used/Reference

Soil Drying and Preparation ASTM D-421-85 (R93) Particle-Size Analysis ASTM D-422-63 (R90) Atterberg Limits ASTM D-4318-93 Proctor Analysis ASTM D-698-91 Moisture Content (mass) ASTM D-2216 -92 Unified Soil Classification ASTM 0-2487-93 Agricultural Soil Textural Class. USDA Textural Classification Chart, (PCA, 1992) Engineering Soil Textural Class. US-FAA Textural Classification Chart, (PCA, 1992)

4.2 Column Preparation

4.2.1 Column Construction

Test cylinders for determination of hydraulic conductivity values with ponded manure

were constructed based upon designs used by Barrington et al. (1987b) and Ghaly (1989).

The cylinders were from 120.6 mm ID acrylic cylinders and were a total of one meter in

length. Manometer tubes were installed at the soil surface, 25 mm below the surface and

at the midpoint of the soil column (Figure 4.1). The manometers were made up of a 6.4

mm ID stainless steel tubing inserted approximately 100 mm horizontally into the cylinder

32

with 3.2 mm diameter holes spaced every 13 mm for the portion within the soil.

Installation of the steel manometer tubes was accomplished by drilling holes into the

saturated soil columns using an electric drill and drilling through the acrylic tubing into the

soil. There was no scarification of the soil after drilling and before tube insertion. Clear

food grade tubing with an ID of 6.4 mm was attached to the stainless steel tube extruding

from the outside of the cylinder. These stainless steel manometers were installed after soil

saturation and before any hydraulic conductivity testing by drilling into the soil columns

with an electric drill, inserting the stainless steel tubes and water proofing with marine

grade sealant on the outside of the column. A 13 mm ID tapered to a 6.4 mm ID drain

insert was installed in the center of the bottom of each column. Clear 6.4 mm ID food

grade tubing was connected from the drain so as to empty vertically down to a sample

bottle (Figure 4.1 ). An air inlet device was installed in the drain line at the tip of the drain

insert to allow free drainage into the sample collection bottles. Later in the study the

vertical outflow tube was re-arranged for an "elbow" outflow tube so as to prevent air

entry through the manometers (Figure 4.2). An air inlet device was installed at the top of

the elbow to allow free drainage into the sample bottle.

33

Hexighm Giunn 121aniD 127an00

Figure 4.1 Initial Soil Column Setup for Manure Seepage Study

Figure 4.2 Final Soil Column Setup for Manure Seepage Study

34

4.2.2 Column Soil Packing

Prior to packing, the soils were dried, ground for 2 minutes, sieved through a 4. 7 5 mm

sieve, brought to optimum moisture content (ASTM D-698-91) and allowed to equilibrate

for a period of one week. Soils were compacted into the cylinders in 50 mm layers to a

200 mm total thickness. Each layer was compacted using a manufactured hammer of the

same weight per unit area as a standard proctor hammer (1233.5 kg/m2) dropped from a

height of 300 mm (ASTM D-698-91 ). The soil surface was scarified with a wire brush

between each layer. Soil compaction effort was 90% of Standard Proctor Density (ASTM

D-698-91 ). Simulation of Proctor Density was achieved by calculation of the amount of

wet soil required for each layer and by marking the column in 50 mm intervals. Each layer

required 6 to 12 hammer blows to compact to 50 mm, with the soils with the highest clay

content requiring the highest amount of hammer blows. The packing was meant to

simulate a minimum construction compaction level of 90% of Standard Proctor density

which the USDA Soil Conservation Service Technical Note 716 (1993) specifies as the

minimum compactive effort required when constructing an earthen manure storage with

their Type I and II soils. This level of compaction is thought to be obtained through the

normal operation of construction equipment during construction with no _specific effort

placed on additional compaction (USDA SCS 1993, Barrington et al. 1989). Three

replicates of each soil were completed for a total of 21 columns. The columns were

35

installed in a controlled temperature room at 7°C, a normal annual average for shallow

Prairie groundwater systems (Gillies, 1996). For the purpose of other studies the

replicates will be disassembled at various times for chemical analysis and microscopic

examination.

The bulk density of the soil in the column was calculated from the packed soil moisture

content, the mass of the soil packed into the column and the dimensions of the column.

This value of bulk density was used to calculate porosity with an assumed soil particle

density of 2650 kg/m3• The resulting porosity was used to calculate the void ratios for

each column. All calculations of bulk density, porosity and void ratio were after Hillel

(1980). Effective void diameter for each column was calculated after Barrington and

Jutras (1985) and Barrington and Broughton (1988). They used Equations 2.3 and 2.4

which describes the effective soil pore or void diameter by transforming a given soil into

one of a single particle size of equivalent fluid permeability.

4.3 Hydraulic Conductivity Determination

4.3.1 Initial Hydraulic Conductivity Determination With Water

The soils, as packed in their columns, were allowed to saturate with tap water under a

surface ponding of 600 mm for a period of two weeks. Hydraulic conductivity of the

entire soil column was then determined by maintaining a constant head of tap water and

measuring outflow with time. It was assumed that the hydraulic conductivity of the s~nd

36

base was large enough so that resistance to transport was negligible relative to the soil

material (flow distance of 200 mm). Exftltrate tap water was returned to the top of the

columns to maintain solution concentration in each column. Hydraulic conductivity values

were calculated using Darcy's law for fluid flow through a porous media.

4.3.2 Hydraulic Conductivity Measurement With Ponded Manure

About four weeks after initial saturation with tap water, the ponded head of water was

removed and manure was added without allowing the water in the soil to drain. Seepage

was collected in bottles sealed against evaporation. Seepage rates were determined by

weekly weighing the amount of exftltrated. When sufficient exftltrate was collected (20

to 50 ml) for each column the exftltrate was then taken for chemical analysis. It often

took between one and four weeks to collect sufficient sample for analysis.

The manure was fresh manure from the pen gutters of a local hog barn and had about

1.5% dissolved solids and about 5.1% suspended solids (Table 4.3). Manure analysis was

done by the Environmental Engineering Laboratory of the Dept. of Civil Engineering,

University of Saskatchewan. Total N in was by Kjeldahl and total diss~lved solids was by

evaporation. Na, K, Cl, N03, pH, and electrical conductivity are values measured in

solution while Nii. and Total P are values in solutions from dissolved solids.

37

Table 4.3 Chemical Analysis of Hog Manure Used in Column Tests

Property Value Units

Na 613 mg/L K 2,900 mg/L NH4 4,550 mg/L Cl 4,440 mg!L N03 10 mg/L TotalP 4,360 mg/L Total N (Kjeldahl) 6,107 mg/L pH 8 Electrical Conductivity 39,250 uS/em Total dissolved solids 15,775 mg/L Total suspended solids 51,525 mg/L

Within two (2) days of manure application, dewatering (air entry through manometers) of

the soil columns occurred. The soil columns were then resaturated using a siphon tube

attached to the drain insert on the bottom of each column and the apparatus altered

(Figure 4.2) to ensure the soil columns remained saturated.

From November 8, 1994 (Day 3) to December 13, 1994 (Day 38) the columns were

observed to ensure manometer water levels had stabilized and to ensure that any

manometer level drops did not effect the quantity of water measured in the collections

flask From December 13, 1994 to the time of writing (June, 1996), the columns have

been monitored for effluent flow rate and samples taken for chemical analysis of the

exfiltrate. As exfiltrate flows through the soil columns, raw supernatant from liquid hog

manure stored in 20 L pails is applied to the top of the column to maintain a constant head

of approximately 600 mm. The chemical analysis and long term effects of ponded manure

are not within the scope of this study, therefore the exfiltrate chemical analysis will not be

presented and only the hydraulic conductivity of the columns from December 13, 1994 to

38

May 9, 1995 will be presented and discussed. May 9, 1995 was chosen for the cutoff of

the data presented and analyzed in this thesis as this is the date when one column of each

set was dismantled under another study and a 24 hour cooler failure near the end of May

1995 introduced new phenomenon which will be further investigated under other studies.

When manure was ponded on the soil columns there was a period when the pressure at the

manometers reduced below the level of the manometer allowing air entry into the system

(Figure No. 4.4). The outlet tube position was adjusted to above the soil surface, the

columns were saturated with water from the bottom and the system was allowed to

equilibrate. From manure ponding to the time when the outflow and manometers

stabilized was from November 5, 1994 (Day 0) to December 13, 1994 (Day 38). On May

9, 1995 (Day 185) one of the columns from each set was disassembled in conjunction with

a separate study. For these reasons I will split the analysis into two periods, Day 0 to Day

38 (P1) and Day 38 to Day 185 (P2). Further, to give representative values at the

beginning and end of the second period, I will use an average of the first five (5) readings

(Day 38 to Day 73) and define this time period as T1 and an average of the last five (5)

readings (Day 157 to Day 185) and define this time period as T2.

I will report on both P1 and P2 for the objective of analyzing the effect of manure

clogging with time and I will limit my reporting to period P2 for the objectives of

analyzing the effect of manure clogging with depth and the effect of texture upon

clogging. The latter two objectives can not be discussed due to lack of data during the

period Pl.

39

1994 1995 Event/ Date September October November December January February March Aoril Mav

I I I I I I I I

Column Packing ,....., I I I I I I I I I

Pending With Water !--t!-!-r-! I I I I

I I I I I I

K test with Water

I~ I :(P.1) l(P?) !.., "'-.1/i ....... r _,."I ...-:

Application of Manure

Observations ........ Adjustment of Apparatus

I (T2) Manometer Level Stablization ~ ~ 1(T1)

...d_ ........ : ' :, ~ '-i I / '! .....-:

Readings and Observation I I

Heating Event No.1 I I I I I

I! Dismantled One Coulmn of Each I I I I I I I

Heatino Event No. 2 I • I +-

Figure 4.4 Schedule of Events

Hydraulic conductivity (K) was calculated using Darcy's Law for constant flow in a

saturated layered system and the assumptions outlined in Barrington and Madramootoo

(1989) were applied with Darcy's Law to manure slurries infiltrating soils .. The hydraulic

conductivity of the entire soil length (about 200 mm) was calculated by measuring the

seepage rate (flux) and determining the hydraulic gradient based upon the ponded manure

depth (about 600 mm) and by assuming that the sand base has negligible resistance on

fluid passing through it. This measured hydraulic conductivity of the entire soil column

will be referred to as the apparent hydraulic conductivity (Kapp) after Barrington et al.

(1987). With manometer measurements it was possible to determine the hydraulic

conductivity of three layers; K1 at d1, manure seal at the soil surface; K2 at d2, between

the soil surface and a depth 25 mm; and K3 at d3, between the manometers at 25 mm and

lOOmm.

40

Measurements of apparent of the soil columns, the hydraulic conductivities of the

individual layers and results of calculations of apparent hydraulic conductivity, using

Equation 2.5, were plotted against time and various soil physical and chemical properties.

The calculations of apparent hydraulic conductivity were based on using the hydraulic

conductivity of the soil-manure interface with a thickness of 5 mm and the use of the

hydraulic conductivity of the soil with water for the remaining layers. These figures were

used to interpret the results and compile conclusions to answer the objectives set out in

Section No.1.

41

5.0 RESULTS AND DISCUSSION

5.1 Soil Properties

5.1.1 Physical Soil Properties

The soils used in the columns ranged in clay content from 9% to 33% and in sand content

from 20% to 75% (Table 5.1). Soils No.3, 4, 5, and 6 have similar clay and sand contents

with only slight variations; clay content ranged between 12% and 17%, while sand content

ranged from 41% to 55%. As many guidelines propose a minimum clay content of 15%

for self-sealing in earthen hog manure storages (Barrington and Jutras, 1985)(Barrington

and Broughton, 1988) (British Columbia, 1991 and 1992) (USDA SCS, 1993)(0ntario,

1994), these soils selected from different locations will provide a good evaluation of this

guideline.

Based on the Unified Soil Classification the soils ranged from an SM to a CH (Table 5.1).

The Plasticity Index of the soils ranged from non-plastic for Soil No.7 (sandy loam or

SM) to a high of 35 for Soil No. 1 (clay loam or CH). Plasticity Index of the loam soils

(ML to CL) ranged from 7% to 15%. The USDA SCS (1993) Technical Note No. 716,

which is used by many state regulatory agencies, recommends a minimum Plasticity Index

of 10%.

42

Table 5.1 Physical Properties of Soils Used in Columns

SOIL Clay Sand LL PI Unified Agricultural Engineering {< 2 Jlm) {> 75 Jlm) Soil Soil Textural Textural

(Ofo) {o/o) {o/o) {o/o) Classification Classification Classification 1 33 20 53 35 CH clay loam silty clay 2 24 34 32 7 ML loam clay-silt 3 12 42 24 9 CL loam sandy silt 4 17 47 22 7 CL-ML loam clay-sand 5 14 41 28 15 CL loam sandy silt 6 13 55 24 4 sc sandy loam silty sand 7 9 75 N/A NP SM sandy loam silty sand

LL = Liquid Limit PI = Plasticity Index Unified Soil Classification- Sand is> 75 Jllll, Clay is> 2 Jllll, ASTM D-2487-93 Agricultural Soil Textural Classification- Sand is> 50 Jllll, Clay is> 2 Jllll, (PCA, 1992) Engineering Textural Classification- Sand is> 62.5 Jllll, Clay is> 4 Jllll, (PCA, 1992)

5.1.2 Chemistry

The pH of all soils was between 7.8 and 8.1 (Table 5.2) but electrical conductivity of the

saturated paste extracts indicated Soils No. 1 through 5 had EC's ranging from 3400

JlS/cm to 6000 JlS/cm (Table 5.2) with Soils No.1, 3, and 4 being in the range of saline

soils (4000 JlS/cm)(Hillet 1982). None of the soils had high S.A.R. (Sodium Adsorption

Ratio) that would have caused dispersion problems upon wetting (Hillel~ 1982). The

Cation Exchange Capacity (CEC) of the soil ranged from a low of 7.7 meq/lOOg for Soil

No. 3 (loam or CL) to a high of 21 meq/lOOg for Soil No. 1 (clay loam or CH). None of

the soils had a CEC higher than 30 meq/lOOg as recommended by Barrington and

Broughton (1988).

43

Table 5.2 Soil Chemical Properties of Soils Used in Columns

SOIL pH EC Sodium CEC f..LS/cm Adsorption Ratio meq/100g

1 7.9 6000 3.8 21 2 7.7 3400 1.5 20.2 3 8.1 4500 1.5 7.7 4 7.8 4300 1.0 8.1 5 7.8 3800 0.5 10.3 6 7.9 1300 1.1 11.6 7 8.1 2200 2.7 8.3

5.1.3 Soil Column Properties

Soil properties following compaction into the columns are summarized in Table 5.3. The

columns were packed to 90 to 92% of Standard Proctor density (ASTM D-698-91). Their

bulk densities thus ranged from 1500 kglm3 to 1830 kg/m3• Soils No. 1 and 4 had the

lowest effective void diameters of 0.19 and 0.22 Jlm respectively with Soil No. 7 the

greatest effective void diameter of 0.64 Jlm. All soils except Soil No.7 had an effective

void diameter of < 0.45 Jlffi as recommended by Barrington and Jutras ( 1985) and

Barrington and Broughton (1988).

Table 5.3. Soil Physical Properties Following Compaction into the Columns.

SOIL Optimal Max. Stand. Moisture o/o Stand. Porosity Effective Hydraulic Moisture Proctor Content Proctor Void Dia. _ Conductivity Content Density Density (de) with Water

(0/o) (kg/m

3) (o/o) (

0/o) {0/o) (J..tm) (cm/s)

1 20.2 1640 19.4 91 44 0.19 2.9E-06 2 17.5 1740 17.8 90 41 0.24 3.2E-O& 3 10.7 1980 10.8 91 32 0.31 1.8E-05 4 11.2 1990 11.2 92 31 0.22 4.8E-05 5 12.8 1910 12.8 92 34 0.29 5.8E-05 6 14.5 1780 14.2 91 39 0.42 2.3E-05 7 12.6 1710 12.2 92 40 0.64 1.5E-04

44

5.2 Construction Criteria and Soil Properties

The soils may be rated as to their suitability for use of liners in earthen lagoons according

to current criteria used by various provincial and state regulations. Three of the soils

(No.1, 2, and 4) meet the minimum clay content of 15% (Barrington and Jutras, 1985;

Barrington and Broughton, 1988; British Columbia, 1991 and 1992; USDA SCS, 1993;

Ontario, 1994). All of the soils except Soil No.7 meet the effective soil pore diameter of

0.45 J.tm for non-ruminant slurries (Barrington and Jutras, 1985; Barrington and

Broughton, 1988). None of the soils meet the hydraulic conductivity of 1 x 10-7 crnls

suggested by many regulatory agencies, nor that of 1.3 x 10-6 cm/s used by USDA

Technical note 716; and according to Technical Note 716 only two soils (No.1 and No.5)

have a Plasticity Index greater than 10. None of the soils have a CEC greater than 30

meq/100g as suggested by Barrington and Broughton (1988) for being suitable in retaining

cation transport According to current criteria in Saskatchewan (1992), British Columbia

(1991, 1992), Manitoba (1993), Ontario (1994), and Quebec (Gangbazo et al. 1989), only

Soils No.1, 2, and 4 meet the requirements for use as liner material for the construction of

an earthen hog manure storage.

5.3 Hydraulic Conductivity with Water

Individual column hydraulic conductivities, ranged from 1.8 x10-6 cm/s for Column No. 2

(Soil No. 1) to 1.68 x 104 crnls for Column No. 20 (Soil No.7). Averages of the two

trials of three replicates for each soil type yielded values of 2.9 x 10-6 cm/s for Soil No. 1,

45

conductivities ranging from 1.8 x 10-5 cm/s to 5.8 x 10-5 cm/s for Soils No. 2 through 6,

and 1.5x104 cm/s for Soil No.7. There was a close agreement between the three replicates

of each soil type (Figure 5.2). None of the soils attained a hydraulic conductivity of less

than 10-7 crn/s as is required by many of the regulatory agencies reviewed (British

Columbia, 1991and 1992; Manitoba 1993; Ontario 1994; Quebec (Gangbazo et al. 1989);

Minnesota (Brach et al. 1992); USDA SCS, 1993).

5.4 Manure Ponding Conditions

5.4.1 Column Apparent Hydraulic Conductivities

The apparent hydraulic conductivity of the soils tested demonstrated reduction in

hydraulic conductivity (Table 5.4) ranging from one order of magnitude (Soil No.1) to

three orders of magnitude (Soil No.7). All the soil intervals, delimited by the

manometers, showed a decrease in hydraulic conductivity relative to that measured with

water (Table 5.4). The lowest hydraulic conductivity was at the top manometer

(assuming a manure seal of 5 mm) having values of about 2.4 x 1 o-9 cm/s for all soils.

The conductivity between the 25 and 100 mm manometers (K3) had the highest

conductivties as measured with ponded manure (Table 5.4).

On November 5, 1994 (Day 0), 600 mm of manure was ponded on the soil columns.

Within 3 to 6 weeks most columns exhibited apparent hydraulic conductivities near 1 x

10-7 cm/s (Figure 5.1) regardless of their texture. This drop in hydraulic conductivity

concurs with other research (Culley and Phillips, 1982; Barrington et al., 1987a, b). This

46

drop was regardless of the apparent hydraulic conductivity measured with water, whether

it was high, as with the sandy material (Soil No.7) or low as with the clay rich material

(Soil No.1) (Table 5.4). The reduction in apparent hydraulic conductivity for all columns

with time followed an exponential decrease (Figures 5.1 and 5.2) similar to that reported

by Culley and Phillips (1982), Rowsell et al. (1985) and Barrington and Madramootoo,

(1989).

Table 5.4 - Summary of Hydraulic Conductivities

Soil Time Period Interface Oto 25 mm 25 to 100 mm Measured *Calculated Measured K Apparent K Apparent K with Water

K1 K2 K3 Kapp Kcal KH20 No (cm/s) (cm/s) (cm/s) (cm/s) (cm/s) (cm/s)

1 Day 38-73 2.8E-08 3.0E-07 2.9E-07 1.0E-07 7.9E-07 2.9E-06 Day 157-185 1.3E-08 9.6E-08 1.3E-07 3.7E-08 4.0E-07

2 Day 38-73 4.4E-09 5.4E-07 1.6E-06 1.1 E-07 1.7E-07 3.2E-05 Day 157-185 2.2E-09 7.5E-08 3.2E-06 6.0E-08 8.8E-08

3 Day 38-73 3.8E-09 6.0E-08 2.1E-06 9.5E-08 1.4E-07 1.8E-05 Day 157-185 1.8E-09 7.9E-08 1.3E-06 5.7E-08 7.4E-08

4 Day 38-73 2.9E-09 5.4E-07 2.6E-06 1.1E-07 1.2E-07 4.8E-05 Day 157-185 2.2E-09 1.3E-06 2.5E-06 7.4E-08 8.8E-08

5 Day 38-73 3.9E-09 1.3E-06 2.5E-07 1.2E-07 1.6E-07 5.8E-05 Day 157-185 3.3E-09 5.9E-07 1.1 E-06 1.0E-07 1.3E-07

6 Day 38-73 5.3E-09 2.2E-07 6.1 E-07 9.7E-08 1.9E-07 2.3E-05 Day 157-185 2.3E-09 2.0E-08 2.0E-07 4.5E-08 9.2E-08

7 Day 38-73 5.5E-09 2.1E-07 7.0E-06 1.3E-07 2.2E-07 1.5E-04 Day 157-185 2.6E-09 2.7E-07 7.0E-06 7.5E-08 1.1 E-07

*Calculated using Kl with a 5 mm interface layer and the measured K with water for the remainder of the soil.

47

rearranged outflow tubes day failures in cooling system

10·8

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425

Time since start of manure application (days)

Figure 5.1. Hydraulic conductivity of soils in columns (each point is the average of three columns)

The change in apparent hydraulic conductivity with time from Day 0 to Day 38 can not

report on or discuss as the apparatus was altered and readings did not stop fluctuating

until Day 38. Any readings obtained are plotted in Figure 5.2 but these values may not

representative of all three replicates during this time period. They do, however, serve to

indicate that the exponential regression does fit the data obtained. With the exception of 2

one day failures in the cooler (Figure 5.1), which resulted in temperatures of about 20-25°

C for less than 24 hours, all column apparent hydraulic conductivities stayed near that of 1

x 10-7 cm/s for the duration of more than 400 days (Figure 5.1). For the purpose of this

study we are examining the results acquired during the first 200 days as explained in

Section 4.3 .2.

48

()~

Apparent Hydraulic Conductivity and Water Hydraulic Conductivity vs Time Since Manure Application

1_0

E_05

...----C_o_l_u_m_n_s_N_o_._1....:..,2....:..,_a_n_d_3....:.(S_o_i_I_N_o_. _1.:...,) .---.--K-w-c1-·

m Kw C2

.·:· Kw C3

- - >:: - -Kw Ave

X KappC1

• KappC2

+ KappC3

KappAve

0 50 100 150 200 Time Since Manure Application (days)

Apparent Hydraulic Conductivity and Water Hydraulic Conductivity vs Time Since Manure Application

1_0

E_04

...---Co_l_u_m_n_s_N_o_._7....:..,_8.:....., _a_n_d_9_(!,_S_o_ii_N_o_. 3~):_ r--.--K-w_c:7_,

a Kw C8

.:::. Kw C9

- -X- -Kw Ave 1.0E-06

X Kapp c:1

1.0E-07 • Kapp C8

+ Kapp C9

1.0E-08 +----...----r-----..-------1 • KappAve

0 50 100 150 200 Time Since Manure Application (days)

Apparent Hydraulic Conductivity and Water Hydraulic Conductivity vs Time Since Manure Applicatr-io=n~-----.

1_0

E_03

Columns No. 19,20, and 21 (Soil No.7) • 11 Kw C20

Kw C19

.. ::: Kw C21

=§ ~ 0 1.0E-05 , ftS()"::: .. ::s t:

- -X- -Kw Ave

:.c Kapp C19

• Kapp C20 'g. ~ ~ 1.0E-06 :I: 0

0 1.0E-07 + Kapp C21

0 50 100 150 200 - - •- - Kapp Ave

Time Since Manure Application (days)

Figure 5.2- Change of Apparent Hydraulic Conductivity With Time (values of Kw for each column or those measured prior to manure application and

lines are "best fit" using exponential fitting)

49

As listed in Table 5.4, the measured apparent hydraulic conductivity for all columns was

reduced to near 1.0 x 10-7 cm/s. The average measured apparent hydraulic conductivity

for all columns during time Tl was 1.1 x 10-7 cm/s (s.d. = 0.1 x 10-7 crnls) and reduced to

an average of 6.9 x 10-8 cm/s (s.d. = 1.9 x 10-8 crnls). This reduction in measured

apparent hydraulic conductivity could be due to particulate matter penetrating into the soil

columns and, with time, thickening the clogged layer (Culley and Phillips, 1982; Rowsell

et al. 1985; Barrington and Madramootoo, 1989). Soil No.1 (having 33% clay content)

may also have undergone physical swelling and chemical alteration to decrease it's

measured apparent hydraulic conductivity with time (Barrington and Madramootoo,

1989). The reduction in measured apparent hydraulic conductivity with time from time

periods T1 to T2 ranged from 13% for Soil No. 5 to 64% for Soil No. 1 (Figure 5.3)

I ~

Averag3 Apparert H,Ualjic Con:ll.£ti\1ty vs lirre Sirce Marue Application Day38(Dec.13,1994)to Day157(Miy9,1995) ,_ ............................................................................. ·················-·································································-··········-·]

• * • •

~~ 1.0E..()7r-_j~~rl~~~~~t~;::j~~¥=~~==-f:S<:·ojl:~j( .. ~ .. ~,--l ~ SQ. No.4

Sell No.2

i Soil l'+l. 7

;t Soii N;;, 3

Soil'*'· 6

Soil No). 1

•

1.0E.()8 +---------'1----------~--------l--------l-------! 20 70 120 170 220

lime Since Maru&Applicalion {days)

• Slif\b.1

!I!Siil'b.2

:· Slil'b.3

.:•:Siillb.4

:aSiil<b.5

• Slillb.6

+ Slil<b. 7

Figure 5.3- Apparent Hydraulic Conductivity Change With Time (each point is the average of three columns and lines are "best fit" using exponential fitting)

50

5.4.2 Soil Manure Interface

A black amorphous layer 3 mm to 7 mm in thickness was observed through the acrylic

column at the surface of each soil. This observation of a visually dark layer was also

reported by Rowsell et al. (1985). When the columns were disassembled this black layer

could be separated from the underlying soil but had a fragile rather than ')elly-like" nature,

as it broke and cracked upon separation. Upon drying this black layer tended to be

absorbed into the fibrous manure mat or into the soil. A cloth covered manometer tube

inserted through the ponded manure to within 25 mm of the black layer indicated that

settled manure solids had no affect upon hydraulic conductivity reduction. All the

columns exhibited a drastic reduction in head at the surface manometer relative to that

when just water was used for measurement It is assumed that the black layer was the

'seal' or clogged layer resulting in the large reduction in flow rates. As it was not possible

to measure the overall thickness of the "seal", 5 mm was used to represent this thickness

for all columns because this was the thickness visible on the edge of the column. The

average hydraulic conductivity of this clogged layer (K1) for Soils No.2 through 7, as

calculated from manometer level readings, was 4.3 x 10-9 cm/s (s.d.= 1.0 x 10-9 crn/s)

during T1 and decreased to an average of 2.4 x to-9 cm/s (s.d.= 0.5 x 10-9 crn/s) during

T2. The average hydraulic conductivity of the clogged layer (Kl) for Soil No. 1, as

calculated from manometer level readings, was 2.8 x 10-8 cm/s during Tl and decreased to

an average of 1.3 x 10-8 crn/s during T2. These low conductivity readings appears to be

the result of particulate matter clogging the surface pores causing "a reduction in the size

or volume of pore spaces" (Davis et al. 1973). The higher apparent hydraulic

51

conductivities of the clay material could be that attributed by Culley and Phillips (1982)

and Rowsell et al. (1985) as rapid clogging in the clay material not allowing penetration of

finer particles with depth which would thicken this layer and lower the conductivity. This

is in contradiction to Barrington et al. (1987b) and Barrington and Madramootoo (1989)

who reported that the conductivity reduction at the clogged layer was directly related to

the particle size distribution of the soil. All of these researchers agree that the reduction in

conductivity at the soil-manure interface of the sandy and silty soils was a result of the

clogging of the smaller pores and the clogging with depth (5 mm to 15 mm) (Rowsell et

al. 1985; Barrington and Jutras, 1983) of the larger pores. The hydraulic conductivity of

the soil-manure interface for Soils No.2 through 6 during Tl or T2 are not significantly

different when the precision of the testing apparatus is considered.

5.4.3 Measured Apparent Hydraulic Conductivity

The apparent hydraulic conductivity, as calculated from the conductivity of the soil­

manure interface (Kl), assumed 5 mm thick, and using the conductivity of the remainder

of the column as the conductivity when just water was used, shows a close agreement

with the measured apparent hydraulic conductivity for Soils No.2 through 6 but not for

Soil No. 1 (Table 5.4). Further, a plot of the measured apparent conductivities and the

calculated apparent conductivities using 3 mm, 5 mm, and 7 mm for the soil-manure

interface (dl) (Figure 5.4), shows that the curves would match with a thickness (dl)of

approximately 6 mm. This agrees with the observations of Rowsell et al. (1985) who

reported a 6 mm thick darkened layer in columns which were disassembled after 30 days

52

of manure ponding. These observations seem to indicate that the hydraulic conductivity of

the soil- manure interface is the dominant factor controlling the apparent hydraulic

conductivity of Soils No.2 through 6. The clay soil (Soil No.1) did not show agreement

between the measured and calculated values of apparent hydraulic conductivity (Table 5.4

and Figure 5.4). The measured apparent hydraulic conductivity of the column was almost

a full order of magnitude lower than the calculated. Since the soil-manure conductivity

was reported to be lower for the clay than the other soils, it would appear that there are

other factors affecting the sealing or clogging of the clay soils with depth. This

observation agrees with those of Barrington and Madramootoo (1989) who concluded

that this additional sealing a result of the smaller pores and the higher adsorption ability of

the clay allowing it to trap the small particulate matter which bypasses the clogged

interface layer and thus reducing the conductivity of the soil with depth.

53

Measured Apparent Hydraulic Conductivity and Calculated Apparent Hydraulic Conductivity vs Time Since Manure Application

1.oE-o5 ,------C_o_l u_m_n_s_N_o_._1....:.,_2.:...., _a_n_d_3_(..:....S_o_i_l _N_o_. _1..:....) __,

.a­:~ u :J 1.0E-06 "g- ~t-4:~-tf~~it~~~?.v"~-~1~~ --+- Kapp Ave

o .!e o E .2 ~ :i 1.0E-07 f! -g. :::a::

_:;:::

1.0E-08 +-----,...----~------....-----1

0 50 100 150 200

Time Since Manure Application (days)

111111 Kcalc (d1 = 3 rrm)

--:::,,_. Kcalc (d1 = 5 mm)

;< Kcalc (d1 = 7 mm)

Measured Apparent Hydraulic Conductivity and Calculated Apparent Hydraulic Conductivity vs Time Since Manure Application

1.oE-o6 .,.----c_o_l u_m_n_s_N_o_._7_,_a_, _a_n_d_9__;_(S_o_i_l _N_o_. _3..;...)__,

()~ ·- > j:g~ ... :J E 1 .OE-07 -g.-g~ :::a:: 0

0

1.0E-08 +------r-----,-----,...-----t 0 50 100 150 200

Time Since Manure Application (days)

--+-Kapp Ave

Ill! Kcalc (d1 = 3 mrn)

~:::-:--- Kcalc (d1 = 5 mrn)

::.;; Kcalc (d1 = 7 mrn)

Measured Apparent Hydraulic Conductivity and Calculated Apparent Hydraulic Conductivity vs Time Since Manure Application

1.oE-o6 .,.-----C_o_l u_m_n_s_N_o_._1_9...:..,2_0....:,_a_n_d_2_1...,1(_S_o_ii_N_o_._7 ..... r)c.....,

()~ 3~7> f! g E 1 .OE-07

"'D "'D () >-c­

:::t: 0 0

1.0E-08 +------.------....------....-------1 0 50 100 150 200

Time Since Manure Application (days)

--+- Kapp Ave

111111 Kcalc (d1 = 3 mm)

--:'::.- Kcalc (d1 = 5 mm)

:<:;: ~calc (d1 = 7 mm)

Figure 5.4 Measure and Calculated Apparent Hydraulic Conductivity vs. Time (values plotted are averages of the three replicates and calculated values are using dl=5 mm, Kl of the soil-manure interface and K as measured with water for the remainder of the soil cloumn)

54

5.4.4 Effect of Clogging With Depth

All soils demonstrated a reduction in hydraulic conductivity with depth (Table 5.4 and

Figure 5.5) Figure 5.5 shows plots of the change in hydraulic conductivity with time and

depth for Soils No. 1, 3, and 7. Data trends as a result of exponential regression are also

indicated. Soils 1, 3, and 7 were chosen as they are representative of the clay, loam, and

sandy soils respectively. Soil No.6 was an exception as it demonstrated data trends

similar to Soil No. 1. All data points are an average of the data obtained from the three

replicates.

Hydraulic conductivities of the top 25 mm of soil (K2) during period Tl ranged from

6.8xlo-s crnls (Soil No. 3) to 1.3 xl0-6 cm/s (Soil No.5) (Table 5.4). From period Tl to

period T2 the hydraulic conductivities of K2 remained relatively constant for Soils 3, 5,

and 7, decreased for Soils No. 1, 2, and 6 and increased for Soil No.4 (Table 5.4)

Hydraulic conductivities of the top 25 mm to 100 mm of the soil (K3) during period Tl

ranged from 2.5x10-7 crnls (Soil No.5) to 7.0 xl0-6 cm/s (Soil No.7) (Table 5.4). From

period Tl to period T2 the hydraulic conductivities of K3 remained relatively constant for

Soils No.2, 3, 4, and 7, decreased slightly for Soils No. land 6 and increased for Soil

No.5 (Table 5.4).

55

Hydraulic Conductivity of Soil Columns vs Time Column No.1, 2, and 3 (Soil No.1)

1.0E-05 ,..----------------------. .?: :~ () 1.0E-06 :J -o_

S i 1.0E-07 .2 ~ 3 !! 1.0E-08 -g. X

++ +++++++++++++++++++

1.0E-09 +---t---+---+---+--1---+--+---+---+---l

1.0E-04

.?: :~ 1.0E-05 u :J -o_ 1.0E-06 g Je (.) E .2 ~ 1.0E-07 3 ! 1.0E-08 -g.

X

1.0E-09

0 20 40 60 80 100 120 140 160 180 200 Time Since Manure Application (days)

(Typical Soils No. 1 and 6)

Hydraulic Conductivity of Soil Columns vs Time Column No. 7, 8, and 9 (Soli No. 3)

.. ·•· .... :~::: ::~{

::{ .;:{ -;·: .. :

' 0 --,.. .·. 0 ... t .:::, •• • •.•. .. i ·. <;> •••

•• ••••••

1S8 Soil nterface

·=·=· Top 25 mm of Soil

:>:: 25 mn to 1 oomn

+ Kwater

--.-Apparent K

1188 Soillnterface

.:::. Top 25 mn of Soil

x 25 mm to 100mn

--f- K with Water

-+-Apparent K

0 20 40 60 80 100 120 140 160 180 200 L-----------'

Tim e Since Manure Application (days)

Hydraulic Conductivity of Soil Columns vs Time Column No. 19, 20, and 21 (Soil No. 7)

1.0E-03 .------------------------,

.?: 1.0E-04 :~ g 1.0E-05

~0 8 E 1.0E-06 u~ 3 1.0E-07 !! "g. 1.0E-08 ::z::

I !

• • ••

I I ! I I I I I I : I

:x: ><~

. ··• •. , ....... . ... ::< ::< .:·:. • • .Jf· .·:·:· /•.

.·:·. }; ,.;:;. .. ·~ ..

.• • i v-- .; ••• .,.,; ·; ..... •••• •••••••••••••• 1.0E-09 +---+----+--+---+-----+--+---~:....._-+--+------l

0 20 40 60 80 100 120 140 160 180 200

Time Since Manure Application (days)

(Typical Soils No. 2, 4, 5, and 7)

11 Soil nterface

.:::.. Top 25 mm of Soil

x 25 mmto 100mm

···+···· K with Water

-+-Apparent K

Figure 5.5 - Change in Hydraulic Conductivity With Time and Depth (values are an average of the three replicates and lines are "best fit" from exponential

regression)

56

On January 12, 1995 (Day 68) a failure in the cooling system where the soil columns were

stored, caused the room the heat to approximately 25°C for less than 24 hours.

Following this heating event, Soil No. 6 demonstrated an increase in hydraulic

conductivity in K3 (soil layer d3) of almost two orders of magnitude and a small increase

in apparent hydraulic conductivity of the entire column (Figure 5.6). This may be an

indication of the idea put forward by Barrington et al. (1987b) that the fermentation of the

manure mat produces gas bubbles which disturb the clogged layer. This may also indicate

that the clogging of soil by manure is partially an exclusion process by which, at depth,

pore channels do not experience flow due to surface clogging but retain much of their

original hydraulic conductivity. When the surface clogging material is removed or

disturbed the pore channels at depth require time to become inactive. The layer governing

the apparent hydraulic conductivity is the soil-manure interface (dl) which would clog

very quickly after disruption and allow the soil column to retain it's apparent hydraulic

conductivity (Culley and Phillips, 1982; Barrington and Madramootoo, 1989)

The above findings are similar to those of Barrington and Madramootoo (1989) who

found a variability in the change in hydraulic conductivity in layers below the soil-manure

interface. Because of this variability between replicates and erratic data from apparatus

inaccuracies, only overall trends of hydraulic conductivities of periods T1 and T2 were

plotted against soil physical and chemical properties (Figures 5. 7 a to 5. 7 e). The figures

are somewhat similar owing to the fact that the properties used for plotting are dependent

on clay content. Exponential regression and visual interpretation was used to determine

the trend (ie. whether hydraulic conductivity was increasing, decreasing, or remaining

57

Hydraulic Conductivity vs. Time Between 25 mm and 100 mm Below the Soil Surface and at the Soil-Manure Interface

1.0E-04 ,..--.......,--......,...--"'t'"""-f_o"'f'"r S_o_l_l N_o"""t.6--.......... ---'Y"'"'"'"'"-.....,

• Colunn f\b. 16

Bl Colunn f\b. 17

:·. Colunn f\b. 18

···~·:~···Ave. (K3)

-Original K with Water

-+-Ave. Apparent K

+ Colunn f\b. 16

D Colunn f\b. 17

o Colunn f\b. 18

-Ave. nterface (K1)

12-Dec- 1-Jan-95 21-Jan-95 10-Feb-95 2-IVar-95 22-Mar-9511-Apr-95 1-IVay-95 21-May-94 95

Figure 5.6 Hydraulic Conductivity vs. Time for Soil No. 6 (showing effect of a minor heating event)

essentially constant) for each column and each layer. These overall trend lines suggest the

effect of clogging with time and depth for the individual layers. The data plotted in

Figures 5.7a to 5.7e demonstrates similar trends between Kl and K2 and similar trends

between hydraulic conductivity with water and K3. This may be an indication of similar

physical and chemical properties in the soil's layers demonstrating similar characteristics

which would indicate that the clogging effect of the soil was limited to the manure soil

interface (Kl) and the top 25 mm of soil (K2). Further, if the reduction in K2 was caused

by the soil-manure interface layer developing .to a depth below the top manometer, then

some of the soil in the top 25 mm (d2) may have remained relatively unaffected by manure

ponding.

58

All figures (5.7a to 5.7e) show that there does not appear to be any significant difference

in Kapp at Tl or T2 for the range of soils tested. Kl was not significantly different for

soils with less than 25% clay content, 65% fines, a PI of 15, a effective pore diameter of

0.2 mm, and a CEC of21. This includes Soils No.2 through 7. Soil No.1 demonstrated a

slightly higher Kl for all properties. Percentage of fines appeared to give the best

agreement with variation in hydraulic conductivity with water. All figures demonstrate a

variability hydraulic conductivity and soil properties for K2 and K3 at Tl and T2. This is

similar to the findings of Barrington and Madramootoo ( 1989) who reported some

variability in hydraulic conductivity with depth.

The reason for conductivity reduction in deeper layers of the soil was not determined.

Water in the deeper manometers became discolored within 2 months and gas production

during monitoring occasionally produced bubbles in the effluent tube, but did not block

flow. Air bubbles were not observed in the manometers. Soil materials near the surface,

at places of tensiometer insertion and the sand base became noticeably discolored

("blackened") within 2 months from the start. Manure particles were observed in some of

the surface manometer tubes. The possibility of organic matter penetration to depth,

bacterial growth and reduction/oxidation reactions within the soil column could be some

reasons for this reduction. Desaturation at the start and gas production during ponding of

manure may have reduced hydraulic conductivity in the columns due to air entrapment.

59

Hydraulic Conductivity of K1 and Kapp at T1 and T2 vs. o/o Clay Content

1.00E-03

I 1.00&04 -2. ~ > 1.00&05 = () ;::, 1.00&06 'C c 0 0 1.00&07 ()

~ 1! 1.00&08 "g.

:::1: 1.00&09

0 5

• • • •• •

Percent Clay Content (o/o< .002 mm)

•

30 35

Hydraulic Conductivity of K2 and K3 at T1 and T2 vs. o/o Clay Content

1.00&03 ,.-.-___,--.....,.....--"1"""""'-........,..--""T""'"-........,r-""""'---""'S 'i' ! 1.00&04 +---+---::•d:r------..:----+~-·--+-----11----+------i ~ •• 1 -~ Kwater > 1.0QE-05 +----t-~Ip-j---f----+-__:::::p:-...._...,=---11------1

~ --=-~=:_~12 ~ ----. ~ 1.00&06 +---+---+-_..._;>--1~ .. IR-;.; +-=~ •.. -4=::::::---....:--..:...::....j----f-----!

o ~ 111 ;:< K2 at T1 - ---m ~ 1.00&07 -t------J--~-1--:~~,., -+-:-K2~a"":"';t r=l ;,::~-~.;:;.-+---+--oil!~:· -!

• Kwater

1111 K1@ T1

::::, K1@ T2

;:<. Kapp@ T1

)C Kapp@ T2

• Kwater

1111 K2 @T1

;:::. K2@ 12

X K3@T1

X K3@12

"5 l! 1.00E-08 +----t--~-··:_·: ---1---+----t--~----!

--Trendlines

"g. :::1: 1.00&09 +---+---+---1---+---+----+---f

0 5 10 15 20 25 30 35

Percent Clay Content (o/o< .002 mm)

Figure 5.7a- Hydraulic Conductivity With Depth at Tl and T2 vs. Percent Clay Content (% < 0.002 mm) (each point is the average of three columns

and lines are "best fit" using exponential fitting )

60

Hydraulic Conductivities of K1 and Kapp at T1 and T2 vs. o/o Fines{< 0.074 mm)

1.006-03

I 1.006-04 +-----+~·----~----+---__.---~ ~ ... ~ 1.006-05 +-----+----+--·---·+------4---~ :g -5 1.006-06 +-----+-----1----+------f------i c 0 0_() 1.006-07 +-----+---~iii.-'-:--~---~-~---:>..--·· -----,;1~,_. -----{ ~ ~ X ~~ X •

t ::::: :~~~~~~:~~~~~~~~:~~~. ~~~~ .. ~ -.:/:: ~~~~-~~~-+r ___ -i 0 20 40 60 80 100

Percentage of Anes (%<0.074 mm)

• Kwater

II! K1@ T1

.::: .. K1 @ T2

;.{ Kapp@ T1

X Kapp@ T2

Hydraulic Conductivities of K2 and K3 at T1 and T2 vs. o/o Fines{< 0.074 mm)

1.006-03 ,..-----,.----y----,-------r-----s

- ..__ Kwater ~ 1.006-04 +------f--=--=...._........,=--l--r---____.:....::...:..:...::: •• =4~ .---+---~ ~ .,. ~~ ~ 1.006-05 +-----t--.:u---1-----1--~-....=+--------i ~ ~K3@T2 ::e:; .... ~ ~ 1.00E-06 -+-----+-K_3_@_T_1--I-~----=~!l!!l_i11111'·<~~o.:=-->< __ +---~ c 1<2 ® r~ ::--:. • .::: -.-__ 8 l_ ___ _J_~~···~~3=~~~~~K2~@~T:~2::~ ____ __J ~ 1.006-07 it .:::. ::: ..

1! ~ 1.006-08 -1-------+-------+-------1--------f--------1

:I:

1.006-09 +-----+----1----1-----4--------4

0 20 40 60 80 100

Percentage of Anes ( o/o < 0.074 mm)

• Kwater

Ill K2 @T1

.:::. K2@ T2

.(•. K3@ T1

X K3@ T2

--Trendlines

Figure 5. 7b - Hydraulic Conductivity With Depth at Tl and T2 vs. Percentage of Fines(%< 0.074 mm) (each point is the average of three columns

and lines are "best fit" using exponential fitting)

61

I .2. ~ > = () ::J "0 c 0 0

.!:! '5 I! "0 >-:I:

Hydraulic Conductivities of K1 and Kapp at T1 and T2 vs. Plasticity Index

1.006-03

1.00&04 ~~

'· • • 1.00&05

• 1.006-06

1.00&07 :: ~~·- ~

r- x i ....

1.006-08 •• Ill ~~ ~

1.00&09 ·t· .:::;

0 10 20 30 40

Plasticity Index (PI in %Moisture Content)

• Kwater

111 K1@ T1

-::::. K1 @ T2

;:< Kapp@ T1

~ Kapp@ T2

Hydraulic Conductivities of K2 and K3 at T1 and T2 vs. Plasticity Index

1.006-07 .:::.~ K2 at T2 .::::

1.00&08 +------+----+----~--~

1.00&09 +----+----+----+----~

0 10 20 30 40

Plasticity Index (PI In% Moisture Content)

• Kwater

111 K2 @T1

.:::.. K2@ T2

X K3@ T1

X K3@T2

--Trend lines

Figure 5. 7c - Hydraulic Conductivity With Depth at Tl and T2 vs. Plasticity Index (each point is the average of three columns and lines are "best fit"

using exponential fitting )

62

Hydraulic Conductivities of K1 and Kapp at T1 and T2 vs. Effective Pore Diameter

i 1.00E-04 -r---t------;---+---+---+----+--=·~-1 t: ••• ~ . ~ 1.00E-05 -r---t------;---+•---+---+---+--~ > = u ::s , c 0 0

1.00E-06 +---t------ir-----+---+----+----1-----l

~-~ 1.00E-09 +---t------1---+---+---1----l-----1

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70

Bfective Pore Diameter (um)

• Kwater

llll K1@ T1

-::::: K1@ T2

::-:: Kapp@ T1

X Kapp@ T2

Hydraulic Conductivities of K2 and K3 at T1 and T2 vs.

I .2. ~ > = u ::s , c 0 0 .2 :; f! , >-

:E:

1.00E-03

1.00E-04

1.00E-05

1.00E-06

1.00E-07

1.00E-08

Effective Pore Diameter

• • ·~l-----1---"" ~· .

;.::

~-Ill -

1.00E-09 +----4---+----+----1------1----+-----t

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70

Bfective Pore Diameter (um)

• Kwater

Ill K2 @T1

.:::. K2@ T2

:.-< K3@ T1

X K3@T2

--Trendlines

Figure 5.7d- Hydraulic Conductivity With Depth at Tl and T2 vs. Effective Pore Diameter (each point is the average of three columns and lines are

"best fit" using exponential fitting)

63

~ .2. ~ ·s: = () :::J , c 0 0 .2 '5 1! , >-::r:

~ .2. ~ > =fi :::J , c 0 0 .2 '5 ftl .. , >-::r:

Hydraulic Conductivities of K1 and Kapp at T1 and T2 vs.

1.00&03

1.00&04

1.00&05

1.00&06

1.00&07

1.00&08

1.00&09

5

• • •

Cation Exchange Capacity

• • •

10 15 20

Cation Exchange Capacity (CEC) (meq/100 g)

25

• Kwater

a K1@ T1

,:::. K1 @ T2

;< Kapp@ T1

:1K Kapp@ T2

Hydraulic Conductivities of K2 and K3 at T1 and T2 vs. Cation Exchange Capacity

1.00&03

1.00&04 • ...,...__ h---• ~ • • Kwater 1.00&05

"' K2 @T1 • ;~ K3 at T1 ~· K2@T2

1.00&06 X:::=: K~ atT? v.: :::::

II ·.·.· >< ;.~ K3@ T1 K2 at T1 m IIi! ...

X J: K3@ T2 1.00&07 iii& .~=

K2 atT2 --Trendlines .·.·.

1.00&08

1.00&09

5 10 15 20 25

Cation Exchange Capacity (CEC) (m eq/100 g)

Figure 5.7e- Hydraulic Conductivity With Depth at Tl and T2 vs. Cation Exchange Capacity (each point is the average of three columns and lines are

"best fit" using exponential fitting)

64

The reduction in hydraulic conductivity for the top 25 mm was similar to that of the

interface which may indicate that this reduction was due to the thickening of the clogged

layer with time (Rowsell et al. 1985; Barrington and Madramootoo, 1989).

The reduction in hydraulic conductivity in the top 25 mm to 100 mm of the soil (K3) may

be due to entrapped air, gas production from small particles in flow channels (Barrington

and Madramootoo, 1989), or the "change in friction coefficients or in reduced size or

volume of pore spaces"(Davis et al. 1973). A visual darkening of exfiltrate was noticed as

the experiment progressed. This may be an indication of very small particulate matter

passing through the soil pores. These small particles could have clogged selective pores

with depth causing a reduction in hydraulic conductivity which would be less than that at

the soil manure interface (Barrington and Madramotoo, 1989).

5.4.5 Effect of Texture and Cation Exchange Capacity (CEC) on Clogging

Figures 5.7a through 5.7e show the change in hydraulic conductivity with time and depth

versus percent clay content(%< 0.002 mm), percentage of fines< 0.074 mm, Plasticity

Index, Effective Pore Diameter, and Cation Exchange Capacity respectively. These

figures all demonstrate that K1 and K2 decreased with time and that K3 remained

relatively constant and similar to the hydraulic conductivity with water. If the reduction in

K2 is caused by the thickening of the clogged layer with time, then the conductivity of the

lower layers would seem to remain constant or unaffected over time once the initial

65

clogged layer forms. This observation is similar to that of Barrington and Madramootoo

(1989).

Figures 5. 7 a to 5. 7b also show that there does not appear to be any effect of textural

properties on the soil,s ability to clog by manure. There is an indication that soils with

clay contents higher than 30 percent are less affected by the manure clogging. This may

indicate that the final hydraulic conductivity may become more dependent on clay content

than on the manure clogging as the clay content of the soil increases above 25% (Figure

5.7a). This agrees with the findings of Barrington et al. (1985 and 1987). Common sense

would also indicate that very granular soils would also be less susceptible to clogging with

manure. Still, these findings should cover a wide range of soils typically used for

construction of earthen manure storages on the Canadian Prairies.

5.5 Sources of Error

The experimental apparatus and procedures could have introduced several sources or

error. Some of these sources are:

• the apparatus did not lend itself to accurate measurements (a differel}.ce of

approximately 15 mm in the water levels in the manometers would give a difference in

results of one order of magnitude), • difference in atmospheric pressure caused by cooling and ventilating equipment may

have caused erroneous level readings,

• evaporation losses were assumed to be negligible from measurements performed on

independent sample bottles,

• reading of water levels was accomplished with a steel tape graduated to 1 mm,

• gas production from fermentation could have caused erroneous readings, and • the manometers could have experienced some clogging effecting level readings.

66

6.0 CONCLUSIONS

The purpose of this study was to extend previous studies investigating the clogging of soil

by ponded hog manure and to clarify the meaning and the magnitude of the "manure seal".

Specific objectives are related to the effect of clogging upon soil hydraulic conductivity:

1) to measure the effect of clogging with time,

2) to measure the effect of clogging with depth, and

3) to determine the effect of soil texture upon clogging.

All soils experienced an exponential decrease in apparent hydraulic conductivity for the

duration of the study. Soils having a clay content less than 25% experienced a reduction

in hydraulic conductivity which started upon contact of the manure with the soil surface.

Within 5 days these soils' apparent hydraulic conductivity was reduced to below 10-6 crn/s

and to 10-7 crn/s within 25 days. This represented a reduction in apparent hydraulic

conductivity of 2 to 3 orders of magnitude. The reduction in apparent hydraulic

conductivity with the clay soil gradually decreased for the duration of the study.

The reduction in apparent hydraulic conductivity was a result of clogging of the soil pores

at the surface of the soil. This was evidenced by the differences in hydraulic conductivity

of the different layers within the soil columns. The soil-manure interface was the

governing layer which controlled infiltration into the soil and the apparent hydraulic

conductivity of the soil columns. This governing layer was 5 mm to 7 mm in thickness

67

and increased in thickness with time. The reduction in hydraulic conductivity with depth

was thought to be caused by clogging of very small pores by particulate matter flowing

through the soil and air entrapment in the larger pores caused by gas production from

fermentation.

The lower layers maintained their original flow characteristics, which are dependent on

texture, while the upper layers which clogged with manure showed no difference in flow

characteristics between soil textures. The clogging of the soil at the soil-manure interface

was more effective in the soils with less than 25% clay content. The soil with more than

25% clay content experienced reduction in hydraulic conductivity with depth which was

thought to be caused by retention of ions and organic matter causing hydration and

reduction in pore size.

This study demonstrates that the reduction in hydraulic conductivity of soils under ponded

manure is caused by clogging of soil pores at the soil-manure interface and that this

clogged layer which governs the infiltration of solution into the soil is concentrated in the

top 25 mm of soil and is further governed by the top 5 mm to 7 mm. Soils below this

layer are not significantly affected and retain their ability to conduct flow.

More study is required to determine the effect of the clogged soil-manure interface and the

soil physical and chemical properties in reducing the migration of solute down through the

soil profile. Once this is determined, the limits of soils suitable for the construction of

earthen manure storages can start to be qualified.

68

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