EPA-600/2-77-217
December 1977
URBAN RUNOFF TREATMENT METHODS
Volume I - Non-Structural Wetland Treatment
by
Eugene A. Hickok, Marcus C. Hannaman and
Norman C. Wenck
Eugene A. Hickok and Associates
Wayzata, Minnesota 55391
Grant No. S-802535
Project Officer
Hugh Masters
Storm and Combined Sewer Section
Wastewater Research Division
Municipal Environmental Research Laboratory (Cincinnati)
Edison, New Jersey 08817
This study was conducted
in cooperation with
Minnehaha Creek Watershed District
Wayzata, Minnesota 55391
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmen-
tal Research Laboratory/ Cincinnati, U.S. Environmental Protec-
tion Agency, and approved for publication. Approval does not
signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute en-
dorsement or recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was created because of
increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony
to the deterioration of our natural environment. The complexity
of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in
problem solution and it involves defining the problem, measuring
its impact, and searching for solutions. The Municipal Environ-
mental Research Laboratory develops new and improved technology
and systems for the prevention, treatment, and management of
wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and
treatment of public drinking water supplies, and to minimize
the adverse economic, social, health, and aesthetic effects of
pollution. This publication is one of the products of that re-
search; a most vital communications link between the researcher
and the user community.
This report defines the role that wetlands play in the hydro-
logic cycle, the character and impact of urban runoff on wetlands
and the expected water quality changes by supporting wetland
biota with organics and nutrients inherent in the runoff as pollu-
tants. Biological assessments detected no environmental impacts
on the wildlife or vegetation as a result of this project.
Francis T. Mayo
Director
Municipal Environmental Research Laboratory
111
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ABSTRACT
A major concern of the Minnehaha Creek Watershed District,
a natural watershed basin encompassing the area that drains
into the Lake Minnetonka - Minnehaha Creek system, near Wayzata,
Minnesota, is the water quality of its lakes. A significant
impact on lake waters is known to be caused by stormwater run-
off; providing control and treatment methods from this pollu-
tion source is a large and complex problem. The methods de-
veloped by this project may be implemented as an urban storm-
water runoff control practice in many of the urban centers of
the country that have unused adjacent wetlands.
This project has demonstrated the treatability and effec-
tiveness of non-structural methods to improve the quality of
stormwater runoff from urban areas using natural wetlands.
The wetland used in the study retained 77 percent of all
phosphorus and 94 percent of the total suspended solids entering
the site during the evaluation period.
It has been shown that the mechanism utilized by organic
soils in the removal of nutrients and contaminants is the re-
sult of physical, biological and chemical mechanisms.
The physical trapping of contaminants by organic soils is
the result of the characteristic fine texture of the material.
The fine textures permit physical screening of sediment trans-
ported to the marsh and also tend to reduce the velocity of
groundwater movement. The relatively slow velocity increases
the non-structural wetland treatment methods. This report can
be used as a guide in the wise and prudent use and management
of wetlands, especially in urban and developing areas. A de-
tailed environmental assessment indicated that no impacts were
detected on the wildlife or vegetation as a result of this
project.
This report was submitted in fulfillment of Grant No. S-802535
by the Minnehaha Creek Watershed District and their consultant,
Eugene A. Hickok and Associates under the sponsorship of the
U.S. Environmental Protection Agency. This report covers the
period November, 1974 to October, 1975 and work was completed
as of November, 1976.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables viii
Abbreviations ix
Acknowledgments x
1. Introduction 1
2. Conclusions 3
3. Recommendations 5
4. Background 6
5. Site Description 13
6. Site Development and Instrumentation 26
7. Methodology 35
8. Results 38
9. Discussion 94
References 96
Appendices
A. Ecology Report - Phase I 99
B. Ecology Report - Phase II 108
C. Methods of Sample Collection and Analysis 115
D. Penman Method for Calculation of Evapotranspiration. 118
Glossary 120
v
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FIGURES
Number
1 Location Map - Minnehaha Creek Watershed District. . 7
2 Photographic Views of Lake Minnetonka and the
Wayzata Wetland 8
3 Location Map - Wayzata Wetland 12
4 Soils Map 14
5 Stratigraphic Log of Wetland Soils 16
6 Wayzata Wetland Watershed Boundaries 18
7 Typical Photographic Views of Drainage Groups I - IV 19
8 Groundwater Contour Map 22
9 Hydrologic Cycle 23
10 Monthly Precipitation Distribution Minneapolis-
St. Paul Area (1936-1975) 24
11 Instrumentation of Watershed 27
12 Instrumentation of Wetland 29
13 Photographs of Instrumentation of Wetland 32
14 Hydrograph - Wetland Discharge 43
15 Evaporation Pan Data - Wetland vs. University of
Minnesota, St. Paul 44
16 Pollutograph of May, 1975 Storm - Drainage Group II,
Subwatershed II 50
17 Relationship of Wetland Outflow, Ammonia Nitrogen
Concentrations and Total Phosphorus Concentrations 54
18 Groundwater Fluctuation - Observation Well 1 .... 57
19 Carbon Dioxide Production - Control Area, Stations
7-12 61
20 Carbon Dioxide Production - 24 Hours vs. 72 Hours,
Station 7. . . 62
21 Microbial Counts vs. Rainfall/Runoff Events -
Stations 7 and 13. 64
22 Depth to Groundwater - Stations 4 and 10 67
23 Depth to Groundwater - Stations 2 and 8 68
24 Carbon Dioxide Production - Stations 4 and 10,
24 Hour 69
25 Carbon Dioxide Production - Stations 4 and 10,
72 Hour 70
26 Surface Microbial Counts - Stations 4 and 10 .... 71
27 Subsurface Microbial Counts - Stations 4 and 10. .. 72
28 Carbon Dioxide Production - Stations 2 and 8,
24 Hour 73
29 Carbon Dioxide Production - Stations 2 and 8,
72 Hour 74
VI
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FIGURES (continued)
Number Page
30 Surface Microbial Counts - Stations 2 and 3 75
31 Surface and Subsurface Microbial Counts vs. Total
Phosphorus Concentration in Soil Water - Station 6 77
32 Surface and Subsurface Microbial Counts vs. Total
Phosphorus Concentration in Soil Water -
Station 10 78
33 Surface and Subsurface Microbial Counts vs. Total
Phosphorus Concentration in Soil Water -
Station 5 79
34 Phosphorus Adsorption Isotherms - Stations 4 and 10. 82
35 Total Coliform, Total Suspended Solids and Bio-
chemical Oxygen Demand Concentrations in Sump
Discharge Water 84
36 Total Coliform, Total Suspended Solids and Bio-
chemical Oxygen Demand in Outlet Discharge Water . 86
37 Ammonia Concentration and Oxidation Reduction Po-
tential in Sump Discharge. . . . . , 87
38 Ammonia Concentration in Soil Water - Stations
3 and 9 , . 89
39 Ammonia Concentration in Outlet Discharge 90
40 Total Phosphorus Concentration in Sump Discharge . . 92
41 Total Phosphorus Concentration in Outlet Discharge
Water 93
vii
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TABLES
Number Pag(
1 Watershed Characteristics - Impermeable Area 21
2 Precipitation, November 1, 1974 - October 31,
1975, centimeters ~q
3 Runoff Coefficients • • • • 40
4 Empirical Coefficient - Penman Equation [45
5 Evapotranspiration - Wayzata Wetland 46
6 Wetland Flow Discharge 47
7 Comparison of Stormwater Runoff Quality ..!!!!! 49
8 Comparison of Annual Pollutant Loads ! ! 51
9 Annual Nutrient Inflows ! ! ! 52
10 Discharge Quantities From Wayzata Wetland
November, 1974 - October, 1975 53
11 Comparison of Average Heavy Metal Concentrations. ! ! 55
12 Comparison of Nutrient Concentrations in the
Groundwater 59
13 Comparison of Heavy Metal Concentrations in the
Groundwater 59
14 Vegetative Mass Production - Wayzata Wetland! ! ! ! ! 80
15 Phosphorus Adsorption Characteristics - Wayzata
Wetland Soils
Vlll
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LIST OF ABBREVIATIONS
ha — hectare
ha-m — hectare meter
ac — acre
ac-ft — acre foot
kg — kilogram
yr — year
Ibs — pounds
cm — centimeter
sq mi — square mile
m — meter
ft — foot
cm/sec — centimeters per second
gpd/sq ft — gallons per day per square foot
F — Fahrenheit
C — Celsius
in — inch
1 — liter
gpm — gallons per minute
mis — milliliters
gal — gallon
km — kilometer
FITC — fluoriscene isothiocyanate
IX
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ACKNOWLEDGMENTS
The authors wish to acknowledge the support of the Board of
Managers of the Minnehaha Creek Watershed District including
Lawrence Kelley, President, David Cochran, Vice President,
H. Dale Palmatier, Secretary, James Russell, Treasurer and
Albert Lehman, Manager. Special thanks are due Mr. Kelley who
spent numerous hours with the planning and fund raising ac-
tivities for the project.
Appreciation is extended to those numerous private citizens
and foundations who supported the project financially and poli-
tically. The cooperation of personnel and city council members
of the City of Wayzata made the acquisition and use of the pro-
ject site possible and is greatly appreciated. The property
owners surrounding the site permitted access across their pro-
perty which is gratefully appreciated. The assistance of Dr.
Edwin L. Schmit, Department of Soils Science, University of
Minnesota, St. Paul and Dr. James A. Jones, Department of
Biology, Macalester College, St. Paul, in the areas of micro-
biology and ecology are greatly appreciated.
The suggestions, comments, encouragement and guidance pro-
vided by Mr. Richard Field, Chief Storm and Combined Sewer Sec-
tion, United States Environmental Protection Agency and Mr. Hugh
Masters, Project Officer, were invaluable. The support of Mr.
Darwin R. Wright and Mr. William A. Rosenkranz during the de-
velopment stage of the project is also appreciated.
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SECTION 1
INTRODUCTION
Wetlands have been identified as having a certain capacity
for the renovation of polluted waters. Urban stormwater runoff
contributes significant pollution loads to urban lakes and an
economically and ecologically acceptable method of control is
required. This study was designated to evaluate the effective-
ness of wetlands for water renovation and to identify the mech-
anisms and processes which take place.
A wetlands is a complex hydrologic, chemical and biologi-
cal system which can result in the transformation of various
elements in runoff water into compounds which may improve the
quality of the discharge water or, to the contrary, have a
significant deleterious effect on the quality of the water be-
ing discharged.
The wetland selected for this study has a total watershed
size of approximately 28.3 ha (70 ac) with a wetland area of
approximately 2.8 ha (7 ac). This conforms to the 10:1 ratio
typical of many land-surface to water-surface relationships in
the region. The watershed has a well developed drainage
system with much of the area being drained by storm sewers.
Several types of urban land use exist.
An environmental inventory was taken before and after the
project and observations of the wildlife and vegetation have
been made.
Flows into and from the wetland and groundwater monitoring
wells were analyzed for a variety of parameters from November,
1974 through May, 1976.
The study included intensive microbial monitoring to deter-
mine the microbiological activity of the wetland and its impor-
tance to the nutrient cycle. A unique staining method called
"fluoriscene isothiocyanate total count" (FITC) was used which
gives a one-step method of counting the bacteria population in
soil and water samples. Microbial numbers together with nutri-
ent loads and carbon dioxide production were utilized to deter-
mine the capacity of the microbial community to utilize storm-
water loads.
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The primary benefits from this study are the identification
and determination of the feasibility of improving the quality of
stormwater runoff by utilizing natural wetlands. Scientific
data required to help justify the protection of natural wet-
lands were also obtained.
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SECTION 2
CONCLUSIONS
1. The mechanism for the renovation of stormwater by non-struc-
tural wetlands appears to be a combination of physical en-
trapment, microbial transformation and biological utiliza-
tion.
2. The annual runoff coefficients ranged from 0.07 for the open
space and single family drainage group to 0.32 for the shop-
ping center and traffic corridor drainage group.
3. Groundwater discharge provides 18 percent of the total water
runoff input to the Wayzata wetland.
4. The tributary phosphorus loading ranged from 0.11 kg/ha/yr
(0.60 Ibs/ac/yr) to 0.39 kg/ha/yr (2.1 Ibs/ac/yr) from the
undeveloped and single family drainage group to the shop-
ping center and traffic corridor drainage group respective-
ly.
5. Evaporation rates in the wetland are greatly reduced during
periods when the vegetation is dense.
6. The Wayzata wetland retained 78 percent of all total phos-
phorus and 94 percent of the total suspended solids enter-
ing the site during the study period.
7. The Wayzata wetlands organic soil contained approximately
2,868 kg/ha-m (780 Ibs/ac-ft) of phosphorus, 5.5 times
the phosphorus holding capacity indicated by phosphorus
isotherms for the soil.
8. There appears to be a net loss of ammonia from the wetland
which is caused by the transformation of nitrogen compounds.
9. Phosphorus and ammonia nitrogen concentrations of the dis-
charge water do not correlate for short term, day to day,
comparisons but do correlate seasonally.
10. Discharge of nutrients from the wetlands is related to the
seasons.
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11. The water level management technique, where effective, did
appreciably increase the surface microbial activity.
12. Microbial activity decreased dramatically when wetland soils
were submerged and become anaerobic.
13. Microbial activity is significantly affected by soil temp-
erature with higher activity during warmer temperatures.
14. Surface bacteria counts appear very responsive to runoff
events, possibly due to the phosphorus load, with counts
increasing in number after each event.
15. The population of anaerobic organisms deep in the organic
soils [76 cm (30 in)] (76 cm) illustrate a direct relation-
ship to phosphorus concentration.
16. The microbial activity in the wetland appears to be the
initial and most important mechanism for removing phos-
phorus from the soil water solution.
17. Phosphorus appears to be the limiting nutrient during the
summer when microbial growth conditions are optimum.
18. Dewatering of the pilot zone produced approximately 2.4
times the vegetative mass produced in the control zone.
19. The biological assessments detected no environmental im-
pacts on the wildlife or vegetation type and abundance as
a result of this project.
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SECTION 3
RECOMMENDATIONS
1. A general policy of wetland preservation and phosphorus re-
moval with non-structural treatment methods should be adopt-
ed.
2. The drainage from selected wetlands should be managed and
possibly be aerated before allowed to discharge to the re-
ceiving body.
3. Careful consideration must be given to the distribution of
stormwater to wetlands.
4. The Wayzata wetland study should be continued to determine
nutrient transformations, ammonia to nitrate conversion, the
phosphorus capture mechanisms and the hydrologic balances.
5. Additional research and uniform procedures are required in
the following areas:
a. Define the various factors of the hydrologic budget of
wetlands including evapotranspiration rates, evapora-
tion rates and groundwater movement.
b. Define the microbial activity during aerobic and anaerobic
conditions for typical wetland types.
c. Define the importance of the plant growth cycle and water
level management techniques or changes in effluent water
quality.
d. Define the treatment life expectancy of the wetland and
its benefits and costs in stormwater treatment.
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SECTION 4
BACKGROUND
During the calendar years of 1974 and 1975 the Minnehaha
Creek Watershed District, in cooperation with the Environmental
Protection Agency, implemented a rigorous study designed to de-
termine the impacts of urban stormwater runoff on the wetlands
of the District.
A wetland has been defined in the new "Interim Classifica-
tion of Wetland and Aquatic Habitats of the United States", by
the United States Fish and Wildlife Service (1), as... "land
where the water table is at, near or above the land surface
long enough each year to promote the formation of hydric soils
and to support the growth of hydrophytes, as long as other en-
vironmental conditions are favorable".
The specific wetland site was selected because it, in the
opinion of the researchers, best approximated a typical wetland.
See Figure 1, Location Map - Minnehaha Creek Watershed District,
for the location of the watershed in reference to the Minne-
apolis - St. Paul Metropolitan area and Figure 2, Photographic
Views of Lake Minnetonka and the Wayzata wetland.
The Minnehaha Creek Watershed District encloses 47,760 ha
(184 sq mi) on the western edge of the Twin Cities Metropolitan
area and, since its formation, has been charged with the pro-
tection of the resources of the watershed. Consequently, it
would naturally follow that the Minnehaha Creek Watershed Dis-
trict Board of Managers would seek definitive answers to the
following questions:
1. What role do wetlands play in the watershed's hydro-
logic cycle?
2. What is the character of the runoff entering the wet-
lands?
3. What impact does the runoff have on the wetlands?
4. What impact do the wetlands have on the quality of
the runoff waters?
5. Can wetlands be managed in order to enhance the quality
6
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MOUND FILTE
PLANT
j ti
Figure 1. Location Map - Minnehaha Creek Watershed District
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a. Lake Minnetonka
b. Wayzata Wetland
Figure 2. Photographic Views of Lake Minne-
tonka and the Wayzata Wetland
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of discharge waters?
It was the objective of this project to provide answers to
the above questions as completely as possible and in a form that
would assist others in the wise and prudent use of wetlands.
OBJECTIVES
The wetland project had three specific objectives that
would dictate the wetland selected and formulate the study ap-
proach. Those objectives focused in these principal areas:
1. Identification and characterization of the watershed
ecosystems including the hydrologic balance and the
nutrient balance.
2. Interaction of hydrologic and nutrient balances with
the wetland ecosystem including water level, microbial
activity and nutrient discharge.
3. Implementation and evaluation of a controlled wetland
ecosystem including microbial activity, nutrient bal-
ance and impacts.
METHOD OF APPROACH
The above objectives were accomplished in six major tasks,
as follows:
Task I. Develop a planning and control technique for the
entire project.
Task II. Select a wetland for the project and acquire ac-
cess rights.
Task III. Design, purchase, construct and install the in-
strumentation and modifications to acquire the required
data.
Task IV. Collect and analyze data, perform environmental
assessments, modify data acquisition systems, review data
for completeness and collect additional data.
Task V. Data evaluation, statistical data analyses and
development of hydrologic and nutrient balances and models.
Task VI. Prepare a final report.
These task breakdowns were used to develop a comprehensive
work plan which was used and refined as the project progressed.
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SITE SELECTION
In view of the project scope, selection of a suitable wet-
land was critical. It was paramount that all parameters in the
watershed ecosystem be identified and controlled.
A program dealing with the implementation and evaluation of
a controlled ecosystem and a wetland is defined in the previous-
ly mentioned interim classification. Therefore, an extensive
preliminary survey was made for several wetlands to select an
ideal wetland for the project.
Four wetland sites were evaluated as potential sites. The
final selection was based on 15 criteria. These criteria in-
cluded:
A. Essential Characteristics:
1. Defined wetland.
2. Variety of urban runoff quality (highway, shopping
center, commercial, residential, etc.).
3. Well defined watershed.
4. Well defined inlets.
5. Well defined outlets.
6. Public ownership.
7. Availability.
B. Desirable Characteristics:
1. Management size.
2. Accessibility.
3. Representative wetland for region (10:1 ratio).
4. Availability of suitable sampling points.
5. Groundwater level above lake level.
6. Sanitary sewered region.
7. Suitable wetland configuration for management and
control area.
8. Near laboratory facilities.
10
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The selection was based upon the highest composite score.
The scoring was as follows: Items 1 through 7 were given a value
range between 1 and 10 and items 8 through 15 were given a value
range between 1 and 5.
Major faults encountered in evaluation of the four wetlands
were: private ownership and poorly defined inlets and outlets.
Such wetlands were not acceptable for the project. The Wayzata
wetland site, which had the highest composite score, was chosen
for the study. See Figure 3, Location Map - Wayzata Wetland.
The Wayzata wetland is located in the heart of the City of
Wayzata (population 4,500) a suburb in the Minneapolis - St.
Paul Metropolitan area.
The wetland site is also located within the legal boundar-
ies of the Minnehaha Creek Watershed District and its drainage
is tributary to Lake Minnetonka.
11
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'%/jwATERSHiD
BOUNDARY
**)/*
**
WAYZATA
WETLANO
LAKE
MINNETONKA
Figure 3. Location Map - Wayzata Wetland
12
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SECTION 5
SITE DESCRIPTION
The total watershed system utilized in the Wayzata wetland
project consists of an area of 29.4 ha (72.6 ac). The total
sub-basin consists of 3.06 ha (7.55 ac) of wetland and 26.3 ha
(65.1 ac) of upland or tributary watershed.
SOILS AND GEOLOGY
The area of the wetland project is covered by glacial drift
deposited by the Grantsberg sublobe of the late Mankato Glacia-
tion. This drift is composed of relatively recent materials
derived through the rewashing of older deposits. The parent
material for soils of the wetland watershed is glacial till,
glaciolacustrine deposits and organic material.
Two major soils make up the wetland watershed, they are the
Hayden loam and the Cordova silty clay loam. The remainder of
the soils in the watershed consist of either hydric soils or
areas of cut and fill. See Figure 4, Soils Map, for the location
of the specific soils.
The Hayden series consists of deep, well drained, loamy
soils that formed in loamy glacial till. These gently sloping
to very steep soils are convex areas on knolls and hillsides as
shown in Figure 4.
The native vegetation was mixed hardwood forest. Much of
this forest has given to urbanization, however, several areas of
the watershed along the periphery of the wetland harbor trees
that appear to be remnants of the original hardwood forest.
Hayden soils have high available moisture capacity and
moderate permeability. The water table is at a depth below
1.5 m (5 ft) in all seasons. Hayden soils have low organic
matter content and medium fertility. The subsoil is generally
high in phosphorus.
The Cordova series consist of deep, poorly drained soils
that formed in loam glacial till. These soils are on broad
flats and in drainageways. As illustrated in Figure 4, the
native vegetation is mixed hardwood forest.
13
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LEGEND
CO
Cu
HbB
HBC
H1B
Ma
Data from Soil Conservation Service
Cordorva silty clay loam
Cut and fill land
Hayden loam, 2 to 6 percent slopes
Hayden loam, 6 to 12 percent slopes
Heyder complex, 2 to 6 percent slopes
Marsh
Figure 4. Soils Map
14
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Cordova soils have high available moisture capacity, inter-
nal drainage is slow, and the permeability is moderately slow.
During the wet periods, the water table is at a depth of 30.5 to
91 cm (1 to 3 ft). Fertility and organic matter content are
high.
The remainder of the soils in the wetland watershed are or-
ganic soils. At this particular site these soils are formed on
Glaciolacustrine deposits. The mineral soils underlying the
organic soils sediments are silty clay in the upper 61 to 150
cm (2 to 5 ft) and silt loam below that depth. The peat or or-
ganic soils of the wetland range in thickness from 15.0 cm
(0.5 ft) to over 6 m (19.7 ft). Values for the percent of or-
ganic matter of each separate soil profile are also shown. See
Figure 5, Stratigraphic Log of Wetland Soils, for a representa-
tive log of the organic soils.
The maximum percent organic matter occurs at a depth of
approximately 50 cm (1.7 ft). It is also interesting to note
that the percentage of organic matter at the 400 cm (13 ft)
depth is 32 percent. The peat is well supplied with calcium,
but it is low in content of available potassium and phosphorus.
The importance of the above information on soils will be-
come apparent when groundwater quality and quantity is related
to the soils.
TOPOGRAPHY
The topography of the area is a result of a melting gla-
cier. The depression forming the wetland is probably the re-
sult of stagnated ice. The actual wetland is centrally located
and surrounded by moderately rolling terrain. The maximum re-
lief is approximately 18.3 m (60 ft).
VEGETATION
The vegetation of the upland portion of the watershed
basically consist of natural wooded areas with oak, elm, bass-
wood, maple and ash as the main species. Urbanization has re-
placed most of the woods with lawns; however, with the excep-
tion of the fertilizer applied, the change in vegetation has
had little effect on the underlying soil.
The wetland has a dense growth of natural vegetation as
high as eight feet through the summer season which produces a
thick vegetative cover. See Appendix A for ecology evaluations.
Lush and varied, this vegetation is comprised of 38 species.
Reed canary grass, willows and dogwoods are most conspicuous.
Distribution of various other plant types is related to soil
moisture conditions within the wetland.
15
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Depth
Centimeters
50 —
100 —
150 —
200 —
250 —
300 —
350 —
400
450 —
500 —
Material
Peat, dark brown, fibrous
(Percent Organic
(Matter
69.4
Peat, orange -brown,
very fibrous
Muck, grayish, little fiber
Muck, black
Peat, brownish, fibrous, becomes
darker & less fibrous with depth
__ Muck, black
Muck, brown, trace of sand
__ Muck, light brown, silty
Silt, gray, some orange -brown
fibers
Clay, light gray, some sand
88.2
52.1
39.3
42.6
3.4
13.7
32.0
Figure 5. Stratigraphic Log of Wetland Soils
16
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Predominant vegetation in the wetlands include:
Grasses: Phlaris (reed canary);
Cattails: Typha latifolia;
Forbes: Equatorium pupureum (purple boneset),
Lythrum salicaria (purple loosestrife);
Trees and shrubs: Cprnus (dogwood), Salix (willows)
Ribes (black currant), and Sambucus
canadensis (elderberry)
DRAINAGE
The wetland is directly tributary to Lake Minnetonka and
has a total watershed area of 29.4 ha (72.6 ac). The subwater-
shed boundaries and drainage system are generally well defined
with rolling topography and urban development.
The watershed was divided into five drainage groups based
upon the degree of similarity of the various subwatersheds. A
total of 13 subwatersheds made up the five groups. See Figure 6,
Wayzata Wetland Watershed Boundaries.
Drainage Group I includes subwatersheds 1, 2, 5 and 7. It
has a total area of 8.57 ha (21.17 ac) or 29.9 percent of the
total watershed area. The watersheds are typically undeveloped
or have single family homes on large lots, and are heavily wood-
ed. A typical photographic view of Drainage Groups I - IV is
shown in Figure 7. This group has very low population density.
Drainage Group II includes subwatersheds 3, 4 and 11 and
has a total area of 5.03 ha (12.44 ac), 17.1 percent of the
total watershed. This group consists of single family homes on
small lots. See Figure 7. This group has the highest popula-
tion density of the wetland watershed.
Drainage Group III includes subwatersheds 6, 8 and 9 and
has a total area of 4.66 ha (11.52 ac), 15.9 percent of the
total watershed. This area is characterized by having approxi-
mately 50 percent occupied by small businesses located along a
major traffic corridor. See Figure 7. The remaining portion
consists of a very sparsely developed, heavily wooded area. A
total of 44 percent of this drainage group consists of impervious
cover material such as roofs, parking lots or highways.
Drainage Group IV includes subwatersheds 10 and 12 and has
a total area of 8.05 ha (19.88 ac), 27.4 percent of the total
watershed. The area is characterized by a major traffic corridor
(U.S. Highway 12). See Figure 7. A total of 55 percent of the
area in Group IV has an impervious cover.
17
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Source: Mark Kurd
Drainage Group
I
II
III
IV
V
Subwatersheds
1, 2, 5 & 7
3, 4 & 11
6, 8 & 9
10 & 12
13
Figure 6. Wayzata Wetland Watershed Boundaries
18
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a. Drainage Group I
b. Drainage Group II
Figure 7. Typical Photographic Views of
Drainage Groups I - IV
19
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c. Drainage Group III
d. Drainage Group IV
Figure 7. Continued
20
-------
Drainage Group V includes subwatershed 13, the wetland it-
self, and has an area of 3.06 ha (7.55 ac), 10.4 percent of the
total watershed.
Each drainage group has an associated runoff value at which
rate the subwatershed supplies runoff to the wetland.
Table 1 tabulates the amount of impermeable surface area in
each drainage group. Drainage Group I has the least amount of
impermeable area, 3 percent, and Drainage Group IV has the great-
est percent impermeable area with 55 percent. Approximately 26
percent of the total wetland watershed has impermeable surfaces,
either in private drives, roof tops, highways or shopping cen-
ters.
TABLE 1. WATERSHED CHARACTERISTICS - IMPERMEABLE AREA
Total Impermeable
Drainage Sub- Area Area
Group Watershed ha ha
Percent
Impermeable
I
II
III
IV
V
1,2,5&7
3,4&11
6,8&9
10&12
13
8.57
5.03
4.66
8.05
3.06
TOTAL 29.37
7.52
3
17
43
55
AVERAGE 26
GROUNDWATER
In the vast majority of wetlands, groundwater is the most
important physical and chemical factor of a particular wetland
ecosystem. It will be illustrated later in this report that the
local groundwater table is in intimate contact with the Wayzata
wetland.
The groundwater regime for the Lake Minnetonka area and
the wetland specifically is very complex in that the lake and
surrounding wetlands are hydraulically connected to the glacial
till aquifer. The groundwater gradient in the glacial drift of
the wetland watershed is toward the wetland, consequently, the
wetland is a point of groundwater discharge. See Figure 8,
Groundwater Contour Map.
The glacial till aquifer is also a source of a limited
amount of groundwater recharge for underlying artesian aquifers.
It has been estimated that vertical permeability of the glacial
till is in the order of 4.0 x (10)~7 to 3.6 x (10)~6 cm/sec
(0.01 to 0.08 gpd/sq ft) with an average value in the order of
1.3 x (10)~6 cm/sec (0.03 gpd/sq ft) (2). See Figure 9, Hydro-
logic Cycle.
21
-------
096.33
FLUME 4
96.61
FLUME
-^
\
O96.}|
FLUME 3
-A
PERIMETER OF WETLAND
X
\ _^
^-^:i1«*
NOTE: GROUNDWATER ELEVATIONS
ARE BASED ON LOCAL DATUM AND
ON APRIL 1975 MEASUREMENTS
QWATER EiEVA
/
WELl NUMBE
DIRECTION OF FLOW
Figure 8. Groundwater Contour Map
22
-------
A 06
I
1
\
3
(0
c
<0
'to
0>
*-<
k.
(0
O)
l_
0)
c
3
0
•H
O
>i
u
o
•H
t^
O
rH
O
M
Tl
(U
Cn
•H
23
-------
CLIMATOLOGY
The study area is close to the geographical center of the
continent; thus, the climate is predominantly the continental
type characterized by generally mild subhumid summers and rela-
tively long, severe winters. All climate features tend to ex-
tremes. Temperatures ranged from -36°C (-34°F) in January, 1936
and January, 1970 to 42°C (108°F) in July, 1936. Monthly pre-
cipitation ranged from a trace in December, 1943 to 20.4 cm
(8.03 in) in May, 1962. Abrupt changes in temperature and pre-
cipitation are common and are caused by the pressure systems
that cross from west to east. Because relief is low, topographic
influence on climate patterns is insignificant. Rainfall is
greatest during the summer, when it is most favorable for vege-
tative growth. The average growing season is 166 days. About
55 percent of the annual precipitation is during the period May
through August.
The seasonal areal distribution of precipitation is shown
in Figure 10, Monthly Precipitation Distribution Minneapolis -
St. Paul Area (1936-1975). The annual precipitation over the
wetland watershed area was computed to be 72 cm (28.3 in) during
the study period.
20 r—
10
I I I
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Time-Months
Figure 10. Monthly Precipitation Distribution Minne-
apolis-St. Paul Area (1936-1975)
24
-------
Evapotranspiration is highly dependent on climatic events
and is an important factor in the water resources of an area.
The United States Geological Survey utilized two methods to ob-
tain evapotranspiration values for use in a water budget for
the metropolitan area. Two methods were used, the Thornthwaite
and Manther method (3) and the energy balance (4).
The average annual evapotranspiration calculated for the
area was approximately 57.15 cm/yr (22.5 in/yr); the potential
evapotranspiration was approximately 62.23 cm/yr (24.5 in/yr).
The energy-balance method for determining evapotranspira-
tion yields a value of 57.15 cm/yr (22.5 in/yr) of evapotrans-
piration.
Because these values represent a substantial portion of
the total water budget, a complete climatological station was
installed in the marsh in order to determine if the micro-climate
of the marsh ecosystem was of the same order of magnitude as the
previously calculated volumes. The results of this climatologi-
cal station will be discussed in detail in the section on water
balance.
25
-------
SECTION 6
SITE DEVELOPMENT AND INSTRUMENTATION
Site development and instrumentation centered around ob-
taining quantitative data to establish the characteristics of
runoff and to construct a detailed nutrient and hydrologic bal-
ance for the wetland ecosystem.
The second aspect of site development and instrumentation
was to determine the effectiveness of the wetland management
area.
TRIBUTARY WATERSHED
A total of five 15.2 cm (6 in) parshall flumes were in-
stalled in the watershed. Four flumes were installed in repre-
sentative drainage systems that flow into the wetland. The par-
shall flumes were capable of gaging the flow from as low as
0.063 I/sec (1 gpm) to as high as 12.6 I/sec (200 gpm) and is
shown in Figure 11, Instrumentation of Watershed. The fifth
flume was installed at the outlet. Each of the inlet flumes were
equipped with automatic samplers and flow recorders so as to
record as many runoff events as possible. Preceding each flume
was a roughing filter of coarse gravel utilized to remove coarse
sediment from the runoff.
For pre-selected runoff events, the inlet flumes were
equipped with automatic water quality samplers set to sample
every 15 minutes with a one hour composite and a 28-hour capa-
city. A total of 33 runoff events were monitored. A flume
was installed at the outlet of the wetland area and was equip-
ped with a continuous water level recorder.
Sixteen 3.5 cm (1.4 in) outside diameter polyvinylchlo-
ride observation wells were installed in the wetland area and
ten observation wells were installed in the upland areas around
the wetland. A typical observation well is shown on Figure 11.
The depth of well installation varied between 1.2 m (3.9 ft)
and 5.5 m (18 ft) below land surface. The wells were sealed
with sheet plastic at the soil surface to prevent surface
seepage from entering the well. See Figure 12, Instrumenta-
tion of Wetland, for location of the observation wells within
26
-------
a. Inlet Flume - Drainage Group II
b. Typical Flume
Figure 11. Instrumentation of Watershed
27
-------
c. Observation Well 14
d. Wetland Weather
Station
Figure 11. Continued
28
-------
DIVIDER BOX
PILOT
II
ZONE 4
200 FT
61.0M
CONTROL
II
10 ZONE
11
o
100 FT
30.5M
200 FT
61.OM
OBSERVATION WELL
12
100 FT
30.5M
QCLIMATOLOGICAL STATION
= UNDER DRAIN
• OXIDATION REDUCTION PROBES
Figure 12. Instrumentation of Wetland
29
-------
the wetland area.
A complete weather station was installed in the wetland at
the transition of grasses to cattails and sedges to measure all
climatological parameters. Recording instrumentation included:
temperature-humidity recorder, precipitation gage, two U.S. Wea-
ther Bureau evaporation pans and two anemometers. See Figure 11.
Research indicates little is known about the micro-climate
of wetlands. The dense vegetation shades the underlying soil
and stifles the wind. The wetland is located in a depression
near Lake Minnetonka, a 5,700 ha (14,000 ac) water body. These
are important factors in determining evapotranspiration rates in
wetlands.
A unique climatological monitoring system was installed
utilizing two evaporation pans, one in the wetland and one in the
adjacent uplands. The wetland pan was installed in such a man-
ner that the bottom of the pan was always in contact with the
water table so that the temperature of the water in the evapora-
tion pan would approximate the wetland soil water temperature.
Two anemometers were installed at this site. A critical low
speed anemometer was placed at a height of 0.5 m (1.6 ft) and a
second anemometer at a height of 5.5 m (18 ft) above the wetland
soil surface.
Temperature and relative humidity recording devices were
also installed near the wetland evaporation pan.
The second evaporation pan was installed in a typical U.S.
Weather Bureau fashion in the uplands. A time driven automatic
precipitation recorder was maintained in the upland site and
precipitation was recorded in the wetland evaporation pan.
WETLAND MANAGEMENT AREA
The perimeter of the Wayzata wetland is subject to aerobic
states as the water level drops below soil surface between run-
off events and therefore suitable for the control of water
levels. Two inlets supply runoff to this area. This area is
sufficiently isolated so that slight modifications only were
needed to establish a controlled surface water system which could
be closely monitored.
Approximately one acre was designated as the study area.
A pentagon configuration was chosen for the study area to con-
form with the natural geography of the area. The area was sur-
veyed to establish water flow boundaries.
Half of the area was designated the pilot zone to be used
in the dewatering study, the other half to be used as a con-
trol zone. Water tables, soils and vegetation of the two areas
30
-------
are similar.
The study area was subdivided into twelve stations to ob-
tain more detailed observations of the water table and soil
activity. Eight stations each were designated for the control
and the pilot area. Four stations were located immediately
outside the perimeter of the study area to monitor the effects
of the water management process on the area outside. Figure 12
shows the layout of the control and monitoring instrumentation.
Oxidation-reduction potentials were determined by install-
ing five electrodes at 15 cm (0.5 ft) intervals at a depth of
2.5 m (8.2 ft) below the soil surface in the pilot station 3 and
control station 9.
Chambers to monitor carbon dioxide generated by the soil
bacteria were installed at twelve stations within the study
area. In situ chambers were constructed from 3.8 1 (1 gal)
glass jars with the bottoms removed. The jars were inserted
5 cm (2 in) into the soil. Surface vegetation was removed from
within the chambers to minimize the influence of carbon dioxide
assimilation by plants.
MODIFICATIONS
A system suitable for the programming of controlled water
levels was installed within the wetland. All construction was
performed manually so as to minimize the impact on the natural
wetland. Identical systems and methods were used to prepare
the control and the pilot zone.
The modifications included:
1. A polyethylene barrier was used to line the channels
from the parshall flumes to the wetland perimeter to
prevent water penetration into the ground so that all
recorded water volumes would enter the wetland as sur-
face water.
2. A polyethylene barrier was buried to a depth of 91 cm
(3 ft) surrounding the perimeter of the control and
pilot zone to prevent seepage from surrounding ground-
water.
3. A divider box constructed of untreated redwood was in-
stalled at the junction of the inlet with the wetland
to equally split water volumes to the control and pi-
lot zone or to direct the water flow as desired. See
Figure 13, Photographs of Instrumentation of Wetland.
4. An underdrain system of perforated plastic tiles was
installed 91 cm (3 ft) below the soil surface to
31
-------
a. Divider box
b. Perforated Plastic Underdrain •*
Figure 13. Photographs of Instrumentation of Wetland
32
-------
c. Sump
d. Sump Installed
Figure 3.3. Continued
\ *
33
-------
direct water to the control sump.
5. A sump constructed of 122 cm (48 in) corrugated pipe,
152 cm (5 ft) deep with a sealed bottom was placed
vertically in the ground to which the drain tiles were
connected through control valves. See Figure 13.
6. An electrical sump pump was installed in the sump to
pump water out of the dewatered area to a peripheral
wetland area. See Figure 13.
34
-------
SECTION 7
METHODOLOGY
MONITORING
Overview
Sampling and analysis was performed periodically to deter-
mine the water quality in various parts of the wetland system
from November, 1974 to October, 1975. The frequency of sampl-
ing and analytical parameters were determined from preliminary
sampling. Water quality and volumes were monitored for all water
flowing into the wetland, out of the wetland as well as the
groundwater within and around the wetland. Precipitation, evap-
oration, temperature, relative humidity and wind were monitored
during the study period.
An intensive evaluation of the soil activity and soil en-
vironment in the wetland was performed for a six month period,
June, 1975 through November, 1975. Parameters used to evaluate
the soil activity included direct counts of soil bacteria and
measurement of the generation of carbon dioxide by the soil
bacteria.
Special emphasis was placed on data collection during the
summer months of June, July and August, 1975, when the wetland
system is most active, and the sampling frequency was increased
during this period. The following paragraphs describe the moni-
toring which took place during the project.
Surface Water Quality
Discrete and flow composited samples of four wetland in-
lets during runoff events were collected and analyzed for total
coliform, total suspended solids, ammonia nitrogen, total
phosphorus, biochemical oxygen demand and oxidation reduction
potential (list A). A total of 130 runoff samples were col-
lected from 17 separate runoff events during the year November,
1974 - October, 1975. Selected composite samples of the runoff
were analyzed for iron, copper, lead, zinc and nickel (list B).
Samples of the discharge from the wetland were collected
and analyzed for the parameters in list A, November through
35
-------
freeze-up on December 7, 1974 on a daily basis. Daily sampling
was resumed April 7, 1975, spring thaw, and continued until
June 12, 1975. Six-hour composite samples were taken from June
12, 1975 through June 27, 1976 and twice daily (morning and
afternoon) samples were collected from July through October,
1975. Weekly composite samples from the wetland discharge were
analyzed for the list B parameters from April, 1975 to October,
Samples were collected from the sump of the pilot zone on
an hourly basis from June 16 through July 12, 1975 (dewatering
cycle I) and analyzed for the list A parameters. During (de-
watering cycle II) July, 1975 through November, 1975 two samples
were collected daily and were analyzed for the list A parameters.
Weekly composite samples from the sump were analyzed for the
list B parameters from June 16, 1975 through October, 1975.
Surface Water Quantity
Flows were recorded at the wetland inlets during 19 separ-
ate runoff events from May, 1975 to September, 1975.
Flow from the wetland outlet was recorded on a daily basis
during November and December, 1974 and April and May, 1975.
The flow was recorded continuously from June, 1975 to October,
1975.
The electrical consumption of the sump pumping system was
recorded on a daily basis during the month of July, 1975 to de-
termine the volume pumped during the dewatering process.
Groundwater
The observation wells in the pilot and control zones were
sampled and analyzed for the list A parameters 18 times. The
observation wells were sampled monthly from November, 1974
through April, 1975, twice per month during May and June, 1975
and weekly during July and August, 1975.
Groundwater levels were measured at the observation wells
in the pilot and control zones twice a month from November, 1974
to June, 1975, daily during June, 1975 and three times a week
from July, 1975 to August 13, 1975. The groundwater level of
the peripheral observation wells was measured during Julv and
August, 1975. ^ *
Soil Activity and Environment
Carbon dioxide generation was monitored at 12 stations four
days per week by 24-hour periods from June, 1975 to September,
1975. During October and November, 1975 carbon dioxide genera-
36
-------
tion was measured twice a week.
Weekly, carbon dioxide generation was measured by 72-hour
periods from July, 1975 to September, 1975.
Soil bacteria counts of surface soil samples were perform-
ed weekly from June, 1975 to mid-September, 1975. Two soil
bacteria counts were performed per month from mid-September, 1975
to October, 1975. Each of 15 stations was monitored 20 times.
Soil bacteria counts of subsurface soils were performed at
stations 4, 5, 6 and 10 from June 16, 1975 to September 11, 1975
on a weekly basis.
Soil temperatures were monitored at 12 stations on a daily
basis from July 7 to July 18, 1975. Twice per week soil tempera-
tures were measured during the period from July 21, 1975 to
September 25, 1975. During October and November, 1975 soil
temperatures were recorded weekly.
Oxidation reduction potential of soils was monitored for
stations 3 and 9 (see Figure 12) at five depths from July 7 to
July 21, 1975 on a daily basis. During the period from July 23
to August 13, 1975 the oxidation reduction potential was re-
corded three times per week.
Other Measurements
Precipitation, air temperature, relative humidity and wind
velocity data were recorded continuously from November, 1974
to October, 1975.
Pan evaporation data was continuously recorded from June,
1975 to October, 1975. Daily manual measurements were also
taken during July and August, 1975.
37
-------
SECTION 8
RESULTS
IDENTIFICATION AND CHARACTERIZATION OF THE WATERSHED
The identification and characterization of the watershed
can best be analyzed in three separate but related categories,
the hydrologic or water balance, the nutrient balance and the
resulting impacts on the wetland.
Water Balance
The water balance of the ecosystem consists of the follow-
ing parameters:
Water Inflows (Gains)
A-L = Precipitation directly on wetland
B-L = Runoff from the tributary watershed
Ci = Groundwater inflow
Water Outflow (Losses)
AQ = Evapotranspiration (transpiration and evapora-
tion) from the wetland
B0 = Discharge at outlet of the wetland
C0 = Groundwater seepage
If the above terms are arranged in the following equation,
the change in storage (AS) of water in the wetland can be de-
scribed:
(Ai + Bi + Cj.} - {AO + B0 + C0> = AS Eq. 1
It can be stated that the value for AS will approximate
zero because the water level in the wetland was the same at the
end of the study as at the start.
It must be pointed out that the long term AS for a particu-
lar wetland ecosystem will not be at equilibrium because re-
search has shown that a wetland in the region accumulates or-
ganic matter at a rate of approximately 1 cm (0.4 in) per year
(7), although the literature states a wide range of values
38
-------
-p
u
o
H
^
in
O\ >i
H nj
S
1
I
0)
c
HJ
O
Q
0
2
(0
Q
vo
CO
o
CM O 00 00
o co co co
H O O O
CM ^a1 in
in o o
in oo oo
in o o
^P 00 VO H
H H ^r vo
H O O CO
in o r>
CM CM CM
0 0 H
in co in
o H CM
o o o
o
H
0
o
t~- in vo co ^j1
O CM ^* O CTl
EH H o EH O CM O
EH EH
in oo co
CM in CM
O EH O O EH
H H
(Ti
in oo r~
o co •
• • o
o o
TJ« o co in in in
VO H CO CM H in
O 0 O 0 0 CO
o inococo CMO T
COH VOCMCMH OH CO
OO HOEHCMO HO CM
H
o in H co
H CM in CM
O EH O O 00
inocr\ocMCM vo H co
EHEH
-------
(8, 9, 10). Assuming that the organic soil contains 80 percent
moisture it can be seen that the system will not be at equili-
brium but will actually be storing water.
The three water inputs to the wetland are direct precipita-
tion, runoff and groundwater inflow and will be discussed in the
following paragraphs.
Direct Precipitation—
During the period from November 1, 1974 to October 31, 1975
a total of 77.7 cm (30.6 in) of precipitation fell directly on
the wetland as shown on Table 2. This is 5.8 cm (2.3 in) above
the 31 year normal. Of the total precipitation, 78 percent fell
during the period April through August.
The precipitation falling directly on the wetland, 3.06 ha
(7.55 ac) contributed a total of 2.38 ha-m (19.3 ac-ft) of
water to the water balance.
Runoff—
The average runoff coefficient for the entire watershed
tributary to the wetland was 0.156.
The runoff coefficients ranged from 0.071 for Group I to
a high of 0.32 for Group IV. See Figure 5 for the location of
each drainage group and also Table 3 for areas and average run-
off coefficients.
TABLE 3. RUNOFF COEFFICIENTS
Drainage
Group
I
II
III
IV
ha
8.57
5.03
4.66
8.05
Area
ac
21.17
12.44
11.52
19.88
Percent of
Tributary
Watershed
33
19
18
31
Runoff
Coefficient
0.07
0.09
0.09
0.32
Average for total tributary watershed - 0.156
Utilizing these general coefficients of runoff, a total of
3.19 ha-m (25.9 ac-ft) of water was added to the wetland water
balance equation via surface runoff.
Groundwater Inflow—
The groundwater inflow into the wetland comes from basin
storage and remains relatively constant.
40
-------
In order to determine the groundwater contribution to the
wetland area a flow net analysis was conducted using the follow-
ing equation:
Q = KiA Eq. 2
Q = Flow, I/day (gpd)
K = Coefficient of permeability cm/sec (gpd/ft )
i = Hydraulic gradient
A = Cross sectional area through which flow occurs
Permeability tests were conducted on two representative
groundwater monitoring wells. The results of these tests indi-
cate that permeability of till was in the order of 5 x 10"4
cm/sec (10.64 gpd/ft^).
A review of the groundwater levels recorded at the monitor-
ing locations during the study period illustrates that the
groundwater gradient tributary to the wetland remained relative-
ly stable at approximately one percent. See Figures , page 22.
Using these values in equation 2, the average daily ground-
water contribution to the wetland is approximately 0.38 - 0.50
I/sec (6-8 gpm) or 1.20 ha-m (9.7 ac-ft) annually.
The permeability of the organic soils was not considered as
a factor in the groundwater contribution because much of the or-
ganic soils consisted of very fibrous peat which was extremely
permeable typical to those values reported by Boelter (11).
Using a method developed by Kunkle (12) it is possible to
separate basin storage discharge or groundwater inflow from the
annual hydrograph. Two assumptions are made in constructing the
line separating basin-storage discharge from the other runoff
components. First, the minimum discharge values at the beginning
and end of the groundwater year are assumed to represent ground-
water discharge from basin storage. This assumption is based on
the premise that at the beginning and end of the groundwater
year, groundwater storage is at a minimum. Therefore, bank
storage has been depleted and, provided that there has been no
recent precipitation, all the discharge is coming from basin
storage. The second assumption is that groundwater discharge
from basin storage varies only to a minor extent throughout the
groundwater year and that fluctuations tend to cancel one
another.
The second assumption is most valid for the typical ground-
water year. During a typical groundwater year the amount of dis-
charge is closely balanced by an equal amount of recharge. This
phenomenon is observed when the minimum discharge values at the
beginning and end of the groundwater year are very nearly equal.
This fact is also exhibited by the relatively constant ground-
41
-------
water gradient in the till tributary to the wetland.
Figure 14, Hydrograph - Wetland Discharge, illustrates the
daily discharge plotted on a semi-logarithmic scale. This il-
lustration was used to evaluate the groundwater inflow and wet-
land responsiveness to precipitation.
The dashed line connecting the low flow at each end of the
study period represents the groundwater discharge into the wet-
land. This value is approximately 0.38 I/sec (6 gpm) or 1.19
ha-m (9.7 ac-ft) annually and agrees well with the groundwater
contribution calculated from the flow net analysis.
The study period, November 1, 1974 - October 31, 1975, was
chosen because it represented a groundwater year as illustrated
by Figure 14. During November, 1974, September, 1975 and Octo-
ber, 1975 the discharge from the wetland stabilized at approxi-
mately 0.38 I/sec (6 gpm).
In summary the total water inputs to the wetland ecosystem
water budget for the groundwater year is as follows:
Precipitation 2.38 ha-m 19.3 ac-ft
Surface Runoff 3.19 ha-m 25.9 ac-ft
Groundwater Inflow 1.20 ha-m 9.7 ac-ft
6.77 ha-m 54.9 ac-ft
Therefore, the total water input equalled approximately
6.77 ha-m (54.9 ac-ft) from November 1, 1974 through October
31, 1975.
The second portion of the water balance consists of deter-
mining the water losses from the wetland. These losses occur as
evapotranspiration, groundwater seepage and discharge from the
wetland outlet.
Evapotranspiration Losses—
Since the wetland is located in a depression, it was decided
to instrument the watershed with data collection equipment that
would provide the necessary input to calculate the evapotrans-
piration rate using the Penman method (13).
The Penman equation is based on a complete theoretical ap-
proach, showing that evapotranspiration is inseparably connected
to the amount of radiative energy gained by the surface. See
Appendix D for equation.
Results of the wetland evaporation pan were somewhat star-
tling in the fact that the evaporation values during the height
of the growing season departed substantially from evaporation
42
-------
(1)
.a
o
w
•H
Q
CD
St
tn
O
}-i
TJ
ffi
MOld
•H
CM
43
-------
rates recorded by the University of Minnesota, St. Paul, some
55 km (34 mi) away.
The values recorded during the entire year show little ag-
reement with the exception of a general decline during the sea-
son. The University of Minnesota values were substantially
higher. Figure 15, Evaporation Pan Data - Wetland vs. Univer-
sity of Minnesota, St. Paul, illustrates the difference in
evaporation rates. It is of interest to note that the two
stations responded almost the opposite to the wet period during
May and June, 1975 with wet periods tending to reduce the
University values for this period, whereas the values for the
wetland increased. The increase in the rate of evaporation in
the wetland may be due to a general warming as a result of the
runoff entering the wetland. During the period July to mid-
September both stations showed the same response to the climatic
conditions. However, a sharp increase in the rate of evapora-
tion was recorded at the University of Minnesota station from
mid-September through October, whereas the wetland pan con-
tinued to decline. There is no apparent explanation for
this difference in response to climatic conditions.
20
15
10
o
c
o
+•>
03
I
to
111
c
to
a.
/ Climatological Year
1975 University of
Minnesota Pan,
St. Paul Campus
Wayzata
Wetland Pan
_L
_L
_L
_L
JL
_L
JL
J
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Time-Months
Figure 15. Evaporation Pan Data - Wetland vs. University
of Minnesota, St. Paul
44
-------
The total evaporation from the wetland during the period
November 1, 1974 to October 31, 1975 was 64.3 cm (25.3 in). It
was not possible to compare this value directly with the Univer-
sity of Minnesota station because many of the months used in
this study were not recorded at the University of Minnesota
station. At the end of May the vegetation was approximately
30 cm (12 in) in height, consequently, the vegetation probably
had less effect on the rate of evaporation; however, as the
season progressed, the height of vegetation has an apparent in-
verse effect on the rate of evaporation from the wetland.
Utilizing the Penman equation (see Appendix D), the calcu-
lated rate of evapotranspiration for the wetland was approximate-
ly 58.59 cm (23.06 in) during the 1975 growing season. Table 4
gives a complete list of coefficients utilized to calculate the
rate of evapotranspiration for the wetland.
TABLE 4. EMPIRICAL COEFFICIENT - PENMAN EQUATION
Time
(month)
Radiation
(cal/cm~l
day-2)*
Relative
Humidity
(percent)
Maximum
Possible
Sunshine
(hours)*
Average
Wind
Velocity
(MPH-18ft)
Average
Monthly
Temperature
April
May
June
July
Aug.
Sept.
Oct.
807.5
913.3
997.1
928.4
810.8
663.8
467.1
70.0
60.0
68.9
58.7
66.6
69.8
58.0
13.5
14.9
15.6
15.3
14.1
12.6
11.0
11.2
9.7
8.9
9.0
7.8
8.4
9.4
3.8
15.5
20.4
24.6
22.0
14.3
12.1
*Source; U.S. Weather Bureau - Minneapolis-St. Paul Airport
Table 5 indicates the values of evapotranspiration at the
Wayzata wetland. This value agrees with the values (55.9 - 59.4
cm) estimated for the area by the United States Geological Sur-
vey. As a result of this work and work by Lawrence (14), it
should be pointed out that there is a need for research in this
aspect of a wetland water budget. It was apparent to workers
in the wetland that noticeable differences in relative humidity
existed within the wetland depending upon the type of vegeta-
tion present. The wetland area appeared to contain hot spots.
These observations were also made by Lawrence. Empirical for-
mulas utilized to calculate the rate of evapotranspiration can
vary as much as 100 percent depending upon where and how the
data is gathered in a given wetland. Daily pan evaporation
values for the wetland indicated stable conditions in that there
was little day to day fluctuation. The wetland evaporation ap-
peared to respond more to seasonal warming and cooling. The
wetland evaporation pan was in contact with the soil water sys-
tem and closely approximates the actual role of evaporation.
45
-------
TABLE 5. EVAPOTRANSPIRATION - WAYZATA WETLAND
Evapotranspiration Evapotranspiration
Month (centime te r s)
April
May
June
July
August
September
October
5.10
9.78
11.38
14.04
9.17
5.36
3.76
58.59
2.01
3.85
4.48
5.53
3.61
2. 11
1.48
23.07
Given an evapotranspiration rate of 58.59 cm (23.07 in) from
a wetland area of 3.06 ha (7.55 ac) a total of 1.79 ha-m (14.52
ac-ft) of water was lost from the wetland through evapotranspira-
tion during the growing season, April 1, 1975 to October, 1975.
Groundwater Losses—
It can be assumed that there are no significant groundwater
losses from the wetland because groundwater contour maps pre-
pared from monitoring well data indicate that the wetland area
is a point of discharge for the local glacial till. Figure 8,
page 22, illustrates the direction of flow. Consequently, the
groundwater losses are considered zero in the water balance
equation.
Surface Discharge—
A parshall flume with a continuous water level recorder was
installed at the outlet of the wetland. A total of 5.44 ha-m/yr
(44.17 ac-ft/yr) of water was discharged from the wetland through
the outlet. See Table 6 for monthly totals, and Figure 10, page
24, for daily variations in discharge.
It is of interest to note the impact the hot, dry summer had
on the discharge for the wetland. As can be seen from Figure 14,
page 43, periods during early June, July and August, 1975 the
evapotranspiration rate exceeded the groundwater recharge rate
consequently reducing the minimum flow to less than the esti-
mated base flow of approximately 0.33 I/sec (6 gpm).
The total water losses from the wetland ecosystem are as
tollows:
Evapotranspiration (E.T.) 1.79 ha-m 14.52 ac-ft
Discharged at Wetland Outlet 5.44 ha-m 44.17 ac-ft
7.23 ha-m 58.69 ac-ft
46
-------
TABLE 6. WETLAND FLOW DISCHARGE
Discharge
Year
1974
1974
1975
1975
1975
1975
1975
1975
1975
1975
1975
1975
*0utlet
some
Hectare-meter
Month (ha-m)
November
*December
* January
*February
*March
April
May
June
July
August
September
October
either completely frozen or
portion of the above months
0.13
0.002
—
—
0.015
1.69
1.19
1.48
0.43
0.33
0.09
0.08
5.437
frozen for
Acre-feet
(ac-ft)
1.06
0.02
—
—
0.12
13.70
9.69
11.98
3.49
2.69
0.75
0.67
44.17
Storage—
Utilizing water balance Equation 1, page 38 /
Precipitation + Runoff + Groundwater - Outflow = Balance (AS)
{2.38 + 3.19 + 1.20} - {1.79 + 5.44} = 0.46 ha-m
it appears that 0.46 ha-m (3.45 ac-ft) was removed from wetland
storage during the study period.
Nutrient Balance
The same basic equation utilized in the water balance is
also applicable to use in the nutrient balance.
The following factors are considered part of the wetland
nutrient balance.
Nutrient Inflows (Gains)
Aj[ = Nutrients in the precipitation directly on wet-
land
Bi = Nutrients in the runoff from tributary watersheds
Ci = Nutrients in the groundwater inflow
47
-------
Nutrient Outflow (Losses)
A0 = Nutrients in the evapotranspiration from the
wetland
B0 = Nutrients in the discharge at the outlet of the
wetland
Co = Nutrients in the groundwater seepage
DO = Nutrients in materials removed from the wetland
Unlike the water balance, nutrient losses from evapotrans-
piration and groundwater seepage are not factors in the total
nutrient budget. No known nutrients are lost from the wetland
as a result of evapotranspiration and no materials were removed
from the study wetland. Groundwater discharges to the wetland,
therefore, there is no groundwater seepage from the wetland.
Consequently, the nutrient balance would be as follows:
{Ai + Bi + Gil - B0 = AS Eq. 3
It is one of the primary objectives of this report to de-
termine the relative value of AS. It has been assumed simply
because of the accumulation of organic matter that AS will show
a net gain in nutrients in the wetland. However, the relative
magnitude of change in AS is the important aspect of the study.
Precipitation—
Research has indicated that precipitation contains small but
finite amounts of potential nutrients.
A number of studies (15, 16, 17, 18) indicates that the
total phosphorus occurring in precipitation varies between 0.002
mg/1 to 0.03 mg/1. With the exception of the data collected by
Krupa (18), the above results were obtained from relatively un-
developed areas.
Assuming a mean concentration of 0.03 mg/1 for phosphorus,
0.75 mg/1 for ammonia nitrogen concentration and 1 mg/1 for
total suspended solids, the following nutrients were added to
the wetland nutrient budget by precipitation:
phosphorus, 0.7 kg/yr (1.6 Ibs/yr);
ammonia nitrogen concentration, 17.8 kg/yr (39.3 Ibs/yr);
and total suspended solids, 24 kg/yr (52 Ibs/yr)
Runoff Quality—
The quality of the runoff water which reaches the wetland
from the area tributary is variable, and appears to be a func-
tion of land use (impermeable area) and season of the year.
In terms of land use, drainage group II consists of single
48
-------
family, small lots and the highest average concentration of
total phosphorus and ammonia nitrogen concentration of the four
drainage groups tributary to the wetland area. Whereas drainage
group IV, shopping centers, etc. (56 percent impermeable) had the
lowest average concentration as shown in Table 7.
TABLE 7. COMPARISON OF STORMWATER RUNOFF QUALITY
SPRING, 1975
SUMMER, 1975
FALL, 1975
Drainage TP NH3-N TSS TP NH3-N TSS TP NH3~N TSS
Group mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 mg/1
I 2.2 3.33
II 2.4 3.87
III 2.0 2.85
IV 1.9 2.55
Average 2.1 3.15
780
559
580
614
633
NOTE: Above concentrations
0.
0.
0.
0.
0.
37
73
22
09
35
are
4.
5.
5.
2.
4.
13
44
13
86
39
1200
3800
374
200
1394
0.
0.
0.
0.
0.
30
42
22
25
30
4.
4.
4.
3.
4.
33
97
00
81
28
70
60
68
100
75
based on weighted values
calculated from specific runoff events that occurred
during the study period.
TP = Total phosphorus
NH3-N = Ammonia nitrogen
TSS = Total suspended solids
Because of the weather that was experienced during the win-
ter of 1974-1975, no runoff occurred from December until April,
consequently, quality values were not assigned for a winter
period but were included in the spring values.
As can be seen from Table 7, a great deal of variation
occurs in the quality of runoff water as a result of seasonal
ranges. The highest phosphorus values were recorded during the
April runoff which included the time period December through
May, with the greatest concentration running off with early
rains and snow melt. However, as illustrated by Figure 16,
Pollutograph of May, 1975 Storm Drainage Group II Subwatershed
II, high levels of phosphorus still occurred late in May.
During the summer months, June through August, the level of
phosphorus in the runoff dropped substantially. However, the
relative position of the various drainage groups in respect to
total concentration remained the same with Group II still showing
the highest values.
The phosphorus values during the fall months, September
through November, generally equalized for all of the drainage
groups.
Drainage Group II recorded the highest average concentra-
49
-------
000
TOTAL SUSPENDED SOLIDS (TSS)
i N. I I 1
50 60 70 80 90 100
AMMONIA NITROGEN (NH3)
,0 20 30 40 50 60 70 80 90 100
20 2 2 20
10 1 1 10
0000
Figure 16. Pollutograph of May, 1975 Storm -
Drainage Group II, Subwatershed II
50
-------
tion for ammonia nitrogen concentration, during the spring sea-
son, however, during the summer and fall season, this correla-
tion did not exist.
A comparison of annual quantities of pollutants delivered
to the wetland by the various drainage groups is presented in
Table 8.
TABLE 8. COMPARISON OF ANNUAL POLLUTANT LOADS
TotalAmmoniaTotal Suspended
Drainage Phosphorus Nitrogen Solids
Group (kg/ha/yr) (kg/ha/yr) (kg/ha/yr)
I 0.11 0.34 84
II 0.17 0.54 241
III 0.13 0.47 54
IV 0.39 1.13 163
Weighted Average 0.21 0.64 133. 8
Drainage Group IV, shopping centers, has the highest annual
contribution of nutrients followed by Drainage Groups III, II and
I, respectively.
Keup (19) reviewed the sources of phosphorus in flowing
water based on the contributing watershed area, and found the
areal contribution to vary between 0.001 and 0.026 kg/ha/yr
(0.006 and 0.14 Ibs/ac/yr). In general, the more densely popu-
lated agricultural areas of the Midwest were highest.
The average phosphorus value of the runoff from the study
area is 0.21 kg/ha/yr (1.13 Ibs/ac/yr). This agrees with the
findings by Keup and also results by Sorenson (20). Sorenson's
findings indicate that the average annual contribution to French
Lake, a drainage area approximately 5.6 km (3.5 mi) west of the
project area, was approximately 0.21 kg/ha/yr (1.13 Ibs/ac/yr).
The French Lake watershed is similar to the Wayzata wetland
watershed.
Groundwater Contribution—
As illustrated earlier, the groundwater contribution to the
wetland area remained relatively constant during the entire
period of investigation. However, the values for phosphorus and
ammonia nitrogen concentration were variable.
Groundwater quality tributary to the wetland was establish-
ed from observation wells located up gradient from the wetland
and in mineral soils. See Figure 12, page 29, for location of
the observation wells.
51
-------
The phosphorus values recorded in the observation wells
varied from a low of 0.06 mg/1 to a high of 18.0 mg/1 with an
average value of 2.2 mg/1.
As mentioned earlier, the soils that make up the tributary
watershed were deposited by the Grantsberg sublobe, a material
naturally high in phosphorus.
Routine groundwater sampling of shallow wells in the Lake
Minnetonka area commonly encounter wells having phosphorus values
in this range (21).
The ammonia nitrogen concentrations in the observation
wells varied from 1.9 mg/1 to 30.0 mg/1 with an average value of
8.3 mg/1.
As a result of those observations it has been calculated
that the groundwater inflow supplied 26.6 kg (58.7 Ibs) phos-
phorus and 100.5 kg (221.6 Ibs) ammonia to the wetland during
the period of study.
Total suspended solids were not determined for the ground-
water contribution because the observation well screen (slotted
pipe) would not effectively screen the organic soil out during
pumping. The normal contribution from this source is low. The
total nutrient inflow into the wetland as a result of direct
precipitation, stormwater runoff and groundwater discharge for
ammonia, phosphorus and total suspended solids is shown in
Table 9.
TABLE 9. ANNUAL NUTRIENT INFLOWS
Phosphorus
Ammonia-N
Total Suspended
Solids
Precipitation
Surface Runoff
Groundwater
kg/yr
0.7
33.8
26.6
Ibs/yr
1.6
74.6
58.7
kg/yr
17.8
103.3
100.5
Ibs/yr
39.3
227.8
221.6
kg/yr
24
17010
Ibs/yr
52
37500
Total Inflow 61.1
Nutrient Outflow—
134.9
221.6
488.7 17034 37552
As expressed in the nutrient balance equation, the only
means by which nutrients leave the wetland is in the discharge
water passing through the outlet.
Discharge flows were recorded and water quality sampling
and analyses were performed. Nutrient quantities have been de-
termined from composite samples as shown in Table 10.
52
-------
TABLE 10. DISCHARGE QUANTITIES FROM WAYZATA WETLAND
NOVEMBER, 1974 - OCTOBER/ 1975
Month
NOV
DEC
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
Total
Phosphorus
(kg)
0.29
0.004
0.02
3.28
2.56
4.38
2.09
0.38
0.05
0.14
13.19
Ammonia
Nitrogen
(kg)
1.36
0.04
1.00
73.95
85.47
103.01
44.20
6.91
2.01
1.31
319.26
Total Suspended
Solids
(kg)
36.48
1.33
0.47
209.31
213.19
176.90
240.41
120.75
8.48
17.65
1024.97
Water
(kg(10)6)
1.31
0.03
0.15
16.84
11.96
14.77
4.30
3.32
0.93
0.82
54.43
The table illustrates the monthly discharge of phosphorus,
ammonia nitrogen concentration and total suspended solids from
the Wayzata wetland. The seasonal variations are very similar
to those exhibited in runoff quality. Figure 17, Relationship
of Wetland Outflow, Ammonia Nitrogen Concentrations and Total
Phosphorus Concentrations, shows the relationship to outflow,
ammonia nitrogen concentration and total phosphorus to time.
Removal—
Completing the nutrient balance for phosphorus it can be
illustrated that for the study year, November, 1974 through
October, 1975, 78 percent of all phosphorus entering the wetland
was retained in some form. Net gain in wetland is calculated to
be 47.9 kg/yr.
The ammonia nitrogen balance indicates that greater quan-
tities of ammonia nitrogen left the wetland than entered the
system. Net loss from the wetland would be 97.3 kg/yr.
The results of the ammonia nitrogen values will be dis-
cussed in greater detail in the following section, however, it
appears that the increased ammonia nitrogen in the discharge
water is the result of the transformation of nitrogen compounds.
Completing the balance for total suspended solids shows
that 94 percent of the total suspended solids entering the wet-
land system are retained, i.e., 16,009 kg/yr.
The total suspended solids component of urban stormwater
runoff is often the parameter which exceeds effluent limitations,
53
-------
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54
-------
therefore, the removal efficiency is an important aspect of the
wetland system.
Heavy Metals—
The average concentrations of heavy metals; zinc, lead,
copper and cadmium for the stormwater runoff and the outlet from
the wetland are shown in Table 11. The table shows that the
runoff from highway and shopping center land use has signifi-
cantly higher concentrations of all the metals than the unde-
veloped and large residential land use. The table also shows
the average concentrations of the metals in discharge from the
wetland. The reduction in concentration of all the metals but
cadmium appears significant.
TABLE 11. COMPARISON OF AVERAGE HEAVY METAL CONCENTRATIONS
Drainage
Group
Zinc
yg/i
Lead
yg/i
Copper
yg/i
Cadmium
yg/i
I - Undeveloped and resi-
dential large lots
II - Single family on
small lots
III & IV - Highway and
shopping center
Wetland Outlet
10
11
15
2.2
26
26
71
2.5
12
19
19
3.3
0.4
0.9
1.4
0.3
Wetland Ecosystem
The interactions of the water and nutrient balances within
the wetland ecosystem including water level, water quality, nu-
trient discharge and microbial activity are discussed in this
section.
The Wayzata wetland exists because the rate of deposition
of organic matter exceeds the rate of decomposition.
It has been established (7) that the rate of accumulation of
organic matter in a wetland at a similar stage of development
was approximately 1.3 cm/yr (0.5 in/yr).
It should be recognized that the rate of peat accumulation
is not a uniform process but rather depends on many factors,
each of which influences the rate and amount of accumulation.
Soper (22) concluded that in the lake states region of the
United States, organic deposits which accumulate in ponds or
lakes generally go through the following succession stages:
1. Stonewort-waterweed stage (Chara-Philotria associes),
2. Pondweed-water lily stage (Potamogenton-Nymphaea
55
-------
associes),
3. Rush-wild rice stage (Scirpus-Zizania associes),
4. Bog-meadow stage (Carex associes),
5. Sphagnum-bog heath stage (Andromeda-Ledum associes),
6. Tamarack-spruce stage (Larix-Picea associes).
The rate of deposition of organic matter is considerably
slower in the first three pond stages than in the latter three
bog stages. Accumulation of organic matter reaches its great-
est rate in the sphagnum-bog heath stage. The Wayzata wetland
is nearing the end of the bog-meadow stage.
Groundwater or saturated soil conditions and the resulting
control they have on the microbial activity and the decomposi-
tion of the organic matter is in part the cause for the exist-
ence of the wetland.
With increased activities of man, the wetland condition has
been altered by a restriction that has been formed by the con-
struction of LaSalle Avenue along the southern boundary with an
outlet consisting of 25 cm (10 in) clay tile. The result of
these alterations is to generally lower the normal seasonal
water level, resulting in greater stormwater storage capacity.
To some degree, this increases the retention time of the storm-
water in the wetland, however, resulting water level fluctuation
is in excess of those that occurred naturally. The fluctuation
is illustrated in Figure 18, Groundwater Fluctuation - Observa-
tion Well 1.
Groundwater observation well 1 is located near the entrance
of the pilot zone and has a ground elevation of 29.2 m (95.80
ft). This is approximately 0.70 m (2.3 ft) above the invert
elevation of the outlet flume.
As illustrated in Figure 18, the groundwater levels in the
wetland are very responsive to precipitation and runoff events.
The maximum fluctuation recorded during the study period was
0.46 m (1.5 ft) from a low elevation on December 30, 1974 to a
high elevation on June 17, 1975. The water level elevations re-
corded at observation well 1 were generally 0.31 m (1 ft) above
those recorded at the outlet, indicating a hydraulic gradient of
approximately 0.0014.
The wetland or organic soils are the result of the deposi-
tion of plant and other organic material at a rate greater than
the decomposition rate. These plant materials when first de-
posited contain substances readily used and hence rapidly de-
composed by microorganisms to meet demands for the carbon and
energy needed in their growth. With the readily available
components used up in a few days to a few weeks, the bulk of the
residues are degraded or partially degraded at a slower rate.
Cellulose components, for example, are broken down relatively
56
-------
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L»
^^
LU
UJ
LL
_J
UJ
UJ
_J
DC
UJ
5
£
95.80
95.60
95.40
9520
95.00
94.80
*
94.60 -
94.40 -
94.20 -
94.00
Ill
I I I i
NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT
Time -Months
Figure 18. Groundwater Fluctuation - Observation
Well 1
completely and rapidly, whereas lignin and lignified material is
modified slowly over periods of months and years. The more re-
sistant organic matter which thus slowly accumulates serves as
not only the nutrient base for microorganisms, but a physical
base as well. Root penetration into the accumulating organic
matter provides microorganisms with more available organic
materials than leak out of the roots or are contributed when
roots die. Roots also serve to introduce oxygen into the or-
ganic environment close to the root surfaces.
The high moisture content and the compact structure of the
organic soil allow surface layers to become slowly aerated as
the water table drops. Under these conditions fresh organic
matter is utilized by aerobic microorganisms with concomitant
consumption of oxygen, leading to the depletion of oxygen in the
saturated organic soil. With oxygen consumed and respiratory
carbon dioxide released, the saturated organic soil becomes
anaerobic, and the microbiological activity is continued only
by those forms that can grow in the absence of oxygen.
57
-------
Anaerobic metabolism results in only partial decomposition
of the organic environment, and it follows that the fresh resi-
dues of one year become deposited on the still only partially
degraded remnants of previous years.
The microbial population of the wetland is in equilibrium
with the organic soil environment. The equilibrium is manifest-
ed in terms of population density, the magnitude of which is de-
termined largely by the nutritional availability of the organic
matter. A change in the environment in the form of fresh plant
residue additions (autumn leaf fall, frost-die-back) will be re-
flected in a sharp increase with population density. A less pro-
nounced change occurs with slow aeration and will be more evi-
dent as a change in the nature of the microbial population than
as a marked population increase.
The quality of the groundwater in the wetland was extremely
variable for all parameters analyzed. Table 12 presents the
concentration of ammonia nitrogen and total phosphorus measured
in observation wells 1, 5 and 9. The ammonia nitrogen concentra-
tion in observation well 1 varied from a low of 1.61 mg/1 to 15
mg/1. Observation well 5, located in the pilot section, has the
smallest range of concentration, from 7.19 mg/1 to 24.29 mg/1,
but had the highest average concentration of ammonia nitrogen,
15.19 mg/1. Observation well 9 showed the greatest range in
concentration of ammonia nitrogen from 5.7 mg/1 to 28.5 mg/1.
Observation well 9 is located in the control section. Observa-
tion wells 1 and 9 averaged 5.78 mg/1 ammonia nitrogen concen-
tration and 11.95 mg/1, respectively.
Observation well 1 recorded the lowest total phosphorus
concentration range from 0.01 mg/1 to 0.76 mg/1 with an average
concentration of 0.23 mg/1. Observation well 5 had the highest
average total phosphorus concentration, 0.85 mg/1 with a range
of 0.07 to 2.63 mg/1. The total phosphorus concentration
in observation well 9 ranged from 0.09 mg/1 to 1.66 mg/1 with
an average concentration of 0.62 mg/1.
A statistical analysis did not reveal any correlation be-
tween the total phosphorus and ammonia nitrogen values recorded
in the groundwater.
Table 13 indicates little change in heavy metal concentra-
tions during the study period in the groundwater of the wet-
land. The lead concentration ranged from <0.1 yg/1 to 0.8 yg/1
and zinc concentrations ranged from 0.01 yg/1 to 5.0 yg/1.
The importance of the microorganisms as agents of mineral-
ization and degradation, in natural environments is amply recog-
nized (23). When it becomes of interest to define these func-
tions in relation to a particular environmental situation, cer-
tain inherent difficulties must be recognized. Microorganisms
58
-------
TABLE 12. COMPARISON OF NUTRIENT CONCENTRATIONS
IN THE GROUNDWATER
Observation
Well 1
Date
11-5-74
12-13-74
12-30-74
1-29-75
2-17-75
3-3-75
3-11-75
4-1-75
5-15-75
5-27-75
6-6-75
6-16-75
7-2-75
7-11-75
7-18-75
8-7-75
11-4-75
Average
NOTE: TP
TP
mg/1
0.18
0.01
0.01
0.01
0.76
0.37
0.06
0.26
0.22
0.62
0.02
0.67
0.13
0.10
0.16
0.07
0.19
0.23
= Total
NH3
mg/1
10.13
1.61
2.76
2.19
4.30
4.76
1.94
5.50
4.50
14.02
7.77
3.10
15.00
4.95
9.19
5.17
3.03
5.88
phosphorus
Observation
Well 5
TP
mg/1
0.26
0.81
2.63
0.30
2.05
—
—
—
0.87
0.29
0.53
1.34
0.97
0.32
0.28
0.07
1.17
0.85
NH3
mg/1
7.19
20.31
13.68
15.31
17.09
—
—
--
11.0
21.03
24.29
7.62
23.31
13.00
15.91
10.25
8.28
14.88
Observation
Well 9
TP
mg/1
0.28
0.66
1.66
0.68
0.33
—
—
—
0.50
0.09
0.15
1.50
0.42
0.19
0.72
0.11
1.34
0.62
NH3
mg/1
8.17
6.67
8.90
12.19
11.96
—
—
—
10.00
28.50
11.77
5.71
16.31
14.38
16.38
6.50
7.83
11.81
NH^ = Ammonia nitrogen
TABLE 13. COMPARISON OF HEAVY METAL CONCENTRATIONS
IN THE GROUNDWATER
Observation
Date
1-29-75
2-17-75
3-3-75
4-17-75
5-15-75
5-27-75
7-11-75
Average
Well
Lead
yg/i
0.20
<0.20
0.40
<0.10
<0.20
0.10
<0.10
0.19
1
Zinc
yg/i
0.60
1.70
5.00
0.02
1.70
0.05
0.06
1.30
Observation
Well
Lead
yg/i
__
<0.20
—
0.10
0.10
—
<0.10
0.12
5
Zinc
yg/i
_ _
0.40
—
0.75
0.04
—
0.01
0.30
Observation
Well
Lead
yg/i
<0.20
0.20
__
0.80
<0.10
—
—
0.32
9
Zinc
yg/i
0.70
0.80
—
0.24
0.03
—
--
0.44
are nondescript morphologically, but extremely diverse, flexible,
and responsive in their metabolic activities. These properties
combined with the extremely small size of the microorganisms and
59
-------
the extreme complexities of natural environments sharply limit
the analytical approaches which are both feasible and practical.
A significant indicator of microbial activity in natural
environments is the amount of carbon dioxide evolved per unit
time and the number of bacteria in the microbial environment.
These parameters are especially useful because they reflect an
overall summation of metabolic rates of a diverse population,
and provides an indication of the amount and degradability of
the major organic materials. Because the usual routine measure-
ment of carbon dioxide evolution is subject to many shortcomings,
close attention was paid to the design of the carbon dioxide ex-
periment and to analysis of the resulting data.
The carbon dioxide evolved from the soils ranged from 7 to
310 mg per day for the 24-hour trials to 260 mg per day for the
72-hour trials. The daily average levels were lower for the 72-
hour trial than the 24-hour trial. This indicates that atmos-
pheric carbon dioxide made significant contributions to measure-
ments. The 72-hour chambers were exposed one time, in the ini-
tial preparation for a sampling, to the atmosphere at which time
air filled the chamber before it was sealed. Values obtained
over the 72-hour period were averaged and divided by three to
obtain the 24-hour value. The atmospheric contribution would
thus be one-third the amount as for the 24-hour samplings. The
longer trial period should, therefore, be a more accurate mea-
sure of the actual carbon dioxide production by the micro-flora.
The 24-hour samplings are important in monitoring short-term
fluctuations in activity and are important in that the daily
fluctuations are illustrated. Unfortunately the actual fluc-
tuation is somewhat dampened by the atmospheric contribution.
Microbial activity as reflected by carbon dioxide was moni-
tored at 12 stations which are all located in and around the
management area. Microbial activity as reflected by carbon
dioxide evolved did differ substantially in carbon dioxide pro-
duction between stations 7 and 12, however, the response to en-
vironmental conditions were very similar. Data based on 24-hour
periods, for samples measured daily at these stations are shown
in Figure 19, Carbon Dioxide Production - Control Area, Stations
7-12. The carbon dioxide evolved at station 7 was significantly
greater than that at station 12, however, this probably is the
result of the higher water table. Data from these stations
were compared because both were outside the management area
and are intended to reflect natural conditions.
Also plotted on Figure 19 are the 41 rainfall/runoff events
that occurred during the sampling period. As is illustrated,
there generally was a sharp decrease in the rate of carbon di-
oxide evolution following major rainfall/runoff events. Figure
20, Carbon Dioxide Production - 24 hours vs. 72 hours, Station 7,
shows the degree of variation between the 24-hour and 72-hour
60
-------
2501-
200
O 150
=>
o
O
oc
Q.
jjj 100
s
o
to
QC
<
O
50
STATION 7
STATION 12
JUNE JULY AUGUST SEPT OCTOBER
eg Time -Months
QC
LLJ
i 6
H
uj 5
O
z 4
_J 0
_J «*
I a
DC 1
0
.
•
-
_
"II
!
,
ili
Hull 1
li III. Ill ih 1 i 1 1 i
Time-Months
Figure 19. Carbon Dioxide Production - Control
Area, Stations 7-12
61
-------
250
-,200
O)
Z150
O
H-
O
=>
O
O
£100
111
Q
§
O
QQ
QC
<
O
50
72 HOUR PERIOD
. 24 HOUR PERIOD
JUNE JULY AUGUST
Time-Months
SEPT OCTOBER
UJ
p 5
i 4
O
-J 3
LL 9
Z
QC 1
0
__
-
-
-
Lh
I
II
JUNE
Li
.J
J_J
j
JULY AUGUST
Time -Months
_ II IN
SEPT OCTOBER
Figure 20. Carbon Dioxide Production - 24 Hours vs
72 hours, Station 7
62
-------
carbon dioxide evolution at station 7. These values are not ad-
justed for the atmospheric contribution to carbon dioxide and
consequently the 24-hour carbon dioxide values are uniformly
higher than those for the 72-hour run. However, the response to
environmental conditions is very similar.
Estimation of microbial number is feasible and is a useful
indicator to compliment carbon dioxide evolution studies.
Direct counts of bacteria for surface soils overall ranged
from 9 x 10° to 164 x 10° bacteria per gram of dry soil. Largest
populations were observed during the month of July for most sta-
tions. Conditions favorable for growth were optimum in the
latter half of July; water was absent from the soil surface and
ground temperature peaked. Fluctuating populations of slightly
decreased size were observed during the fall samplings.
Direct microscopic enumeration of total bacteria per gram
of marsh soil was carried out throughout the sampling period.
Counts taken at stations 7 and 13 served as controls to
monitor sample variability and the basic reproducibility of the
methodology used for direct microscopic counts.
Station 7 was located near the management area and conse-
quently subjected to some degree of alteration, whereas station
13 was located in a relatively undisturbed area of the wetland.
These two sites are located in areas that are similar in vegeta-
tion and micro-relief. The data are presented in Figure 21, Mi-
crobial Counts vs. Rainfall/Runoff Events, Stations 7 and 13.
Population densities ranged from approximately 30 x 10°" to 100 x
10° bacteria per gram of dry soil. The bacteria population were
cyclic with some degree of regularity. Figure 17, page 54, il-
lustrates that the lowest values were recorded during early June
and late July, whereas the highest values were also recorded
June and July.
The microbial activity is expected to be related to soil
temperature, however, during late July a sharp decline in or-
ganisms was recorded, not only at stations 7 and 13 but at
virtually all stations monitored. The soil temperature peaked
during July and August and values up to 25°C (77°F) were record-
ed which are just within the optimal range of mesophilic growth.
Soil temperatures were very stable and no abrupt changes were
recorded, consequently, it is apparent that some factor other
than soil temperature was responsible for the decrease in soil
bacteria.
Comparing the soil bacteria counts for both stations 7 and
13 with rainfall/runoff events, it is apparent that surface bac-
terial counts respond to rainfall/runoff as indicated in Figure
21.
63
-------
DEWATERED
120 H
JUN
JUL
AUG
Time -Months
SEP
OCT
Figure 21. Microbial Counts vs. Rainfall/Runoff Events -
Stations 7 and 13
Episodes of high rainfall caused sharp decreases in the
rates of carbon dioxide evolution, as levels dropped to half the
pre-precipitation value or even more than that. Return to pre-
vious carbon dioxide release rates occurred three to four days
after a rainstorm in both the control and dewatered areas. The
effect of the heavy rainfall on carbon dioxide evolution was
probably due to the increased moisture content of the surface
zones. With the pre-rainfall equilibrium of dissolved/gaseous
carbon dioxide altered by soil saturation, a greater proportion
of the carbon dioxide was dissolved until a new equilibrium was
attained. Microbial activity may also have slowed somewhat with
sudden saturation of the habitat, but this probably was less im-
portant than the carbon dioxide solution effects.
64
-------
The basic agreement between the two stations is obvious,
attesting to the validity of the counting procedures and to the
reliability of the fluctuations observed.
Wetland Management
One of the main objectives of the wetland study was to
evaluate possible methods or techniques in which the nutrient
removal capacity of a wetland could be enhanced. With this
objective in mind, a management area was set up consisting of
two individual test plots.
It was theorized that by regulating the water level in the
wetland the microbial activity could be increased and consequent-
ly the nutrient removal capacity of the wetland enhanced. The
specific objectives were to determine that if by regulating the
water level, could the microbial activity be stimulated, and if
so, what would be the resulting impact on water quality changes?
The data collection stations associated with the pilot zone
and those associated with the control zone were located as shown
in Figure 12, page 29.
The pilot zone was dewatered twice during the summer of
1975. The first dewatering occurred during the period June 16
through August 1 and the second period was August 26 through
November 11.
Pumping at a rate of 120 gpm, approximately 36 hours of
pumping was required before maximum dewatering of the pilot zone
was attained.
A continuous pumping rate of 15 gpm was required to keep
the area dewatered.
Comparisons were made on paired sets of stations with one
member of the pair in the control zone and the other member lo-
cated in the pilot zone. The pilot zone was subject to manipu-
lation of the water table, while counterpart stations in the
control zones were subjected to the normal water table of the
marsh.
When the data was analyzed for all stations, it became evi-
dent that water table changes did cause substantial changes in
the microbial system where water level management was effective.
The water table of the pilot zone was lower than the control
zone by several inches for most stations and three feet for
station 4. Thus, station 4 was the driest location within the
65
-------
wetland. The highest water table was consistently found at
station 10, often this area was covered by standing water. Com-
parison of these two stations would be expected to show the
greatest microbial differences because soil conditions of the dry
station 4 would greatly differ from the wetter station 10.
Stations 4 and 10 demonstrate the distinct differences in
water table expected of pilot versus control zone stations.
Pumping capacity at station 4 was obviously adequate to lower the
water table significantly and hence allow for substantially
better aeration than occurred in the more nearly saturated soil
of station 10.
A summary of the data derived from measurements of the depth
of water table below the soil surface for paired stations 4 and
10 is shown on Figure 22, Depth to Groundwater - Stations 4 and
10.
Located in the pilot zone and subjected to pumping, site 2
can be seen to be virtually identical to the unpumped counter-
part site 8 in terms of water level.
The corresponding data for paired stations 2 and 8 is pre-
sented similarly on Figure 23, Depth to Groundwater - Stations
2 and 8.
The course of carbon dioxide evolution at stations 4 and 10,
based on 24-hour periods of carbon dioxide absorption, is summar-
ized on Figure 24, Carbon Dioxide Production - Stations 4 and 10,
24-hour. Although some variations are evident, the trend is
clearly in the direction of higher respiratory activity at the
well drained station 4 than at the counterpart station 10 where
the water table remained within 25.4 cm (10 in) of the surface.
It is of interest to point out the difference in response of
carbon dioxide production at stations 4 and 10 following the
rainfall events of July 1 and August 1, 1975 during which
5.59 cm (2.20 in) and 5.72 cm (2.25 in) of precipitation were
recorded, respectively. Carbon dioxide production at station
4 shows a gradual response as a result of the rainfall events
whereas station 10 responded with almost an immediate drop in
carbon dioxide production following the July rainstorm event.
It appears that the carbon dioxide production at station 10 was
much more responsive to rainfall events, however, there was
little correlation. This can partially be explained by the fact
that runoff did not occur with each rainfall event, consequently
the magnitude and intensity of the rainfall event had some
bearing. Results for the 72-hour absorption experiments are
similar but disclose greater differences in carbon dioxide evolu-
tion between stations 4 and 10 as shown on Figure 25, Carbon Di-
oxide Production - Stations 4 and 10, 72 hour. Respiratory ac-
tivity remained at high and relatively stable rates from late
July through mid-September.
66
-------
DEWATERING CYCLE I
0 r-
i 20
O
DC
£ 40
^^ *
O
h-
I
l-
fe 130
15,0
170
STATION 10 (CONTROL)
STATION 4 (PILOT)
15
JULY
31
15
AUGUST
Figure 22. Depth to Groundwater - Stations 4 and 10
67
-------
DEWATERING CYCLE [
O
w»
oc
LJJ
20
40
60
o.
LU
Q
STATION 2 (PILOT)
STATION 8 (CONTROL)
15
JULY
31
15
AUGUST
Figure 23. Depth to Groundwater - Stations 2 and 8
68
-------
STATION 4
JUL AUG SEP OCT
JUL AUG SEP OCT
Figure 24. Carbon Dioxide Production •
Stations 4 and 10, 24 Hour
69
-------
DEWATERED
o
•^.
0
o
D
Q
O
DC
Q_
LU
O
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OC
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200
150
100
50
y
--/
//
//
JULY
STATION 4
\ STATION 10
AUGUST
SEPTEMBER
Figure 25. Carbon Dioxide Production - Stations 4 and 10,
72 Hour
Enumeration data for paired stations 4 and 10 are given in
Figure 26, Surface Microbial Counts, Stations 4 and 10. These
data are for surface samples. Populations ranged from about 15
x lOVgram in early spring to approximately 10 times that as the
maximal population occurring in mid-summer. Bacterial numbers
increased from early June through early August, with generally
lower numbers through September and October. There were clearly
greater numbers of bacteria per gram at surface station 4 (well
drained) than at surface station 10 (high water table). Addi-
tional counts were made at stations 4 and 10 from subsurface
samples taken at a depth of 76 cm (30 in). These data are sum-
marized in Figure 27, Subsurface Microbial Counts Stations 4
70
-------
DEWATERED
150 -
100
50
STATION 10
FROZEN
OCT
1974
MAY JUNE
JUL
AUG
1975
SEP
OCT
NOV
DEWATERED
150
100
50
STATION 4
FROZEN
OCT
1974
MAY JUNE
JUL
AUG
1975
SEP
OCT
NOV
Figure 26.
Surface Microbial Counts -
Stations 4 and 10
71
-------
and 10. In contrast to the surface samples, the two subsurface
stations were very similar with respect to population density
and seasonal patterns. These findings are consistent with the
concept that surface populations are more diverse and numerous
than subsurface populations. The high population recorded for
the subsurface stations 4 and 10 during early June is difficult
to interpret. Hydrologically the wetland was very active and
significant flows in the order of 200 gpm were occurring at the
outlet. Consequently, the soil water system was actively moving
and the high early counts may be in response to the availability
of nutrients.
O
CO
LL
O
DEWATERED
II
^ 40
DC
O
DC
LU
°- 30
00
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<
£ 20
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1 1°
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1 • \ STATION 10
MHMMM I *
1 \ \ — — STATION 4
/ :- ^
1 '• ^
I \ \ *
1 • » :"
— 1 : \
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/ : \ / :
I 1 f ; • j
1 \ \ / i A * vX \
| \ \ j\ 5 /JC \ Jr \
— ' \ Y: \ I ^\ \
\; *
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1 L.
JUN
JUL
AUG
SEP
Figure 27. Subsurface Microbial Counts - Stations 4
and 10
72
-------
in
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300
250 -
200 -
K 150h
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Q.
100 -
STATION-2
JUN JUL AUG SEP OCT NOV
300 f-
STATION-8
250
200
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JUN JUL AUG
I 1 I
SEP OCT NOV
Figure 28. Carbon Dioxide Production
Stations 2 and 8, 24 Hour
73
-------
Microbial activity as reflected by carbon dioxide evolved
did not differ substantially between stations 2 and 8. Data,
based on 24-hour periods, for samples measured daily at these
stations are shown on Figure 28, Carbon Dioxide Production -
Stations 2 and 8, 24 hour. Periods during which the pumps were
operative in the pilot zone are also shown in the figure, appear-
ing as horizontal lines near the top of the graph. Pumping was
relatively ineffective and microbial activity (carbon dioxide
evolved) was only slightly lower at unpumped, control station 8
than at pilot station 2. Stations 2 and 8 must be treated as
duplicate samples since they were chosen originally for similari-
ties in vegetation and location, and since the expected variable,
water level, proved to be similar in each. Agreement between
these duplicate samples were good. Carbon dioxide evolution
over a 72 hour period in the vicinity of stations 2 and 8 is
shown on Figure 29, Carbon Dioxide Production - Stations 2 and
8, 72 hour.
Q
*-.
0
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111
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DEWATERED
200 I—
150
100
50
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/ /
JULY
Figure 29
•A
•A
/v
' y\
/
\ /
\ /
STATION 2
V^STATION 8
AUGUST
SEPTEMBER
Carbon Dioxide Production - Stations 2 and 8,
72 hour
74
-------
Results of counts on paired stations 2 and 8, which varied
only slightly in depth of water table, showed general agreement
in total numbers. The data are summarized in Figure 30, Sur-
face Microbial Counts, Stations 2 and 8. Population densities
ranged from about 20 x 108/gram to 100 x lOVgram. Numbers were
lowest in early June/ increasing throughout June, and high dur-
ing July. After a decline in the second half of August, num-
bers were steady through much of September and October.
I II
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QC
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1-
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90
80
70
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50
40
30
20
10
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£ ^DEWATERED-^
*
; I
•— A • ••
• • * *••
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1 \" ^STATION 8
1 1 1 1 i 1
JUNE
JULY AUGUST SEPT OCTOBER NOV
Figure 30. Surface Microbial Counts - Stations 2 and 8
One of the main objectives of the Wayzata wetland project
was to determine the impacts the wetland has on the quality of
stormwater passing through the wetland and also if any water
quality improvement that occurs in the wetland can be enhanced.
As mentioned earlier, the pilot and control management area
was set up and regulated in order to determine if water level
management in the wetland would stimulate microbial activity
and consequently enhance the water quality passing through the
wetland ecosystem.
Figures 31, 32 and 33 were constructed utilizing the data
phosphorus levels in the soil water, surface and subsurface mi-
crobial populations.
75
-------
Figure 31, Surface and Subsurface Microbial Counts vs. Total
Phosphorus Concentration in Soil Water - Station 6, is con-
structed from data obtained at monitoring station 6 and obser-
vation well 6. Monitoring station 6 is located outside the
management area approximately 2 m (6.6 ft) from monitoring sta-
tion 5.
The most vivid feature of Figure 31 is the apparent rela-
tionship between soil water phosphorus levels and subsurface
microbial populations during the month of June and early July.
Figure 31 also indicates that when the level of phosphorus drops
below some given value, the phosphorus level ceases to have an
effect on the population of subsurface microbes. However, Fig-
ure 32, Surface and Subsurface Microbial Counts vs. Total Phos-
phorus Concentration in Soil Water - Station 10, does not illu-
strate this relationship. This may be due to the high water
table condition at site 10 resulting in less variation in the
type of microbes present.
There appears to be an almost inverse relationship between
surface microbes and subsurface microbes and surface microbes
and phosphorus.
The same relationship between subsurface microbes and total
phosphorus is well illustrated at monitoring stations 5 and 10.
Also, there appears to be an inverse relationship between sur-
face microbes and subsurface microbes and total phosphorus. How-
ever, this relationship is not as apparent as is illustrated
on Figure 31 of monitoring station 6.
There does not appear to be any relationship between ammonia
nitrogen and biochemical oxygen demand parameters monitored at
the sites and the surface and subsurface microbe population.
The apparent inverse relationship between aerobic microbes
and total phosphorus could be the result of microbial immobili-
zation of phosphorus resulting in lower equilibrium - solution
levels. These results appear to agree with results obtained by
B.B. Singh (24).
The most visible and the ultimate impact of the management
program was the vegetative response to dewatering. A one meter
square area was selected in both the pilot and control zone.
The selection process required that these areas be as vegetative-
ly similar as possible. The dominate vegetation was reed canary
grass (Phalaris arundenacea). The vegetation was clipped ap-
proximately every ten days and immediately weighed. The first
clipping occurred on July 10, 1975 and the final clipping oc-
curred on August 12, 1975.
The results of the clipping are presented in Table 14.
76
-------
DEWATERED
100
o
•H
-P
td
0)
u
£
o
u
0)
cu
CO
o
o
EH
80
60
40
Total
Phosphorus
20
/ I
Surface FITC
I I
I i
Subsurface FITC
100
80
a
rd
M
tn
0)
X
CO
•P
C
40 §
20
Jun
Figure 31.
Jul
Aug
Sep
Oct
Surface and Subsurface Microbial Counts vs. Total
Phosphorus Concentration in Soil Water - Station 6
77
-------
PEWATERED
100 i—
A
I SURFACE FITC
TOTAL"
PHOSPHORUS I
i /
r\
I \
/ I
V /
v
SUBSURFACE
1.0
CD
0.8
DC
0.6 z
ui
O
Z
O
O
0.4
CO
DC
O
r
CL
CO
0.2
JUNE
JULY
AUG
0.0
SEPT
OCT
Figure 32.
Surface and Subsurface Microbial Counts vs. Total
Phosphorus Concentration in Soil Water -
Station 10
78
-------
.DEWATERED
100i—
80
O
"Z.
O 60
cc
I-
•z.
LLJ
O 40
•z.
O
O
CO
O
i
Q.
CO
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I
0
TOTAL PHOSPHORUS
r
SURFACE FITC /
••«•—SUBSURFACE FITC
100
80
oc
O
60 DC
LU
Q.
oo
O
40
20
CO
I-
"Z.
15
O
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CD
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JUNE
Figure 33.
JULY
AUG
SEPT
OCT
Surface and Subsurface Microbial Counts vs. Total
Phosphorus Concentration in Soil Water - Station 5
79
-------
TABLE 14. VEGETATIVE MASS PRODUCTION - WAYZATA WETLAND
Vegetative Mass, kg/rn^
Pilot Zone Control Zone
July 10, 1975 2.04 0 749
July 21, 1975 0.518 0*269
August 1, 1975 0.173 0*084
August 12, 1975 0 . 110 0*087
Total 2.84
1.19
The results of this relatively brief monitoring of vegeta-
tive mass indicates that the vegetative growth in the dewatered
zone produced approximately 2.84 kg/m2 during the test period,
whereas the control zone produced 1.19 kg/m2. On a one term
basis it appears that the dewatered pilot zone produced approxi-
mately 2.4 times the vegetative mass produced in the control
*-7S*\ T"\ y—\
zone.
Phosphorus sorption and desorption characteristics of soil
is affected by organic residues (24) .
Phosphorus has been shown to be the limiting nutrient in
the lake eutrophication cycle and therefore, has a special sig-
nificance to the Lake Minnetonka area. Consequently, an in-
depth study was conducted on the marsh soils in order to estab-
lish the ultimate fate of phosphorus in the wetland. A total of
18 organic soil samples were collected in the vicinity of sta-
tions 4 and 10 for phosphorus analysis.
In order to check the validity of the results, three core
samples were taken at stations 4 and 10. Three soil samples
were selected from each individual core. The first sample was
taken at approximately the 5 cm ( 2 in) depth, the second at ap-
proximately the 30 cm (17 in) depth and the third at approximate
ly the 60 cm (24 in) depth.
n «*cThe results of these analysis indicate that approximately
0.045 percent of the wetlands organic soil is phorphorus.
The average bulk density of the organic soil has been es-
tablished at approximately 641 kg/cu-m (40 Ibs/cu-ft) . This value
agrees well with the values reported in United States Department
of Agriculture Circular 290 (R) .
Assuming a bulk density of 641 kg/cu-m (40 Ibs/cu-ft) and an
nV9QQ^ Concentration of 0.045 percent phosphorus, approximately
0.288 kg/cu-m (0.018 Ibs/cu-ft) of phosphorus is present in the
organic soil.
In order to add more insight into the complex nature of the
80
-------
phosphorus cycle, phosphorus adsorption isotherms were construct-
ed for the wetland soils. A method developed by A. W. Taylor and
H. Kieuishi (25) for constructing phosphorus adsorption isotherms
was utilized.
The results are calculated in terms of the ratio x/(1.0 +
log c), where x is the weight of phosphorus adsorbed in the soil
in mg/kg (ppm) and c is the final phosphorus concentration in
mg/1. This ratio provides an index of the adsorption capacity
of the soils. Together with data on the bulk density of the
soil, the relative depth of the soil horizons and the anticipated
composition of the influent water, this ratio may be used to
calculate the adsorption capacity of the soil.
To determine the phosphorus adsorption, a five gram sample
of each soil was added to a 100 ml volume of a solution contain-
ing 30 ppm phosphorus and 0.13 percent KCl and shaken for 18
hours on a reciprocating shaker. The suspension was then fil-
tered and an aliquot of clear solution removed for analysis.
The final phosphorus concentration was determined colorimetri-
cally using the ammonium molybdate-ascorbic acid procedure.
Table 15 indicates that at a phosphorus concentration of
1 mg/1, the range in phosphorus adsorption isotherm at stations
4 and 10 illustrates the shape of the isotherm for the various
soils.
TABLE 15. PHOSPHORUS ADSORPTION CHARACTERISTICS -
WAYZATA WETLAND SOILS
Sample
1
2
3
4
5
6
Station
4
4
4
10
10
10
Depth
(cm)
5
30
60
5
30
60
Phosphorus
Adsorption
(ppm)
(1 mg/1)
81.3
28.5
35.8
35.6
26.5
Phosphorus
Adsorption
(ppm)
(30 mg/1)
232
269
431
264
251
339
The average measured value for phosphorus in solution at
stations 4 and 10 was approximately 0.9 mg/1. Consequently, one
would assume that the amount of phosphorus present in the wetland
soils would be in the order of 26 to 81 ppm or 165 to 518 kg/ha-m
(45 to 141 Ibs/ac-ft). However, the digestive results indicated
that approximately 2,868 kg/ha-m (780 Ibs/ac-ft) of phosphorus
was present in the organic soil. Consequently, the organic soil
in the Wayzata wetland presently contains from 5 to 17 times the
amount of phosphorus that the isotherm indicates that it should
hold as indicated in Figure 34, Phosphorus Adsorption Isotherms -
81
-------
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Stations 4 and 10.
These values are high for an organic soil, however, they
appear reasonable when considering the relatively larger percent
of inorganic material present in the soil profile as shown in
Figure 5, page 16.
It is apparent that the phosphorus is fixed in some organic
form, possibly as part of the vegetative fiber.
If this additional phosphorus is organically based, stimula-
tion of the biological system will remove greater quantities of
phosphorus. The results of the vegetative plots indicate that
significant quantities of organic matter were produced. Research
(26) has shown that by the time a plant has obtained approximate-
ly 25 percent of its total dry weight it has acquired 75 percent
of its total phosphorus needs. Experimental results by Spangler
et al. (27) indicate that frequent harvesting of bulrushes re-
moved greater quantities of phosphorus than a single harvest
even though the total organic matter removal was not substan-
tially greater.
Sump Water Quality
The frequent analysis of water quality for the sump pumping
station provides a detailed picture of nutrient concentrations.
The control of water elevations within the pilot area would be
expected to alter the water quality at the sump, the result of
changing environmental conditions and thus biological activity.
A comparison of water quality for sump versus outlet would be
comparable to pilot zone versus control zone. Pilot zone versus
control zone comparisons yielded significantly different water
quality for three parameters: ammonia nitrogen, phosphorus and
total suspended solids. Biochemical oxygen demand, total coli-
form and oxidation reduction potential appear to be minimally
affected by manipulation of water levels. The effect of dewater-
ing upon the pilot zone was distinctly different for the two de-
watering cycles, I and II, studied attesting to the pronounced
effect uncontrollable parameters have upon the pilot zone.
Sump Water Quality - Total Coliform—
Total coliform counts of the sump follow an erratic pattern,
ranging from 0-322 colonies per 100 mis. See Figure 35, Total
Coliform, Total Suspended Solids and Biochemical Oxygen Demand
Concentrations in Sump Discharge Water. The standard mean was
59. The appearance of the occasional high counts does not
appear to be related to any monitored parameter. Such fluctua-
tions in total coliform counts are common. The source of the
coliform are natural soil inhabitants and animal fecal contamina-
tion. It is considered that within these observed ranges for
total coliform contaminated water would not be a problem.
83
-------
DEWATERED
16
14
12
10
Q
6 -
BOD,
JUN
JUL
AUG
DEWATERED
SEP
OCT NOV
JUN
JUL AUG SEP OCT NOV
300
200-
o 100-
JUN
Figure 35
JUL
AUG
SEP
OCT
NOV
Total Coliform, Total Suspend-
ed Solids and Biochemical Oxygen
Demand Concentrations in Sump
Discharge Water
84
-------
Total coliform of the sump and outlet were similar but no
distinct patterns were observed. See Figures 35 and 36. The
mean value was slightly lower for the sump. The outlet ranged
0-240 colonies per 100 mis, the mean was 71 over the same period.
Sump Water Quality - Biochemical Oxygen Demand—
Biochemical oxygen demand values of the sump ranged from
0-16 mg/1 fluctuating greatly (see Figure 35). Values were
slightly higher through September. Outlet values of biochemi-
cal oxygen demand ranged 0-14 over the same period. See Figure
36, Total Coliform, Total Suspended Solids and Biochemical Oxy-
gen Demand in Outlet Discharge Water. The value of comparing
biochemical oxygen demand over time and location is highly
questionable, the nature of oxidizable material is unknown and
variable. However, within the restriction of the wetland a
comparison of biochemical oxygen demand may be fairly accurate.
There does not appear to be a significant difference in bio-
chemical oxygen demand for sump and control zones.
Sump Water Quality - Total Suspended Solids—
Total suspended solids of the sump showed a definite pattern
(Figure 35). Highest values were found during dewatering cycle
I, significantly lower values were seen during dewatering cycle
II. Preceding and through the first two weeks of dewatering
cycle I the wetland was infiltrated with stormwaters as a result
of the excessive precipitation in June. The high volume of water
stirs up the wetland soils as a result of increased flow rate and
increases the suspended solids concentration.
Total suspended solids concentration values were greatly re-
duced through dewatering cycle II during which less precipitation
fell. The wetland soils received smaller increments of inflow
resulting in lower flow rates such that suspended solids settle
out. The need for controlled flow rates is seen as a means of
reducing total suspended solids.
Total suspended solids values of the outlet were subject to
larger fluctuations than the sump. See Figure 36. Outlet
values ranged 0-270 mg/1, sump values ranged 0-104 mg/1 over the
same period. The high peaks observed at the outlet were due to
disturbance of sediments in the bed of the outlet channel. These
high peaks were reduced or absent for the sump due to the dif-
ference in manner of discharge for the outlet and sump.
Sump Water Quality - Ammonia Nitrogen—
Ammonia values in sump discharge ranged from 0.1-15 ppm,
with concentrations fluctuating greatly June through July but
remaining almost constant from September through November. See
Figure 37, Ammonia Concentration and Oxidation Reduction Poten-
85
-------
125
BOD
NOV DEC
1974
APR
MAY
JUN JUL
1975
300
0200
a
Q
TSS
NOV DEC
1974
APR MAY
JUN JJL
1975
AUG SEP
OCT
f 300
;ioo
TC
NOV DEC APR MAY JUN JUL
1974 1975
AUG SEP
OCT
Figure 36. Total Coliform, Total Suspended Solids and
Biochemical Oxygen Demand in Outlet Dis-
charge Water
86
-------
500
400
300
200
14 r—
DEWATERED
JUN JUL AUG SEP OCT NOV
Figure 37. Ammonia Concentration and
Oxidation Reduction Potential
in Sump Discharge
87
-------
tial in Sump Discharge. The fluctuating ammonia nitrogen concen-
trations observed in July were quite mysterious in light of the
constant water levels over this period. It appears that the
fluctuations observed are the result of nitrification and deni-
trification by bacteria. Nitrates were not measured but nitrifi-
cation could occur as indicated by the oxidation reduction poten-
tial. Patrick found that an oxidation reduction potential of 300
or greater was necessary for nitrification (28). Through July
this potential was exceeded several times corresponding to de-
creased ammonia nitrogen values. The fluctuating observed for
oxidation reduction potential and ammonia nitrogen values may be
due to the depletion of oxygen within the environment by the ni-
trifying bacteria followed by a replenishment of oxygen as the
water aerates.
Water quality pumped from the pilot zone and sampled at the
sump differed significantly from water quality sampled at the
piezometers. The source of the sump is groundwater pumped from
the upper three feet of soil. Ammonia nitrogen concentration ap-
pears to be affected most as can be seen by comparing Figures 37
and 38, Ammonia Concentration in Soil Water - Stations 3 and 9.
Ammonia nitrogen concentration at the sump were generally half
the ammonia concentrations of groundwater at the piezometer
sump. This appears to point out the importance of aerating to
improve the water quality. Further evidence of the pronounced
effect of aeration was seen in August. The lysimeter was not
pumped, groundwater was left standing in the holding tank over a
three week period and sampled daily. Ammonia nitrogen concentra-
tions were extremely low, 1-2 ppm, as this water was exposed to
air. Upon exposure to air the ammonia nitrogen concentrations
present as the dissolved ammonium ion may be volatized and lost
as the gaseous form ammonia nitrogen to the atmosphere.
Dewatering of the pilot zone was done two times as indicated
by the black bars on Figure 37. Through dewatering cycle I,
ammonia nitrogen of the outlet and sump are within similar
ranges and both fluctuate greatly. See Figure 37, page 87, and
Figure 39, Ammonia Concentration in Outlet Discharge, for ammonia
concentrations of sump and outlet. Peak concentrations of the
sump and outlet correlate with the highest ammonia values occur-
ring on the same day. The two cycles of dewatering differed sig-
nificantly in resultant ammonia nitrogen concentrations.
During dewatering cycle II the ammonia nitrogen values of
the sump are twice the concentration of the outlet. The higher
ammonia values observed for dewatering cycle II in the pilot
zone may be due to the increased activity of the soils microbes
at station 4 in the pilot zone, as seen in carbon dioxide pro-
duction, Figure 24, page 69. Less new cell synthesis was ob-
served through the fall months but maintenance metabolism would
be continuing. With less new growth or microbes, less nitrogen
would be required but an energy source would still be needed,
88
-------
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90
-------
producing carbon dioxide.
The greater quantity of organic material used by the mi-
crobes of the pilot zone, as observed in high carbon dioxide
evolution over dewatering cycle II results in the subsequent re-
lease of ammonia nitrogen concentrations through deamination of
the organic matter used as an energy source. The higher soil
activity of the pilot zone consequently produces higher ammonia
nitrogen in the sump.
Sump Water Quality - Total Phosphorus—
Total phosphorus concentrations of the sump ranged from 0.01
to 1.24 mg/1 as shown in Figure 40, Total Phosphorus Concentra-
tion in Sump Discharge Water. A fluctuating pattern was seen,
concentrations increased and decreased by a factor greater than
two within a short period, one to two days. The phosphorus
concentrations appear to be highly unpredictable. Through the
period of July and September through October, water elevations
were constant and phosphorus continued to fluctuate greatly in-
dicating no direct relationship between water elevation and
phosphorus.
Comparison of total phosphorus, pilot zone to control zone
during dewatering cycle I shows similar ranges, however, peak
concentrations for sump and outlet do not coincide. The outlet
peaks lag the sump peaks by several days. See Figure 40 and
Figure 41, Total Phosphorus Concentration in Outlet Discharge
Water. This appears to indicate a mass movement of phosphorus
carried by the groundwater through the wetland.
Through dewatering cycle II, higher concentrations of phos-
phorus were seen in the pilot zone over the control zone. It is
uncertain as to whether this is related to the biological ac-
tivity phenomena described for ammonia. Whereas ammonia is
relatively constant over this period, phosphorus fluctuates
greatly.
Phosphorus Ammonia Nitrogen Correlation—
There does not appear to be a direct relationship between
phosphorus and ammonia nitrogen within the pilot zone for short
term comparisons. This is best exemplified in the month of
September, ammonia nitrogen concentrations are constant whereas
phosphorus concentrations fluctuated. June through July both
ammonia and phosphorus are fluctuating, however, the fluctua-
tions do not appear to coincide.
Seasonally phosphorus and ammonia nitrogen concentrations
do follow a similar pattern, higher concentrations were observed
June through July, lower concentrations were observed September
through November.
91
-------
0.0
DEWATERED
JUN
JUL
AUQ
SEP
OCT
NOV
Figure 40. Total Phosphorus Concentration in Sump Dis-
charge
92
-------
o
CO
z
O
z
UJ
O
z
O
O
CO
3
oc
O
I
CL
(0
O
I
Q.
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
FROZEN
I I I
NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT
1874 1878
NOV
Figure 41.
Total Phosphorus Concentration in Outlet
Discharge Water
The ranges for samples taken throughout the year are in a
ratio of nine ammonia to one total phosphorus, the accepted ra-
tio of nitrogen to phosphorus in a biological system. This in-
dicates that the majority of the nitrogen is of the ammonia form.
The failure of ammonia nitrogen and phosphorus to correlate,
short term, is probably due to the alteration of nitrogen states.
Where the wetland system is a contributing watershed to a
recreational lake, it is desirable to reduce the nutrient flow
to the lake. As the groundwater flows to the lake it carries
this large load of nutrients to the lake. For an undisturbed
system the inflow of nutrients would be desirable as a constant
supply of nutrients in an equilibrium necessary to primary pro-
duction and thus beneficial to fish and other aquatic life.
However, many recreational lakes are out of equilibrium from
poor sewage practices and thus unstable and unable to handle the
nutrient load of groundwater.
93
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SECTION 9
DISCUSSION
•14-u Thu hydrologic balance of the project watershed and wetland,
although typical, present very complex problems relative to
groundwater movement and losses from evaporation and evapotrans-
piration. The biological and chemical aspects of the ecosystem
are closely related to the water level. High water levels
create an anaerobic environment; an aerobic system is estab-
lished with continuing low water levels. The state of the wet-
lands, aerobic or anaerobic, ultimately determines the type and
amount of activity.
The wetland received water from the following three sources,
with the percentage from each source shown in parenthesis; direct
precipitation (35 percent), surface runoff (47 percent) and
groundwater inflow (18 percent).
The losses from the wetland were by means of evapotranspira-
tion (25 percent) and surface discharge (75 percent).
The sources of phosphorus, the major nutrient of interest,
f?othe-,wetland ™fre surface runoff (55 percent), groundwater in-
flow (44 percent) and precipitation (1 percent). Based on the
waS-S. A e equation' 78 Percent of the phosphorus entering the
wetland was removed, while 94 percent of the suspended solids
were removed.
Review of the detailed environmental assessments, presented
in Appendices A and B, indicate that no impacts were detected on
the wildlife or vegetation as a result of this project.
The microbial activity within the wetland appears to be the
most important mechanism influencing the improvement of the
quality of the water passing through the site. The detailed in-
vestigations correlating microbial activity with water levels
and total phosphorus concentration indicate that a rapid increase
in microbial population follows the runoff events. increase
?r°cess aPPears to follow the classic growth pattern
in microorganisms in a batch culture. Initially, all
********** in excess of the requirement of the micro-
and growth is unrestricted. During this period,
94
-------
called the constant growth phase, the concentration of microor-
ganisms increases at an exponential rate. At some concentration,
one of the nutrients becomes growth limiting and the culture
proceeds into the declining growth phase. In response to the
increasing competition of the microorganisms for the remaining
limiting nutrient, the rate of growth decreases until growth
finally halts. At this point, the limiting nutrient has been
depleted and the replacement of those organisms that die is not
possible. Consequently, the microorganism concentration de-
creases in what is termed the endogenous or auto-oxidation phase.
When microorganisms are introduced to a growth medium to which
they are unacclimated, there occurs prior to the constant growth
phase, a lag phase in which the microorganisms become adjusted
to the culture environment.
Modifications of the classic pattern occur as the results of
varying ratios of nutrients to microorganisms in the culture
medium.
After an initial lag phase, growth proceeds in the constant
growth phase with the concentration of microorganisms increasing
expotentially. The microorganisms remove from the culture nutri-
ents required for growth, and the concentrations of the latter
will decrease.
Organic material assimilated by a microorganism furnishes
both the elements out of which protoplasm is constructed and the
energy necessary for its synthesis.
The process found in the wetland appears to be one which
involves an initial lag period, with a rapid growth period, fol-
lowed by a declining growth period caused either by limited
quantity of nutrients or by physical removal (by falling water
levels) of the nutrients from the microorganisms activity sites.
Additional work in the area of optimizing the microbial
processes is being performed, as part of the second portion of
this grant, in organic soil filtration units and development of
support data is anticipated.
The relative ineffectiveness of dewatering the wetland may
be caused by the fact that additional acclimation is required
once the stormwater is added to the system.
95
-------
REFERENCES
1. U.S. Fish and Wildlife Service, "Interim Classification of
Wetland and Aquatic Habitats of the United States", U.S.
Department of the Interior, March, 1976.
2. Norvich, R.F., Ross, T.G. and Brietkrietz, Alex, "Water Re-
sources Outlook for the Minneapolis-St. Paul Metropolitan
Area", U.S. Geological Survey, 1973.
3. Thornthwaite, C.W. and Mather, J.R., "Instructions and Tables
for Computing Potential Evapotranspiration and the Water Bal-
ance", Drexel Institute of Technology, Publication in Clima-
tology", Volume X, No. 3, 1957.
4. Blad, Elaine L. and Baker, Donald G., "A Three-Year Study of
Net Radiation at St. Paul, Minnesota: Jour. Applied Meteor-
ology", Volume 10, 1971.
5. U.S. Environmental Protection Agency, "Methods for Chemical
Analysis of Water and Wastes", 1974 Edition.
6. APHA, AWWA and WPCF, "Standard Methods for the Examination of
Waste and Wastewater", 13th Edition.
7. Sears, P.B. and Janson, E., "The Rate of Peat Growth in the
Erie Basin", Ecology, 1933.
8. Olson, J.S., "Energy, Storage and the Balance of Producers
and Decomposers in Ecological Systems", Ecology, 1963.
9. Reader, R.J. and Stewart, J.M., "The Realtionship Between
Net Primary Production and Accumulations for a Peatland in
Southeastern Manitoba", Ecology, 1972.
10. Lusman, G.A., "The Rate of Organic Matter Accumulation on the
Sedge Mat Zone of Bogs in the Itasca State Park Region of
Minnesota", Ecology, January, 1953.
11. Boelter, D.H., "Hydraulic Conductivity of Peats", Soil
Science, 1965.
12. Kunkle, G.K., "The Baseflow Duration Curve, A Technique for
the Study of Groundwater Discharge From a Drainage Basin".
Jour. Geophysical Research, Volume 76, No. 4.
96
-------
13. Schwab, Frevert, Edminster and Barnes, "Soil and Water Con-
servation Engineering", John Wiley & Sons, New York, 1966.
p. 80.
14. Lawrence, D.B., Bonde, A.N. and Ives, J.D., "Ecosystem
Studies at Cedar Creek Natural History Area", III Water Use
Study Proceedings, Minnesota Academy of Sciences, 1961.
15. Voight, G.K., "Amer. Midi. Natur.", 1960.
16. Chalupa, J., "Sb Ved. Pr. Vys. Sk. Chemickotechnol. Par-
dubice (Prague)", Fac. Technol. Fuel. Wat. Vol. 4, Pt. 1
(English Summary, "Water Pollution Abstract, Volume 35
No. 5, Abs. No. 660) .
17. Tamm, C.O., "Physiol. Plant", 1951.
18. Krupa, Sagar, University of Minnesota, Unpublished.
19. Keup, L.E., Water Research", Volume 2, Pergamon Press,
Great Britain, 1968.
20. Sorenson, K.E., "A Program for Preserving the Quality of
Lake Minnetonka", 1971.
21. E. A. Hickok and Associates, "Minnehaha Creek Watershed Dis-
trict Hydrologic Report", 1971.
22. Soper, E.K., "The Peat Deposits of Minnesota", Minnesota
Geological Survey Bulletin 16, 1919.
23. Waksman, S.A., "Principles of Soil Microbiology", Williams
and Wilkins Co., Baltimore, Md., 2nd Edition. 1932.
24. Singh, B.B. and Jones, J.P., "Phosphorus Sorption and De-
sorption Characteristics of Soil as Affected by Organic
Residues", Soil Science Society of America Journal, Volume
40, No. 3, May-June, 1976.
25. Taylor, A.W. and Kieuishi, "Journal of Soil Water Conserva-
tion", 1967.
26. Seatz, Lloyd F. and Stanberry, Chauncy O., "Advances in
Phosphate Fertilization", 1960, Soil Science Society of
America Journal.
27. Spangler, Frederic L., Sloey, William E. and Fetter, C.W.,
Jr., "Artificial and Natural Marshes as Wastewater Treat-
ment Systems in Wisconsin", Presented at Freshwater Wet-
lands and Sewage Effluent Disposal: Ecosystem Impacts,
Economics, and Feasibility, May, 1976.
97
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28. Patrick, W.H., Jr. and Tusneem, M.E., "Nitrogen Loss from
Flooded Soil", Soil Science Society of America Journal,
1960.
98
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APPENDIX A
ECOLOGY REPORT - PHASE I
(Status of the Biota at the Beginning of the Project)
by
James A. Jones, Ecologist
GENERAL COMMENTS
For some time it has been widely accepted that the wetland
plays an important role in conditioning water which comes as
runoff from the hard surfaces such as streets and parking lots.
In some situations part of this water may be derived as surface
drainage from highly fertilized lawns. Runoff water has been
shown to be enriched with dissolved chemicals and it has the
potential of carrying toxic agents. When this water flows dir-
ectly into lakes the lakes tend to become overenriched result-
ing in undesirably heavy blooms of blue-green algae. It is pro-
posed that the marsh functions as a biological filter system in-
corporating the undesirable agents from the water as it slowly
filters through before entering the lake.
The present study is concerned with establishing specific
values for the effects of the marsh on the drainage water; exam-
ining the feasibility of increasing the effectiveness of the
marsh; and identifying the impact of the experimental procedures
on the life of the marsh.
OBJECTIVES OF THE ECOLOGICAL STUDY
The specific objectives of the ecological portion of the
study relate to measuring the biological effects on the marsh
of the various controlled alterations of the environment. The
study will include a vegetative analysis of the control and ex-
perimental plots and a faunal and floral analysis of the open-
water marsh outside the plots to establish the original biologi-
cal status and to identify any alterations in the biota accom-
panying and possibly induced by the experimental techniques.
THE EXPERIMENTAL AND CONTROL PLOTS
Description
The plots chosen for study meet the dictionary definition
99
-------
of "wetland" — "a track of low, wet, soft land". The water
level during this, a rather "normal", season (1974) has varied
from a shallow covering in the early spring to about three feet
below the surface in late July. Several showers in early August
returned the water table to about six inches below the surface.
The substrate of the plots is of plant material in various
stages of decomposition and preservation (as peat) with seeming-
ly negligible but as yet undetermined siltation from runoff.
The vegetation of the plots is dense and represented by a
variety of species which characterize the ecological age of the
wetland. By growth form, species were identified as two trees,
nine shrubs, three grasses, three sedges, and seventeen forbes.
In initial appearance one is impressed by the predominance of
willows, dogwoods, and reed canary grass.
The two plots are similar in species composition and in the
relative abundance of the species. The homogeneity of the vege-
tation of the plots is further accentuated by the lack of marked
zonation in species distribution although there is some clumping
due to vegetative reproduction.
In general, the species are those common and widespread
over central Minnesota. They are tolerant of the varied mois-
ture conditions to which they are subjected in this habitat.
Two species, Typha latifolia (cattail) and Sagittaria sp.
(arrowleaf) are characteristic, and tolerant of higher water
levels and may be near their dry-tolerance limit in this habitat
partly because of the low water table at certain times and
partly because of the severe competition provided by the reed
canary grass and the various shrubs.
From the viewpoint of succession, the appearance of two
species of trees on the plots, Acer negundo (box elder) and
Fraxians pennsylvanica (green ash), and one species just off
the plots, Populus deltoides (cottonwood) give evidence of the
late stage of wetland succession. Poa sp. (bluegrass), Eupa-
torium perfoliatum (white boneset), and Urtica gracilis (sting-
ing nettle) are tolerant of more dry conditions and are perhaps
near the limit of their moisture tolerance in this habitat.
It should be noted that all species considered are hardy,
tolerant, perennials and will be altered only by marked water-
level alteration over an extended period of time.
Methods
Initial work on the vegetation analysis was begun in early
July before I knew exactly the limits of the study plots. At
that time plants were collected and identified from an extensive
100
-------
area of the wetland much of it lying outside the plots as they
came to be surveyed and marked out later. All of the plants
now found in the plots occur extensively outside the plots;
only a couple of species found outside the plots do not occur
within them. This indicates the representative nature of the
study*
Several techniques for vegetation analysis were considered
including the line transect, a one-meter wide transect, and
random one square meter quadrants. When the study plots were
designated their relatively small size, compared to viewing
the entire marsh, made detailed mapping of conspicuous features
seem the most functional. This was facilitated by the sub-
division of the study plots into 25-feet wide subplots with
the installation of tile for water level control.
Since the dense stand of the several species provides
more than 100 percent cover it was impossibly confusing to place
all plants on the same chart. Thus one chart includes trees
and shrubs; a second includes reed canary grass and cattails;
and a third includes conspicuous forbes and minor grasses and
sedges.
Findings
The vegetation of the study plots is lush and varied.
Thirty-eight species of plants have been identified as com-
prising the vegetative complex (see species list). No species
has attained exclusive dominance over any extensive area al-
though reed canary grass and the larger bush willows have suc-
ceeded in so doing to a limited extent. The distribution pat-
tern for several species is to grow as a dense clone in one or
more limited areas then as scattered individuals over a wider
area. This pattern is exhibited by cattails, dogwoods, sedges,
reed canary grass, purple loosestrife, black currant, purple
bonest, and white boneset. Because these are the large and
conspicuous forms, the distribution was most impressive. The
herbs of lower growth forms undoubtedly display somewhat the
same pattern in some cases but I was more impressed by their
more scattered distribution under the overstory of the larger
forms.
Black ash and box elder occur sparsely over the plots as
young trees mostly less than four feet tall. Either the con-
ditions are becoming more suitable for their germination and
growth and they are about to take over as the next stage of
succession or they are perpetually starting seedlings which
grow for a couple of years than die out because of the en-
vironment. I believe the latter to be the case but it will
be interesting to watch their response in relation to the
experimental procedures to be carried out.
101
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All species give the appearance of health and vigor. All
are undergoing flowering and seed production (exclude two ferns
and two trees).
Trampling, slashing, and ditching, as necessary activities
of the project, are having an undetermined and unpredictable
effect on about 15 percent of the marsh. Already, within two
weeks from the time of disturbance due to slashing and trampl-
ing, recovery is apparent in some areas; the ditching effects
may be longer lasting. In any event development on these dis-
turbed areas will be observed and recorded.
See the accompanying list of species for plant composition
and for plant distribution. The expressions for abundance,
abundant (A), common (C), and rate (R) are subjective values and
expressed on the basis of frequency of observation in relation to
other species. If a species is present as isolated individuals
but occurs widely over the plots it is classed as common. To
be abundant the species occurs in dense stands and then as in-
dividuals over a wide area.
THE OPEN-WATER PORTION OF THE WETLAND
Description
The open-water area of the wetland is restricted to about
one acre located near the center of the marsh. It was about
eight inches deep when measured on August 16, 1974. Although
the bottom at eight inches was capable of supporting the weight
used for sampling (1 3/4 inch pipe coupling) it really repre-
sents the top of several feet of unconsolidated ooze and plant
fragments.
The open-water is being reduced around the perifery by bog-
like encroachment of surrounding vegetation. It was possible
to approach the open-water within about ten feet by walking on
the quaking roots. However, between these clusters of roots
it was possible to thrust a lathe down five feet without con-
tacting any firm bottom. By laying 4x8 sheets of 1/4-inch
plywood on the quaking rooted plants it was possible to get to
the very edge of the open water to take samples with dip nets
and to dip samples for plankton analysis.
Methods
Sampling was performed from the edge of the open water.
After much experimentation two techniques were established for
sampling. Plankton was taken by holding a one-gallon plastic
bucket on the end of a stick and allowing it to fill very
slowly and carefully to avoid disturbance of the bottom ooze.
This sample was then poured through a coarse-mesh insect net
102
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into the plankton net. The coarse-mesh net removed most of
the duckweed and other floating material while the small plank-
ters, it is felt, passed through relatively unaffected. The
same technique will be used for the follow-up study.
Larger organisms including snails, fingernail clams, and
insects, were collected by random thrusts with the insect net
among the roots, bottom ooze, plant fragments and floating
duckweed. This material was then worked over manually and the
organisms picked out in the laboratory.
Finally life forms and activity on and about the marsh were
observed and recorded.
Findings
The examination of the open-water portion of the marsh
demonstrated conclusively that it is a healthful, living habi-
tat. The limited span (season) of time over which the investi-
gation was conducted (late July and early August) limit the
organisms to those which were in "bloom" at that time. The
highly organic quality of the environment further limits the
species to those of special tolerance also. However, in spite
of the limiting factors, great diversity of life forms is ap-
parent.
At least two broods of ducks were reared on the marsh. One
brood of five young woodducks with the mother and one brood
of five young mallards with their mother were observed. Green
herons, four at one time, were observed in July and August sug-
gesting that they were reared there.
Many young toads, very recently metamorphosed, were ob-
served on the higher marsh suggesting that they passed the tad-
pole stage in the marsh water. Leopard frogs are present near
the water and over the marsh.
Anthropods were broadly represented in the collections.
Back-swimmers, water scavenger beetles of two species, damsel-
fly naiads, mosquito larvae and other diptera larvae were ab-
undant. Cladocera were represented by Ceriodaphnia and Simo-
cephalus. Copepods were represented by two cyclopid types
identified to the genera Cyclops and Eucyclops. No live ostra-
cods were collected although fossil shells occurred in the
plankton collections suggesting their recent demise.
Mollusks were represented by three species of snails in-
cluding Helisoma trivolvis, a small species of Stagnicola, and
a Planorbula, and one species of fingernail clam in the genus
Musculium.
Annelids were represented by at least three species; flat-
103
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worms, one species; rotifers, seven species; porifera, one spe-
cies; protozoa by fifteen species identified to genus and many
species not identified; algae, by eight species identified to
genus and many species of diatoms not identified.
The surface of the open water was completely covered by
duckweed including Lemna minor, Lemna trisulca, and Wolffia sp.
No submerged or floating leaved aquatic plants were observed in
the open water.
Encroachment around the perifery is being accomplished by
several species of plants including cattails, purple loosestrife,
arrowleaf, smartweed, a mint, an umbelliferae, and a spike rush.
Quantitative determinations are restricted to the forms
collected by straining a measured volume of water through the
plankton net. The name "plankton" has been advisedly applied
to thise category. Because of the few sexually mature adults
(needed for species identification) and the many developing
stages the two species of copeponds are simply referred to as
cyclopids. Counts are as follows:
Number Number
Organism per liter Organism per liter
Phacus 150 Nauplius 1920
Monostyla 960 Cyclopidae 750
Lecane 420 Ceriodaphnia Present
Lepadella 300 Simocephalus Present
Platyias 340
Salphina 300
Diaschiza 30
See the attached list of identified species. All in all I
conclude that this is a healthy late-stage marsh community of a
type found in abundance in the metropolitan area and over much
of the state. Adequate evidence is available to evaluate any
marked alteration in the quality of the environment caused by
the experimental techniques of the marsh evaluation study.
104
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REPRESENTATIVE LIST OF THE FLORA OF THE STUDY PLOTS
SCIENTIFIC NAME
(or genus only)
Acer negundo
Fraxinus pennsylvanica
Salix (2 spp.)
Cornus sp.
Ribes
Sambucus canadensis
Rubus pubescens
Vitis vulpina
Rhamnus catharticus
Viburnum opulus
Dryopteris thelypteris
Onoclea sensibilis
Phalaris arundinacea
Calamagrostis canadensis
Poa sp.
Carex (3 spp.)
Scirpus atrovirens
Typha latifolia
Sagittaria sp.
Caltha palustrius
Mentha arvensis
Lycopus asper
Lycopus americanus
Rumex sp.
Urtica gracilis
Lysimachia thyrsiflora
Eupatorium purpureum
Eupatorium perfoliatum
Impatiens capensis
Lythrum salicaria
Asclepias incarnata
Stellaria longifolia
Campanula aparinoides
Solidago sp.
Polygonum sagittatum
Epilobium sp.
Chelonia glabra
Cirsium sp.
Aster sp.
Aster sp.
COMMON NAME
Box Elder
Green Ash
Willows
Dogwood
Black Currant
Elderberry
Swamp Raspberry
Wild Grape
Buckthorne
Highbush Cranberry
Marsh Shield Fern
Sensitive Fern
Reed Canary Grass
Blue-joint Grass
Blue Grass
Sedges
Leafy Bulrush
Cattail
Arrowleaf
Marsh Marigold
Peppermint
Water Horehound
Water Horehound
Dock
Stinging Nettle
Tufted Loosestrife
Purple Boneset
White Boneset
Spotted Jewelweed
Purple Loosestrife
Swamp Milkweed
Long-leaf Chickweed
Marsh Bellflower
Goldenrod
Tear-thumb
Willowherb
Turtlehead
Thistle
White Aster
Purple Aster
ABUNDANCE
(R, C, or A)
C
C
C
C
C
C
R
R
R
R
R
R
A
C
R
R to C
R
A
C
R
C
R
R
R
R
C
C
R
C
A
R
R
R
R
C
R
R
R
R
R
105
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REPRESENTATIVE
THE OPEN-WATER
Algae, Blue-Greens
Oscillatoria
Algae, Greens
Cosmerium
Closterium
Euglena
TracheImonas
Phacus
Mougeotia
Oedogonium
Ulothrix
Algae, Diatoms (Many)
Protozoa, Amoeboid
Arcella
Centropyxis
Difflugia
Protozoa, Ciliates
Stentor
Stylonichia
Spirostomum
Chilodonella
HalterTa
Frontonia
Cyclidium
Vorticella
Trachelophyllum
Paramecium
Coleps
Urocentrum
Protozoa, Flagellates
Peranema
Anthrophysa
Oikomonas
Monas
Bodo
OF ORGANISMS FROM
PORTION OF WETLAND
Porifera
Spongilla fragillis
(Spicules only)
Flowering Plants on Water
Lemna minor
Lemna trisulca
Wolffia sp.
Flowering Plants in Water (None)
Rotifers
Rotaria
Platyi
las
Salpina
Monostyla
Diaschiza
Lecane
Lepadella
Platyhelminthes
Stenostomum
Annelida
Chaetogaster
Pristina
Another unidentified
Mollusca, Gastrapods
Helisoma trivolvis
Stagnicola
Planorbula
Mollusca, Pelecypoda
Musculium
106
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REPRESENTATIVE OF ORGANISMS FROM
THE OPEN-WATER PORTION OF WETLAND (cont.)
Crustacea, Cladocera
Simocephalus
CeriodaphnTa
Crustaces, Copepods
Cyclops
Eucyclops
Crustacea, Amphipods
Hyalella
107
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APPENDIX B
ECOLOGY REPORT - PHASE II
(Status of the Biota After One Year)
by
James A. Jones, Ecologist
GENERAL COMMENTS
One year has elapsed since the initial examination of the
vegetation of control and experimental plots and the faunal and
floral analysis of the open-water portion of the wetland outside
the plots. During this period the hydrolegists, biologists,
chemists and engineers of E. A. Hickok and Associates have com-
pleted installation of a superb array of water control and water
monitoring devices and developed mechanisms for monitoring the
activity of the microorganisms of the wetland substrate (and
other) .
Significant to the ecology portion of the study there has
been a difference in the treatment given the experimental and
control plots of the study area. The water level in the experi-
mental plot has been lowered by pumping then allowed to fill
again several times during the course of the year.
Significant also have been the fact that the spring and
early summer have been exceedingly wet maintaining a somewhat
greater amount of water over the whole wetland than normal. The
relative effect of the natural phenomenon and the artificial con-
trols will not be assessable. The effort of this portion of the
study will be to identify any differences between the experiment-
al and the control plots and to compare the present biota of the
open-water wetland with that of one year ago.
THE EXPERIMENTAL AND CONTROL PLOTS
Methods for Reassessment
Plot maps of the 1974 survey were used to determine the
lines followed in that survey. This was necessary because re-
growth and recovery of the vegetation has been sufficient to
obliterate the paths established in the installation of the
tile and the plastic sheeting. However, conspicuous forms of
vegetation such as trees, willow clumps and the larger herbs
made it possible to orient myself at all times. Many specific
108
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plants on the lines and at points of intersection were identi-
fiable. Using this technique for orientation I traced each of
the trails three times—once for trees and shrubs, once for
grasses, sedges and cattails, and once for other herbs. Many
of the trails were covered additional times to double check and
confirm impressions (see Figures 1, 2 and 3 for distribution of
vegetation).
Vegetation of the wetland outside the control and experi-
mental plots was examined also, especially as it pertained to
willows.
Findings
Two generalizations can be made:
1. There are noticeable changes in the wetland.
2. There are no detectable differences in the changes
between the test and control plots.
The larger willows have suffered the death of some major
stems as well as of lesser branches. Careful examination shows
that this is not a unique occurrence of this year but that major
stems have died in years past not only on the study plots but
over the wetland outside the plots. Older dead stems are on the
ground by the willow clumps and overgrown with grasses of pre-
vious years. Dead and dying stems are found outside the study
area in this wetland and in other wetlands in the metropolitan
area. Vital young growth is apparent in most clumps.
There is an increase in the amount of touch-me-not (Impat-
iens capensis) in both the test and the control plots.
There is an increase in the number and vitality of the cat-
tails in both plots; this is especially noticeable in the test
plot because of the greater abundance of cattails there. Many
more stems are producing seeds this year than last. New stems
one to two feet tall are present in both plots.
There is an increase in the amount of mint (Mentha arvensis)
related especially to the paths formed last summer. The slight-
ly reduced competition of the previously well established cover
due to last summer's disturbance probably gave the mint a better
chance.
The several small (seedlings and saplings) ash (Fraxinus
sp.) and box elder (Acer negundo) apparent last summer could not
be found and no new ones were found this summer.
The reed canary grass appears to be acquiring even a great-
er dominance over the western half of the plot although this is
109
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difficult to establish. (Perhaps the clipping data will give
some indication.) My impression may be prejudiced by the fact
that no trails were established over most of the area this sum-
mer requiring me to break new trails through it.
Two other plants, though still rare are definitely more
abundant, the wetland marigold (Caltha palustris) and the arrow-
head (Sagittaria sp.).
Conclusions
Based on the information that I can bring to bear on the
question I conclude that there is no difference in the response
of the vegetation of the control and experimental plots result-
ing from the "difference in treatment" afforded them over the
past year.
However, there are changes in both plots. While I am re-
luctant to hypothesize on the causes of the changes, the summa-
tion of the observations strengthens my feeling that the changes
are definitely toward the direction of a greater amount of water.
The woody plants (willows and trees and to some extent the red-
ozier dogwood) are under stress while the more typically aquatic
herbacious plants are thriving and increasing. The great major-
ity of the species have a wide tolerance and are not noticeably
affected, however.
Further, since both sides of the study area are similarly
affected, I am confident that any effect on the vegetation that
might have been apparent due to the experimental activity has
been overridden by natural forces over the whole wetland.
THE OPEN-WATER PORTION OF THE WETLAND
Method of Reassessment
Sampling was performed from the edge of the open water as
was done previously. It was necessary to place a new piece of
plywood at the edge of the wetland for support. (Anyone ap-
proaching the open-water edge should be warned of the lack of any
solid support for several feet into the bottom once the support-
ing root structure of the sedges and cattails is passed.)
The sample was taken using a dip net and a plankton net as
was done for the original samples last summer. They were taken
to the laboratory and examined under the dissecting scope then
under the compound microscope as was done previously.
Findings
I can detect no significant difference in the open-water
wetland in the two examinations. No ducks were observed on my
110
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single visitation but that is not to say there are none in the
wetland. Last summer they were only seen once in several visits
then only after a prolonged period of quiet observation.
No leopard frogs were observed.
More toads than last year were observed which indicates
that conditions were satisfactory for amphibian reproduction.
The same anthropods, mollusks, and lesser animal phyla were
observed in flourishing numbers, many of them in reproductive
phases and developmental stages.
The surface of the open water is again covered by the three
species of duckweed. Again no submerged or emergent rooted
aquatics were apparent. The bottom is probably just too un-
stable to support rooted aquatics. Succession into the open
water is from the periphery with the same formation as last year
apparent.
No attempt is made at quantitative determinations this time
but in scanning the microscope fields it is apparent that the
same species are present. There are less nauplius stage cope-
pods at this time but the adults of Cyclopidae are carrying
egg sacs which will be developing into nauplius larvae shortly.
Comparing the species list of 1974 with a list that might be
prepared now, there is no significant difference. One addition-
al algae (Spirogyra) is noted; one rotifer (Rotaria) was not ob-
served; an additional cladoceran (Pleuroxisj and an additional
copepod (Ectocyclops) were observed this year. It is apparent
that the diversity index is high indicating a healthful com-
munity. Once this is established the number of species listed
is directly proportional to the amount of time spent looking
and the number of samples examined. Thus the deletion or ad-
dition of a few examples is not meaningful for our purpose here.
Conclusions
I conclude that the activity on the wetland over the past
year has had no measurable effect on the life and vitality of
the open-water portion of the wetland as measured by the composi-
tion of the biota of the plants and animals of the open water.
Ill
-------
NORTH
25'
GRASSES, SEDGES AND CATTAIL
LEGEND
3 GRASSES (90% POA) o
SEDGES
CATTAILS
Figure 1. Distribution of Grasses, Sedges and Cattails
50'
112
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TREES AND SHRUBS
TW-SALIX SP.
A- FRAXINUS PENNSYLVANICA
B - ACER NEGUNDO
C^CORNUS SP.
E-SAMBUCUS CANADENSIS
G-VITIS VULPINA
R=RIBES SP
HC = VIBURNUM OPULUS
Bu=* R. CATHARTICUS
BW= SALIX SP.
Figure 2. Distribution of Trees and Shrubs
113
-------
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Figure 3. Distribution of Dominant Forbes
114
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APPENDIX C
METHODS OF SAMPLE COLLECTION AND ANALYSIS
OVERVIEW
All methods used in the performance of this project were in
accordance with accepted methods specified by various agencies
and organizations including the Environmental Protection Agency,
U.S. Weather Bureau, U.S. Geological Survey, American Society of
Testing Materials, University of Minnesota, American Public
Health Association and the American Water Well Association.
SURFACE WATER QUALITY
All water samples were collected in 500 ml (0.13 gal)
"whirl-pak" bags sterilized with ethylene oxide. Discrete
samples of stormwater runoff were collected using automatic
samplers, equipped with automatic starters, at 15 minute inter-
vals.
Composite samples of stormwater runoff, where required,
were prepared from the discrete samples. The volume of flow
passing through each flume was used to prepare the composite
samples.
Samples of water from the wetland pilot zone were collect-
ed at the sump both automatically and manually.
The analysis of all chemical parameters were performed in
accordance with Methods for Chemical Analysis of Water and
Wastes, U.S. Environmental Protection Agency (1974 Edition) (5)
and Standard Methods for the Examination of Waste and Wastewater
(13th Edition) (6) .
TABLE 1. METHODS FOR ANALYSIS OF CHEMICAL PARAMETERS
Total Suspended Solids - Filtered through glass filter paper,
dried at 103UC and weighed.
Ammonia Nitrogen - Nesslerization colorimetric analysis.
Total Phosphorus - Ammonia persulfate digestion with ammonium-
mo lybate-ascorbic acid colorimetric analysis.
Biochemical Oxygen Demand - Dissolved oxygen change over five day
incubation.
115
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TABLE 1 (continued)
Total Coliform - Plate count on m-f Endo-Broth differential
medium.
Oxidation Reduction Potential - Redox meter measurement.
SURFACE WATER QUANTITY
The quantities of water flowing into and out of the wetland
were determined using auto-start Stevens Type F flow recorders
mounted on parshall flumes. The flumes were calibrated and a
stage-discharge relationship was used to determine the flow
rates from stage measurements. The time factor was determined
rrom the flow record.
GROUNDWATER
Groundwater levels were measured in the observation wells
and expressed as centimeters below the soil surface. The top of
the casings were determined from local benchmarks.
The observation wells were sampled by pumping the standing
water from the well and allowing the wells to refill. A tyqon
tube was inserted through the top of the well and the sample
pumped directly into the sampling container.
SOIL ACTIVITY AND ENVIRONMENT
Direct counts of microorganisms were taken from fresh soil
suspensions stained with FITC and expressed as number of bacteria
per gram of dry soil. Direct microscopy method utilized a sam-
ple taken from the natural environment, diluted quantitatively,
and a known volume placed over a given area of microscope slide
Following appropriate staining, the preparation is examined under
the microscope and all microorganisms in a given field of the
microscope are counted. Recent improvements in the staining of
microorganisms have greatly facilitated the detection and the
ditferention of microorganisms from inert particles. Of par-
ticular _ usefulness is the method of staining with FITC followed
by examination and enumeration by fluorescent microscopy, with
this system, microbial cells react with the FITC and are visible
due to the fluorescence subsequently emitted from those cells;
inert and background particles do not react with the FITC and
are not seen under the microscope. Both surface and subsurface
soils were sampled.
mu KC?fb°n dioxide evolution from the soil was measured in situ.
The bottoms of one gal glass jars were removed and the jar¥ IH=~
serted 5 cm (2 in) into the soil. When capped this created a
closed chamber of fixed area to which the soil surface was ex-
116
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posed. A crucible was suspended from the lid, 10 mis of one
normal (five normal over 72-hour period) solution sodium hydrox-
ide was placed in the crucible and the lid screwed tight, after
24 hours, or 72-hours, the sodium hydroxide was quantitatively
collected and carbonate ions precipitated with barium chloride.
The sodium hydroxide was back titrated with standard hydro-
chloric acid and the milligrams of carbon dioxide absorbed was
computed.
Soil temperatures were monitored throughout the sampling
period at 12 stations. Soil temperatures at all stations were
found to be the same on a given day within the wetland. A bi-
metallic thermometer was inserted 5 cm (2 in) into the soil and
the temperatures recorded to the nearest Celsius degree.
The oxidation reduction potential of the soils was deter-
mined using platinum probes and a Corning AG3 portable pH meter.
OTHER
Precipitation data were collected using a Stevens Type SR
and a Stevens Type QR recording precipitation gage.
Air temperature and relative humidity were recorded con-
tinuously using a Science Associates Model 257 hygrothermograph.
Wind velocity data were recorded continuously using Science
Associates Model 436 and 442 anemometers with strip chart record-
ers.
Pan evaporation values were determined manually using a
U.S. Weather Bureau hook gage and continuously using a Stevens
Type F level recorder.
117
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APPENDIX D
PENMAN METHOD FOR CALCULATION OF EVAPOTRANSPIRATION
H = E + A + S+C
where H = net radiant energy available at the earth's surface,
E - energy used in evaporating water,
A = energy used in hearing air,
S = energy used in hearing the water, and
C = energy used in heating the surroundings of the water.
He reasoned that energy used in heating the water and its
container could be neglected and that the evaporation of water
could be predicted from the equation.
E = H - A
Combination of this equation with Dalton's law results in
an expression for E in which all needed values are available from
meteorological data. The Penman equation is:
_ AH + EaY
E " A +
where E = evaporation from a free-water surface in mm/day,
A_ de _
dT Ta ~ sl°Pe of the curve of vapor pressure at
saturation versus air temperature, Ta, in
mm Hg/°F,
Ea = 0.35(es - ed) 0'51+QV2
es = saturation vapor pressure at air temperature T=, in
mm Hg,
63 = actual vapor pressure of the air in mm Hg,
= 6.6
2 logh n
where V2 = average wind velocity in mpd at a height of 2 meters,
Vh = observed wind velocity at a height of h feet, and
118
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H = net radiant energy available at the surface expressed
in ram of water evaporated per day by that energy.
H is calculated from
H = Ra(l - r)0.18 + °'55n - aTa4(0.56 - 0.092/ed)
N
0.10
where Ra = mean extraterrestial radiation in mm of water per day,
r = radiation reflection coefficient (0.05 for water
surface) ,
n/N = ratio of actual to possible hours of sunshine,
a = Stef an-Boltzmann constant (2.01 x 10~9 mm day""l °K~^),
Ta = air temperature °K (°C, absolute) ,
eci = actual vapor pressure of air, mm Hg, and
y = constant in wet and dry bulk hygrometer equation
(0.27 for temperature in °F and vapor pressure in
mm Hg) .
119
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GLOSSARY
aerobic: describes an environment containing oxygen and microbes
which grow in the presence of oxygen
anaerobic: describes an environment lacking in oxygen or
microbes which grow in lack of oxygen
ecosystem: all interacting parts of the biological and non-
biological community
eutrophication: the process of nutrient enrichment of a body of
water in which an inbalance is created as nutrient concen-
trations increase at a faster rate than utilized by the
biological community
evaporation: the physical process of water loss by heat energy
conversion of water from the liquid to the gaseous state
evapotranspiration: the combined process of physical loss
(evaporation) and biological loss, transpiration, of water
from a system
fluorescene isothiocyanate total count (FITC): a staining pro-
cedure utilizing fluorescent and direct microscopic counts
for differentiation and enumeration of bacteria in a soil
suspension
mesophillic: describes the class of microorganisms which grow in
the temperature range of 16-46°C, most soil microorganisms
are of the mesophillic class
nitrification: the process of oxidation of nitrogenous compounds
to nitrate in a soil system by a class of microorganisms
known as nitrifying bacteria
phosphorus isotherm: the equilibrium curve of phosphorus in
solution versus phosphorus sorbed to soil particles, over
a range of concentrations. Each soil type has a charac-
teristic phosphorus isotherm
sorbtion: the process by which nutrients are bound to soil
particles by an ionic charge
120
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/2-77-217
3. RECIPIENT'S ACCESSION«NO.
, TITLE AND SUBTITLE
URBAN RUNOFF TREATMENT METHODS
Volume I - Non-Structural Wetland Treatment
5. REPORT DATE
December 1977 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
, AUTHOR(S)
Eugene A. Hickok, Marcus C. Hannaman and
Norman C. Wenck
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORG \NIZATION NAME AND ADDRESS
Eugene A. Hickok and Associates, Engineers for
the Minnehaha Creek Watershed District
P.O. Box 387
Wayzata, Minnesota 55391
10. PROGRAM ELEMENT NO. ]_BC611
ROAP: SOS 2; Task: 03
11. CONTRACT/GRANT NO.
S-802535
12. SPONSORING AGENCY NAME AND ADDRESS Cin. / OH
Municipal Environmental Research Laboratory--
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati. Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final 1974-1976
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
P.O. Hugh E. Masters (201)-321-6678 FTS 340-6678
16. ABSTRACT
A significant impact on lake waters is known to be caused by storm-
water runoff; providing control and treatment methods from this pollu-
tion source is a large and complex problem. The methods developed by
this project may be implemented as an urban stormwater runoff control
practice in many of the urban centers of the country that have adjacent
wetlands.
The wetland used in the study retained 77 percent of all phosphorus
and 94 percent of the total suspended solids entering the site during
the evaluation period.
It has been shown that the mechanism utilized by organic soils in the
removal of nutrients and contaminants is the result of physical, bio-
logical and chemical mechanisms.
This report was submitted in fulfillment of Grant No. S-802535 by the
Minnehaha Creek Watershed District and their consultant, Eugene A
Hickok and Associates under the sponsorship of the U.S. Environmental
Protection Agency.
17.
a.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Swamps, Surface water runoff,
Material balance, Treatment,
Filtration, Water pollution
Non-structural, Treat
ment system, Wetland
utilization, Runoff
control, Wetland eco-
system, Water balance
Nutrient balance,
Microbial immobiliza-
tiorL
19. SECUI
13B
13. DISTRIBUTION STATEMENT
RELEASE UNLIMITED
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
131
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
121
«U.S. GOVERNMENT PRINTING OFFICE: 1978— 757-140/6650
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