United States
Environmental Protection
Agency
Region 8
1860 Lincoln Street
Denver, Colorado 80295
EPA 008/3-79-00 t
oEPA
Lake Cochrane Perimeter
Road-Sediment Traps Project
Final Report
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EPA 908/3-79-001
LAKE COCHRANE PERIMETER ROAD-SEDIMENT TRAPS PROJECT
FINAL REPORT
by
Jerry L. Siege!
East Dakota Conservancy Sub-District
Brookings, South Dakota 57006
EPA CLEAN LAKES GRANT NO. S804248-01-2
Project Officer
Ronald M. Eddy
Environmental Protection Agency, Region VIII
Water Division
Denver, Colorado 80295
April, 1979
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DISCLAIMER
This report has been reviewed by the Water Quality Division
U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protec-
tion Agency, nor does mention of trade names or commercial prod-
ucts constitute endorsement or recommendation for use.
DISTRIBUTION
Document is available to the public through the National Technical Infor-
mation Service, Springfield, Virginia 22161.
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ABSTRACT
Lake Cochrane is one of the few deep high quality prairie
lakes in northeastern South Dakota. Local interests tried un-
successfully for several years to develop measures to reduce
sediment inflow. The proposal to develop sediment traps as a
part of the lake's perimeter road system was selected for a grant
award under EPA's "Clean Lakes" program initiated in 1975.
This small lake preservation project utilized the technical
and/or financial resources of every level of government. For an
allocated cost of about $20,000, three sediment traps were de-
veloped to control the sediment inflow from 66% of the lake's
watershed area. By incorporating the sediment traps into the
perimeter road system, 2700 feet of new gravel road, the sediment
traps, and a new boat access area were constructed at a cost of
$34,700. In addition, two of the sediment traps have been uti-
lized as fish rearing ponds.
Due to limited data and numerous sediment-nutrient producing
activities occurring concurrently, it has been difficult to eval-
uate the impact of the project on the lake. Preliminary evidence
indicates good suspended solids removal in the sediment traps.
There is evidence, however, that temporary storage of runoff wa-
ter may not provide any nutrient removal. A comprehensive eval-
uation program needs to be developed.
The completed project has demonstrated a low cost, effective
technique for reducing sediment inflow into a lake which may have
application in other areas.
111
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CONTENTS
Abstract iii
Figures and Tables v
1. Introduction 1
The Lake Cochrane Resource 1
Problems Affecting the Lake 1
Push for Action to Restore Lake 3
2. Conclusions and Recommendations 4
3. Development of Lake Preservation Project .... 6
Development of Project Concept and
Grant Proposal 6
Technical Aspects of Multi-Purpose
Project Features 7
Multi-Agency Participation in Project
Development 10
Objectives of the Demonstration Project . . 11
Project Activities During Grant Period. . . 11
4. Results and Discussion 15
Economic Feasibility of the Technique , . , 15
Technical Effectiveness 16
Concurrent Impact of Other Activities. 16
Summary of Project Water Quality Data. 16
Project Evaluation through other
Research 18
Operation of Sediment Traps 18
Effect of Design and Use for Fish
Rearing 18
Nutrient Removal Efficiency 19
References. . , 20
Appendix 21
iv
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FIGURES AND TABLES
FIGURES
Number Page
1 Map showing Lake Cochrane, the lake water-
shed, and surrounding area 2
2 Schematic design of two sediment traps
incorporated into construction of the new
road g
3 Schematic design of the existing road as
redesigned to function as a sediment trap. . . 9
TABLES
Number Page
1 Design Summary for all Three Sediment Traps. . . 10
2 Lake Cochrane Chlorophyll a_ Data 17
3 Average Values of Selected Water Quality
Parameters 17
4 Analysis of Sediment Trap Inflow/Outflow -
March-April, 1978 18
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SECTION 1
INTRODUCTION
THE LAKE COCHRANE RESOURCE
Lake Cochrane is a very pretty 366-acre lake located close
to the South Dakota-Minnesota border in Deuel County, South
Dakota. The lake has intermitten surface water inflow, very
infrequent surface outflow, and moderate groundwater recharge.
Although the Prairie Coteau region in northeastern South Dakota
has about 250 natural lakes, Lake Cochrane is one of a very few
having a maximum depth greater than 200 feet.
The lake was ranked into the first priority grouping by the
South Dakota State Lakes Preservation Committee (1977), meaning
that it was ranked as one of the top ten lake resources of east-
ern South Dakota.
The lake is unique in this area in that it did not experi-
ence a noticeable algal bloom until the summer of 1971. Prior
to this 1971 algal bloom, most local people felt that the lake
would remain "crystal clear" forever.
Figure 1 is a map showing Lake Cochrane, its drainage area,
and the surrounding area.
The total direct drainage area of the lake is very small at
about 765 acres.
PROBLEMS AFFECTING THE LAKE
The major watershed problem affecting the lake before this
project was developed was the sediment-nutrient inflow from three
small drainage areas located on the southwest side of the lake.
Heavy shoreline and lake bottom sediments found in that area pro-
vided strong evidence that these three watershed inflows were
adversely affecting the lake.
The other main input of lake sediments and nutrients prior
to 1976 was erosion and runoff resulting from sometimes careless
construction of lakeshore residences. Although there are a num-
ber of lakeshore residences, seepage from domestic wastes has
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Culver
Lake
— Sediment Trap
location
Indirect
drainage ar
Direct
» ^Drainage
|i Area
South Slough
16|15
-------
been minor due to a strong push to install sealed tanks as op-
posed to septic tanks and drainfields.
PUSH FOR ACTION TO PRESERVE THE LAKE
The urgency for reducing sediment and nutrient inflows re-
ceived a strong boost from the 1971 algal bloom which was the
first major evidence that this lake was becoming euthrophic.
This interest received another boost in study reports prepared
by Dr. Lois Haertel (1972), a biologist at South Dakota State
University, and by Douglas Hansen (1973), a Watershed Biologist
for the South Dakota Department of Game, Fish and Parks. Both
reports strongly recommended development of sediment control
measures for the lake.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
This project accomplished the stated project objective of
demonstrating a low cost, effective technique for reducing sedi-
ment inflow into a lake by incorporating sediment traps into
either existing or new roads located along the perimeter of the
lake.
Nearly every high quality, heavily used lake has some type
of access road developed around all or a portion of the perim-
eter of the lake. The landowners along this road system are
generally willing to participate in efforts to preserve the lake
because the quality of the lake directly affects their land val-
ues and their enjoyment of the lake.
Limited water quality data collected as a part of this pro-
ject and research conducted by Dr. Haertel (1978) has provided
evidence that temporary storage of runoff water will provide a
significant reduction of suspended solids but may not provide any
nutrient removal. This is a significant conclusion since a large
portion of lake sediments in many prairie lakes is organic mater-
ial produced within the lake itself. Thus, trapping inorganic
sediments in watershed control structures while allowing nutri-
ents which stimulate lake productivity to pass through will re-
duce but will not stop the filling of a lake with sediment and
will not likely improve lake water quality.
The development of sediment control was cost effective under
this multi-purpose technique because the road function financed a
portion of the cost of the (a) earth fill, (b) structures to
carry water through the roadway and (c) land rights.
This technique in many instances would have the following
advantages:
(a) Because land requirements for developing sediment
control measures are reduced, land rights are also
generally easier to secure.
(b) The sediment control structures by being located on
the perimeter road are located relatively close to the
lake; thus sediments are restricted from adjacent
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lands which often contribute a high percentage of
the lake's sediment load.
(c) By being located on a road, access for operation
and maintenance purposes is much easier.
It is recommended that a comprehensive, well-planned moni-
toring program be developed which is geared to evaluating the
efficiency of these sediment traps and their specific impact
on the quality of Lake Cochrane.
The project facilities offer an opportunity to research
the effectiveness of two different sediment trap designs. More
importantly, the sediment traps with controlled drawdown tubes
offer an important research facility for making a thorough
evaluation of the impact of temporary versus more permanent
water storage on nutrient removal efficiency. As noted above,
the initial evaluation of this project has indicated that tempo-
rary water storage may not have a positive impact on lake water
quality beyond restriction of inorganic sediments. There are
many important questions in this regard that need to be answered
before large amounts of public funds are used to develop sedi-
ment and/or nutrient control measures for shallow glacial lakes
in the United States.
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SECTION 3
DEVELOPMENT OF LAKE PRESERVATION PROJECT
DEVELOPMENT OF PROJECT CONCEPT AND GRANT PROPOSAL
In the early 1970's various local and state interests in
eastern South Dakota began searching in earnest for methods and
programs to accomplish the goal of developing sediment control
measures for Lake Cochrane. They explored the possibility of
reconstructing an existing township road crossing the lake's
largest drainage course to make it function as a sediment trap.
At the same time there was a strong interest in completing the
perimeter road system around the lake's western side where the
next two largest drainage inlets are located. Unsuccessful at-
tempts were made to secure funds through the U.S. Department of
Agriculture, South Dakota's Water Resources Institute and other
programs.
The project did not fit any ongoing program in the early
1970's.
The U.S. Environmental Protection Agency, in releasing the
first $4 million of funds appropriated under Sections 104(h) and
314 of PL92-500 in 1976, stressed that high priority would be
given to lake preservation and/or restoration proposals that
(a) would demonstrate innovative new techniques,
(b) would attack sources of lake problems such as sediment-
nutrient inflows, and
(c) could have wide application.
The East Dakota Conservancy Sub-District, working with other
local interests, developed a project proposal to construct three
low-cost sediment traps; the first by redesigning and reconstruc-
ting an existing township road and the other two by altering the
design of a proposed new perimeter road where it would cross the
two other main drainage inlets. The proposal was one of eleven
projects in six states initially funded under the new federal
"Clean Lakes" program.
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TECHNICAL ASPECTS OF MULTI-PURPOSE PROJECT FEATURES
The multi-purpose project features were as follows:
(a) Construction of 2700 feet of gravel road, this completing
the lake's perimeter road system.
(b) Development of three sediment traps, thus reducing the
sediment inflow 'from 66% of the lake's total direct
drainage area.
(c) Development of a major new boat access area. This access
area was developed as a multi-purpose use of a needed
project borrow pit.
(d) Multi-purpose use of two of the sediment traps as fish
rearing ponds by the South Dakota Department of Game,
Fish and Parks.
The two sediment traps incorporated into the construction
of the new road (known as Sites 1 and 2), shown in Figure 2, were
designed with manually controlled drawdown openings to allow
permanent storage of water if desired up to the top of the riser
pipes.
A schematic diagram of the sediment trap developed by re-
construction of the existing road (known as the Cochrane Site)
is shown in Figure 3. Water cannot be permanently impounded be-
cause it has an uncontrolled drawdown tube.
Table 1 contains summary design information for all three
sediment traps.
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00
3:1 Side
slopes
Outflow to
lake
28 ft. wide
Gravel roadway
24" Overflow and
drawdown tube
Riprap to protect earthfill
when water level is high
Manual control for
drawdown tube
30" Drop inlet
riser pipe
Riprap to reduce
outlet erosion
Core trench
9" Drawdown
opening
Figure 2. Schematic design of two sediment traps incorporated into construction
of the new road.
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32 ft. wide
Gravel roadway
3:1 Side Slopes
Riprap to reduce
erosion near outlets
30" Overflow tube
4 ft. high
athern bertn
12" uncontrolled
Drawdown tube
Watershed
Inflovs
Figure 3. Schematic design of the existing road as redesigned to
function as a sediment trap.
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TABLE 1. DESIGN SUMMARY FOR ALL THREE SEDIMENT TRAPS
Design Feature
Drainage Area (Acres)
Height of Fill (Feet)
Pool height at main
overflow tube (Feet)
Storage at main
overflow tube (Ac-ft)
Length - Main
overflow tube (Feet)
Diameter - Main
overflow tube (Inches)
Diameter - Riser
pipe (Inches)
Diameter - Drawdown
tube or opening (Inches)
Controlled drawdown tube
New
North
Site
41
15
10
5.0
108
24
30
9
Yes
Road
South
Site
57
19
11
3.4
128
24
30
9
Yes
Existing Road
Cochrane Site
411
7
4
11.6
84
30
12
No
MULTI-AGENCY PARTICIPATION IN PROJECT DEVELOPMENT
It is pertinent to review the participation of the six main
governmental entities involved in the development of the overall
project.
At the local level, Deuel County and Norden Township played
a strong role by financing the construction of the new road and
securing easements for the entire project. The county also
handled the construction contracts for the project.
At a multi-county level, the East Dakota Conservancy Sub-
District provided a $10,000 grant toward the additional cost of
incorporating the three sediment traps into the road system.
The Sub-District also applied for and administered the EPA
"Clean Lakes" grant and served as overall project coordinator
At the state level, the Department of Game, Fish and Parks
contributed $3,000 in cash and designed and supervised the con-
struction of the new road portion of the project.
At the federal level, the Soil Conservation Service, as-
sisting the local Deuel County Conservation District, designed
and supervised the reconstruction of the Cochrane Site and EPA
provided a $9,906 grant toward the allocated cost of incorpo-
rating the three sediment traps into the road system.
10
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Whenever a large number of entities are involved in the
financing, design, construction and/or operation of a project,
there is the strong likelihood that problems will develop. The
five non-federal entities sought to avoid such problems by dis-
cussing in detail and arriving at clear-cut agreements on all
aspects of project development. These agreements were incorpo-
rated into a five-party Memorandum of Agreement which all
parties signed.
OBJECTIVES OF THE DEMONSTRATION PROJECT
According to the grant application, the objective of the
project was to demonstrate a simple low-cost method of reducing
lake sediment and nutrient inflow which should have wide appli-
cability in the United States and to demonstrate the technique
for both existing and planned new perimeter road systems.
PROJECT ACTIVITIES DURING GRANT PERIOD
It was noted in the original grant proposal that the Soil
Conservation Service would design all project works. When all
the non-federal entities met on August 21, 1976 and developed
a Memorandum of Agreement for the project, it was decided to have
the Department of Game, Fish and Parks design Sites 1 and 2 since
the Department had offered to design and supervise construction
of the road itself.
After the EPA grant was officially awarded on January 8,
1976 local entities took immediate steps to secure needed pro-
ject easements and to ready the project for construction.
In early March the Project Manager notified Barbara Schroe-
der, who was placed in charge of the project by EPA officials in
Denver, that Deuel County was ready to open bids for the project
and asked for instructions. Construction bids were opened for
the new road portion of the project on March 29, 1976 with six
firms bidding. Halstead and Lewis Construction of Brookings,
South Dakota submitted the low bid of $21,089.47 which was ac-
cepted by the county commissioners.
Bids were opened by the commissioners for the Cochrane Site
on April 20. The commissioners awarded the contract to Annet
Construction, Inc. of Milbank, South Dakota who submitted a low
bid of $6,912.
On June 8, Bruce Perry, EPA-Denver, informed the Project
Manager that John Brink was replacing Barbara Schroeder as Pro-
ject Officer. On June 22, Mr. Brink toured the project and
noted he was impressed with the construction work in progress.
The Game, Fish and Parks Department Engineer noted after a
June 23 inspection of the new road portion of the project that
11
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it was complete except for dressing the ditches, placing riprap
and cleanup. He indicated that his department would seed the
project area later in the fall.
On July 14, the Soil Conservation Service Area Engineer and
Deuel County States Attorney notified the Project Manager that
three problems had developed concerning the Cochrane Site: (1) a
pipe specification change had resulted in an increased cost of
about $350; (2) access driveways to two lake lots had been omit-
ted in the plans, and (3) the landowner on the south side "under-
stood" that the county was going to do some private work for him
if he gave a "free" easement for the project work. Meetings with
the county, township and contractor were set by the Project Man-
ager. Although the access driveways cost $600 and the landowner
was offered and paid a fair price for his easement, these prob-
lems were resolved without any additional EPA grant.
On July 29, John Brink, EPA Project Officer, called and
asked the Project Manager to submit monthly reports. After re-
viewing the Project Grant Agreement, however, it was determined
that the only monthly activity required was water quality moni-
toring. After a discussion of local laboratory limitations,
Mr. Perry and Mr. Brink agreed during August to accept the bi-
monthly monitoring program in progress.
By September, the construction work under both contracts was
complete except for grass seeding. Mr. Brink toured the project
area on September 20 and noted that with establishment of this
grass cover the project would be satisfactorily completed.
On October 21, a dedication ceremony was held at the Shady
Beach Resort on Lake Cochrane. The ceremony was well attended
by local residents and received excellent area news coverage.
Stuart McDonald and Barbara Schroeder represented EPA.
Sites I and II were seeded and mulched prior to the dedica-
tion. The Cochrane Site was not seeded at that time due to a
standoff between Deuel County and the contractor regarding the
seeding work.
During the spring runoff of 1977 all three sediment traps
filled with water. Personnel were not able to get to the project
area in time to collect water quality samples of the inflow and
outflow of the sediment traps because the lake was located in a
remote location, the runoff was unseasonably early, and the
perimeter road was blocked with snow because it was not main-
tained during the winter season.
The Department of Game, Fish and Parks successfully reared
walleyes that spring in Sites 1 and 2. They opened the drain
tubes in late May to collect the fingerlings for distribution to
Lake Cochrane and other lakes.
12
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Bruce Perry, current EPA Project Director from Denver,
toured the project on May 26. He was very favorably impressed
with the project but urged the Project Manager to resolve the
grass seeding stalemate at the Cochrane Site.
In October the Project Manager located a free source of
native grass seed and asked the Game, Fish and Parks if they
would seed and mulch the area for the $200 contained in the con-
struction contract for the seeding work. At a meeting between
the county commissioners, Game, Fish and Parks and the Project
Manager, on October 11, the seeding issue was resolved.
On October 18, the Project Manager set up a meeting between
Jack Opitz, Department of Game, Fish and Parks (who was respon-
sible for operating structure Sites 1 and 2) and Dr. Lois Haertel,
SDSU Botony-Biology Department, to discuss her concern that the
lake received a heavy nitrogen load when the sediment traps were
emptied into the lake in early summer for fish removal. Mr. Opitz
agreed to leave the drain tubes closed and remove the fish in
another manner the following year to allow better nutrient re-
moval .
On October 19, Mr. Opitz provided notification that he had
inspected the project area ana found that the 1976 seeding pro-
gram was pretty well established.
On November 23, the Department of Game, Fish and Parks com-
pleted the seeding and mulching work on the Cochrane Site.
On November 30, final grant payment was requested from EPA
for the completed work and Bruce Perry, EPA-Denver, was notified
that the work was successfully completed.
In the spring of 1978 two sets of water samples of the sedi-
ment traps inflow-outflow were collected with considerable diffi-
culty. The Project Manager determined that unauthorized person-
nel desiring a higher lake level had opened the drain tubes prior
to the spring runoff. The tubes were closed in time to catch
most of the runoff and were padlocked to prevent this from hap-
pening again. The inflow was heavy enough so that water flowed
through the overflow tubes of all three sediment traps.
New EPA Project Officer, Debbie Patterson of Denver, in-
spected the project with the Project Manager on April 26. Sites
1 and 2 were still filled to the top of the risers (overflow
tubes) whereas the uncontrolled Cochrane Site was completely
drained down. Grass was well established on the project area.
The project was selected by EPA for presentation at the
August 22-24 National Lakes Restoration Conference in Minnea-
polis. The Project Manager made the presentation.
13
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Fish were not reared in Sites 1 and 2 during 1978. The
north site (Site 1) held water all year whereas Site 2 eventually
drained dry due to a leak in the drain tube. This leak was cor-
rected in late 1978.
14
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SECTION 4
RESULTS AND DISCUSSION
ECONOMIC FEASIBILITY OF THE TECHNIQUE
The cost of developing the sediment traps was reduced below
the costs of normal development under this lake preservation
technique because the raod function financed a portion of the
cost of
(a) the earth fill,
(b) structures to carry water through the roadway, and
(c) needed land rights for the structures.
The full cost of reconstructing the existing road was allo-
cated to the lake project since the road was already suitable
for transportation purposes. The existing road fill and road
easements reduced the costs of this construction, however.
Due to these multi-function cost savings, the cost allocated
to the sediment traps was slightly less than $20,000.
The $20,000 allocated to the lake preservation project cov-
ered the following items not required in normal road construc-
tion:
(a) Flood easements for the sediment pool areas;
(b) Rip-rap of the face of these areas;
(c) Increased fill height and width to provide desired
water storage;
(d) Excavation and refilling of a core trench, and
(e) Increased costs resulting from design changes in the
drainage structures; the added cost resulting from the
need for caulked, close-riveted seams, water seepage
collars and secondary overflow tubes is somewhat counter-
balanced because when water can be stored behind the road
fill, the diameter and thus the cost of the main drain
tubes can be reduced.
15
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TECHNICAL EFFECTIVENESS
Concurrent Impact of Other Activities
It is somewhat difficult at this point to draw definite
conclusions on the impact of the completed sediment traps on
lake water quality because very limited project data have been
collected on the actual inflow-outflow of the sediment traps.
It is very difficult to evaluate the sediment traps using in-
lake data because of the concurrent impact on the lake of a
number of sediment-nutrient producing construction activities.
This construction has included a number of lakeshore homes, a
new state park area on the north side of the lake, and the pro-
ject works including the associated new road.
In addition, the lake area exprienced a severe drought
during 1974-77 which reduced normal surface and groundwater in-
flows and resulted in a lower than normal lake level.
Summary of Project Water Quality Data
There were no funds in the EPA grant to cover water quality
monitoring. During the period of the grant, water quality sam-
ples were generally collected bi-monthly by the Project Manager
under a cooperative East Dakota Conservancy Sub-District/Depart-
ment of Environmental Protection lake monitoring program. Sam-
ples were analyzed by the State Health Laboratory in Pierre. It
was difficult to meet grant requirements for chlorophyll a data
since none of the main water quality laboratories in the state
were equipped to analyze chlorophyll a_.
The grantee did contract with Randall Brich, a Department of
Biology graduate student at South Dakota State University, in
July, 1977 for collect of chlorophyll a. data which is shown in
Table 2.
16
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TABLE 2. LAKE CHOCHEANE CHLOROPHYLL a DATA
Chlorophyll £ mg/1 -
Station Average of 3 grab samples
8/16/77 9/4/77 9/22/77
1-S
3-S
3-B
(southwest
(northeast
(northeast
bay - surface)
quadrant
quadrant
- surface)
- bottom)
12
13
11
.1
.1
.3
11
10
11
.2
.4
.6
11.
13.
12.
4
2
9
All water quality data collected under this grant agreement
has been transmitted to the EPA regional office in Denver.
Table 3 contains average annual values for selected water
quality parameters for the period 1975-1978.
TABLE 3. AVERAGE VALUES OF SELECTED WATER QUALITY PARAMETERS
No. of Samples
Conductivity
Suspended
Solids
NH3-N
Ortho PO^-P
Total P04-P
Unit
micromho
mg/1
mg/1
mg/1
mg/1
1975
3
3053/22
99
.125
.022
.034
1976
5
2782/23
28
.11
.018
.037
1977
4
3535/24
103
.34
.011
.036
1978
4
2700/23
87
.28
.014
.087
Table 4 contains values for selected constituents from sam-
ples collected and analyzed from the three sediment traps during
the spring runoff of 1978.
17
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TABLE 4. ANALYSIS OF SEDIMENT TRAP INFLOW/OUTFLOW
Parameter
Cochrane Site
(uncontrolled
drawdown)
Inflow/Outflow Inflow/Outflow Inflow/Outflow
March 29, 1978
Suspended
Solids
NH3-N
TKN-N
Ortho PO^-P
Total P04-P
Suspended
Solids
NH3-N
TKN-N
Ortho P04-P
Total P04-P
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
121
.23
1.65
.089
.168
54
.15
.72
.060
.075
17
.48
1.21
.150
.192
April 4,
25
.19
.80
.108
.135
25
.037
1.67
.033
.111
1978
40
.34
1.71
.027
.075
31
.07
.086
.082
.131
23 33
.19 .04
.073 .82
.018 .044
.038 .062
-
-
-
-
-
8
.07
.70
.053
.067
These limited samples indicate good removal of suspended
solids in the sediment traps.
Project Evaluation through other Research
Dr. Lois Haertel (1978) has evaluated lake water quality
and algal abundance before, during and after construction of the
sediment dams through a grant funded by the Office of Water Re-
sources Research and Technology. Her data is much more complete
than the project data noted above. The most recent project
evaluation report is contained in the Appendix.
OPERATION OF THE SEDIMENT TRAPS
Effects of Design and Use for Fish Rearing
Multi-purpose use of two of the sediment traps as fish rear-
ing ponds imposed two requirements in this case (a) the sediment
traps had to be designed with manually controlled devices to
close the drain tubes during spring and early summer and (b) ef-
ficient removal of the fingerlings required emptying the water
in the sediment trap which allowed nutrient-laden runoff water
to pass into the lake as noted below.
18
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Use of the sediment traps for fish rearing might have either
a desirable or undesirable impact on nutrient concentrations in
the ponds. This aspect should be evaluated further.
Nutrient Removal Efficiency
For sediment control purposes only a structure is designed
to reduce the velocity of water to the point that suspended sol-
ids will drop to the bottom of the pool area. This requires
very little storage time except for the very fine sediment par-
ticles .
Theoretically a significant portion of the phosphorus load
will be trapped along with these sediments because phosphorus is
presumed to be attached to the soil particles. The limited sam-
pling from the spring runoff of 1978, however, did not indicate
good phosphorus removal. The phosphorus may be attached to the
very fine particles which do not readily settle and stay at the
bottom of the pond.
Nitrogen is dissolved in the runoff water and according to
Dr. Haertel is probably equal in importance to phosphorus as a
limiting factor in algal production in Lake Cochrane. A long
detention period will be required for nitrogen removal in the
sediment pools because the nitrogen will need to be taken up by
plant growth.
19
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REFERENCES
1. Haertel, L. 1972. Ecological factors influencing production
of algae in northern prairie lakes. South Dakota Water Re-
sources Institute, Brookings, South Dakota.
2. Haertel, Lois. 1978. Effect of sediment control dams on the
water quality of Prairie Lake. Annual Report #A-061-SDAR
submitted to OWRT.
3. Hansen, D. R. 1973. Watershed inventory of Lake Cochrane,
Deuel County, South Dakota, 1971-1972. South Dakota
Department of Game, Fish and Parks.
4. State Lakes Preservation Committee. 1977. A plan for the
classification-preservation-restoration of lakes in north-
eastern South Dakota. State of South Dakota and the Old
West Regional Commission.
20
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APPENDIX. INDEPENDENT PROJECT EVALUATION REPORT
Agreement No. 14-34-001-7088
Effect of Sediment-Control Dams
on the Water Quality of a Prairie Lake
OWRT Project No. A-061-SDAK
FCCSET (COWRR) Research Category: 6B
Proj . Began—Month: March Year: 1977
To be completed—Month: June Year: 1979
Principal Investigator: Lois Haertel
Student Assistant: Randall Brich
A. Research Project Accomplishments:
(1) Purpose of the Research Project
Three sediment control dams were constructed on Lake Cochrane
South Dakota during the summer of 1976 with the purpose of de-
creasing the sediment and nutrient influx into the lake. For-
tunately, 4 years of prior data had been collected from Lake
Cochrane through other OWRT projects and a background data base
was already present. The purpose of this project has been to
evaluate the impact of the sediment control dams on water quality
and algal growth both during and after construction of the dams.
(2) Lake Water Quality Response to the Sediment Control
Structure
Sampling has been conducted approximately biweekly over 3
open water seasons both during the construction of the sediment
control dam and the 2 seasons after its construction. Table 1
compares the results from 7 years of lake water quality data.
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Table 1. Comparison of selected mean values from Lake Cochrane
over 6 years of sampling
Water transparencey
(Secchi, m.)
Algae (chlorphylla,
, \ '
ppb)
Zooplankton (calcu-
lated filtering
rate, % water
vol/day)
Chemical parameters
N03-N
NH3-N
Organic N
Ortho P04-P
Total P04-P
Ac id-hydrolyzable
P04-P
1970
2.0
10
75
(ppm)
.05
.06
1.12
.01
.03
1971
1.3
19
21
.03
.02
1.55
.02
.10
1972
1.3
18
23
.02
.00
1.35
.01
.02
1975
1.6
13
87
.02
.04
1.27
.04
.16
1976a
1.2
14
41
.01
.15
1.38
.02
.05
1977
1.1
12
58
.03
.44
1.48
.04
.22
1978^
1.2
10
115
.07
.46
1.18
.01
.05
a) The sediment control structures were built in 1976.
b) Data computed through 7/26 (zooplankton), 8/16 (chemical
data) and 8/31 (chlorophyll and Secchi disc readings).
Mean chlorophyll a_ and organic nitrogen values are definitely
lower in 1978 than in any years after 1970. Whether this is a
response to the lower phosphate levels in 1978, or the higher zoo-
plankton estimated grazing rate is difficult to tell. Inorganic
nitrogen levels remain high in 1978. Water transparency (secchi
disc) levels are still poor in 1978; the low chlorphyll values
suggest that this is partially due to non-algal turbidity. Al-
though erosion from construction operations and from the steep
slopes of the sediment control structures and boat landing areas
is suspected as a cause of the low 1976 and 1977 transparency
readings, better growth of vegetation on those slopes should have
lessened that source of input in 1978. One cottage owner has com-
pletely laid bare a steep slope draining directly into the lake
for private construction, and erosion off that slope may be con-
tributing to the poor water transparency in 1978.
(3) Water Quality Measurements Above and Below the Sediment
Control Dams
Due to an administrative oversight, the sediment dams were
left open for much of the 1977 season. Thus, few measurements
above and below the dams could be taken during that year. Two of
the dams were kept closed during the 1978 season. Measurements
were taken above and below the one dam that experienced seepage.
The other dam was water tight and never had water going over the
riser tube on any sampling date. Nutrients trapped behind that
22
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dam were assumed to be effectively sealed off from the lake. Mea-
surements taken above and below the second dam showed a surpris-
ing phenomenon. On 5/3/77, 4/20/78 and 5/16/78, water was going
over the riser tube (Fig. 1) and flowing into the lake by the de-
signed overflow method. On those dates, the measurements were
higher above the dam than below (Table 2), as would be expected
if settling or biological uptake behind the dam were reducing the
quantities of nutrient going over the riser tube and through the
culvert. However, on most subsequent dates, water was not going
over the riser tube and seepage, possibly through a bad connec-
ting joint at the base of the riser tube, had to be assumed to be
the source of the water coming out. On almost all of those dates,
nutrient concentrations were substantially increased rather than
diminished below the sediment control dams. A possible source of
the enrichment of the water with nutrients could have been perco-
lation through the sediments behind the dam. The substantial in-
crease in nutrient concentrations may not represent a threat to
the water quality of Lake Cochrane, because the quantity of water
draining out is small, and on most dates does not flow directly
into the lake but on to a large flat vegetated beach area. The
vegetation may be removing most of the nutrients before they get
to the lake. However, the possibility of stopping the leakage
should be investigated.
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N>
Table 2. Difference
Year
Date
# reps
Dam #
Above-
below:*
N03-N
NH3-N
Org.-N
Ortho-P04
Total-PC>4
HC03
C03
Si
between Measurements of
1977
5/3 9/20
.47 -.
.05 -.
0
.02
.06
0
0
-0.4
01
10
05
02
09
-
-
—
Variables above and below Sediment Coi]
1978
4/20
1
#2
.20
.10
-.18
-.02
-.02
120
0
—
5/16
2
#2
.06
-.05
-.12
-.01
.01
-65
5
-2.1
5/31
2
#2
-.95
-.32
.02
-.05
.04
76
0
7.5
6/14 6/28 7/12
222
#2 #2 #2
-.04 -.08 -.02
-.15 -.60 -.70
.28 -.31 .23
-.73 -1.22 -.12
-.97 -1.57 -.59
-109 -89 -85
000
-9.8 -8.8 6.7
7/26
2
#2
-.11
.45
-.22
.08
-.48
-111
0
-8.4
8/17
2
#2
-.26
-.33
-.05
.18
.10
-144
-5
-22.0
8/31
2
#2
-.24
-.23
.77
.34
.32
-114
-39
-21.3
trol Dams (ppm)
1977
Mean
.23
-.03
-.03
.02
.08
0
0
-.02
1978
Mean
-.16
-.20
.05
-.17
-.36
-58
-4
-15.3
*A negative value means the concentration was higher below the sediment control dam
than above it.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
• NO.
'EPA 908/3-79-001
; AND SUBTITLE
2.
3. RECIPIENT'S ACCESSION NO.
Lake Cochrane Perimeter Road
Final Report
- Sediment Traps Project
5. REPORT DATE
April 1979
6. PERFORMING ORGANIZATION CODE
Jerry L. Siegel
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
East Dakota Conservancy Sub-District
Brookinqs, South Dakota 57006
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
S8 04248-01-2
•^SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
1860 Lincoln Street
Denver, Colorado 80295
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
•^SUPPLEMENTARY NOTES
Lake Cochrane is one of the few deep high quality prairie lakes in northeastern
South Dakota. Local interests tried unsuccessfully for several years to develop mea-
sures to reduce sediment inflow. The proposal to develop sediment traps as a part of
the lake's perimeter road system was selected for a grant award under EPA's "Clean
Lakes" program initiated in 1975.
This small lake preservation project utilized the technical and/or financial re-
sources of every level of government. For an allocated cost of about $20,000, three
sediment traps were developed to control the sediment inflow from 66% of the lake's
watershed area. By incorporating the sediment traps into the perimeter road system,
2700 feet of new gravel road, the sediment traps, and a new boat access area were con-
structed at a cost of $34,700. In addition, two of the sediment traps have been uti-
lized as fish rearing ponds.
Due to limited data and numerous sediment-nutrient producing activities occurring
concurrently, it has been difficult to evaluate the impact of the project on the lake.
preliminary evidence indicates good suspended solids removal in the sediment traps.
There is evidence, however, that temporary storage of runoff water may not provide any
nutrient removal. A comprehensive evaluation program needs to be developed.
The completed project has demonstrated a low cost, effective technique for reduc-
ing sediment inflow into a lake which may have application in other areas.
^^^•••^••••••^^•••^••n^H^^BMMMM^M^BHMMMMaMHBBWHHMBMMMWMn^MVMMniBa^Ba^B^BMvnMMMnMMMMIBMBMBB^BMB^^^^^HBHH^HnMHM^Bi^^BBIMMaiM^H^MHMBBMMai^^
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFIERS/OPEN ENDED TERMS
COSATi Field/Group
Lakes
Sediments
Nutrients
Clean Lakes
Sediment traps
Non-point sources
Lake Coclirane
STATEMENT
Unlimited
19. SECURITY CLASS fTHtl Report)'
Unclassified
20. SECURITY CLASS (TMspage>
Unclassified
21. NO. OF PAGES
31
23. PRICE
"*^|^[ P»rm 2220-1 (R«v. 4-77) PREVIOUS IOITION is OBSOLCTC
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