Team Pole Creek
Pole Creek Lake
Restoration Project
Final Report
November 15, 2007
Team Pole Creek
Pole Creek Lake
Restoration Project
Final Report
November 15, 2007
Team Members:
Mark Beres
Aigerim Meimanova
Siti Abdullah Razi
Khairina Khairul Anuar
John Steuben
Executive Summary
Our team was given the task of recommending solutions to several severe issues that have arisen concerning Pole Creek Valley Lake, located in Tabernash, Colorado. Our client, Mr. Sid Logemann, has specified several problems which must be addressed. They are:
· Leakage from Pole Creek Lake.
· The poor state of repair of Pearl Ditch, which feeds the lake.
· Algae bloom and other biological issues within the lake.
· Wildlife control in the area that surrounds the lake.
In order to address these issues, our team broke the work into several smaller subsystems, each of which roughly corresponds to one of the issues in the list above. Two team members were given the task of controlling the lake's leakage, as this issue is of primary importance. One team member was to analyze Pearl Ditch, one to examine the biological health of the lake, and one to examine the animal control issues.
After thorough investigation, our team is prepared to recommend individual solutions to each of the above issues. We recommend that the liner of Pole Creek Lake should be examined, and patched with a liquid plastic resin such as PVC. Furthermore, we feel that Pearl Ditch should be lined with a flexible polyethylene liner containing more than 5% carbon (to prevent sun damage). The lake should be treated with a barely straw extract to eliminate algae and microbial pests. The wildlife in the area surrounding the lake should be controlled via a live-trapping scheme.
In designing solutions to each of these issues, cost effectiveness was one of our foremost concerns. As this project is to be paid for by the homeowners in the Pole Creek Valley subdivision, keeping cost to a minimum was of utmost importance. We predict that the cost of materials for the entire project will be approximately $18,450.00. Unfortunately, due to the unpredictable rates charged by contractors, we cannot provide a reliable and accurate estimate regarding the installation and labor costs for this project. A contractor specializing in irrigation and water management should be contacted to provide an estimate before these solutions are implemented.
It has been our pleasure to work with Mr. Logemann, and we feel that the solutions we are recommending meet all of our client's specifications exactly. We feel that we have recommended durable, long lasting solutions, that will incur only minimal costs to the homeowners of Pole Creek Valley subdivision.
Table of Contents
Executive Summary 1
List of Figures and Tables 3
Introduction and Background 4
Project Background 4
Subsystem Division 4
Analysis of Subsystems 5
Lake Leakage 5
Background 5
Lake Measurements 5
Liner Measurements 6
Liner Replacement 7
Liner Repair 7
Recommendations and Cost Analysis 8
Pearl Ditch 8
Background and Possible Solutions 8
Liner Selection 9
Technical Considerations and Installation 10
Cost Analysis 11
Project Integration 11
Biological Health 12
Background 12
Technical Specifications 12
Application Time 13
Application Method 13
Cost Analysis 13
Wildlife Control 13
Background and Alternatives 13
Tomahawk Trap 14
Cost Analysis 14
Assembly and Operation 14
Recommendations and Conclusions 15
Summarized Recommendations 15
Total Project Cost 15
Conformation to Specifications 16
Conclusions 16
References 17
List of Figures and Tables
Figure 1: Damaged Lake Liner 5
Figure 2: Emptied Lake Bed 6
Figure 3: Pearl Ditch Bed 8
Figure 4: Liner Options 9
Figure 5: Ditch Cross Section 11
Figure 6: Algal Growth on Pond Surface 12
Figure 7: Tomahawk Trap 14
Figure 8: Drift Method Setup 15
Table 1: Subsystem Selection Table 4
Table 2: Liner Sections Table 7
Table 3: Materials Price Listing 16
1: Introduction and Background
1.1: Project Background
Pole Creek Valley Lake is situated in Tabernash, Colorado, and is owned by the Pole Creek Valley subdivision. The city of Tabernash also has water storage rights in the lake. Regrettably, the lake is currently in a state of distress. We were able to visit Pole Creek Lake earlier this month, and we were able to speak with our client, Mr. Sid Logemann, concerning these issues. According to Mr. Logemann, the lake's largest problem is water leakage, which is extensive. The lake has also fallen into poor biological health, and is host to surface algae and other organisms. Additionally, the inlet of the lake, Pearl Ditch, is in poor repair, there is silt accumulation at the lake's inlets, and there is a large population of rodents present at the lake. Our project goal is quite simple: we must provide a plan for the remediation of these issues, to be presented to the Pole Creek Homeowners Association.
When we spoke to Mr. Logemann, he was able to provide us with construction blueprints for the lake, as well as a water study conducted on the lake water. A water engineer from the city of Tabernash was also able to give us data concerning the rate of water loss from the lake. We were also able to make a number of observations at the lake site, namely that the liner had already been poorly patched in one location, and had become exposed over large areas on one edge of the lake.
1.2: Subsystem Division and Background
As we developed solutions for Pole Creek Lake, we needed to focus our research on certain specific problems. We divided the project into a number of subsystems, each of which was the responsibility of one or two team members. Each subsystem corresponds roughly to one of the issues outlined in section 1.1. However, we felt that we might not be able to provide an adequate solution to all of these problems, given our limited manpower and timetable. Resultantly, we constructed the following decision table to evaluate the lake's issues, and to group them into subsystems. The factors we considered in this process were; the importance to the client, the effect on the overall lake system, the cost, the feasibility of completing the subsystem in a semester's time, and the team's expertise in the subsystem's area. A value of five was best (most important or lowest cost), while a value of 1 was worst. All categories carried an equal weight in the decision making process.
Table 1: Decision Table for Subsystem Selection.
Issue\Factor / Importance to Client / Effect on Lake System / Cost / 1 SemesterFeasibility / Team Expertise / TOTAL
Lake Leakage / 5 / 5 / 1 / 4 / 4 / 19
Pearl Ditch / 5 / 4 / 2 / 5 / 4 / 20
Lake Health / 5 / 5 / 2 / 5 / 3 / 20
Silt Control / 2 / 3 / 3 / 3 / 3 / 16
Animal Life / 4 / 3 / 2 / 5 / 4 / 18
As you can see from above, the Silt Control issue ranked somewhat lower than its counterparts. We therefore felt that it may be more beneficial to direct our resources elsewhere, particularly to the leakage issue. As the lake's leakage was the paramount issue, we split it into two separate subsystems, each to be handled by one team member.
After discussion among our team, the following consensus was reached. Mark Beres and Aigerim Meimanova would analyze the leakage of the lake itself. John Steuben was responsible for the Pearl Ditch subsystem. Siti Razi was responsible for the biological health of the lake, and Khairina Anuar was responsible for the wildlife control issues.
2: Analysis of Subsystems
2.1: Lake Leakage
Background
Pole Creek lake is loosing water at what appears to be a very rapid rate. The loss of water has trigged a number of additional issues. Of foremost concern, the liner on one edge of the lake has become completely exposed, which has allowed it to become damaged (see Figure 1). The water loss may also be responsible for the growth of algae in the lake, and the generally poor health of the lake. It is obvious that finding an appropriate remedy for the leakage will have a significant positive impact on the overall lake condition [1].
Lake Measurements and Data
For all the measurements below the best method of approximation was used.
Surface Area of the Lake: 7.65 acres = 333,234 ft2 [2]
Approximate Volume of the lake: 1,841,820 ft3
Maximum [2]: Length 333.284 ft
Width 999.851 ft
Depth 9 ft
Average [2]: Length 283.291 ft
Width 849.873 ft
Depth 7.65 ft
Water Loss [3]: June: +0.135 ft
July: -0.105 ft
August: -0.027 ft
September: -0.08 ft
Total: -0.077 ft
The total volume drop was 0.077 ft*333234 ft2 equaling 25659 ft3, which is 1.393% of the lake’s volume, in four months. This value is approximately four times greater than the expected loss in this length of time.
Liner Measurements and Data
There are several factors that affect the determination of the size of the liner. The covering material should be large enough to cover the outside edges of the lake, and to form overlaps where sections are joined together. Since the lake has already been drained, it can be seen that the lake’s bottom is nearly flat (see Figure 2). The size of the lake bottom is a good approximation of the surface area of the liner.
Liner length [4]: 355 ft
Width [4]: 1020 ft
Liner Area: 362,100 ft2
Pond Volume [4]: 1 3,776,848 gallons = 1,841,700 ft3
Option One: Replacement of Entire Liner
The most apparent method of liner replacement is to purchase and install a single-section geomembrane such as the one currently installed. The current liner, a Bentomat ST geomembrane, could be used again, or a different product could be used if it offered some advantage. This option is, however, somewhat impractical. On the average, we found that a liner of this type cost about $0.39 per square foot. This translates to a replacement cost, for materials alone, of $143,350.00. We do not feel that this is a reasonable or cost effective solution.
Another option is to purchase rolls of material in a generic size, and to trim them to fit the lake. The material cost is significantly reduced by doing this. However, there is one disadvantage: there is a large possibility of creating leaks where individual pieces are joined together. The table below details the necessary dimensions and prices of liner sections to be purchased. An approximate total cost for materials to replace the liner in this fashion is $17860.00. This is a much smaller price, and this option may be more feasible as a result.
Table 2: Liner Section Sizes, Costs, and Quantities.
Weight (lb) / Width (ft) / Length (ft) / Price ($) / # of rolls1550 / 50 / 100 / 1900 / 6
310 / 10 / 100 / 380 / 5
1240 / 40 / 100 / 1520 / 2
13330 / 1300 / 430 / 17,860 / 13
Option Two: Liner Repair
In some instances, it is much more cost effective to locate and seal breaches in the existing liner than to replace the liner wholesale. Since the size of the lake is comparatively small and the lake has been recently drained, it is very easy to locate the leakages. According to the evidence our team has obtained researching this project, the lake is likely to have a large number of small leaks as opposed to several major ones. One practical solutions in this circumstance could be pouring a liquid plastic into the liner breach, and allowing it to harden, sealing the leak. A PVC (poly-vinyl-chloride) plastic is typically used in this application. Liner breaches should be locatable by simple inspection of the lake bed. This option is very affordable, bulk PVC plastic can be acquired at a cost of about 45 to 49 cents per pound. The amount of material needed will depend on the number and size of liner ruptures discovered.
Other repair options may exist as well. Concrete or shock-crete liner repair was considered, but it was discovered to be surpassingly expensive. Another common repair is to create a gley (a biological liner) by cutting grass and other green vegetation, and packing it six to eight inches thick in the pond basin, then trampling it by foot. The gley (hydric soil) sits for two weeks and rots, but it doesn't decompose because of anaerobic conditions. The gley forms a gel and after two weeks the pond is filled. A gley lining will only hold water for a few years. Resultantly, this option is not very practical either.
Recommendations and Cost Analysis
The repair option is decidedly the most cost-effective. The option that we consider to be the most efficient is the usage of melted PVC plastic to seal liner ruptures. At the given cost of 49 cents per pound, it is unlikely that the cost of materials will exceed $1,000.00. The labor cost is difficult to predict, and a contractor should be contacted for a quote
There are a few considerations that should be observed while the liner is being repaired. The pond should, of course, be completely dry when work begins. Additionally, the lake bed should be left to settle for a short period before being refilled. The scheduling of work should be such that work occurs at the same time on both Pole Creek Lake and Pearl Ditch, in order to reduce downtime. If possible, the same contractor should be used for both projects, and materials for the two subsystems should be purchased together to reduce shipping costs.