LOWA
Effect of Low Impact Landscaping (LOWA LILs) On Lake Contamination
(The Geosyntec Project)
THE GEOSYNTEC PROJECT
The "Geosyntect Project" is part of the LOWA 319 Grant designed to demonstrate the long-term effect that LOWA LILs have on the E-coli concentrations and on nutrient pollutants in the Lake of the Ozarks.
Program Description
Under this program, 9 coves in the focus area are being tested for phosphorus, nitrogen, total suspended solids, and E. coli. Three of the coves are undeveloped, 3 coves are treated by a regional waste water treatment plant, and 3 coves are with septic tanks.
During the first year (2011), these coves will be sampled in a 20-week water collecting program (run by Geosyntec with volunteers providing the boats, captains, and collecting), then a focused program of LOWA LILs will be encouraged, and then in the grant’s 3rd year, another 20-week water collecting program will happen.
Samples are analyzed by Lake Ozark Environmental and the results verified by Geosyntec through the grant.
Year One Study Is Complete
The discussion below reflects completion of the first year of this study. The 20 week study on these same coves will be repeated in 2013.
The teams of LOWA volunteers who religiously collected these samples in a timely fashion week after week are to be highly congradulated. LOWA thanks each and every one of them.
A Layman’s Summary of the Geosyntec 2011 Report
Geosyntec is a top-rated Environmental Consulting firm which has contracted to LOWA to perform a three year study, 20 weeks per year in years 1 and 3, on specific coves within the LOWA 319 grant area of the Lake of the Ozarks to evaluate the effect LOWA LILS might have on improving the lake water quality. Geosyntec has provided an outstanding and comprehensive report which is available on this web-site. However, the following summary is being provided for those of us non-scientists who have interest but do not have the time or expertise to fully study and understand the scientific manuscript. The study involved nine coves in sets of three with each set named by Geosyntec as an Experimental Unit (EU). These consisted of one EU with coves serviced by septic tanks, one EU with coves serviced by regional sewer systems, and one EU with essentially undeveloped coves. Layman’s summary of the report follows:
Exec Summary:
- Only differences in results among the three sets of coves were in E.coli counts except for nutrient and Secchi differences which were relative to distance from Bagnell Dam.
- All coves geometric means were well below the 126 max but those coves on septic systems were higher than the others and those on a regional system were higher than those of the reference coves (essentially no waste input).
- Fluorometric survey showed no differences among the study coves
Study Area:
- Described in detail in the report; within the LOWA LILs grant region (Lake Mile mark from zero to 19.)
- Included nine coves of three types with three coves of each type. Coves 1,2, and 3 were on septic systems, coves 4,5, and 6 were on regional sewer systems, and coves 7,8, and 9 were on relatively undeveloped coves.
Results:
- Following is a direct quote from the report referencing results during the first year study: “… lowest geometric mean E. coli of ~2 MPN/100 mLs was collected from Coves 7, 8, and 9 and highest geometric mean E. coli of ~ 26 MPN/100 mLs was collected at Cove 2. Bacteria results between the EUs were as follows; lowest from the reference coves (Coves 7, 8 and 9) and highest in coves with onsite wastewater treatment (Coves 1, 2 and 3). However, bacteria levels in all coves were well below Missouri’s water quality criterion for Whole Body Contact Recreation-A.”
- Except for E.coli, there was no difference in trends as shown by the cumulative running averages as the season progressed of the other parameters among the study coves.
- TSS (total suspended solids) was too low to measure in most cases and the average among the coves ranged from 2.22 to 2.74 mg/l.
- Nitrogen was highest in the spring and gradually declined during the summer only to commence increasing again in the fall.
- TN (total nitrogen) was highest in cove 6 and was near or above the EPA proposed maximum in all coves.
- TP (total phosphorus) was highest in cove 6 and was near double the proposed maximum in all coves.
- E.coli: In marked contrast to the non-septic tank coves, the E.coli in the septic tank coves, while consistently higher than the other two study units, was lowest in the spring but showed an increase in concentration during the recreational season and did not commence to decline until near the end of the season.
- E.coli was highest in the septic tank coves and lowest in the undeveloped coves.
- E.coli concentrations in the non-septic tank coves was highest in the spring and early summer and continuously decreased during the recreational season.
- Cove 2 E.coli: Although none of the coves exceeded the MO-DNR geometric mean maximum of 126 MPN per 100 mls, cove 2 had three occurrences of higher than expected E.coli concentrations with the highest mean average on one occasion being 443 MPN per 100 mls (well above the recommended single sample maximum of 235 MPN).
- Distance from Bagnell Dam Effect:
- Nutrient and TSS results from all coves showed that these values increased as the distance from Bagnell Dam increased.
- Water visibility as measured by the Secchi disc was best (highest) near Bagnell Dam and decreased as distance from the Dam increased.
- Rain Effect
- E.coli, TSS, and TN all increased following a rain event in the regional served and reference coves.
- No such increase was seen, statistically, in the septic tank treated coves for E.coli concentration, but there may have been a slight decrease in TP and TSS in these coves following a rain event.
- Fluorometric Study: On the premise that septic tank leakage would trigger a higher fluorescense reading, a fluorometric study was conducted on two occasions during which a fluorometer was towed around each of the coves. If any such leakage was taking place, it was not picked up by this technique.
- Waterfowl Observation: No increase in E.coli concentration was found as a result of the observed presence of waterfowl.
- Cove 2 E.coli Spikes: The spikes in E.coli in cove 2 may have been caused by the residents using their de-icing pumps to pump the bottom cooler water up to the surface to make swimming more comfortable.
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Above summary by Jerry Walker revised March 20, 2012Read the complete report in pdf format
Discussion Below Preceded and is Independent of the Geosyntec Report Discussed Above:
E-coli Test Results
E-coli test results were available within a few days of the sampling events and reported by Geosyntec to MODNR, LOWA, and the county and state health departments where elevated results were investigated.
What the E-coli Test Results Mean
E-coli test results are reported as "MPN" which stands for "Most Probable Number" of E-coli colonies per 100 milliters of water. This is a typical biological test in which water samples are incubated at a set temperature for a specific length of time in the presence of a culture which is specific to e-coli growth. The number of colonies thus resulting is counted and reported in these studies as MPN per 100 ml of water.
This E-coli testing has been used for a number of years as the standard method of indication of biological contamination of water because the E-coli thus detected are thought to be specific to the guts of warm-blooded animals and therefore a "marker" for potential contamination. While most E-coli strains are harmless, some are extremely dangerous so that the presence of high concentrations of E-coli increases the odds of the presence of a dangerous strain. Standards have been set as guidelines indicative of safe "full-bodied" contact (such as swimming from public beachers). In Missouri, the standard that is followed for public beaches is that recommended by EPA which is:
1.A single-sample recommended maximum level of 235 E. coli colonies per 100 milliliters of water for public swimming areas.
or
2. A geometric mean of 126 E. coli colonies per 100 milliliters of water. A geometric mean is a statistical method used to analyze data collected over a period of time.E-coli Test Results to Date
See LOWA comments and results below and also see an interactive Google map containing all the sample sites with data.
All the raw data is also available on the MODNR website.
Four sample points were sampled in each of nine coves. The complete data set is shown in the DNR site identified above and also in the above cited map. The first graph below shows the average results of those four sample points for all nine coves. Cove 2 had some abnormally high results, particularly during the week 10 sammpling event. The second graph therefore shows the average results for all coves excluding cove 2.
Week 10 data for Cove 2 has therefore been eliminatated from the "Rain Effect" and "Septic Tank Effect" graphs.
Cove 2 abnormalities are under investigation by Missouri DNR. E-coli concentrations in Cove 2 were greatly reduced to a very safe level in subsequent weeks
Residents of the area reported that, during the week-end preceding the week 10 sampling, they had used their deicers the entire weekend in an effort to bring cooler water to nearer the surface for benefit of swimmers. This was not done on subsequent week-ends.
As can be seen from the graph, the test results for all the coves, excluding Cove 2 during the abnomalities discussed above,continue to show very good quality lake water.
"Rain Effect" and Septic Use" Effect
Although the data may be too scarce to be statictically valid, the next two graphs are nonetheless very interesting in that they do demonstrate the effect heavy rains can have on the average E-coli concentration in the Lake coves. Also, the final graph demonstrates the average results to date of the three cove sets of:
- 1. Populated with septic tanks (note: Cove 2 is excluded from data set)
- 2. Served by a regional sewer system
- 3. Relatively undeveloped
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The Rain Effect
The graph below presents the average E-coli concentrations from all sample points collected following a rain event versus the average of that from events collected without such a rain event (except that week 10 for Cove 2 has been eliminated from this data set)
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Type Cove Effect
The graph below shows the average results of the E-coli concentration in those coves served by septic systems versus those served by a regional sewer system versus those that are relatively unpopulated. (Again, Week 10 of Cove 2 has been eliminated from this data set)
