H
ISTORY OF
M
EADOW
L
AKE
Figure 1.
View of Meadow Lake from the west side of the dam.
The dam that originally created Meadow Lake (shown in Figure 1) was built in the 1960s by the U.S. Department of Agriculture Soil Conservation Service.
1
The dam, referred to as SCS #14, was constructed to provide flood control and sediment retention in the Brushy Creek watershed.
2
Now that houses have been built in the area downstream of the dam, the Texas Natural Resource Conservation Commission (TNRCC) has stated that the dam must safely pass 50% of the probable maximum flood (PMF).
3
For Central
Texas, the probable maximum flood is 30.5 inches of rain falling in six hours on saturated ground. The largest storm recorded in Texas to date is a 36-inch rain that fell in
18 hours in the Brushy Creek watershed in 1921.
In a recent study conducted by Freese and Nichols, funded in part by Williamson
County and the City of Round Rock, nineteen of the forty-six dams in the Brushy Creek watershed were classified as high hazard dams, including the Meadow Lake dam. The report found that failure of the dams during an extreme flood event would place a significant number of lives at risk. More dams are likely to be reclassified as high hazard as future development occurs. Several options for upgrading the Brushy Creek dams were considered by Freese and Nichols, including the following:

 increasing the height of the dams by adding parapet walls (example can be seen at Lake Arlington Dam) or compacted fill,
 armor plate face of dam to prevent erosion during overtopping (example can be seen at Wirtz Dam),
 “cafeteria” plan including certain structural options with emergency action plans and early warning systems (involves changes to TNRCC regulations).
The costs of the various options were evaluated and summarized as follows:
 estimated cost to modify dams to pass the PMF - $68 million to $89 million
 estimated costs to comply with the “cafeteria” plan option - $10 million.
After evaluation by the City of Round Rock and Brushy Creek WCID, it was concluded that the “cafeteria” plan was the best option.
2
The cafeteria plan has not yet been implemented because the bond elections to fund the upgrades failed. Thirteen out of nineteen of the high hazard dams were in the west portion of the district where recent development has been most intense, so many voters in the eastern portion of the district did not want to pay for upgrading the dams that were many miles away, even though they lived in the downstream portion of the watershed. The recent election in early November 2001 succeeded in separating the
Brushy Creek Water Conservation and Improvement Districts ( WCID) into east and west districts, with dividing lines cutting through Hutto. Once the management of the newly created Western District has been established, funds will again be sought for improvements for the high hazard dams in the Western District, including SCS#14
(Meadow Lake). Jim Nuce, a Brushy Creek WCID director, stated that the improvements that will be made at Meadow Lake will be primarily on the downstream side of the dam.
3

Therefore, construction of the improvements should not have an impact on the current uses of the lake.
Meadow Lake has a surface area of approximately 66 acres, estimated from a recent aerial photograph which was stretched to scale using the ArcView Image Analyst
Extension. Aerial photos from 1995 and 2000 are included in Appendix A and show the full extent of the watershed. It is evident from the photos that there has been a lot of residential development within the past five years. This development is expected to continue in upcoming years.
D
ESIGNATED
U
SES OF
M
EADOW
L
AKE
All water bodies in Texas are expected to have general uses such as navigation, agricultural water supply, and industrial water supply wherever they are achievable.
Meadow Lake is expected to support the following additional uses as described in various sections of the Texas Administrative Code (TAC)
4
:

High Quality Aquatic Life 30 TAC § 307.4(h)(3) “Perennial streams, rivers, lakes, bays, estuaries, and other appropriate perennial waters which are not specifically listed in Appendix A or D of §307.10 of this title are presumed to have a high aquatic life use and corresponding dissolved oxygen criteria.”

Contact recreation 30 TAC § 307.7(b)(1)(A)(i) “Contact recreation applies to all bodies of freshwater except where specifically designated otherwise.”

Sustainable Fishery 30 TAC § 307.3(a)(58)
“lakes and reservoirs greater than or equal to 150 acre-feet and/or 50 surface acres”

The Texas Administrative Code has an additional aquifer protection use designation for some water bodies, but this use currently applies only to portions of those segments that are within the recharge zone.
30 TAC § 307.7(b)(2)(A)(ii). Meadow Lake lies within the Edwards Aquifer Recharge Zone, so it is possible that it may later be required to meet drinking water standards if the code is modified to include all water bodies that are within the recharge zone, rather than just the designated segments.
5
W
ATER
Q
UALITY
S
TANDARDS
The water quality standards for Meadow Lake consist of a set of criteria developed to protect the uses that have been set forth in the Texas Administrative Code.
Protection of Aquatic Life: High Quality Aquatic Life Use
For protection of the high aquatic life use, minimum acceptable levels of dissolved oxygen are established as shown in Table 1.
Table 1.
Dissolved Oxygen Criteria for the protection of aquatic life.
Dissolved Oxygen
Criteria, mg/L
Freshwater Freshwater mean/ minimum in Spring mean/ minimum
Habitat
Character- istics
Aquatic Life Attributes
Species
Assemblage
Sensitive Diversity Species species Richness
5.0/3.0
5.5/4.5
Highly diverse
Usual asso- ciation of regionally expected species
Present High High
Trophic
Structure
Balanced to slightly imbalanced
- Dissolved oxygen means are applied as a minimum average over a 24-hour period.
- Daily minima are not to extend beyond 8 hours per 24-hour day. Lower dissolved oxygen minima may apply on a site-specific basis, when natural daily fluctuations below the mean are greater than the difference between the mean and minima of the appropriate criteria.
- Spring criteria to protect fish spawning periods are applied during that portion of the first half of the year when water temperatures are 63.0F to 73.0F.
Reference: Figure 30 TAC §307.7(b)(3)(A)(i)

To protect aquatic life, the Texas Administrative Code also establishes criteria for many toxic substances. In table 30 TAC §307.6(c)(1), criteria are listed for freshwater and saltwater for aquatic life. Meadow Lake is a freshwater lake, so the acute and chronic criteria for protection of aquatic life in freshwater are listed in Table 2.
Table 2.
Toxic Materials Criteria for Aquatic Life Protection
Criteria in Water for Specific Toxic Materials
AQUATIC LIFE PROTECTION
(All values are listed or calculated in micrograms per liter)
(Hardness concentrations are input as milligrams per liter)
Parameter
Aldrin
Aluminum (d)
Arsenic (d)
Cadmium (d)
Carbaryl
Chlordane
Chlorpyrifos
Chromium (Tri) (d)
Chromium (Hex) (d)
Copper (d)
Cyanide † (free)
4,4'- DDT
Demeton
Dicofol
Dieldrin
Diuron
Endosulfan I (alpha)
Endosulfan II (beta)
Endosulfan sulfate
Endrin
Guthion
Heptachlor
Hexachlorocyclohexane
CASRN Freshwater Acute Criteria Freshwater Chronic
Criteria
309-00-2
7429-90-5
3.0
991w
7440-38-2 360w
7440-43-9 0.973w
e (1.128(ln(hardness))-1.6774)
63-25-2 2.0
57-74-9 2.4
2921-88-2 0.083
16065-83-1 0.316w
e (0.8190(ln(hardness))+3.688)
18540-29-9 15.7w
7440-50-8 0.960w
e (0.9422(ln(hardness))-1.3844)
57-12-5 45.8
50-29-3
8065-48-3
115-32-2
60-57-1
330-54-1
959-98-8
33213-65-9
1031-07-8
72-20-8
86-50-0
76-44-8
58-89-9
1.1
---
59.3
2.5
210
0.22
0.22
0.22
0.18
---
0.52
2.0
---
---
190w
0.909 w e (0.7852(ln(hardness))-3.490)
---
0.004
0.041
0.860w
e (0.8190(ln(hardness))+1.561)
10.6w
0.960w
e (0.8545(ln(hardness))-1.386)
10.7
0.001
0.1
19.8
0.002
70
0.056
0.056
0.056
0.002
0.01
0.004
0.08
(Lindane)
Lead (d)
Malathion
Mercury
Methoxychlor
Mirex
Nickel (d)
Parathion (ethyl)
7439-92-1 0.889w
e (1.273(ln(hardness))-1.460)
121-75-5 ---
0.792w
e (1.273(ln(hardness))-4.705)
0.01
7439-97-6
72-43-5
2.4
---
1.3
0.03
2385-85-5 --- 0.001
7440-02-0 0.998w
e (0.8460(ln(hardness))+3.3612) 0.997w
e (0.8460(ln(hardness))+1.1645)
56-38-2 0.065 0.013

Pentachlorophenol
Phenanthrene
Polychlorinated
Biphenyls (PCB's)
87-86-5
85-01-8
1336-36-3 e (1.005(pH)-4.830)
30
2.0 e (1.005(pH)-5.290)
30
0.014
Selenium
Silver, as free ion
Toxaphene
7782-49-2
7440-22-4
8001-35-2
20
0.8w
0.78
5
---
0.0002
Tributlytin (TBT) 688-73-3 0.13 0.024
2,4,5 Trichlorophenol 95-95-4 136 64
Zinc (d) 7440-66-6 0.978w
e (0.8473(ln(hardness))+0.8604) 0.986w
e (0.8473(ln(hardness))+0.7614)
† Compliance will be determined using the analytical method for cyanide amenable to chlorination or by weak acid dissociable cyanide.
(d) Indicates that the criteria for a specific parameter are for the dissolved portion in water. All other criteria are for total recoverable concentrations, except where noted. w Indicates that a criterion is multiplied by a water-effects ratio in order to incorporate the effects of local water chemistry on toxicity. The water-effects ratio is equal to 1 except where sufficient data is available to establish a site-specific, water-effects ratio. Water-effects ratios for individual water bodies are listed in
Appendix E when standards are revised. The number preceding the w in the freshwater criterion equation is an EPA conversion factor.
Reference: 30 TAC §307.6(c)(1)
Protection of Human Health (Contact Recreation)
For contact recreation, human health criteria include allowable levels of E Coli, which are indicator organisms used to assess the potential danger of viruses and other pathogens that may be present in the water.
30 TAC § 307.7 (b)(1)(A)(1) The geometric mean of
E. coli should not exceed 126 per
100 ml. In addition, single samples of E. coli should not exceed 394 per 100 ml.
Contact recreation applies to all bodies of freshwater except where specifically designated otherwise in §307.10 of this title.
Protection of Human Health (Sustainable Fishery)
The water body is also considered to be a sustainable fishery, and limits for various toxic materials have been set to reduce the human health risk of exposure through fish consumption.
Table 3 lists concentration criteria in freshwaters to prevent contamination of fish to ensure that they are safe for human consumption. These criteria

apply to freshwater which have sustainable fisheries, and which are not designated or used for public water supply.
Table 3.
Toxic Materials Criteria for Sustainable Fishery
Criteria in Water for Specific Toxic Materials
HUMAN HEALTH PROTECTION
(All values are listed or calculated in micrograms per liter)
COMPOUND CASRN FW Fish Only
µ g/L
Acrylonitrile
Aldrin
Arsenic (d)
Barium (d)
Benzene
Benzidine †
Benzo(a)anthracene
Benzo(a)pyrene
Bis(chloromethyl)ether
Cadmium (d)
Carbon Tetrachloride
Chlordane‡
Chlorobenzene
Chloroform
Chromium (d)
Chrysene
Cresols
Cyanide (free)#
4,4' - DDD
4,4' - DDE
4,4' - DDT
2,4 - D
Danitol
Dibromochloromethane
1,2 - Dibromoethane
1,3 - Dichloropropene
Dieldrin† p -Dichlorobenzene
1,2 - Dichloroethane
1,1 - Dichloroethylene
Dicofol
Dioxins/Furans
107-13-1
309-00-2
7440-38-2
7440-39-3
71-43-2
92-87-5
56-55-3
50-32-8
542-88-1
7440-43-9
56-23-5
57-74-9
108-90-7
67-66-3
18540-29-9
218-01-9
§
57-12-5
72-54-8
72-55-9
50-29-3
94-75-7
39515-41-8
124-48-1
106-93-4
542-75-6
60-57-1
106-46-7
107-06-2
75-35-4
115-32-2
1746-01-6
1,380
1,292
3,320
8.1
13,116
---
0.010
0.007
0.007
---
0.721
10.9
0.00426
---
---
106
0.00347
0.810
0.810
0.0193
---
8.4
0.0213
71.6
0.335
161
0.002
---
73.9
5.84
0.217
1.40E-07

(TCDD Equivalents)†
Endrin
Fluoride
Heptachlor†
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorobutadiene
Hexachlorocyclohexane (alpha)
Hexachlorocyclohexane (beta)
Hexachlorocyclohexane (gamma)
(Lindane)
Hexachloroethane
Hexachlorophene
Lead (d)
Mercury ‡
Methoxychlor
Methyl Ethyl Ketone
Nitrate-Nitrogen as total Nitrogen
Nitrobenzene
N -Nitrosodiethylamine
N -Nitroso-din -Butylamine
PCB's (Polychlorinated Biphenyls)
Pentachlorobenzene
Pentachlorophenol
Pyridine
Selenium
1,2,4,5 - Tetrachlorobenzene
Tetrachloroethylene
Toxaphene†
2,4,5 - TP (Silvex)
2,4,5 - Trichlorophenol
Trichloroethylene
1,1,1 - Trichloroethane
Vinyl Chloride
72-20-8
7782-41-4
76-44-8
1024-57-3
118-74-1
87-68-3
319-84-6
319-85-7
58-89-9
67-72-1
70-30-4
7439-92-1
7439-97-6
72-43-5
78-93-3
14797-55-8
98-95-3
55-18-5
924-16-3
1336-36-3
608-93-5
87-86-5
110-86-1
7782-49-2
95-94-3
127-18-4
8001-35-2
93-72-1
95-95-4
79-01-6
71-55-6
75-01-4
1.34
---
0.00265
1.1
0.0198
3.6
0.413
1.45
2.00
13,333
---
0.243
323
0.014
50.3
1,069
612
12,586
415
278
0.053
25.3
0.0122
2.22
9.94E06
---
233
7.68
13.5
0.0013
6.68
135

* Based on Maximum Contaminant Levels (MCL's) specified in 30 TAC §290 (relating to Water
Hygiene).
† Calculations based on measured bioconcentration factors with no lipid correction factors (7.6 and 3.0) applied.
‡ Calculations based on USFDA action levels (1 mg/kg) in fish tissue. Saltwater BCF = 40,000 and freshwater BCF = 81,700.
§ Consists of m, o, and p Cresols. The standards are the same for all three. CASRNs for cresols are 95-48-7 for o-Cresol, 108-39-4 for m-Cresol, and 106-44-5 for p -Cresol.
# Compliance will be determined using the analytical method for cyanide amenable to chlorination or weak-acid dissociable cyanide.
(d) Indicates the criteria is for the dissolved fraction in water. All other criteria are for total recoverable concentrations.
Other Useful Guidelines
The site-specific criteria presented in Table 4 have been established for the downstream segment, Brushy Creek. Although not legally required for Meadow Lake, these criteria could be used as a possible guideline for Meadow Lake. Water leaving
Meadow Lake eventually enters Brushy Creek, which is listed on the 303d list because of high total dissolved solids (TDS).
6
Table 4. Site Specific Criteria for Brushy Creek
BRAZOS RIVER BASIN
USES
CRITERIA
Segment
No.
Segment
Name
1244 Brushy
Creek
Recreation Aquatic
Life
Domestic
Water
Supply
Cl -1 SO
4
-2
(mg/L) (mg/L)
TDS
(mg/L)
Dissolved
Oxygen
(mg/L) pH Range
(SU)
CR H PS/AP 3 200 150 800 5.0 6.5-9.0
Indicator
Bacteria
1
#/100ml
126/200
R ESEARCH TO D ETERMINE P OTENTIAL C RITERIA OF C ONCERN
Temp
(F)
91
It would be highly expensive and time consuming to evaluate all of the criteria established for Meadow Lake. The toxic materials criteria list is particularly extensive.
The list was narrowed down using a variety of data sources:

Investigation of potential sources of toxic materials


Texas 303d list

Typical concentrations of pollutants in storm runoff

USGS study of pesticides in streams across the U.S.

Studies and constituents of concern in Texas

Ecological Incident Information System
Investigation of potential sources of toxic materials
Information about the likely sources and environmental fate for compounds on the criteria list was obtained from the Agency for Toxic Substances and Disease Registry
(ATSDR). ATSDR is an agency of the U.S. Department of Health and Human Services.
7
Information obtained from this resource is shown in the right-hand column of the toxic materials standards table for Meadow Lake in the next section of this report (Table 8).
303d list for Texas
In order to narrow down the list of potential water quality threats for in Meadow
Lake, the Texas 303d list was another useful tool for examining common reasons for failure to meet criteria in this region. Meadow Lake is in the Brushy Creek watershed.
This segment, 1244, is listed on the 303d list due to high TDS.
For other Texas waters, some of the reasons for being listed are given below. It is not expected that Meadow
Lake will experience problems with many of these criteria, but the list is presented to gain a feel for the types of problems that may occur in this region of the country.
6
 mercury in fish tissue
 selenium in fish tissue
 atrazine and alachlor in drinking water

 total dissolved solids,
 zinc not protecting acute or chronic aquatic life criterion
 lead, chronic aquatic life, human health fishery
 cadmium, chronic aquatic life

DDE, PCBs, chlordane, dieldrin in fish tissue, toxaphene
 heptachlor epoxide in fish tissue
 dioxin
 arsenic (point source)
 chlorophyll a
 sulfate
 low D.O.
 pathogens
Concentrations of Pollutants in Storm Runoff
Many studies have been performed in attempt to obtain the concentration of various pollutants in storm runoff. In 1990, the City of Austin developed standard pollutant concentrations to be used for calculating pollutant loads due to runoff from developed sites in the Austin area. Table 5 shows the concentrations estimated for single family developments with greater than 15% impervious cover, as well as the concentrations for runoff from undeveloped sites.
8
Table 5.
Pollutant Concentrations in Storm Runoff
Pollutant Undeveloped Sites
Concentration (mg/L)
TSS 55
TP
TN
0.04
0.54
Single family >15% I.C.
Concentration (mg/L)
110
0.16
2.0

BOD
Pb
FC
8
0.003
4000
Zn 0.008
Reference: City of Austin Environmental Criteria Manual 8
8
0.02
8,400 / 100ml
0.04
In order to determine the potential for any of the criteria for these substances to be exceeded, a simplified water quality model was created for Meadow Lake, using the waste load inputs suggested by the City of Austin, as well as data from various other sources. Some of the studies referenced include:

The National Urban Runoff Program (NURP) research by the EPA, 1983
 “Urban Runoff Quality and Treatment”, Gibb et al. 1991
 “Updating the U.S. Nationwide Urban Runoff Quality Database”, Smullen and
Cave, 1998
 “Controlling Urban Runoff: A Practical Manual for Planning and Design”
Schueler, 1987
USGS pesticide study
A 1999 report by the USGS provides statistical analysis of pesticides in a large study of approximately 58 sites across the U.S. that were monitored during 1992-1995.
The insecticides detected most frequently in water include diazinon, carbaryl, chlorpyrifos, malathion. The insecticides detected most frequently in sediment and fish tissue are organochlorine insecticides such as DDT, which were banned years ago.
9
Texas studies and constituents of concern
In the Dallas/Fort Worth Metroplex, the storm water constituents identified as constituents of concern with high priority included diazinon, chlordane, fecal coliforms

and fecal streptococcus, TSS, cadmium, chromium, copper, lead, and zinc.
10
In Barton
Springs (Austin, Texas) the pesticides detected include atrazine, carbaryl, diazinon, and simazine, especially during rain events.
11
Several other studies mentioned diazinon as a chemical of concern as well.
Ecological Incident Information System
The EPA Ecological Incident Information System (EIIS) shows that two pesticides, carbofuran and diazinon, are responsible for 55% of the bird deaths reported through March of 1999. In addition to carbofuran and diazinon, other pesticides high on the list of reported bird mortality incidents include chlordane, fenthion, chlorpyrifos, brodifacoum, parathion, and famphur.
12
I NITIAL E VALUATION OF T OXIC M ATERIAL C RITERIA FOR M EADOW L AKE
For Meadow Lake, there are some toxic substances that have criteria to protect both of the following uses.
 aquatic life use
 sustainable fishery
When there is a toxic material that affects two separate uses of the lake, it is useful to identify the more limiting criteria for the water body. For example, chlordane is a toxic material listed in the tables for protection of both aquatic life and human health. For the two potentially affected uses of Meadow Lake (aquatic life and sustainable fishery), the criteria for chlordane are shown in Table 6 and the smaller (more limiting) criteria is selected as the chlordane criteria for Meadow Lake. The same procedure was followed for mercury as shown in Table 6. For chlordane, the aquatic life use has the more

stringent criteria. For mercury, the use of the water as a sustainable fishery has a more stringent criteria than the criteria for protection of aquatic life.
Table 6.
Example toxic material criteria evaluation
Toxic Freshwater Freshwater Freshwater
Material Sustainable
Fishery
Acute Criteria Chronic
Criteria
Chlordane 0.0213 2.4 0.004
Mercury 0.0122 2.4 1.3
Use with
Highest
Standard
Aquatic
Life
Sustainable
Fishery
Limiting
Criteria
0.004
0.0122
Using this same procedure for all toxic materials affecting more than one use of the water, a final listing of the criteria for toxic materials can be created for Meadow Lake.
For some of the criteria, total hardness and pH values were needed to calculate the numerical criteria. Meadow Lake is in the Brazos River Basin. Figure 30 TAC
§307.6(c)(8) lists the following values to be used for the Brazos River Basin.
Table 7.
Brazos River Basin hardness and pH values for criteria calculation
Basin Number/Name pH (s.u.) Hardness (CaCO
3
) mg/L
7.4 160 (12) Brazos River Basin
Reference: 30 TAC §307.6(c)(8)
The limiting criteria associated with the currently designated uses of Meadow
Lake are summarized in Table 8. In addition, a preliminary estimate is given for the potential need to monitor each of the toxic materials. Even though many of the toxic chemicals listed were banned many years ago, some are highly persistent and may remain in the environment for decades or more. Some of these same chemicals have a tendency to bioaccumulate in fish tissue and also become ecologically magnified in the food chain.

Table 8.
Listing of most stringent toxic material criteria for Meadow Lake
COMPOUND CASRN Most
Stringent
Criterion of
Designated
Uses
µg/L
Use corresponding with criterion listed in this table
Preliminary estimated of need for monitoring at
Meadow Lake
Acrylonitrile 107-13-1 10.9
Aldrin
Aluminum (d)
Arsenic (d)
309-00-2 0.00426
7429-90-5 991w
7440-38-2 190w
Atrazine
No current EPA criteria, but EPA Notice of Intent to develop criteria (1999).
Barium (d) 7440-39-3
Under development
---
Sustainable
Fishery
Sustainable
Fishery
VERY LOW: Measurable amounts of acrylonitrile are found primarily near factories and hazardous waste sites.
VERY LOW: EPA banned agricultural use (insecticide for corn,cotton, etc.) in
1974. Used as termiticide until 1987. Converts to dieldrin by photolysis.
Aquatic Life
(acute)
LOW: Natural contributions from weathering of soils containing aluminum (often associated with acidification). Point sources
(none in watershed).
Aquatic Life LOW-MED: reported the range of arsenic in 32 fertilizers as 2.2–322 ng/g.
Arsenic is also often found in urban storm water samples.
Some reports say criterion is not low enough.
MED-HIGH: frequently used herbicide for crops in this county.
Benzene
Benzidine †
Benzo(a)anthracene
71-43-2
56-55-3
106
92-87-5 0.00347
0.810
Sustainable
Fishery
Sustainable
Fishery
Sustainable
VERY LOW: Natural erosion of sedimentary rocks. Higher concentrations in groundwater than surface water.
LOW: Primarily from point sources. Accidental spills from gasoline storage tanks.
VERY LOW: Industrial sources. Rarely detected.
LOW: Atmospheric

Benzo(a)pyrene
Cadmium (d)
Carbaryl
Carbofuran
Carbon Tetrachloride
Chlordane‡
Chloroform
Chlorobenzene
Chlorpyrifos
50-32-8
63-25-2
56-23-5
57-74-9
108-90-7
67-66-3
7440-43-9
2921-88-2
0.810
1.49
2.0
N/A
8.4
0.004
1,380
1,292
0.041
Bis(chloromethyl)ether 542-88-1 0.0193
Fishery
Sustainable
Fishery
Sustainable
Fishery
Aquatic Life
Aquatic Life
(acute – no chronic value listed)
Sustainable
Fishery deposition, industrial effluent, urban runoff, oil spills.
LOW: Atmospheric deposition, industrial effluent, urban runoff, oil spills.
VERY LOW: rapidly hydrolyzed in water to yield formaldehyde and HCl, half-life 38 seconds.
LOW-MED: potential sources phosphate fertilizer, sewage sludge fertilizers, and natural weathering of minerals.
LOW-MED: Used on 1% of sorghum crop acreage in
Texas in 1997. Not used on corn/cotton in 1997.
Frequently detected in U.S. streams (USGS study).
MED: Used on corn, cotton, sorghum (commonly grown in Williamson County) in
Texas in 1997. Frequently detected in U.S. streams
(USGS study). Number 1 on list of bird kill incidents
(EIIS).
VERY LOW: evaporates within a few days, primarily industrial sources.
Aquatic Life LOW: Insecticide formerly used on crops such as corn.
(EPA cancelled 1978)
Termiticide use cancelled
1988. May persist for decades in the environment.
Sustainable
Fishery
VERY LOW: industrial waste, biodegrades rapidly in surface waters (typically one week)
Sustainable
Fishery
Aquatic Life
VERY LOW: industrial and municipal point sources.
Possible atmospheric deposition (rain).
MED-HIGH (current):

Common insecticide (tradename Dursban) Rapidly associates with sediment.
LOW (future) Sales for lawn use will be discontinued in Dec 2001.
Watershed rapidly converting to residential, so any remaining farm use for corn/sorghum (limited) should have negligible impact within this watershed.
Aquatic Life LOW: naturally occurring and point sources.
Aquatic Life
Chromium (Tri) (d) 16065-83-
1
Chromium (Hex) (d) 18540-29-
9
Chrysene 218-01-9
261.6w
10.6w
Copper (d)
Cresols
Cyanide # (free)
4,4' - DDD
4,4' - DDE
Dibromochloromethane
1,2 - Dibromoethane
7440-50-8
§
57-12-5
72-54-8
72-55-9
124-48-1
106-93-4
8.1
18.4w
13,116
10.7
71.6
0.010
0.007
0.335
4,4' - DDT
Danitol
50-29-3
39515-41-
8
0.001
0.721
Demeton
Diazinon
No current EPA criteria, but EPA Notice of Intent to develop criteria (1999).
8065-48-3 0.1
0.08
(New York
State criteria, also other sources recommend)
Sustainable
Fishery
Aquatic Life
LOW: point sources and spills.
LOW: industrial and municipal point sources, also natural sources.
Sustainable
Fishery
VERY LOW: biodegredation rapid
(<1week), septic tanks potential source, but very few in this watershed.
Aquatic Life VERY LOW: point sources
Sustainable
Fishery
Sustainable
Fishery
LOW: DDT banned in 1972
(primary metabolites DDE and DDD)
Aquatic Life
Sustainable
Fishery
Aquatic Life
Sustainable
Fishery
Aquatic Life MED-HIGH (current): most commonly detected pesticide in U.S. waters
FUTURE (low): EPA will ban sale for indoor use in
Dec 2001, outdoor uses banned Dec 2003.
Sustainable
Fishery
LOW: gasoline additive and soil fumigant, industrial point source

1,3 - Dichloropropene 542-75-6
Dicofol
Dieldrin†
115-32-2
60-57-1
Endrin
161
19.8
0.002
1,2 - Dichloroethane 107-06-2
1,1 - Dichloroethylene 75-35-4
Dicofol
73.9
5.84
115-32-2 0.217
Dioxins/Furans
(TCDD Equivalents)†
1746-01-6 1.40E-07
Diuron 330-54-1 70
Endosulfan I (alpha) 959-98-8 0.056
Endosulfan II (beta) 33213-65-
9
Endosulfan sulfate
0.056
1031-07-8 0.056
Guthion
Heptachlor†
Heptachlor Epoxide
(breakdown product of heptachlor)
86-50-0 0.01
76-44-8 0.00265
1024-57-3 1.1
Hexachlorobenzene
72-20-8 0.002
118-74-1 0.0198
Sustainable
Fishery
Aquatic Life
Sustainable
Fishery and
Aquatic Life
LOW: point sources, soil fumigant
LOW: Although aldrin and dieldrin are no longer permitted for general use, dieldrin, in particular, has been detected in many waterways and cropping soils.
VERY LOW: point sources Sustainable
Fishery
Sustainable
Fishery
VERY LOW: point sources
Sustainable
Fishery
Sustainable
Fishery
VERY LOW: possible source chlorinated pesticides, but rarely present above level of detection.
Aquatic Life
Aquatic Life LOW: insecticide point and
Aquatic Life non-point sources.
Agricultural application on
Aquatic Life only 2% of cotton crop acreage in 1997 in Texas.
Cotton is a common crop in
Williamson County, though more acreage is used for the crops corn and sorghum.
Aquatic Life VERY LOW: organochlorine pesticide, all uses voluntarily cancelled in
1986 in U.S.
Aquatic Life
Sustainable
Fishery
Sustainable
Fishery
LOW: insecticide commonly used on corn crops in the 1970s. Almost all uses banned by 1988.
Currently only allowed for fire ant control in power transformers. Half life 3.5 days in water.
Sustainable
Fishery
LOW: pesticide use voluntarily cancelled in
1984. Persistent compound with long half life (several years or more)

Hexachlorobutadiene 87-68-3
Hexachlorocyclohexane
(alpha)
319-84-6 0.413
Hexachlorocyclohexane
(beta)
319-85-7 1.45
Hexachlorocyclohexane
(gamma) (Lindane)
58-89-9 0.08
Hexachloroethane
Hexachlorophene
Lead (d)
Malathion
Mercury ‡
Metolachlor
Methoxychlor
67-72-1
70-30-4
278
0.053
7439-92-1 4.58w
72-43-5
N/A
0.03
Methyl Ethyl Ketone 78-93-3 9.94E06
Mirex 2385-85-5 0.001
Nickel (d)
121-75-5
3.6
0.01
7439-97-6 0.0122
7440-02-0 233.9w
Sustainable
Fishery
VERY LOW: by-product of chlorinated hydrocarbon synthesis. Primarily point sources.
Sustainable
Fishery
Sustainable
Fishery
VERY LOW: found in technical-grade HCH, hasn’t been produced since 1983 in
U.S., but may be found at hazardous waste sites
Aquatic Life LOW: insecticide lindane commonly used on fruit, vegetables, and forest crops, but not on typical crops in this county (corn, sorghum, cotton)
Sustainable
Fishery
Sustainable
Fishery
VERY LOW: primarily point sources
Aquatic Life LOW-MED: Point sources and urban runoff. Sorbed to sediments and suspended solids.
Aquatic Life MED: pesticide used on common crops in this county (cotton, sorghum), commonly detected in U.S. streams (USGS study)
Sustainable
Fishery
LOW-MED: natural sources, point sources, atmospheric deposition
(rain), bioconcentrates and biomagnifies
Sustainable
Fishery
MED: frequently detected in
Texas reservoirs
Aquatic Life VERY LOW: Pesticide for control of insect larvae, esp. cranberry crops
Aquatic Life LOW: Use ceased 1976.
Used for fire ant eradication program in southeastern
U.S. for 10 years. Current risk primarily hazardous waste sites.
Aquatic Life LOW: Runoff from

Nitrobenzene
N -Nitrosodiethylamine 55-18-5
Pentachlorobenzene
Pentachlorophenol
98-95-3
608-93-5
87-86-5
233
7.68
6.68
8.56
N -Nitroso-din -
Butylamine
Parathion (ethyl)
924-16-3 13.5
56-38-2 0.013
PCB's (Polychlorinated
Biphenyls)
1336-36-3 0.0013
Phenanthrene
Pyridine
Selenium
Simazine
Silver, as free ion
1,2,4,5 -
Tetrachlorobenzene
Toxaphene
2,4,5 - TP (Silvex)
85-01-8 30
110-86-1 13,333
7782-49-2 5
7440-22-4
95-94-3
Tetrachloroethylene 127-18-4
0.243
323
8001-35-2 0.0002
93-72-1
0.8w
N/A
50.3
Tributlytin (TBT) 688-73-3 0.024
2,4,5 - Trichlorophenol 95-95-4 64
Trichloroethylene 79-01-6 612
Sustainable
Fishery
Sustainable
Fishery
Sustainable
Fishery
Aquatic Life
Sustainable
Fishery weathering, atmospheric deposition
VERY LOW: point sources
VERY LOW: industrial point sources
LOW: main sources today are the environmental cycling process, accidental spills metabolizes to pentachlorophenol
Sustainable
Fishery
Aquatic Life
Aquatic Life
Sustainable
Fishery
VERY LOW: In the past, widely used as a pesticide and for wood treatment.
Currently a restricted-use pesticide.
VERY LOW: haz waste sites and industrial sources
Aquatic Life LOW: weathering, volcanic eruptions, combustion of coal, industrial sources
Aquatic Life
(acute)
LOW: natural and point sources, possible in sewage sludge used as fertilizer.
MED: frequently detected in
Texas reservoirs and streams.
Sustainable
Fishery
Sustainable
Fishery
VERY LOW: high volatility, point sources
Aquatic Life LOW-MED: widely used insecticide on crops such as cotton until restricted in
1982. Attaches to sediment,
BCF ~ 10,000, also biomagnifies.
Sustainable
Fishery
Aquatic Life
Aquatic Life
Sustainable VERY LOW: volatile, most

1,1,1 - Trichloroethane 71-55-6 12,586
Vinyl Chloride
Zinc (d)
75-01-4 415
7440-66-6 155.6w
Fishery
Sustainable
Fishery
Sustainable
Fishery
Aquatic Life releases to atmosphere
VERY LOW: industrial sources, volatilizes
VERY LOW: most releases by PVC manufacturers, volatilizes
LOW-MED: Natural sources, point sources such as mining or urban, nonpoint sources from fertilizers.
* Based on Maximum Contaminant Levels (MCL's) specified in 30 TAC §290 (relating to
Water Hygiene).
† Calculations based on measured bioconcentration factors with no lipid correction factors (7.6 and 3.0) applied.
‡ Calculations based on USFDA action levels (1 mg/kg) in fish tissue. Saltwater BCF = 40,000 and freshwater BCF = 81,700.
§ Consists of m, o, and p Cresols. The standards are the same for all three. CASRNs for cresols are 95-48-7 for o-Cresol, 108-39-4 for m-Cresol, and 106-44-5 for p -Cresol.
# Compliance will be determined using the analytical method for cyanide amenable to chlorination or weak-acid dissociable cyanide.
(d) Indicates the criteria is for the dissolved fraction in water. All other criteria are for total recoverable concentrations. w Indicates that a criterion is multiplied by a water-effects ratio in order to incorporate the effects of local water chemistry on toxicity. The water-effects ratio is equal to 1 except where sufficient data is available to establish a site-specific, water-effects ratio. Water-effects ratios for individual water bodies are listed in Appendix E when standards are revised. The number preceding the w in the freshwater criterion equation is an EPA conversion factor.
In addition to the toxic material criteria currently given for Meadow Lake, there may be other toxic materials for which criteria have not yet been established, or materials that may cause toxicity when combined with other toxic substances. In 1999, the EPA published its intent to develop aquatic life criteria for diazinon and atrazine.
13
Even though there are no wastewater discharges into Meadow Lake or the upstream tributaries, there is always a possibility that a combination of various toxic substances could have chronic or lethal affects on the aquatic life. If more than one toxic

substance is found to occur in the water body, it would be reasonable to conduct biological tests to determine the potential for acute or chronic affects, even if they do not exceed the criteria on an individual basis. Due to the vast number of combinations of toxic materials possible, it would be unreasonable to develop criteria for every iteration.
Once certain toxic materials have been identified in a water body; however, it would be easier to conduct tests using combinations of the toxic materials identified. Site-specific criteria are sometimes needed depending on the combination of toxic materials present.
Exposure to smaller doses of multiple pesticides may lead to decline in health and eventual death, especially in times of food shortage when fat reserves are needed to maintain energy.
Many toxic materials exhibit varying degrees of toxicity depending on the environmental conditions. Organomercury compounds, for example, “interact with elevated temperatures and pesticides, such as DDE and parathion, to produce additive or more-than-additive toxicity, and with selenium to produce less-than-additive toxicity.”
14
The appropriate criteria for toxic materials are not always agreed upon by scientists. For example, a study of arsenic conducted by the U.S. Fish and Wildlife department in the 1980s reported the following recommendation, but the criteria has not been modified by the EPA.
“But the current criterion for freshwater life protection of 190 μg As
+3
/l (EPA
1985; Table 7), which is down from 440 μg As
+3
/l in 1980 (EPA 1980), is unsatisfactory. Many species of freshwater biota are adversely affected at <190
μg/l of As +3 , As +5 , or various organoarsenicals (Table 4). These adverse effects include death and malformations of toad embryos at 40 μg/l, growth inhibition of algae at 48 to 75 μg/l, mortality of amphipods and gastropods at 85 to 88 μg/l, and behavioral impairment of goldfish ( Carassius auratus ) at 100 μg/l. It seems that some downward adjustment in the current freshwater aquatic life protection criterion is warranted.” 15

Special Investigation: Diazinon
Currently, the State of Texas does not have any specific water quality criteria for diazinon. The Texas Administrative Code does mention diazinon; however, and some requirements for attempting to control it. For example, wastewater dischargers are required to conduct whole effluent toxicity tests, and the cause of toxicity is sometimes found to be diazinon. When diazinon is found to be the reason for failure of the whole effluent toxicity test, dischargers are required to begin a public education and awareness campaign to control introduction of diazinon to the wastewater system, as well as begin a monitoring program for diazinon, as described in 30 TAC §307.6(e).
In 1999, the EPA published a Notice of Intent to develop criteria for diazinon.
13
The New York state chronic criteria for protection of aquatic life is 0.08 ug/L.
16
This level was also recommended in the U.S. Fish and Wildlife study on diazinon published in 1986.
17
Diazinon was the most frequently detected insecticide in the USGS monitoring study of streams across the United States.
9
Recently, the EPA decided that sale of diazinon for home lawn uses must end on December 31, 2003.
18
Once supplies have been exhausted by homeowners that may be stocking diazinon in anticipation of the cancellation of sales, concentrations of diazinon will quickly cease to be a concern for
Meadow Lake, due to its relatively short half-life.
F
UTURE
W
ATER
Q
UALITY
S
TANDARDS FOR
P
ROTECTION OF
W
ILDLIFE
Wildlife Standards have not yet been developed by the EPA or the TNRCC for protection of wildlife in Texas. Concentrations of various toxic substances in water are of particular concern to water birds and other animals whose diet consists primarily of

fish. For human health criteria, it is assumed that fish are only a part of the diet, whereas some species of birds and mammals feed solely on fish and other aquatic organisms.
Therefore, their exposure risk is greater than the risk posed to humans. In addition, people in the U.S. typically purify water prior to drinking it and even drink bottled water in many cases, whereas wildlife drink directly from lakes and streams. The EPA recently listed the first ever wildlife criteria, in the Great Lakes Initiative (GLI). Criteria were listed for DDT, dioxin, PCBs, and mercury, as shown in Table 9.
19
Table 9.
Wildlife Criteria for Great Lakes Initiative
Chemical
DDT and metabolites
Mercury (including methylmercury)
PCBs (class)
Criteria (μg/L)
1.1E-5
1.3E-3
1.2E-4
2,3,7,8-TCDD 3.1E-9
In addition to the GLI criteria published by the EPA, the state of New York has proposed Wildlife Bioaccumulation Criteria. If similar criteria are ever implemented for protection of the wildlife in Texas, some of the current criteria may need to be made more stringent. For example, the Hexachlorobutadiene criteria would be 0.7 ug/L.
Octachlorosyrene would need to be added to the list with a criteria of 0.005. 2,3,7,8-
TCDD would be added with a criteria of 2x10 -8 .
16

B
IRDS OF
M
EADOW
L
AKE
Figure 2.
Great Egret feeding at Meadow Lake.
Meadow Lake supports a wide variety of bird species which may be exposed to contaminants in and around the lake through a variety of exposure routes. Primary exposure can occur through skin exposure, inhalation, or direct consumption of a contaminant. Direct consumption would include things such as drinking the lake water or consuming solid substances such as lake sediments, or eating a granule of pesticide on the shore near the lake. Secondary exposure can occur through consumption of fish or other aquatic life that have accumulated toxins in their tissues. Birds may also be exposed by eating vegetation that has been sprayed with a contaminant, or by eating invertebrates that were killed with pesticides.
Knowledge of various exposure routes is increasing through examination of sites where birds have died. At times of food shortage and during migration, birds must draw energy from their fat reserves, so accumulation of toxins in these tissues is of extreme concern. In addition, the combined effects of several pesticides are not generally studied due to the complexity and cost of this type of analysis, which would require numerous

iterations for various combinations of toxic materials. Studies conducted on each chemical individually may yield criteria that are insufficient to protect birds that are exposed to multiple chemicals in their environment. There have also been recent concerns about possible effects on endocrine systems and reproductive success of species. These type of sublethal effects could be detrimental to the species and result in population declines.
Birds that may be particularly susceptible to potential contaminants are water birds such as cormorants (Figure 3) which swim through the water and eat fish from the lake on a regular basis. Double-crested cormorants normally contain the greatest concentrations of chemical contaminants among several water birds tested in the Great
Lakes.
20
Figure 3.
Double-crested Cormorants at Meadow Lake.

Smaller birds eat relatively more food, and the belted kingfisher is one example of a common pisciverous bird with a high food intake. Kingfishers eat primarily fish and aquatic organisms, and they have been found to eat between ½ and 1¾ times their body weight per day. At Meadow Lake, kingfishers are often seen near the edge of the lake and along tributaries to the lake during storms. The high food consumption rate and choice of feeding in storm water that has not yet mixed with lake water may expose these birds to higher amounts of contaminants, such as diazinon.
Table 10.
Birds commonly seen at Meadow Lake (Jenny Rasmussen 1997-2001)
Common Name Jan. Feb. Mar. Apr. May June August October Nov. Dec.
Great Blue Heron
Little Blue Heron
-
-
-
-
-
-
-
-
- -
1 -
-
1 adult&2-3imm. 1
1
- 2 - 2
1
-
1
-
- Green-backed Heron -
Yellow-crowned
Night Heron
- - - - - 2 adult&1-2imm. - -
Great Egret
Snowy Egret
Cattle Egret
-
-
-
White Ibis -
Greater Yellowlegs -
American Coot
Cormorants
Meadowlarks -
-
-
-
-
-
4
8
1
-
-
-
-
2
-
14
-
5
8adult&2-
3imm.
- -
-
-
-
-
-
-
-
-
15
- -
- 1adult&1imm -
- - -
-
15 many many many many many some a few
- - many many - - -
- - many many
-
6
-
2
-
1 many many
-
1
- many
8
Belted Kingfisher -
Gulls -
-
-
1 - - many - -
1 1-2
- -
Mallards 2 -
Northern Shoveler -
Bufflehead
Canvasback
-
- many 4 8 - -
2 8
2 pair
-
2 many! -
- -
2
-
-
-
-
-
-
-
-
Killdeer -
Loggerhead Shrike -
Blue-winged teal -
Chickadee
Northern Shrike
Red-bellied woodpecker
-
-
-
-
-
3 many! 2 5 - -
- 1 - - - -
- 8 - 6 - -
2
-
- -
- -
- heard some -
- - -
-
-
-
-
- 1 - 2 - 2
-
-
-
-
-
-
8
2
2
-
- flock(50) -
-
-
-
1
-
-
17
-
-
-
-
-
-
-
-
-
-
- many
40
6
-
-
1 many
Lesser Scaup
Least Sandpiper
Ring-Necked Duck -
-
-
-
-
-
8
1
1
4 -
- -
- -
- -
- -
- -
-
-
-
-
-
-
-
-
-

Ruddy Duck -
Pied-Billed Grebe -
Eared Grebe
Swallows
-
-
Red-winged
Blackbird
Cardinal
-
-
Scissor-tailed
Flycatcher
Kingbirds
Kinglet
-
White Pelicans
-
-
-
-
-
-
-
-
-
1 -
-
-
-
-
-
-
-
-
-
6
- -
2 -
- -
- 1
- - - - - many many many many -
1
-
-
-
1
-
-
1
4
- -
- -
- many -
-
1
4
- 2
- 1
-
1
-
-
-
-
-
-
- many Many(100+) - many Many -
1
-
-
-
3
-
-
-
-
-
-
-
-
-
- many
At the Patuxent Wildlife Research Center, studies have been conducted to determine the effects of various contaminants on birds and other wildlife. Patuxent is a
Federal research facility that is part of the U.S. Geological Survey Biological Resources
Division. At the request of U.S. Fish and Wildlife staff, contaminants were analyzed for potential effects on aquatic organisms, plants, birds, mammals, and terrestrial invertebrates. Between 1985 and 1998, thirty-four contaminants were reported on in the
Contaminant Hazard Reviews, and the reports are now available on-line at the Patuxent
Wildlife Research Center website.
21
Some of the contaminants studied have been banned by the EPA, but due to their stability, some may continue to remain in the environment for decades.
Pesticides that bioaccumulate and experience ecological magnification often have severe consequences for piscivorous wildlife such as birds. These types of environmental fates were recognized decades ago, with one of the most famous cases being the case of
Clear Lake in California. The pesticide DDD was applied to the lake to control gnats, with concentrations of 14 to 20 ppb in the water. Large numbers of grebes were later found dead, and upon testing of the fish and grebe tissues, it was found that the DDD had concentrations of 5 to 221 ppm in the fish flesh and 1600 ppm in the fatty tissue of a

grebe, thus causing significant mortality. Some samples of visceral fat in fish exceeded
2000 ppm.
22 Bioaccumulation and ecological magnification are also significant human health issues, because humans also eat fish caught from local streams and lakes. Fish are typically only a minor part of the human diet; however, so the danger is likely to be higher for wildlife that feed primarily on fish and other aquatic life. Some small species of aquatic life have been found to become more resistant to pesticides through exposure over a period of time. The likely reason for this is the process of evolution, where more resistant individuals survive and reproduce. It seems likely that the higher animals that reproduce less quickly, such as birds, will experience increased danger by eating from streams where this process has occurred, because they eat the smaller organisms that may have evolved to survive with higher levels of contaminants in their tissues.
Most of the pesticides that were found to significantly bioaccumulate and magnify in the food chain have been banned by the EPA. In recent decades, wildlife kills have continued to result from pesticide use. For example, granular types of pesticides are often fatal to birds because they mistake the granules for food while probing the ground for seeds and grains. Birds also regularly eat small stones to aid in food digestion in the gizzard.
EIIS most frequently sited pesticides in bird kill incidents

Diazinon

Carbofuran

Chlordane

Fenthion

Chlorpyrifos


Brodifacoum

Parathion

Famphur
Carbofuran (trade name Furadan) is extremely toxic to birds, and one granule will kill a small bird.
23 Granules containing only 3% active ingredients have killed sandpipers in Texas. Hawks and scavenging birds have been killed when feeding on prey that has recently ingested carbofuran. In 1994, the EPA banned granular use of the pesticide (with only minor-use exceptions) due to the extreme toxicity to birds that readily ate the granules. The liquid form of carbofuran is not banned. Carbofuran is used on agricultural crops such as corn in Texas, according to the the National Center for Food and
Agricultural Policy ( NCFAP) National Pesticide Use Database.
24
The USDA reports that corn is one of the primary crops grown in Williamson County.
25
Although there is some farming in the Meadow Lake watershed, farming was probably never extensive in the watershed, due to large portions of the watershed that have steep topography.
Studies have shown that some chemicals affect birds to a much higher degree than mammals. For example, diazinon was found to be fifty times more toxic to birds than to mammals. Most birds in a US Fish and Wildlife study died when fed five granules of diazinon.
17
Since the ban of granular carbofuran, diazinon has been ranking number one in bird kills. Even though carbofuran has a higher total number of incidents reported in the EIIS database, diazinon ranks number one for the largest number of bird kills per acre treated. “The number of documented kills, while very large, is believed to be but a very small fraction of total mortality caused by this pesticide. Mortality incidents must be seen, reported, investigated, and have investigation reports submitted to EPA to have the

potential to get entered into a database. Incidents often are not seen, due to scavenger removal of carcasses, decay in a field, or simply because carcasses may be hard to see on many sites and/or few people are systematically looking. Poisoned birds may also move off-site to less conspicuous areas before dying.”
26
Variations in species susceptibility are important when developing water quality criteria, because some of the most sensitive species may not be present in the area. Sitespecific criteria may be justified in some cases. Some pesticide studies have revealed a difference in susceptibility among different species of birds. For example, sublethal effects of mirex were much more obvious in raptors than in non-raptors, reducing their reproductive success. Mirex also bioaccumulates in the food chain, so raptors would be at an increased risk for this reason as well. Mirex, a persistent organochlorine pesticide, was used in the southeast for fire ant control until it was banned by the EPA in 1978.
27 In some cases birds and mammals were found to be resistant to certain contaminants due to their body’s ability to bind contaminants so that they are not bioavailable. One study of cadmium showed that metal-binding metallothioneins were present in large numbers in certain species such as ducks, especially in heavily polluted areas.
When considering potential pesticides that may be present, it is useful to study the past and future land-uses of the contributing watershed. The most commonly detected organophosphorus pesticides in a USGS study of streams across the U.S. were diazinon, chlorpyrifos, and malathion.
28
Diazinon and chlorpyrifos also ranked high on the list of pesticides in the EIIS for causing of bird mortalities. Even though most of the deaths were likely due to direct ingestion of the granular form of the chemical, there is still a

concern about the potential for chronic effects of exposure to smaller concentrations in the lake water or sediments.
Birds are particularly difficult to study in the natural environment, due to their high mobility. Even birds that do not migrate may wander in an area significantly enough to avoid recapture during mist-netting experiments. Counting carcasses in recently sprayed areas is also extremely difficult due to the small size of the carcasses and the speed of removal through natural processes such as being scavenged by insect or larger scavenging animals or birds.
29
As U.S. citizens have become aware of different exposure paths for pesticides to harm wildlife, the government has taken steps to reduce the risks to wildlife, often under pressure from environmental organizations. Evidence of bioaccumulation and ecological magnification led to the banning of many chemicals in the past few decades. Most organochlorine pesticides were banned over ten years ago. Exposure routes have continued to be discovered, such as the granular types of pesticides being ingested by birds and causing death. Migratory birds are still exposed to some of the more persistent and bioaccumulatory types of pesticides when they fly to central and south American during the winter months. Within the next century, it is reasonable to expect that the standard of living in those countries may also rise and allow for greater restrictions and the ability to preserve the quality of life for the birds and other wildlife that share our water resources. Prior to issuing additional regulations, governments must explore the economic and human health pros and cons of pesticide use. In some countries, mosquito control is of primary importance due to the outbreaks of diseases that cause huge loss of human life. In the U.S., where pesticides are used largely to reduce pest damage to crops,

some farmers are discovering the benefits of working with wildlife by attracting purple martins and bats that eat large quantities of insects.
L
AKE
H
YDROLOGY
Inflow due to surface runoff
In order to determine the average yearly inflow to the lake from surface runoff, rainfall data was collected from the National Climatic Data Center for Austin/Mabry.
Camp Mabry is approximately 20 miles southwest of Meadow Lake. This was the closest location available with data for a long historical period. Daily rainfall totals were used from the years 1920 through 2000 to estimate the runoff. It was assumed that each daily total represented a separate storm event, with runoff values calculated using the
SCS runoff curve number method. Curve numbers are a function of soil type and vegetative characteristics, as well as impervious cover. Within the Meadow Lake watershed, soils are assumed to have a high runoff potential (Hydrologic Soil Group D) because they are primarily deep clay soils with high swelling potential.
30
The estimated
SCS curve number at basin build-out is 91, based on residential land use.
31
In order to calculate the inflow (Q) to the lake from surface runoff in the watershed, rainfall amounts were converted to runoff in the following manner. For each day of each year from 1920 to 2000 (each day assumed to represent a potential 24-hr storm event), expected runoff was calculated using the SCS runoff curve number method.
Data and calculations are shown in the spreadsheet entitled “CSTR_MeadowLake.xls” included on the CD included with this report. Figure 4 graphically shows the results of the method for an example month (May 1999). Predicted runoff also varies with the

curve number estimated for various land uses, so the figure shows the results for three example curve numbers.
4
3.5
3
2.5
2
1.5
1
0.5
0
1 2 3 4 5 rainfall runoff (CN 90)
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
21 22 23 24
25 26 27 28
Day of the Month (May 1999)
29 30 31 runoff (CN 80) runoff (CN 70)
Comparison of Runoff for Different Curve Numbers runoff (CN 70) rainfall
Figure 4.
Example runoff depth for example month and various runoff curve numbers.
As shown in the spreadsheet for Meadow Lake, the process of calculating inflow to the lake from surface runoff is as follows. For each land use, the average runoff per year is calculated by adding the runoff totals for each day of the year (and then averaging the yearly totals from 1920 through 2000) and then multiplied by the surface area occupied by that land use, resulting in the estimated volume of surface runoff from that portion of the watershed. Summation of the runoff volume from the various land uses results in a total estimate for the runoff volume entering the lake per year.

Flow characteristics
Figure 5.
Principle Spillway Structure, Photograph November 9, 2001 by Jenny Rasmussen
Figure 6.
Principal Spillway (Orifice Plate Assembly at elevation 716.0) - Photo taken November 9, 2001

The principal spillway is at elevation 716. The top the dam has an elevation of
728, but there is an emergency spillway on the east side of the dam at an elevation of 723.
The water surface typically remains close to the principal spillway elevation (716) or sometimes falls below it as much as several feet during a drought. During a 100-year storm event, the predicted maximum elevation of the water surface is 723.3, which is 7.3 ft above the principal spillway, and 0.3 ft above the emergency spillway. As the water surface rises to this level during the hypothetical 100-year event, the inflow to the lake from its tributaries will eventually slow to a point where it equals the outflow through the spillways. As the runoff from the watershed is further reduced, the outflow from the lake will begin to exceed the inflow, and the water surface elevation of the lake will start to fall again. The outflow rate at various elevations above the principal spillway is shown in Table 11.
Table 11.
Meadow Lake Outfall Rates at Various Flood Stages
31
Elevation
(Ft MSL)
Principal Spillway
(cfs)
Emergency Spillway
(cfs)
Total Discharge
(cfs)
716.00 0
716.39 1.52
716.78 4.31
0
0
0
0
1.52
4.31
717.18 7.91
717.82 11.07
718.47 13.51
719.12 15.57
719.76 17.39
720.41 19.03
721.06 20.55
721.71 21.96
722.35 23.28
723.00 24.53
723.25 25.00
723.50 25.46
723.95 26.27
724.50 27.22
725.50 28.87
0
0
0
0
0
0
0
0
0
0
45.65
91.77
175.32
384.90
862.54
7.91
11.07
13.51
15.57
17.39
19.03
20.55
21.96
23.28
24.53
70.65
117.23
201.59
412.12
891.41

726.75 30.81
728.00 32.84
1659.41
2665.74
1690.22
2698.38
The principal spillway accepts greater flow when the reservoir elevation is higher, due to the greater hydraulic gradient forcing the water through the orifice and then the outflow pipe beneath the dam. Assuming no further rain occurs, the water surface elevation would be reduced back to the principal spillway elevation of 716 within about a month.
This estimate is based on a simplified integration of the volume drained at each outflow rate, beginning with the 100-year water surface and ending at the principal spillway elevation.
The 100-year storm is a rare event; however, and more typical storms would not cause the elevation of the lake to rise more than about 1 foot above the principal spillway.
During a recent 4.4” storm event, the water surface elevation was just over 2ft above the principal spillway. Figure 7 shows a photograph taken after the event, showing a portion of the air vent pipe still visible above the principal spillway.

Figure 7.
Water surface over 2 ft above spillway, following 4.4” rain (Nov 16 2001)
During periods of drought, when inflow to the lake from runoff is minimal, evaporation and other losses result in a reduction of the water surface elevation. After periods of drought, it often takes several storm events to raise the water surface elevation back up to the principal spillway elevation. Average monthly evaporation in this region is shown in Table 12.
Table 12.
Average monthly evaporation (TWDB quadrangle 710).
32
Month n Min Max Median Mean 10%ile 90%ile
Jan 45 1.23 3.20 2.05 2.09 1.49 2.64
Feb 45 1.35 3.72 2.39 2.46 1.76 3.45
Mar 45 2.62 5.32 3.66 3.73 2.87 4.55
Apr 45 2.75 5.94 4.28 4.37 3.48 5.26
May 45 2.88 5.88 4.63 4.55 3.60 5.60
Jun 45 3.96 7.73 6.11 6.08 4.91 7.40
Jul 45 5.13 16.62 7.50 7.53 6.00 8.76
Aug 45 4.78 9.13 6.81 6.89 5.59 8.59
Sep 45 3.95 7.38 5.17 5.35 4.31 6.53
Oct 45 3.06 6.02 4.19 4.42 3.45 5.37
Nov 45 1.84 4.17 2.97 2.98 2.41 3.86
Dec 45 1.31 3.22 2.06 2.20 1.70 2.86
For a drought in the months of June, July, and August (using the mean values of evaporation in those months), the reduction in surface elevation of the lake would be approximately twenty inches due to evaporation alone.

Even during periods of drought, water can be heard coming through the outfall pipe. Without being able to see into the structure, it can only be assumed that some leakage is occurring through the structure, possibly through the 12” slide gate located near the bottom of the spillway structure. This slide gate is designed to allow the lake to be drained if necessary.
Figure 8.
Outflow pipe on the downstream side of the dam. Some flow is evident, even though the lake elevation was below the principal spillway elevation at the time the photo was taken. Some leakage is likely occurring into the principal outflow structure, possibly through a 12” slide gate designed to allow the lake to be emptied if necessary. The high water surface elevation shown here at the pipe is caused by sediment downstream of the outflow causing ponding around the outfall. (November 9, 2001)

Figure 9.
Outflow pipe following 4.4” storm event (November 16, 2001)
S
IMPLIFIED
W
ATER
Q
UALITY
M
ODELING
Outflow from the lake varies based on storm events, and the lake is not likely well mixed in the short span of these storm events, but a CSTR (continuously-stirred tank reactor) model may still be adequate to estimate the potential effects of various pollutant loads. Rather than trying to obtain exact values, the goal of my study was to obtain estimates of the concentrations sufficient to determine if the chemical could be of concern (within an order of magnitude of the criterion).
Estimated Lake Volume = 400 ac-ft.

Estimated Outflow at peak development = inflow runoff
– evap lakesurface
+ rainfall lakesurface
=
1410 ac-ft/yr or 1.95 cfs (refer to CSTR spreadsheet for runoff calculations based on peak development land use).
Equivalent Detention Time
Peak Dev
= V/Q = 400/1410 = 0.28 yrs = 3.4 months
Example analysis of non-conservative substance Diazinon (K>0) using CSTR model
Approximately 25% of the watershed is currently used for residential housing.
Diazinon is a commonly used pesticide on residential lawns. The half-life of diazinon is approximately 42 days, so calculation of K yields (excluding loss to sediment):
0.5 = exp (-K(42 days))
K = 0.5/month
Estimated Outflow (for current land use percentages) = inflow runoff
– evap lakesurface
+ rainfall lakesurface
= 805 ac-ft/yr or 1.1 cfs (refer to CSTR spreadsheet for runoff calculations based on current land use) t = V/Q = 400/805 = 0.5 yrs = 6 months
To calculate the allowable loading for the watershed
33
without exceeding the recommended criterion of 0.08
 g/L:
W allowable
= 0.08 (Q+KV) = 0.08
 g/L * (805/12 ac-ft/month+0.5*400 ac-ft/month)*
43560 ft2/ac * 1000L/35.3147 ft
3
* 1 kg/1E9 ug) = 0.026 kg/month = 0.32 kg/yr
0.32 kg/380 acres residential = allowable runoff load 0.8 gram/acre/year.
This can be compared to the max recommended application rate (by manufacturer) = 113 lb/ac/year AI * 453.6 g/lb * 40% I.C.= 20,550 grams/acre/year applied to ground. Water solubility is about 60 ppm. In a California study, it was estimated that approximately
0.3% of the diazinon applied was carried by runoff into a creek near a residential

neighborhood. This would translate into a runoff load for the Meadow Lake of approximately 60 grams/acre/year in the runoff from the residential areas, far in excess of the allowable 0.8 gram/acre/year estimated by the CSTR model. Thankfully, not all residents choose to apply diazinon year round. In an urban study in Alameda County,
California, it was discovered that the diazinon pollution was coming from a very small percentage of the homes. Stream measurements were approximately 350 ng/L, but when moving up closer to the source, mean diazinon levels measured in street gutters were
3,900 ng/l in all of the street gutter samples, but the range spanned three orders (30 to
70,000 ng/l). Additional sampling in street gutters after professional application at the recommended rate revealed that even runoff from a small percentage of homes is enough to contaminate the water bodies downstream at levels exceeding recommended criteria.
In a study in the Dallas/Fort Worth area, the mean runoff concentration at eleven residential catchments was 1,900 ng/l. If we assume the average concentration in the residential catchments of Meadow Lake to be the 1,900 ng/l measured in the Texas study, the potential loading to Meadow Lake can be determined based on the percentage of the watershed that has a residential land use. Using this loading estimate from the residential areas, the CSTR model (refer to spreadsheet) results in an estimated lake equilibrium concentration of 0.23
 g/L, compared to the suggested criteria of 0.08
 g/L. Monitoring for diazinon in Meadow Lake is therefore estimated to be of high importance in the next few of years, especially as the residential land use continues to increase in the watershed.
Sales of diazinon for lawn application will end in December of 2003, and then it may be another year or so until residents had used their supplies. Some residents surveyed know of neighbors in this area that have already begun stockpiling diazinon in anticipation of

this phase-out, so some may continue to use it for years after sales are prohibited. Based on the California study, even this small percentage of residents using diazinon after sales end could still result in relatively high concentrations of diazinon in the lake.
Potential groundwater interaction
Although no groundwater interaction was assumed in the CSTR model, there is likely some inflow/outflow interaction with groundwater. Especially following storms, inflow could be possible due to the rapid change in topography from the hill north of the lake. Figure 10 shows two wells in this region of Round Rock. Data collected from these wells indicates that the water table is generally between 50 and 100 ft below the surface.
Figure 10.
Well Location Map
34
In periods of drought, the lake may begin losing water to the groundwater.
Measurements of the water surface elevation could be taken throughout the year to estimate the groundwater inflow/outflow. This would be complicated; however, due to

the fact that water appears to be leaking through the principal outflow structure even when the water level is below the spillway elevation. This could be a fun data collection project for future school students at the new Middle School that is currently under construction north of the lake. Data collection might involve things such as the following:

Set up an evaporation measurement station so that students can take daily measurements of evaporation.

A rain gauge would allow students to measure individual storm events.

Installing a weatherproof measurement device either adjacent to the school or attached to the lake outfall structure would allow students to measure the daily water surface elevation of the lake.
M
ONITORING
D
ATA
C
OLLECTED TO
D
ATE
Secchi Depth Transparency
The secchi disk is used to measure the distance a person can see into the water. Higher water clarity is often associated with higher water quality. The secchi depth measurements collected in the Fall of 2001 ranged from 0.6 to 0.75 meters. Secchi depth is reduced by suspended sediment and algae in the water column.
Total Phosphorus
The amount of phosphorus present in the water provides information on the potential of the water body to support growth of algae and other plants. Phosphorus is typically the limiting nutrient, but it is important to note that light penetration is very important in limiting growth of algae and plants, so a high TSS concentration may result in lower than

expected algal growth. The total phosphorus levels were measured on two days at the locations shown in Figure 10. The results are presented in Table 13.
Figure 10. Phosphorus monitoring locations.
Table 13. Total phosphorus measurements.
(results not yet available)
Diazinon (single measurement – not after storm event)
(results not yet available)
Total Coliform
Total coliform testing was performed on three separate occasions during the Fall of 2001.
The first tests indicated the presence of coliform bacteria in only two of the eleven sample locations. There were so many non-coliform bacteria on the filter paper that they may have interfered with the growth of any coliform bacteria colonies.
35 Sample site 8 had a total coliform count of 10, and sample site 8 had a total coliform count of two. The second test did not reveal any coliform bacteria at the eleven sample locations. The oven temperature was found to be out of range, and once again the non-coliform count was
TNTC (too numerous to count) so the first two tests may not have been accurate.
Four days following a 4.4” rain event, samples were obtained at two locations. Both sites revealed significant numbers of coliforms. Texas does not have a criteria for total coliform. The Texas criteria require that E. coli be 126/100ml, but E. coli is only one type of coliform. For comparison to the Texas criteria, a specific test would be needed for E. coli. Some states do have criteria for total coliform. For example, the State of New York requires that “The monthly median value and more than 20 percent of the samples, from a minimum of five examinations, shall not exceed 2,400 and 5,000, respectively.”
16
The

largest measurements obtained for the two sites at Meadow Lake are 880/100ml and
900/100ml respectively, based on the 5 ml sample size (counts multiplied by 20 to estimate count for 100ml). Based on the New York criteria for Class B waters (contact recreation and fishing), the levels at Meadow Lake appear to be well within the range of
1
1
2
2
2
1
1
1 pH those required to support contact recreation. In order to satisfy the Texas criteria; however, specific testing for E. Coli would be needed.
Sample Number Count/filtered volume
91 / 25 ml
113 / 25 ml
127 / 25 ml
125 / 25 ml
44 / 5 ml
127 / 25 ml
84 / 10 ml
45 / 5 ml
Count/100ml
456 / 100 ml
(sum of 4-25ml counts)
880 / 100 ml
508 / 100 ml
840 / 100 ml
900 / 100 ml
The pH measured at Meadow Lake ranged from 8.0 to 8.3 for samples analyzed in the
Fall of 2001.
D.O.
Dissolved oxygen levels vary with depth below the lake surface and with the time of day.
All measurements collected in the Fall of 2001 were above the 5.0 mg/L criterion for the protection of aquatic life.
BOD
(results not yet available)
Trace Metals
(results not yet available)

P OTENTIAL H AZARD A SSESSMENT
Even though no immediate threats to the designated uses of the lake were discovered during the preliminary sampling analysis, it is important to identify potential threats and enact plans to reduce the risk of those threats.
Change in land use over time
The conversion to residential land use may result in additional pesticide and nutrient loading. These additional loads could potentially pose a risk to one or more of the uses of Meadow Lake. Pesticide loads could result in an increase above the allowable limits for pesticide concentrations in the lake water (especially following storm events) or sediments. Nitrogen and phosphorus loading from fertilizer use could accelerate the process of eutrophication and potential fish kills due to low D.O. at night.
In order to evaluate these possible threats to the uses, the simplified CSTR model was used. First, the model was run based on an estimate of the current land uses. Based on the most recent aerial photograph obtainable, approximately 25% of the watershed is currently developed as single-family housing. The remainder of the watershed is primarily covered by grassland and weeds, sometimes used for grazing and agriculture.
The future land use map obtained from the City of Round Rock shows that the majority of the watershed will eventually be developed for residential use. The area west of
Sunrise Blvd is designated for industrial use, which may have more impervious cover, but there is also a similarly sized region that lies within the County and has larger three to five acre residential lots with a low impervious cover. The model for these future land uses was run assuming an urban curve number for the dense residential housing, since the average impervious cover of these other minor land uses will likely be approximately the

same overall impervious coverage as the dense residential housing. The results of the
CSTR model are presented Table 13.
Table 13.
Estimates of lake concentrations for current and future land use.
Model estimate for current Model estimate for future
Phosphorus land use (mg/L in lake) land use (mg/L in lake)
Diazinon
Eutrophication
The CSTR model indicates that there is already a potential for excessive phosphorus loading in the lake, even with the current land uses. As the watershed becomes more fully converted to residential homes, it will be useful to educate homeowners about the effect of fertilizers applied to their lawns. Organic fertilizers are available with a much lower concentration of phosphorus. Loading from natural sources such as bird droppings may also be important.
Even though there may be relatively high phosphorus loads entering the lake, the algal growth may be limited by sunlight penetration. If the suspended sediment concentrations continue to remain high, algal growth may not ever become a significant problem at Meadow Lake. Even if this is the case, the water from Meadow Lake discharges into downstream water bodies which may have different conditions that do result in reduced water quality due to the phosphorus loading. Reduction of phosphorus loading would therefore still be a useful goal, even if no effects are observed at Meadow
Lake.
Dissolved Oxygen

Due to the shallow depth of the lake and warm climate, the development of a hypolimnion with significantly lower D.O. levels is not expected. Winds encourage mixing of the surface water that is in contact with the atmosphere, replenishing the D.O. supply.
Sedimentation
During construction in the watershed, inadequate erosion controls result in greater than normal sediment loadings per year. For example, the current construction site for a new Middle School on the north shore of the lake has caused significant change in the area near the lake.
Figure 11.
Construction Disturbance adjacent to Meadow Lake
This sediment load is likely impacting the organisms living on the bottom of the lake in this area, in addition to the destruction of the previously existing tributary stream and the organisms that lived in and around it. The area was once a prime habitat for many species of shorebirds.

Figure 12.
Disturbed ground on north shore of lake (previous site of natural channel with native vegetation.)
Coliforms
There are not very many septic systems in the watershed. Most wastewater is collected in a sewage collection system and taken to the City of Round Rock treatment plant. The sewage collection system did overflow from several manholes a few years ago and dump raw sewage into the lake. One potential threat to the coliform criteria would be the threat of additional spills such as the spill that occurred several years ago.
Household Hazardous Wastes (HHW)
The watershed is quickly being converted from farmland to primarily a singlefamily residential land use. The improper disposal of hazardous household wastes is one potential threat to the surface and groundwater quality in the watershed. The City of

Round Rock does not have a facility for collecting HHWs, but there is a yearly collection date in April that is available. Further promotion and advertising of this resource would help encourage proper disposal of these harmful chemicals and reduce the risk to the local water resources. A storm drain stenciling project may also be possible if approved by the City of Round Rock. This would help to educate homeowners and help them to understand that water is discharged from the drains directly into the lake. Many people mistakenly think that water is treated at the treatment plant before being released. This is still the case in some areas in the northeast that have combined sewers. It is understandable that some residents are not aware of the current standard practice of constructing separate storm and sanitary sewer lines.
Oil Spills
Accidental spills are also a potential threat to the uses of the lake. Oil leaking from vehicles in the watershed, or accidental larger spills of oil by residents could have devastating effects on the lake. Education of the residents to prevent such accidents is one important tool for reducing this risk. In addition, post-spill emergency action plans are a useful tool to help stop the spread of spills and prevent further damage once they have occurred.

Figure 13.
Oil stored adjacent to Meadow Lake in Edward’s Aquifer Recharge Zone.
36
One complaint has already been filed with the TNRCC due to the storage of oil adjacent to the lake (Figure 13), and the small spill shown in Figure 14. This area is within the Edwards Aquifer Recharge Zone. The contractor had removed the oil prior to the TNRCC inspector’s visit.
36

Figure 14.
Oil spill adjacent to Meadow Lake in Edward’s Aquifer Recharge Zone.
36
Potential threats to wildlife in the region adjacent to the lake
Lakes are very attractive to birds and other wildlife, and many species choose to live within a certain radius of the lake. Purple martins, for example, prefer nesting sites within one to two miles of water bodies such as lakes and rivers. Results of the North
American Breeding Bird Survey found that “martins prefer relatively low elevations where aquatic habitats and their associated insect populations are plentiful.” 37
Due to the potentially dense concentration of bird species within the vicinity of lakes and streams, it would be useful to encourage additional public awareness campaigns within the vicinity of lakes and perennial streams. Most development is currently restricted by the 100-year floodplain, but in many areas, wildlife and water quality would greatly benefit by

additional restrictions that may increase the buffer zone and habitat adjacent to water bodies. The City may be able to purchase easements from land owners prior to development, if funding could be approved through bond elections and public awareness campaigns by environmental groups.
Mowing close to the lake also reduces the water quality benefit and reduces habitat for wildlife. The City is not prohibited by from mowing up to the water’s edge.
Some residents have already complained to the City about mowing in an area that the birds were actively using for breeding. Residents witnessed parent birds sounding alarm calls during the mowing.
36
Additional efforts are likely needed to encourage the City of
Round Rock to modify its mowing schedule around the lake, epecially during the most active part of the breeding season, due to the fact that many of the birds lay their eggs on the ground around the lake.
Planting of non-native species can be detrimental to wildlife and reduce biodiversity. Boats that are used in more than one lake can easily spread invasive aquatic plants, such as Hydrilla.
38
Hydrilla has not been identified yet at Meadow Lake.
Education is one method of reducing the risk of its introduction. One resident, for example, mistakenly thought he was helping by planting willow branches at the water’s edge. Invasive trees such as Chinaberry and Chinese Tallow trees are still sold at most plant nurseries in this area. If people were educated about invasive species, many people would not choose to plant them. Monitoring programs would also be useful by resident plant experts that might see non-native plants and be able to remove them before they spread and take over an area, saving money that would have been necessary if the problem had gotten out of control.

Currently, hunting occurs on the east shore of the lake. Birds are killed both directly by the bullets, and may also be killed by ingestion of lead shots when feeding.
This is an example of one threat to wildlife that will disappear once the watershed has been converted to a residential land use and hunting is no longer permitted in the area.
Cost/Benefit Analyses
The cost/benefit of any plan must be analyzed, but many simple plans can be enacted by concerned citizens in the watershed. It would be impossible to completely eliminate all threats to the water quality. Any issues discovered can be made public and addressed through City meetings and homeowner association meetings to discuss options and alternatives. The Meadow Lake Homeowners Association is one example of a group that is already interested in the lake and will likely provide a good platform for introduction of future issues. Education will allow citizens to make informed decisions.
Setting Priorities
Based on the estimated hazards risks, a public education program can be designed to manage those risks, and spill clean up programs can be activated, such as posting of hotlines and City numbers to call in case of emergency. Use of funding should be directed to programs that will potentially give the most return on the investment in terms of protection for the uses of the lake. Before conflicts of uses occur, use priorities can be evaluated and discussed prior to actual occurrence of conflicts, allowing for alternative solutions to be evaluated and quantified in a cost/benefit analysis.

M
ONITORING
R
ECOMMENDATIONS
Secchi Depth
Secchi depth measurements are very easy to obtain and require no cost once the device has been purchased. Volunteer monitoring could be conducted as often as desired, although it is most useful to standardize the monitoring times and methods. For example, it would be most useful to obtain measurements at the same time of day each time, and to record the weather conditions that might affect the measurement, such as cloud cover.
When obtaining measurements from a boat or kayak, it is best to obtain the measurement on the shady side of the boat. Consistency is important for analyzing trends over time.
When measuring secchi depth, it is also very useful to occasionally estimate the suspended sediment and algae quantities by separate means. This will help to determine the relative affect of each parameter on the secchi depth. These tests are more costly; however, so it is not expected that they would be run very often unless a funding source becomes available.
Total Suspended Solids
Meadow Lake is a relatively shallow lake, so wind may cause the bottom sediments to be mixed into the water column. Suspended solids and algae will both affect the secchi depth measurement, so it is useful to measure the suspended solids to estimate its potential affect on the secchi depth measurements.
Algae
Chlorophyll a is typically measured to estimate the amount of algae present in the water. It is produced in different amounts by different species of algae, so it is not a perfect measuring tool. Due to the cost of taking frequent measurements, this test is not

likely to be completed very often. Instead, visual observations of algae would be useful when monitoring. If more algae is observed, monitoring may become desired at that time.
Dissolved Oxygen
Dissolved oxygen levels are fairly easy to obtain using the monitoring kit available from the Texas Watch program. Lowest levels are expected in pre-daylight hours in the summer, so more frequent monitoring may be desired in the summer.
Diazinon
Due to the cost of measuring for pesticides, diazinon is unlikely to be monitored in the future. The highest concentrations are expected within 2 days after rainfall events of 2” or more. Occasional monitoring may be desired, but diazinon is scheduled to be phased out by December of 2003. The best locations for monitoring pesticides would be where the tributary streams enter the lake from residential areas.
Phosphorus
Coliforms
Monitoring is recommended twice per year after storm events or if any wastewater spills observed. If necessary, signs could be posted to restrict contact recreation for a certain period after a spill has occurred or after storm events.

R EFERENCES :
1.
Owen, Bill. Natural Resource Manager NRCS. (Georgetown, TX: Oct 19, 2001), personal interview.
2.
Round Rock City Council Minutes (May 11, 2000). Regular Session: City
Council Chamber, 221 E. Main Street, Round Rock, Texas.
3.
Nuce, Jim. Brushy Creek WCID Director. (Round Rock, TX: Nov 8, 2001), phone interview.
4.
Texas Administrative Code, Title 30, Environmental Quality.
5.
Davenport, Jim. TNRCC. (Austin: Oct 2001), phone interview
6.
DRAFT Texas 2000 Clean Water Act Section 303(d) List (August 31, 2000).
Texas Natural Resource Conservation Commission. http://www.tnrcc.state.tx.us/water/quality/ last accessed November 17, 2001.
7.
The Extension Toxicology Network (EXTOXNET). A Pesticide Information
Project of Cooperative Extension Offices of Cornell University, Michigan State
University, Oregon State University, and University of California at Davis. http://pmep.cce.cornell.edu/profiles/extoxnet/ last accessed November 17, 2001.
8.
City of Austin, Texas Environmental Criteria Manual . Updated September 2001.
Ohio: American Legal Publishing Corporation, 2001.
9.
The Quality of Our Nation's Waters. U.S. Geological Survey Circular 1225 ,
USGS, 1999. http://water.usgs.gov/pubs/circ/circ1225/ last accessed November
17, 2001.

10.
Regional Urban Storm Water Management Strategy for the Dallas/Fort Worth
Metroplex, North Central Texas Council of Governments (NCTCOG) http://www.dfwstormwater.com/overview.html
last accessed November 17, 2001.
11.
Mahler, B.J. and P.C. Metre. Occurrence of Soluble Pesticides in Barton Springs,
Austin, Texas, in Response to a Rain Event. USGS, 2000.
12.
“Leading Pesticides Causing Avian Mortalities in the United States.” American
Bird Conservancy, 1999. http://www.abcbirds.org/pesticides/IncidentData.htm
, last accessed November 17, 2001.
13.
“Notice of Intent To Revise Aquatic Life Criteria for Copper, Silver, Lead,
Cadmium, Iron and Selenium; Notice of Intent To Develop Aquatic Life Criteria for Atrazine, Diazinon, Nonylphenol, Methyl Tertiary-Butyl Ether (MtBE),
Manganese, and Saltwater Dissolved Oxygen(Cape Cod to Cape Hatteras)”
Federal Register. EPA, 1999.
14.
Eisler, R. "Mercury Hazards to Fish, Wildlife, and Invertebrates: A Synoptic
Review." Contaminant Hazard Reviews Report 10 . US Fish and Wildlife Service,
Biological Report 85(1.10). April 1987
15.
Eisler, R. "Arsenic Hazards to Fish, Wildlife, and Invertebrates: A Synoptic
Review." Contaminant Hazard Reviews Report 12 . US Fish and Wildlife Service,
Biological Report 85(1.12). January 1988
16.
Official Compilation of Codes, Rules and Regulations of the State of New York
Title 6, Chapter X, Part 703: Surface Water And Groundwater Quality Standards and Groundwater Effluent Limitations. State of New York, last amended 1999.

17. Eisler, R. "Diazinon Hazards to Fish, Wildlife, and Invertebrates: A Synoptic
Review." Contaminant Hazard Reviews Report 9 . US Fish and Wildlife Service,
Biological Report 85(1.9). August 1986
18.
“Diazinon Revised Risk Assessment and Agreement with Registrants.” United
States Environmental Protection Agency. Prevention, Pesticides And Toxic
Substances(7506C) Revised January 2001. http://www.epa.gov/pesticides/op/diazinon/agreement.pdf
last accessed
November 23, 2001.
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