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APPENDIX VIII

MOE'S REPORT ON YOUNG'S CREEK SEDIMENT RELEASE

Ministry of the Environment
133 Dalton Avenue
P 'O Box 820
Kingston ON K7L 4X6

Ministère de I'Environnement
133 avenue Dalton
C P 820
Kingston ON K7L 4X6

Moira River Study
Young's Creek Site Investigation Report
July, 2000

The Moira River study undertaken by Golder Associates for the MOE in 1999, noted that sediments in Young's Creek, above the beaver dams. contained elevated levels of a number of metals and metalloids. Concern was expressed regarding potential release of these sediments, and their contaminant load, to the Moira River due to failure of the beaver dams.

During the weekend of June 24-25, 2000, following a period of heavy rains, failure of sections of a number of beaver dams along Young's Creek was reported. Consequently, Eastern Region and EMRB undertook an inspection of the site to determine the extent of the damage to the beaver dams, and the potential impact of the release of contaminated sediments on the Moira River.

The site visit was conducted on July 10, 2000 by Wayne Herrick (Eastern Region), Rein Jaagumagi (EMRB) and Emily Awad (EMRB). Reports by Wayne Herrick indicated that after failure of the beaver dams, debris had collected at the culvert at Old Marmora Road, blocking the flow with the result that the creek crested and overflowed the road. During the site visit on July 10, the water level was relatively low. There was little evidence of sediments deposited in this area.

Inspection of the beaver dam revealed that a section of the dam approximately 6-7m wide and approximately 1.5 to 2m deep had been removed (Figure 1). At this time, the beavers had already begun to repair the damage to the dam. Comparison of water levels with those occurring immediately after the breach (Herrick, Pers. Comm.), indicated that water levels behind the dam had risen approximately 0.6 to 1.0m. An area of sediment up to 7m out from the base of the beaver dam appeared to have been eroded as a result of the breach of the dam.

Visual inspection indicated that there were likely two sources of contaminated sediments: the material held within the dam structure itself, and the area of sediment adjacent to the dam. The volume of material held within the dam structure was estimated on the basis of the length, depth and width of the section of dam that was removed (8m long, 1.75m high and 3m wide at the base). This would have resulted in the release of approximately 21 m³of sediment (~625 ft ³). Since this volume calculation includes the logs and branches used in the construction of the dam. the actual volume of sediment would be less than this estimate.

The area of sediment above the dam would have contributed to a further loss of contaminated sediment. The area eroded was calculated as 8m wide, and up to 7m perpendicular to the dam, for a total of 56m². While such erosion typically assumes a cone-shape, for the purposes of this report. the area has been calculated as a rectangle, so as not to underestimate the area. Visual inspection at the base of the dam indicated that sediment up to 0.6m in depth was eroded. Based on this, the volume of material eroded is calculated as approximately 34 m³, or 1,000 ft³. Total volume of sediment lost from this dam due to failure of part of the structure is calculated as 55 m³ or 1625 ft ³.

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Figure 1: Young's Creek beaver dam above Old Marmora Road July 10, 2000. Area of breach is the low point near the middle of the beaver dam.

Sediment samples were collected from the dam structure, adjacent to the breach, in approximately 0.6m of water. Arsenic levels in these sediments (Table 1) were 650 ppm. Therefore, up to 21 m³ of sediment with arsenic levels at 650 ppm were released during the breach. In addition, sediments sampled in Young's Creek in 1999 yielded arsenic levels up to 3200 ppm. Based on this, it is estimated that a further 36 m³ of sediment with arsenic levels up to 3200 ppm were also released.

In addition to the main dam, a secondary dam had been constructed by the beavers approximately 20m downstream. This dam also appeared to have suffered some damage, since there were signs of recent reconstruction of this structure. Below this dam was an extensive area of cattail marsh before the creek reached Old Marmora Road. This area would have served to retard some of the flow from the breach, and the vegetation would have assisted in settling some of the particles released from the dam.

Figure 2: Secondary beaver dam below main dam, with cattail marsh visible downstream. Young's Creek July 10, 2000

Sediment samples were collected both above and below Old Marmora Road. In both cases, samples were confined to scraping the top 1 cm from the bottom. The results showed an arsenic level of 880 ppm in sediments above the road, and 2300 ppm below the road, just above the confluence with the Moira River. Since samples had not been collected in these locations previously, it cannot be determined if this is due to material released during the dam failures, or due to historical deposition over time.

Sediment samples collected in the Moira River, below Young's Creek at station MR-8, yielded levels of 950 ppm. Sediment were collected adjacent to the river bank, approximately 1 m closer than in 1999. This was necessary since fine sediments could not be located in the area previously sampled (most of the sediments in the river appeared to have been scoured by the high flows). Levels of arsenic in sediments in this area of the Moira River in 1999, at 960 ppm were very similar to levels in July, 2000.

In addition, sediment samples were also collected at Bend Bay (station MR- 11). This was identified as the first major depositional area downstream and the most likely area for any significant deposition of materials released from the beaver dams. The arsenic concentration in Bend Bay sediment was 520 ppm in July, 2000. By comparison, arsenic concentration in Bend Bay in 1999 was 660 ppm. The difference is likely due to variation in distribution of arsenic in sediment, since the exact location sampled in 1999 would not have been sampled. What the results do suggest however, is that were was no increase in sediment levels of arsenic due to loss of sediment from behind the beaver dams.

Sediment samples were also collected in two shoreline locations in Moira Lake, one in the west basin and one in the east basin, that were sampled in 1999. The shoreline location in the west basin corresponded to station ML-1A, and would have been between the 1m and 2m depths sampled in 1999. Arsenic concentration at this station was 170 ppm. which compared well with concentrations at the 1m (110 ppm) and 2m (210 ppm) depth in 1999. Since the result of the July 2000 sampling is within this range, there does not appear to have been an increase in sediment arsenic at this location.

The east basin location corresponded to station ML-3A, again between the 1m and 2m depths. Arsenic concentration in the sediment was 47 ppm in July 2000, which was higher than levels encountered in 1999 (8.8 ppm to17 ppm). However, this may also be due to variation in sediment levels, since the exact locations sampled in 1999 would not have been possible to attain.

In addition to these sediment samples, two additional locations were sampled for sediment arsenic concentrations: Moira River sediments just upstream from the mouth on the west bank of the river (downstream the last recreational property, adjacent to a cattail marsh), and at the 2.5m depth just offshore of the boat launch at Highway 62. Results showed a level of 710 ppm arsenic at the mouth of the river, which is higher than the sediments in Bend Bay. It is unlikely that the relatively small amount of sediment lost from the beaver dams on Young's Creek could have resulted in such levels at the mouth and suggests that these levels are due to historical accumulation of arsenic in sediments. Arsenic levels adjacent to the boat launch are in the range of arsenic concentrations encountered in shoreline areas in the east basin of Moira Lake (8.8 ppm at station ML-3A-1m to 170 ppm at station ML-3B-2m) during the 1999 survey.

The results of the investigation suggest that a minimal amount of sediment was released from the beaver pond during the breach, at that only approximately 55 m³ of sediment was released to the river. The results of water sampling during this period (by OCWA) indicate there was no increase in arsenic levels in the water column. Some of the released sediment would likely have been retained within the marsh area upstream of Old Marmora Road. It is likely that the small amount of sediment that was released to the Moira River was rapidly diluted, and as downstream sediment results indicate, effected no change in sediment concentrations of arsenic in Bend Bay or nearshore areas of Moira Lake.

Arsenic Concentrations (mg/L) following dam washout at sampling station DM 1 on June 25, 2000

Sample Date	DM 7-Upstream of Dam	DM 1-Washout area	DM 8-Downstream of Dam
June 16, 2000	0.019	0.200	0.098
June 22, 2000	0.023	0.500	**see below
June 25, 2000	no sample	0.336	no sample
June 26, 2000	0.017	0.416	0.064
June 27, 2000	0.018	0.546	0.052
June 28, 2000	0.010	0.298	0.042
July 4, 2000	0.020	0.400	0.190
July 5, 2000	0.024	0.240	0.092

** sample not collected-operator allergic to poison ivy

Historical Results 1997

Sample Date	DM 7-Upstream of Dam	DM 1-Washout area	DM 8-Downstream of Dam
June 4, 1997	0.025	0.144	0.028
June 11, 1997	0.040	0.152	0.052
June 18, 1997	0.054	0.142	0.076
June 25, 1997	0.014	0.246	0.044
July 4, 1997	0.019	0.174	0.041
July 10, 1997	0.019	0.126	0.037
July 16, 1997	0.030	0.158	0.036

Historical Results 1998

Sample Date	DM 7-Upstream of Dam	DM 1-Washout area	DM 8-Downstream of Dam
June 4, 1998	0.096	0.222	0.136
June 11, 1998	0.178	0.084	0.172
June 18, 1998	0.082	0.116	0.108
July 2, 1998	0.030	0.384	0.362
July 10, 1998	0.050	0.166	0.134
July 16, 1998	0.062	0.174	0.087

Historical Results 1999

Sample Date	DM 7-Upstream of Dam	DM 1-Washout area	DM 8-Downstream of Dam
June 8, 1999	0.039	0.248	0.062
June 15, 1999	0.058	0.080	0.150
June 24, 1999	0.110	0.142	0.152
June 30, 1999	0.122	0.064	0.164
July 8, 1999	0.162	0.172	0.220

Moira River - Beaver Dam Breach

Moira River - Beaver Dam Breach - June 24/25, 2000

Arsenic Concentrations ( mg/l)

Average Geo.
Mean STDev.

Date of Sampling
From
to
Number of samples

Dm 7-Upstream of Dam
2000	1999	1998	1997
0.019	0.098	0.083	0.029
0.018	0.087	0.071	0.026
0.004	0.044	0.047	0.013

16-Jun	8-Jun	4-Jun	4-Jun
5-Jul	8-Jul	16-Jul	16-Jul
7	5	6	7

Moira River-DM 7-Upstream of Dam

Average
Geo. Mean STDev.

Date of Sampling
From
to
Number Samples

DM 1-Washout Area
2000	1999	1998	1997
0.367	0.141	0.191	0.163
0.349	0.125	0.170	0.160
0.113	0.066	0.097	0.037

16-Jun	8-Jun	4-Jun	4-Jun
5-Jul	8-Jul	16-Jul	16-Jul
8	5	6	7

Moira River-DM 1-Washout Area

Average
Geo. Mean STDev.

Date of Sampling
From
to
Number Samples

DM 8-Downstream of Dam
2000	1999	1998	1997
0.090	0.150	0.167	0.045
0.079	0.139	0.148	0.043
0.049	0.051	0.091	0.014

16-Jun	8-Jun	4-Jun	4-Jun
5-Jul	8-Jul	16-Jul	16-Jul
6	5	6	7

Moira River-DM 8-Downstream of Dam

Prepared by F.J. Reinholz, P.Eng.
Beaver Dam Breach.xls

Table 1: Sediment metals. Young's Creek and Moira River. July 10, 2000 (in µg/g dry weight unless otherwise noted)

As

Ba

Cd

Cr

Cu

Fe

Pb

Mn

Ni

Zn

Be

Mg

Al

Ca

Va

Co

Md

St

Ti

YC above dam

650

190

1.8

36

520

20000

25

270

440

180

2.2

<T

4600

17000

9300

37

750

5.1

60

770

YC below dam

160

92

0.6

<T

10

98

13000

8

<T

250

110

57

0.8

<T

2300

7000

4300

13

240

0.9

<T

19

1200

YC above road

880

240

1.4

51

670

32000

35

830

390

160

1.4

<T

8300

19000

9800

48

910

1.5

<T

62

1000

YC below road

2300

320

1.8

67

900

36000

34

1700

560

190

1.5

<T

6200

17000

11000

41

1400

3

66

680

MR below YC

950

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

MR Bend Bay

520

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A..

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

MR mouth

710

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

ML west shoreline

170

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

ML boat launch

47

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

ML east shoreline

47

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

N.A.

PSQG:LEL

6

n.a.

0.6

26

16

2

31

460

16

120

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

PSQG:SEL

33

n.a.

10

110

110

4

250

1100

75

820

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

N.A. - Not Analyzed
n.a. - not available
<T -trace levels