RyanI have some additional questions on the I540 project - see below:

1. In the documentation Rich submitted (URS Analysis Corrections.PDF,

Attachment 2) in December 2010, there is an event listed on 11/17 of

0.33 inches that was sampled. However, in the documentation you

submitted in March 2011 (Wake County NCDOT Site Summary for Turbidity

TSSdocx-1.docx) this event is listed as occurring on 11/16/2010. Can you

confirm that the 11/17 event in Rich's document is the same as the 11/16

event in your document and can you provide the correct date that the

event occurred? I've included both files as an attachment for your

reference.

Yes, these are the same events. This storm began on 11/16/10 and ended on 11/17/10.

2. For the 11/4-6 event, Rich's document indicates that there were 11

bottles collected at the Basin 3 OUT location. My understanding is that

each bottle contains four individual sample aliquots. Could you provide

the time that each sample aliquot in each of the 11 bottles was

collected? Also, did you record turbidity of each of the 11 bottles? If

so, could you provide the individual turbidity values for each bottle?

The time that each aliquot was collected is listed in the table below:

storm collected on 11/11/10

11/4/2010 11:51:00 AM Bottle 1

11/4/2010 12:34:00 PM Bottle 1

11/4/2010 1:14:00 PM Bottle 1

11/4/2010 1:58:00 PM Bottle 1

11/4/2010 2:43:00 PM Bottle 2

11/4/2010 3:30:00 PM Bottle 2

11/4/2010 4:29:00 PM Bottle 2

11/4/2010 5:40:00 PM Bottle 2

11/4/2010 7:05:00 PM Bottle 3

11/4/2010 8:21:00 PM Bottle 3

11/4/2010 9:45:00 PM Bottle 3

11/4/2010 11:38:00 PM Bottle 3

11/5/2010 1:36:00 AM Bottle 4

11/5/2010 7:45:00 AM Bottle 4

11/5/2010 12:57:00 PM Bottle 4

11/5/2010 1:49:00 PM Bottle 4

11/5/2010 2:06:00 PM Bottle 5

11/5/2010 2:25:00 PM Bottle 5

11/5/2010 2:46:00 PM Bottle 5

11/5/2010 3:07:00 PM Bottle 5
11/5/2010 3:32:00 PM Bottle 6

11/5/2010 4:02:00 PM Bottle 6

11/5/2010 4:40:00 PM Bottle 6

11/5/2010 5:18:00 PM Bottle 6

11/5/2010 6:04:00 PM Bottle 7

11/5/2010 7:00:00 PM Bottle 7

11/5/2010 8:16:00 PM Bottle 7

11/5/2010 9:50:00 PM Bottle 7

11/6/2010 3:53:00 AM Bottle 8

11/6/2010 7:10:00 AM Bottle 8

11/6/2010 9:51:00 AM Bottle 8

11/6/2010 11:35:00 AM Bottle 8

11/6/2010 12:40:00 PM Bottle 9

11/6/2010 1:58:00 PM Bottle 9

11/6/2010 3:39:00 PM Bottle 9

11/7/2010 12:27:00 AM Bottle 9

11/7/2010 3:19:00 AM Bottle 10

11/7/2010 6:05:00 AM Bottle 10

11/7/2010 8:38:00 AM Bottle 10

11/7/2010 11:02:00 AM Bottle 10

11/7/2010 1:31:00 PM Bottle 11

11/7/2010 7:33:00 PM Bottle 11

11/8/2010 12:32:00 PM Bottle 11

11/8/2010 8:23:00 PM Bottle 11

11/9/2010 8:29:00 AM Bottle 12

The turbidity and corrected turbidity is listed in the table below for each of the 11 bottles (The 

bottles were collected on 11/11/2010 and is from the 11/4-6 event):

Location Bottle Date Collected Turbidity (NTU) Corrected Turbidity (NTU)

11.3 c exit 1 11/11/2010 77.9 77.3884896

11.3 c exit 2 11/11/2010 67.1 67.3571904

11.3 c exit 3 11/11/2010 60.9 61.5984816

11.3 c exit 4 11/11/2010 70.8 70.7938392

11.3 c exit 5 11/11/2010 61.9 62.5273056

11.3 c exit 6 11/11/2010 49.3 50.8241232

11.3 c exit 7 11/11/2010 39.3 41.5358832

11.3 c exit 8 11/11/2010 35 37.54194

11.3 c exit 9 11/11/2010 19.08 22.75506192

11.3 c exit 10 11/11/2010 88.9 87.6055536

11.3 c exit 11 11/11/2010 43.3 45.2511792
3. In Rich's document, no sample was collected during the 11/4-6 event

at Basin 4 OUT due to a sampler malfunction. In your document, you

stated that for the 12-16/17 event no sample was collected from the

basin 3 OUT due to unknown reasons. There were other days where influent

samples were collected for one of the basins, but no effluent samples

were collected. Your document indicates that at the basin 4 OUT

location, it was discovered in early January that the sample collection

tubing was torn. Can you confirm that on days when influent samples were

collected, but no effluent samples were collected, it was due to either

sampler malfunctions or other unknown reasons.

There were some times which there were a couple of samples collected from the inlet (2-4 bottles) 

and no samples were collected from the outlet. This could be possible due to relatively low 

volumes entering the basin and the skimmer never raising to a level in which the basin would 

begin to dewater. The basins are designed so that they may not completely dewater by route of 

the outlet skimmer.

For the other cases where there is a large difference between the number of inlet and outlet 

samples (difference of 5 or greater) this would be because of some error. Hypothetical reasons 

could include frozen skimmer, frozen bubbler tube (incorrect level readings), low amount of

standing water to pull samples from, as well as sampler malfunctions (computer and physical 

problems)

4. Similar to question 2, for the events on 2/4-2/5-2/28, there were 21

sample bottles collected at the basin 4 EXIT location. Could you provide

the date/time for each of the individual sample aliquots contained in

each bottle, and the turbidity of each bottle if available.

The time that each aliquot was collected is listed in the table below:

storm collected on 3/3/11

2/4/2011 5:35:00 PM Bottle 1

2/4/2011 6:27:00 PM Bottle 1

2/4/2011 7:11:00 PM Bottle 1

2/4/2011 7:51:00 PM Bottle 1

2/4/2011 8:30:00 PM Bottle 2

2/4/2011 9:08:00 PM Bottle 2

2/4/2011 9:46:00 PM Bottle 2

2/4/2011 10:24:00 PM Bottle 2

2/4/2011 11:03:00 PM Bottle 3

2/4/2011 11:42:00 PM Bottle 3

2/5/2011 12:21:00 AM Bottle 3

2/5/2011 1:02:00 AM Bottle 3

2/5/2011 1:43:00 AM Bottle 4

2/5/2011 2:24:00 AM Bottle 4

2/5/2011 3:05:00 AM Bottle 4
2/5/2011 3:47:00 AM Bottle 4

2/5/2011 4:30:00 AM Bottle 5

2/5/2011 5:13:00 AM Bottle 5

2/5/2011 5:57:00 AM Bottle 5

2/5/2011 6:40:00 AM Bottle 5

2/5/2011 7:21:00 AM Bottle 6

2/5/2011 7:58:00 AM Bottle 6

2/5/2011 8:28:00 AM Bottle 6

2/5/2011 8:58:00 AM Bottle 6

2/5/2011 9:26:00 AM Bottle 7

2/5/2011 9:53:00 AM Bottle 7

2/5/2011 10:20:00 AM Bottle 7

2/5/2011 10:47:00 AM Bottle 7

2/5/2011 11:15:00 AM Bottle 8

2/5/2011 11:42:00 AM Bottle 8

2/5/2011 12:09:00 PM Bottle 8

2/5/2011 12:37:00 PM Bottle 8

2/5/2011 1:04:00 PM Bottle 9

2/5/2011 1:32:00 PM Bottle 9

2/5/2011 1:59:00 PM Bottle 9

2/5/2011 2:28:00 PM Bottle 9

2/5/2011 2:56:00 PM Bottle 10

2/5/2011 3:24:00 PM Bottle 10

2/5/2011 3:53:00 PM Bottle 10

2/5/2011 4:22:00 PM Bottle 10

2/5/2011 4:52:00 PM Bottle 11

2/5/2011 5:22:00 PM Bottle 11

2/5/2011 5:53:00 PM Bottle 11

2/5/2011 6:23:00 PM Bottle 11

2/5/2011 6:54:00 PM Bottle 12

2/5/2011 7:25:00 PM Bottle 12

2/5/2011 7:56:00 PM Bottle 12

2/5/2011 8:28:00 PM Bottle 12

2/5/2011 9:01:00 PM Bottle 13

2/5/2011 9:35:00 PM Bottle 13

2/5/2011 10:09:00 PM Bottle 13

2/5/2011 10:44:00 PM Bottle 13

2/5/2011 11:21:00 PM Bottle 14

2/5/2011 11:56:00 PM Bottle 14

2/6/2011 12:33:00 AM Bottle 14

2/6/2011 1:11:00 AM Bottle 14
2/6/2011 1:48:00 AM Bottle 15

2/6/2011 2:27:00 AM Bottle 15

2/6/2011 3:06:00 AM Bottle 15

2/6/2011 3:47:00 AM Bottle 15

2/6/2011 4:28:00 AM Bottle 16

2/6/2011 5:10:00 AM Bottle 16

2/6/2011 5:53:00 AM Bottle 16

2/6/2011 6:37:00 AM Bottle 16

2/6/2011 7:22:00 AM Bottle 17

2/6/2011 8:07:00 AM Bottle 17

2/6/2011 8:55:00 AM Bottle 17

2/6/2011 9:43:00 AM Bottle 17

2/6/2011 10:34:00 AM Bottle 18

2/6/2011 11:25:00 AM Bottle 18

2/6/2011 12:17:00 PM Bottle 18

2/6/2011 1:10:00 PM Bottle 18

2/6/2011 2:04:00 PM Bottle 19

2/6/2011 3:00:00 PM Bottle 19

2/6/2011 3:58:00 PM Bottle 19

2/6/2011 4:58:00 PM Bottle 19

2/6/2011 6:01:00 PM Bottle 20

2/6/2011 7:07:00 PM Bottle 20

2/6/2011 8:19:00 PM Bottle 20

2/6/2011 9:36:00 PM Bottle 20

2/6/2011 10:59:00 PM Bottle 21

2/7/2011 12:39:00 AM Bottle 21

2/7/2011 2:44:00 AM Bottle 21

The turbidity and corrected turbidity is listed in the table below for each of the 21 bottles (The 

bottles were collected on 03/03/2011 and is from the 2/4-2/5-2/28 events):

Location Bottle Date Collected Turbidity (NTU) Corrected Turbidity (NTU)

11.4 b exit 1 3/3/2011 69.4 66.4222546

11.4 b exit 2 3/3/2011 76.1 72.9534749

11.4 b exit 3 3/3/2011 136.1 131.442015

11.4 b exit 4 3/3/2011 182.8 176.965595

11.4 b exit 5 3/3/2011 175.1 169.459566

11.4 b exit 6 3/3/2011 146.6 141.677509

11.4 b exit 7 3/3/2011 183 177.160557

11.4 b exit 8 3/3/2011 217 210.304063

11.4 b exit 9 3/3/2011 231 223.951389
11.4 b exit 10 3/3/2011 228 221.026962

11.4 b exit 11 3/3/2011 222 215.178108

11.4 b exit 12 3/3/2011 232 224.926198

11.4 b exit 13 3/3/2011 213 206.404827

11.4 b exit 14 3/3/2011 203 196.656737

11.4 b exit 15 3/3/2011 194.7 188.565822

11.4 b exit 16 3/3/2011 179.8 174.041168

11.4 b exit 17 3/3/2011 198.6 192.367577

11.4 b exit 18 3/3/2011 156.8 151.620561

11.4 b exit 19 3/3/2011 145.5 140.60522

11.4 b exit 20 3/3/2011 139.6 134.853846

11.4 b exit 21 3/3/2011 159.4 154.155065

5. Can you provide more information on when the grab samples on 1/4 were

collected at the basin 3 and 4 EXIT locations and what flows these grab

samples represent. It appears that these samples are not correlated with

the 12/16-17 storm event.

No, these grab samples are not highly correlated to the event on 12/16-17. It seemed unusual the 

high amount of samples collected for the inlets of these basins and that there were no samples 

collected at the outlet. It was later discovered the destroyed tubing on basin 4 and therefore no 

samples could be taken. It wasn’t ever definitively determined the reason no samples were taken 

at the basin 3 exit, and could be one of the other reasons aforementioned in the response to 

question 3.

These grab samples were taken on 1/4/2011 when the samples were collected, and would not give 

a good indication of the turbidity and TSS in the water assumed to have been coming out of the 

basin during the 12/16-17 storm event, or any other storm event through this period for that 

matter.

6. Does the water exiting basin 3 flow into basin 4 (or vice versa).

Not necessarily, or at least not directly. The outlet for basin 3 appears to have some of the flow 

go into a diversion swale while some goes into a silt ditch that is 250-300 ft long before it enters 

into basin 4. The proportion of flow going into the diversion ditch and that going into the silt ditch 

leading to basin 4 was never quantified. Surveys from 12-14-10 indicate that a majority of the flow 

did enter into the silt ditch leading to basin 4.

7. Do you have any additional information on the timeline of this

construction project and the level of disturbance and types of

construction activities that occurred in the areas draining to both the

basin 3 and basin 4 locations during the time period when the samples

were collected.
9/14/10

-Project is in Clearing and Grubbing Phase

-Entire area was cleared of vegetation, root raked, etc. some residual vegetation scattered around the 

catchment

-Some piles of trees/vegetation in catchment

-Entire area was strawed and tacked (75% cover)

9/29/10

-High levels of erosion apparent on the side walls of the silt ditch leading into basin 4 observed.

-Similar cover

10/7/10

-Small amount of grass beginning to grow throughout the catchment (15%)

-Cover is similar

11/1/10

-Grading has begun in the catchment

-Very little is strawed/tacked in the catchment

11/23/10

-Straw and tack being applied in the catchment (75% cover)

11/30/10

-Piles of soil located in the catchment with very steep slopes (50-75% Grade)

-Normal degradation of straw (Cover ~70%)

01/4/11

-Minimal land disturbance in the catchment

-Straw Cover ~60%

01/27/11

-No major changes

-Straw Cover ~50%
03/3/11

-Cover similar ~50%

-Minimal changes

Thank you-