Dewatering discharge turbidity sampling and site meeting to check differences in readings between City turbidimeters and site turbidimeters furnished by Syman Company.

Sampling results for 8:50- 9:25 AM:

Pen Can background: 3.75- 5.3 NTU
dewatering water before discharge into canal:
319-361 NTU

Sample of visible plume of dewatering in discharge in Pen Canal 49.1-57.7* NTU.

* Syman test on same grab sample: 29.8 -30.5

Sampling results of dewatering system:
-water detained in pond: 128- 138 NTU
-water after passing through sediment bag and wattle: 85.1 - 92
- dewatering water entering unnamed stream at flume: 109

Additional sampling at 11:30 - 11:40 AM

- Pen Can background: 3.94 NTU
- Dewatering water before discharge into canal:
129 NTU

Sample of visible plume of dewatering in discharge in Pen Canal 34.5 NTU .

The discharge at the recieving water at 11:40 AM was in compliance, increasing turbidity of water in Pen Canal by approximately 31 NTU.

Conclusion:
Dewatering is being treated but then picks up turbidity between the discharge at the site and the discharge into the receiving water, Pen Canal. Mud and eroded sediment from the site and other source is being flushed by the dewatering water. The visible plume when compared to background is in compliance.

Dewatering should be completed by tomorrow if not today. Once pond is dewatered site will continue with stabilization and revegetation of the remaiing disturbed areas.

Syman is taking sample visble plume grab sample that all four meters (Boise (2), ACHD (1), Syman (1)) tested. If taken within 48 hours and successfully kept below high temperature, the result could be meaningful in determining why Hach turbidimeters used by City and ACHD get different (higher NTU) readings than the Lamotte meter used by Syman.

Project is located behind a lock gate. Call me prior to inspection and I can let you in. Phone #: ###-#### Inspection requested via web by Eldon Oyadomari

Approved for construction.