J05 Onsite Evaluation Report.pdf

Onsite Evaluation Report – Peggy Williams – 8205 County Line Road, Warm Springs, OR

Completed by Derek Hancey, P.E.

Test Pit Evaluation – Conducted Nov. 11, 2020:

Overview:

The site’s existing septic system was built in 1984 and utilizes a 1,000-gallon concrete septic tank and 210 LF of drain line. The system has failed and raw sewage is surfacing out of the cleanout and effluent is pooling at the septic tank. On Nov. 11, 2020, suitable soil for a replacement system was found on the NE corner of the lot in the area between the well 100-ft setback, the existing shed, and the fence marking the eastern property line. The test pits were limited at around 36-inches by bedrock and no signs of a seasonal water table were evident.

Home Details:

4 BDRM - 2 BA w/ 8 Occupants Design Flow = 450 GPD (OAR 340-071-0220 Table 1)

Site Sketch: Attached

Test Pit #1

0-18” Soil Group B – Silty Loam, 0% Rocks 18-36” Soil Group A – Sandy Loam, 5% cobbles 3-5” Effective Soil Depth – 36” Bedrock Limited

Test Pit #2

0-9” Soil Group B Silty Loam, 0% rocks 9-36” Soil Group A – Sandy Loam, 5% cobbles 2-5” Effective Soil Depth – 36” Bedrock Limited

Test Pit #3 – Same as TP #2

Test Pit #4 – Same as TP #2

Site Approval:

Home Size: 4BDRM/2BA Design Flow = 450 gpd Required Septic Tank Volume = 1,500 gallons w/ pump chamber Allowable Trench Depth: 18” - 30” Effective Soil Depth: 36” to less than 48” Soil Group B – Silty and Sandy Loam Required Minimum Drainfield Length = 300LF

Narrative Approval: Construct equal distribution conventional gravel drainfield with pumped effluent maintaining 100 feet separation from the site’s well.

Site Photos:

Figure 1 Existing Conditions at Site - Visible Ponding of Septic Tank Effluent

Figure 2 Existing Conditions at Site - Evidence of Raw Sewage Backup at Cleanout

Figure 3 TP #1 near Shed on N. Property Boundary

Figure 4 TP #2 Looking Towards House