STATE OF CALIFORNIA CALIFORNIA NATURAL RESOURCES AGENCY

DEPARTMENT OF WATER RESOURCES DIVISION OF SAFETY OF DAMS

INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS

Inspected by PW Lee Photos taken? Yes X No Date of Inspection 5/2/2018 cc for Owner/Book Date of Report 6/5/2018 DWR 1261 (Rev. 10/09) Sheet 1 of 6

Name of Dam Sand Canyon Dam No. 1029-2 County Orange Type of Dam Earth Type of Spillway Concrete Weir and Open Channel Water is 9.4 feet below spillway crest and 17.9 feet below dam crest.

Weather Conditions Mild, overcast Contacts Made Steve Habiger & Tyler Dillman with IRWD; Doug Harriman & Will Kulikowski with Genterra Reason for Inspection Annual Maintenance Inspection

Important Observations, Recommendations or Actions Taken The spillway stilling basin and downstream discharge channel must be cleared of sediment and vegetation by November 1, 2018. Conclusions From the known information and visual inspection, the dam, reservoir, and the appurtenances are judged safe for continued use.

Observations and Comments Dam

The recently seal coated AC crest was level and uniform. The upstream curb and downstream parapet walls on the crest were well aligned. The upstream slope was recently seal coated and the visible slope appeared satisfactory. The grass covered downstream slope was well mowed, clear of unfavorable vegetation, rodent activity, and contained no signs of instability. The abutments were cleared of vegetation for a distance of 10 feet beyond the groins.

Spillway The spillway approach was clear and unobstructed. The ogee weir and apron concrete was in good condition. The concrete channel walls, joints, and surfaces were intact and in good condition. The channel floor was intentionally designed to be unlined, relying on the native sandstone rock with localized pockets of backfill concrete to convey spillway flow. The stilling basin and downstream channel were completely choked with sediment and vegetation. I was informed no clearing can be done due to environmental restrictions. It should be made clear that the design intent of the stilling basin and downstream channel was to convey spillway flow during storms and prevent flooding. They were not intended for riparian or wildlife habitat. Unless the obstructing entity agrees to accept responsibility for flood damages, as well as damages caused from overtopping of the spillway walls, these features need to be cleared and restored to serve their original design intent.

Outlet The outlet consists of four 24-inch upstream slides gates, and three 24-inch downstream slide gates. The three downstream slide gates were recently replaced in 2016 and the upstream main gate valve was replaced in September 2017. All valves operated smoothly and were cycled satisfactorily.

Seepage There were no signs of seepage at the downstream toe and abutments of the dam, nor at the spillway walls. Seepage collected at the drain vault measured ¼ gpm at the left drain, and dry at the right drain. This is normal.

Electronic Signature:Philip Lee, P.E.Safety of Dams9/5/2018; 2:57 pm

INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS

Name of Dam Sand Canyon Dam No. 1029-2

Date of Inspection 5/2/2018

DWR 1261 (rev. 10/09) Sheet 2 of 6

Observations and Comments Instr. Instrumentation at this dam includes 18 open well piezometers, 2 subdrains, and 6 survey

monuments. The most recent surveillance report submittal was dated August 2016 and included data through the end of December 2016. I reviewed the data and found all water and movement measurements for this reporting period were within the boundaries of historical norms. No unexplained abnormal trends were observed. The instrumentation data indicates the dam is performing satisfactorily and no additional instrumentation is judged necessary at this time.

Crest

INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS

Name of Dam Sand Canyon Dam No. 1029-2

Date of Inspection 5/2/2018

DWR 1261 (rev. 10/09) Sheet 3 of 6

Upstream Slope

Downstream Slope

INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS

Name of Dam Sand Canyon Dam No. 1029-2

Date of Inspection 5/2/2018

DWR 1261 (rev. 10/09) Sheet 4 of 6

Spillway Channel

Stilling Basin Filled with Sediment and D/S Channel Choked with Vegetation

INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS

Name of Dam Sand Canyon Dam No. 1029-2

Date of Inspection 5/2/2018

DWR 1261 (rev. 10/09) Sheet 5 of 6

Spillway Discharge Channel Completely Choked with Woody Vegetation

Downstream 24” Blowoff Gate Valve Operation

INSPECTION OF DAM AND RESERVOIR IN CERTIFIED STATUS

Name of Dam Sand Canyon Dam No. 1029-2

Date of Inspection 5/2/2018

DWR 1261 (rev. 10/09) Sheet 6 of 6

Upstream Main 24” Valve Operator

Upstream 24” Gate Valve Operators