l i--iarza engineering company consulting engineers

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I--IARZA ENGINEERING COMPANY CONSULTING ENGINEERS

O~-09 .......

April 12, 1989

VIA FEDERAL EXPRESS

GENERAL ELECTRIC COMPANY 100 Woodlawn Avenue Pittsfield, MA 01201

Attention: Mr. Ross Clark Environmental Programs

Subject: Rising Paper Company Dam (HECO Project No. 1349L) Inspection and Evaluation Report

Dear Mr. Clark:

Enclosed please find five copies of the "Rising Paper Company Dam, Inspection and Condition Assessment Report ...

Overall, the spillway is in seriously deteriorated condition. Our major concern is the apparent loss of rockfill material from under the downstream spillway apron. Timber piles at the dam toe originally built to restrain this material have reportedly deteriorated. The differential settlement of the concrete slabs on the downstream face downstream is a warning sign that material is being lost from under the concrete.

We have reviewed the exploration program planned by Rising Paper Company. We recommend the following additional studies be included in this program:

an inspection be made of the spillway toe condition including soundings immediately downstream of the dam;

the drilling upstream of the spillway be extended into the foundation; and

slope stability analyses of the right embankment dam.

We believe that these additional studies will provide a better insight to the condition and stability of the project structures.

150 SOUTH WACK ER DRIVE CHICAGO. ILLINOIS 60606-4288

TEL (312) 855-7000 CABLE HARZ ENG CHICAGO TELEX 25-3540 FAX (312) 236 -80 10

Mr. Ross Clark April 12, 1989

Harza appreciates the opportunity to assist General Electric in this matter. Please do not hesitate to contact either myself or Mike Rogers if you have any questions on the findings of this report.

Very truly yours,'/)

liwl David R. Baier, P.E., P.G. Project Manager

#~~ Michael F. Rogers, P.E. Project Engineer

Attachments: As noted.

DRBjmfr

2

INSPECTION AND CONDITION ASSESSMENT REPORT

RISING PAPER COMPANY DAM Housatonic River

Great Barrington, Massachusetts

for

GENERAL ELECTRIC COMPANY Pittsfield, Massachusetts

April 1989

HARZA ENGINEERING COMPANY 150 South Wacker Drive

Chicago, IL 60606


Railroad Bridge. A railroad spur crosses over the lake just upstream of the spillway. The right abutment of the dam also serves as the bridge support abutment. A single pier is located about mid-channel, 50 feet upstream of the spillway crest.

Previous Inspection

The Rising Pond Dam has been monitored very closely in the last few years as interest in the condition and safety of the dam has increased. Photographs 5 through 10 show the condition of the dam during an inspection in August", 1987. The reservoir was lowered for this inspection by diverting water through the penstocks on the left abutment. Photograph 5 shows the shallow reservoir bottom with the reservoir lowered for inspection. Photographs 7 and 8 show cracking and differential settlement of the spillway concrete slabs. Photographs 9 and 10 show deteriorated wood on the upstream side of the crest including a sinkhole near the right abutment.

In October, 1988 another visual. inspection was made by Foresight Land Services. At that time, the reservoir was lowered below the spillway crest by diverting through the old intake structure. Photographs 11 through 14 document the condition of the dam at that time. Comparing Photographs 9 and 10 with Photographs 5 through 10 from the previous year's inspection does not reveal any progressive deterioration. In particular, the size and appearance of the sinkhole seemed to have remained the same.

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INSPECTION

General

A visual inspection of the Rising Pond Dam and appurtenant structures was made on 8 March 1989 by Michael F. Rogers, P.E. of Harza Engineering Company, Chicago, Illinois. Mr. Rogers was accompanied by Mr. Thomas A. Danz of Rising Paper Company, Mr. Jack Cysz, P.E. of Foresight Land Services (a consultant to Rising Paper Company), and Mr. Ross Clark of General Electric Company. The weather was' sunny and clear with temperatures in the low 30's. Approximately 3-inches of flow was passing over the spillway, total flow was estimated to be about 60 cfs.

Intake Structure

The left abutment intake area was the first project feature to be inspected. The intake gates were closed as best possible, but there was still some flow through the penstocks as a result of leakage past the gate. The wooden gate house had been removed during Fall 1988 exposing the three manual gate operators on the upstream end of the concrete well. It appeared that these gates were fully open and that the gate on the downstream end of the well, at the entrance to the 14 foot diameter steel pipe, was closed.

Spillway

The left, (eastern) portion of spillway was visually inspected from the left abutment wall near the intake structure. The reinforced concrete slabs covering the downstream face of the spillway were covered with a thin layer of aerated flow as shown in Photographs 15, 16, 17 and 18. Several areas of differential settlement were noted in the middle slabs (centered top to bottom) on the 2nd, 3rd and 4th monoliths (numbered from the left). The middle slabs of these three monoliths have cracked laterally about mid-span. Settlement in the vicinity of these cracks range from about 4 to 8 inches.

The spillway crest was inspected from the left abutment wall. The water was clear flowing about 3 inches deep over the crest allowing for acceptable visual inspection of the left side of the spillway crest. Photograph 20 is a view of the spillway crest from the left abutment. The steel cap appeared to be in good condition

5


with no signs of distress or failure. There was some debris (mostly logs) accumulated on the crest. This debris is of no consequence. It will likely be washed-out during higher flow periods.

The right (western) end of the spillway was visually inspected from the railroad bridge and the right abutment masonry wall. The crest of the spillway appeared to be in good condition for the total length of the spillway_

A sinkhole was observed approximately 10 feet upstream of the crest, about 30 feet east of the right abutment wall. The sinkhole was about 18 inches in diameter and about 12 inches deep. The crest of the sinkhole was about 12 inches below the crest of the spillway, hence the sinkhole was visible in about 15 inches of water. The was no discernable vortex on the surface and no evidence that sediment particles were being drawn into the hole.

This sinkhole has been observed previously by Rising Paper Company and it's consultant. Pictures supplied to Harza by Foresight (Photographs 5 through 14) show the sinkhole with the reservoir drawn-down for inspection. It is reported that when water is below the spillway crest and above the top of the sinkhole, water flows from the spillway weep holes on the right side only. Dye tests have reportedly been conducted which confirm that the water discharging from the weep holes, at least in part, is drawn from the sinkhole. Photograph 10 shows the partially submerged sinkhole. The size of the sinkhole has only slightly increased since the photo was taken in August, 1987. It was reported that no attempt to fill the sinkhole has been made since its original discovery.

Abutment Retaining Walls

The abutment retaining walls appear in good condition. The left abutment wall is missing a few masonry blocks, and the grout between blocks is generally deteriorated or missing.

The right abutment wall has some hairline cracks, as well as some areas where the existing cementious overlay has been spalled. Investigations using a small hammer indicated that there are areas where the cementious overlay has separated from the underlying concrete, but has not yet completely spalled. A concrete test hammer indicated sound areas had a strength of about 3500 psi; areas where the overlay had separated, the test hammer indicated strengths of about 500 psi.

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EVALUATION AND RECOMMENDATIONS

General

It is understood that General Electric Company neither owns the Rising Pond Dam, nor has plans to be involved with plans being prepared by the Rising Paper Company for the improvement of conditions at the dam. However, recommendations for improving the safety of the project have been developed based on Harza's March, 1989 inspection.

Intake structure

The intake structure, though in a state of disrepair, does not appear to be a threat to the safety of the project. A long-term maintenance plan should include either the repair of the damaged timber trash racks or the permanent closure of the intake structure and penstocks.

Spillway

Overall, the spillway is in seriously deteriorated condition. The loss of material at the toe characterized by a differential settlement of the concrete slabs covering the downstream face, especially on the left side, indicate a potential serious problem with the dam.

stabilize Toe. The loss of material at the toe is a direct result of the scouring of toe protection material present when the dam was rehabilitated in 1953. The scouring is due to inadequate energy dissipation of high velocity flow over the spillway. Based on borehole logs taken in 1949, the natural material in the vicinity of the dam is a highly erodible silty sand. It is noted that the dam is not founded on rock.

It is recommended that steps be taken to stabilize the toe of the spillway and provide either energy dissipation devices such as chute blocks or to provide riprap of sufficient size to resist erosion during high flows.

Repair Concrete Slabs. The differential settlement of the concrete slabs on the downstream face of the spillway will continue to cause cavitation erosion of the concrete. The slabs could also be lifted out of place by dynamically induced uplift under high

8


velocity flow during flood conditions. It is recommended that the concrete slabs on the downstream face of the spillway be repaired as soon as the toe is stabilized. A possible solution would be to remove the existing slabs and replace lost fill material underneath. A thicker, reinforced slab could then be placed over the fill. Slab lifting by pressure grouting should also be considered.

Sinkhole. The sinkhole does not appear to be an immediate concern since the condition does not seem to be worsening. Timber crib dams are designed to allow water to pass through the body of the dam. It appears that no significant amount of material is being removed from the body of the dam since there is no obvious differential settlement of the concrete spillway slabs on the right side of the spillway. It is recommended, however, that steps be taken to reduce flow through the sinkhole. This might be accomplished by injecting a bentonite-type slurry into the hole when the reservoir is drawn-down. Harza has recently worked with this type of material for sealing cracks in the bottom of a reservoir. The sinkhole would then be covered over with a concrete slab (see below).

Crest. The concrete and steel crest of the spillway is in good condition, free of apparent cavitation erosion damage. The timber cribbing immediately upstream of the crest is deteriorating. This condition probably contributed to the development of the sinkhole in this area. Gravel material originally covering this area has been eroded by high velocity flood flows. A possible solution to this condition would be the construction of a concrete cap over the top, extending from the crest about 15 to 20 feet upstream onto the surface of the sediment in the reservoir. This cap could be tied-in to the existing concrete retaining wall upstream, or to a new sheet pile cut-off wall. This condition is not serious, but should be included in long-termed maintenance of the project.

Abutment Retaining Walls

The missing blocks in the left abutment masonry wall should be replaced, and the wall should be tuck pointed or covered with a cementious overlay similar to the right abutment wall.

The loose and spalled areas of concrete on the right abutment wall should be removed to a solid surface and repaired with new material.

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Right Embankment

The most serious concern with respect to the right embankment dam is the oversteepening of the downstream face near the spillway. It is anticipated that the slope will gradually flatten out to a more stable configuration on its own accord by natural processes. The embankment seems sufficiently wide so that the stability of the dam should not be, compromised by this natural adjustment. Confirming stability analyses, however, should be conducted. This condition should continue to be monitored to be sure that the railroad tracks on the crest do not become threatened by sloughing material.

The upstream face of this embankment, including the steel sheet pile wall, appears to be stable and in good condition. No remedial work seems necessary in this area at this time.

Left Embankment

The left embankment appears to be stable and in good condition. No remedial work seems necessary in this area at this time.

Railroad Bridge

The railroad bridge appears to be in significant distress. The differential settlement, having caused significant lateral movement of the tracks, should be a concern to the railroad and the dam owner. It was reported that engineers from the railroad have inspected the bridge and have recommended shimming the support on the downstream end of the pier (these repairs were in progress at the time of the inspection). It is also reported that the spur will return to service after completion of these repairs. It is recommended that the stability of the middle pier and th~ left abutment be further investigated and that traffic across the bridge be limited until these analyses are complete. The condition of the bridge should be routinely monitored.

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CONCLUSIONS

The Rising Pond Dam is in serious condition due to the apparent loss of material from the rock fill body of the timber crib dam. This condition is caused by the scouring of material away from the toe of the dam due to inadequate energy dissipation of spillway flows and the loss of material out the base of the dam into the tailrace.

The bulk of the dam (due to the raising of the original dam) is about 55 years old. The condition of the internal timber members should still be good. However, an investigation program is warranted at this time. The plan under consideration by the Rising Paper Company was discussed during the field inspection.

The scope of the investigation plan includes test borings in the right embankment, railroad pier, and in the area upstream of the spillway. Standpipe piezometers will be installed in the right embankment boreholes and several permeability tests will be taken. This overall scope of this investigation should be adequate to determine the internal condition of the spillway and right embankment structures. However, we suggest the- following additions:

1. The test borings upstream of the spillway are proposed to proceed to refusal. A review of the design drawings indicate that this refusal will probably occur as the drilling operation encounters either the original grouted timber dam or it's grouted cobble foundation. It is recommended that this area be cored and tested for shear and compressive strengths. Also, that the boring be continued below the grouted foundation to establish the soil foundation material type and properties.

2. It is recommended that the investigation program be expanded to include investigations at the toe of the spillway. The stability of the spillway will depend on the amount of scouring at the toe and the extent to which material has been removed from the body of the dam. This investigation could be made by either de-watering the tailrace area or by using divers.

3. The engineering analyses should be expanded to include a slope stability analysis of the right embankment dam.

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REFERENCES

[1] "Rising Paper Co. Dam, MA 00250, Phase I Inspection Report, National Dam Inspection program", Department of the Army, New England Division, Corps of Engineers, Sep. 1979.

[2] Notice of Intent for Removal of Rising Pond Dam on the Housatonic River in Great Barrington, MA submitted in October, 1988. '

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Number Photograph No.

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LIST OF PHOTOGRAPHS

Description Downstream view of spillway prior to 1953 repairs

upstream view of spillway prior to 1953 repairs

Spillway crest after 1953 repairs

Downstream view of spillway after 1953 repairs

De-watered upper reservoir area (26 Aug 87, Foresight)

Railroad spur bridge across river upstream of spillway (26 Aug 87, Foresight)

De-watered spillway; note seepage through weep holes (26 Aug 87, Foresight)

De-watered spillway; note differential settlement of spillway slabs (26 Aug 87, Foresight)

upstream view of de-watered spillway; note broken timber facing (26 Aug 87, Foresight)

Sink hole immediately upstream of spillway (26 Aug 87, Foresight)

De-watered reservoir area immediately upstream of dam (Oct 88, Foresight)

De-watered spillway crest (Oct 88, Foresight)

Sink hole immediately upstream of spillway (Oct 88, Foresight)

Sink hole immediately upstream of spillway (Oct 88, Foresight)

Downstream view of spillway (8 Mar 89)

Downstream view of spillway (8 Mar 89)

Downstream facing concrete (8 Mar 89)

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LIST OF PHOTOGRAPHS (continued)

Number Description

Photograph No. 18: Downstream facing concrete (8 Mar 89)

Photograph No. 19: Submerged planking upstream of spillway (8 Mar 89)

crest

Photograph No. 20: Spillway crest (8 Mar 89)

Photograph No. 21 : Sheetpiles section (8

on upstream Mar 89)

of embankment dam

Photograph No. 22: Railroad bridge pier upstream (8 Mar 89)

of spillway

Photograph No. 23: Sheetpiles spillway (8

on left Mar 89)

abutment downstream of

Photograph No. 24: Housatonic River Channel downstream of project (8 Mar 89)

Photograph No. 25: Downstream (8 Mar 89)

slope of embankment dam section

Photograph No. 26: Left abutment of railroad bridge (8 Mar 89)

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Photograph No.1: Downstream view of spillway prior to 1953 repairs

Photograph NO.2: upstream view of spillway prior to 1953 repairs

Photograph No.3: Spillway crest after 1953 repairs

Photograph No.4: Downstream view of spillway after 1953 repairs

Photograph No.5: De-watered upper reservoir area (26 Aug 87, Foresight)

Photograph No.6: Railroad spur bridge across river upstream of spillway (26 Aug 87, Foresight)

Photograph No.7: De-watered spillway; note seepage through weep holes (26 Aug 87, Foresight)

Photograph No.8: De-watered spillway; note differential settlement of spillway slabs (26 Aug 87, Foresight)

Photograph No.9: Upstream view of de-watered spillway; note broken timber facing (26 Aug 87, Foresight)

Photograph No. 10: Sink hole immediately upstream of spillway (26 Aug 87, Foresight)

Photograph No. 11: De-watered reservoir area immediately upstream of darn (Oct 88, Foresight)

Photograph No. 12: De-watered spillway crest (Oct 88, Foresight)

Photograph No. 13: Sink hole immediately upstream of spillway (Oct 88, Foresight)

Photograph No. 14: Sink hole immediately upstream of spillway (Oct 88, Foresight)

Photograph No. 15: Downstream view of spillway (8 Mar 89)

Photograph No. 16: Downstream view of spillway (8 Mar 89)

Photograph No. 19: Submerged planking upstream of spillway crest (8 Mar 89)

Photograph No. 20: Spillway crest (8 Mar 89)

Photograph No. 21: Sheetpiles on upstream of embankment dam section (8 Mar 89)

Photograph No. 22: Railroad bridge pier upstream of spillway (8 Mar 89)

Photograph No. 23: Sheetpiles on left abutment downstream of spillway (8 Mar 89)

Photograph No. 24: Housatonic River Channel downstream of project (8 Mar 89)

Photograph No. 25: Downstream slope of embankment dam section (8 Mar 89)

Photograph No. 26: Left abutment of railroad bridge (8 Mar 89)

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