INTRODUCTION

Dutch Fork Lake is a 91-acre (normal surface area) Commonwealth-owned impoundment located approximately two miles northwest of Claysville in Donegal Township, Washington County, Pennsylvania. A dam located on Dutch Fork, a tributary of Dutch Fork (Buffalo) Creek, creates the lake. The impoundment is very popular with outdoor recreation enthusiasts in southwestern Pennsylvania. It was constructed in 1959 and is currently managed by the Fish and Boat Commission for public recreation. The lake is managed as a stocked trout lake and contains a good population of warm and coolwater fish species.

DAM AND APPURTENANCES

The Dutch Fork Dam consists of an earth embankment approximately 460 feet long with a maximum height of 42 feet from the downstream toe and a crest width of 12 feet. The flood discharge facilities for the dam consist of a combined primary and emergency spillway located on the left abutment (looking downstream). The spillway structures of the dam consist of a concrete overflow section, a trapezoidal concrete-lined spillway discharge channel that terminates in a concrete-lined plunge pool at the toe level of the dam near the left abutment. The overflow structure of the spillway is an 89-foot-long concrete weir, trapezoidal in cross section, located at an elevation approximately 10 feet below the dam crest. The outlet works consist of a reinforced concrete box culvert and a control tower located at the center of the embankment. The conduit is equipped with trash rack devices on the upstream end with a stilling basin at the discharge end. Stop logs located in the control tower control the flow through the conduit. The stop logs divide the control tower into inflow and outflow chambers. The stop logs in the control tower extend from the invert elevation of the box culvert to the normal pool elevation. The flow entering into the intake chamber of the control tower through the upstream portion of the outlet conduit rises to the normal pool elevation, spills over the stop logs into the outflow chamber, which in turn discharges into the downstream portion of the outlet conduit. The lake can be drawn down below the normal pool elevation by removing the stop logs. The control tower is not equipped with any mechanical device for removing the stop logs. This outlet system constitutes the emergency drawdown facility for the dam.

HYDRAULIC AND HYDROLOGICAL ANALYSIS

In developing the Emergency Action Plan (EAP) for Dutch Fork, a hydraulic analysis of the spillway showed that Dutch Fork Lake Dam could only pass 16% of the Probable Maximum Flood (PMF). PMF flow for Dutch Fork Lake Dam is 86,325 Cubic Feet Per Second (CFS), and the overtopping height would be 11.46 feet.

Downstream from the dam, Dutch Fork generally flows north, meandering through a 200 to 300-foot wide valley, and joins Buffalo Creek 3-1/2 miles downstream from the dam. The area that would be inundated due to a dam failure would extend from the dam to the confluence of Buffalo Run where it meets the Ohio River. Approximately 325 homes and numerous businesses would be inundated if a failure were to occur. It is estimated that failure of the dam would cause more than a few lives lost and significant property damage downstream.

CURRENT STATUS

Precipitation and the resultant flooding that occurred during Hurricane Ivan, September 17-19, 2004, did serious damage to the spillway and stilling basin structures of Dutch Fork Lake Dam. On Monday, September 20, DEP staff noted the damage to the dam structure. Shortly thereafter PFBC staff, in close consultation with DEP dam safety staff, determined that a draw down of the lake was necessary for public safety. On September 24, the Commission publicly announced that the lake was being drawn down and that it will remain drawn down while the Commission pursues the funding needed to address the dam’s deficiencies.

In October 2004, PFBC crews placed rip rap in the spillway to reinforce the remaining spillway. A PFBC maintenance crew also began the draw down in late September by pulling stop logs in the control tower. The lake was completely drawn down in late November 2004, leaving only an empty lake bed.

In early 2005 the PFBC, in cooperation with DEP, began excavating a channel through the spillway structure. The excavation drains the impoundment during a storm and limits its storage volume. Excavation operations concluded in February 2005.

Spillway reinforced with rip rap after Ivan

Channel excavation

Federal disaster relief funding was requested to support the repair and upgrade of the dam and lake. The Commission submitted a request to cover the estimated Dutch Fork Lake repair costs in the spring of 2005, which was denied officially on July 25, 2005. The denial was appealed in September of 2005 and subsequently denied by FEMA on January 11, 2006. The Commission has prepared a letter to serve as its 2rd and final appeal, which will require review and approval of the FEMA office in Washington D.C.

REMEDIATION

Due to both Federal and state regulations, repairs to the spillway structure will not be permitted without upgrading the dam/spillway to store/pass the PMF. This may be accomplished by either increasing the spillway capacity or by armoring (reinforcing) the embankment to allow the water to overtop the embankment without erosion.

Preliminary engineering indicates the most cost effective solution is to build a spillway with the capacity to pass a 100-year storm event (required by regulations) and to armor the embankment with Roller Compacted Concrete (RCC). See photos below for examples of completed construction at other lakes.

PFBC DAM FUNDING NEEDS

Dutch Fork Lake is one of five (5) PFBC lakes drawn down in recent years to address dam safety concerns. The Commission continues to work to secure funding for repairs on each of the dams.

The Commission remains optimistic that a funding source outside of the day-to-day operating revenues in the fish and boat funds will be found and will be available for the substantial infrastructure improvement needs the Commission has. The total need for dam repairs alone is estimated at more than $83 million.

Photos of RCC Construction, Lake Hauto, Carbon County, Pennsylvania
Finished product

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