National Program For Inspection Of Non Federal Dams Fall Brook Reservoir Dam Ma 00869 Merrimack River Basin Leominster Massachusetts Phase I Inspection Report

The impounding structures at Fall Brook Reservoir include a 1392-foot long, 37-foot high main dam with a spillway and outlet, and a 256-foot long, 11-foot high dike. The spillway is located at the south abutment of the dam, and consists of a broad-crested weir 19 feet long with vertical stone masonry training walls that extend the length of the discharge channel. The outlet for the dam consists of a 30-inch diameter cast-iron pipe which discharges at the toe of th dam. The dam is generally in fair condition. The test flood outflow of 2,370 cfs and pool at El 657.6 will overtop the dam by 0.6 feet and the dike by 1.4 feet. The spillway capacity at El 646.2 (the low point on the crest of the dike) is 500 cfs, which is 21 percent of the test flood outflow.

Simonds Pond is approximately 365 feet long and has a hydraulic height of 26 feet. The storage capacity is 86.5 acre-feet. The dam has a concrete cap and stone abutments. The emergency spillway is 48 feet long and occupies the center portion of the dam. As a result of the visual inspection and a review of available data, Simonds Pond Dam is considered to be in poor condition. Major concerns are: significant seepage at the toe of the dam; missing mortar and poor condition of the joints of the spillway; extensive spalling and cracking of the concrete cap on the top of the dam and spillway; deterioration of the spillway apron; extensive spalling of the concrete gatehouse foundation; and inadequate spillway capacity. The test flood inflow was estimated to be 2,500 cfs and resulted in an outflow discharge estimated to be 2,460 cfs, which would overtop the dam by approximately 1.3 feet. The maximum spillway capacity with the water level at the dam crest was estimated to be 700 cfs, which is approximately 28 percent of the test flood discharge.

Rockwell Pond Dam is a 460-foot lon>, 20-foot high earthfill dam built in the 1800's. The 75.7-foot long, modified sharp-crested spillway has a crest at El 416.4. A concrete bridge spans the spillway channel. The main outlet is a 12-inch diameter pipe controlled by a valve which is submerged in a manhole. The following deficiencies were observed at the site: mssing riprap and localized growth of brush and small trees on the upstream face of the right embankment; localized erosion of upstream and downstream earth slopes; voids exposing soil behind the spillway weir wall; cracked or missing mortar from joints in the spillway training walls; spalled concrete and exposed reinforcing steel on the bridge pier; efflorescence and spalling on the underside of the bridge deck; a submerged inoperable valve on the main outlet; and an inoperable slide gate on the intake of the auxiliary outlet. The test flood would overtop the dam by about 1.6 feet. The spillway can discharge 60 percent of the test flood before the dam is overtopped.

The dam is a 470 ft. long earthfill dam with a maximum height of 14 ft. There are deficiencies which must be corrected to assure the continued performance of the dam. Generally the dam is in poor condition. It is small in size with a hazard potential of high. (Author).

Total length of the dam is about 800 ft. with a height of about 22 ft. Although there were some minor deficiencies noted the dam is considered to be in good condition. It is intermediate in size with a hazard potential of high.

The main dam is 600 feet long with a hydraulic height of 21 feet. It contains a sheet piling and concrete upstream cutoff. The dike is 750 feet long with a hydraulic height of 13 feet height. The spillway's capacity with a 8-inch flashboards in place, is about 1,850 cfs or 37 percent of test flood outflow, at the top of dam. With the flashboards in place, the test flood outflow, 5,070 cfs, surcharges the reservior to elevation 741.5. The dam and dike and a small section of Route 2 are overtopped by 0.9 feet. Based on the visual inspection, the dam was in generally fair condition. However, due to the dense vegetation on the downstream slope, apparent seepage in this area could not be adequately inspected. This combined with apparent settlement along the upstream slope and the probable presence of root systems within the embankment give overall rating of the dam as poor. The dike was found to be in generally good condition.

The project is comprised of and 800 foot long, 80 foot hydraulic height, earthfill main dam, and a 18 foot hydraulic height, 1,600 foot long earthfill dike. The main dam has a 78.5 foot long concrete spillway with a 450 foot long concrete and stone outlet channel. The spillway has a capacity of 4,320 cfs (to top of dam elevation 770.5) which is approximately 73 percent of the test flood outflow. The dam and dike are generally in fair condition.

Lake Wampanoag Dam is approximately 660 feet long including the spillway and has a maximum height of approximately 22 feet. It consists of an earth embankment with riprap at the upstream face and a loamed and seeded crest and downstream face. Based on the size classification (intermediate) and hazard potential classification (high), the spillway test flood is the PMF.