Downstream Fish Passage at Hanover Pond Dam Through the Use of an Archimedes Screw Generator

Background: In 2016, an Archimedes Screw Generator (ASG) was installed at the Hanover Pond Dam located in Meriden, CT on the Quinnipiac River to support hydroelectric operations for New England Hydropower Company, LLC (NEHC). The ASG is the rst of its kind implemented in the United States, and while they are largely described as ‘sh-friendly’, adequate scientic literature evaluating sh passage is lacking at these facilities. The Connecticut Department of Energy and Environmental Protection (CT DEEP) with consultation from U.S. Fish and Wildlife Service (USFWS) and Kleinschmidt Associates designed and implemented a study to evaluate American Shad downstream sh passage at Hanover Pond Dam. The objective of this study was to document whether American Shad would enter the darkened penstock, pass beneath the downward closing sluice gate, and utilize the ASG for safe downstream passage. A radio telemetry study was designed with three xed monitoring stations; including one station upstream of the dam, another station within the intake structure, and a third station downstream of the dam. Twenty adult American Shad were collected from Holyoke Dam Fish lift, transported to Hanover Pond, and radio-tagged. Fish were released upstream of the dam and monitored from May 30 to July 15, 2019. Results: In total, 16 sh were detected upstream of the dam, and 8 of those sh passed downstream. Seven of the eight sh that passed through the project (87.5%) utilized the intake of the ASG before being detected at the downstream receiver. One sh passed downstream via the spillway and/or use of a notch in the dam. All sh that passed downstream were detected with subsequent 2-second tag bursts at the downstream monitoring station, suggesting a 100% survival rate through the ASG. Conclusions: These results support the suggestion that the Archimedes Screw Generator is a ‘sh friendly’ operation.


Background
Archimedes Screw Generators (ASG) have been increasing in abundance, as they can operate at low-head sites where larger hydropower operations would not be feasible. AGS's consist of 2 to 5 spiral blades connected to a central shaft similar to a screw. The ASG is contained by a xed trough, which allows the screw to freely rotate. The central shaft of the ASG is connected to a gearbox and a generator to deliver electricity (Simmons and Lubitz, 2017). Also, they can operate at run-of-river mode. Run-of-river operations have little or no water storage facility and operate entirely based upon seasonal river ows.
When compared to conventional ASG turbines are typically described as ' sh-friendly' (Piper et al., 2018).
This ' sh-friendly' claim is supported by the slower turbine rotation speed, lower force, and smaller pressure changes (Piper et al., 2018;Spah, 2001 (Brackley et al., 2015), this would be the rst conducted in the United States and the rst of any sh in the Clupeidae family.
During the spring of 2019, a downstream sh passage study was conducted by New England Hydropower Company, LLC (NEHC) in consultation with the Connecticut Department of Energy and Environmental Protection (CT DEEP) and the U.S. Fish and Wildlife Service (USFWS). The objective of the study was to understand the effects of downstream passage through the ASG. This study quanti ed the proportion of sh that passed via various routes (entrainment, through the shway, and over the dam or spillway) and their survival.

Methods:
Shad Passage Monitoring: Three radio telemetry stations in the Hanover Pond Dam Project area were deployed at the beginning of the study. These stations were installed upstream of the Dam (T01), within the intake structure (T02), and downstream of the Dam (T03). A list of these monitoring stations and equipment is provided in Table 1. The stations were calibrated to ensure complete coverage of the study area. A total of 20 American Shad were tagged and released during the study. TX-PSC-I-80-M Pisces transmitters manufactured by Sigma Eight were used for each sh during the study. The tags were 9.6mm by 26 mm and operated on a frequency of 149.440 MHz. Tags were programmed with a twosecond burst rate, that switched to an eleven-second burst to indicate mortality. The mortality burst was activated by a motionless period of 15 minutes.
Fish selected for release were evaluated for overall condition (minimal scale loss, and vigor) before release. Additionally, only sh that were greater than 400 mm in total length were tagged and released during the study.
Telemetry Analysis: Studies that assess movement of anadromous sh through telemetered river-reaches are complex in nature. Analysis is made di cult with the presence of false positive signals and receivers with potential for overlapping detection zones. False positive and overlapping detections were removed with the assistance of BIOTAS (Nebiolo and Castro-Santos 2021).
We evaluated the rate of movement through the project area with a Nelson Aalen cumulative hazard function. Movement occured over the network of receivers depicted in Figure 2. The initial state for this model was the upstream station (T01). The counting process style data were arranged so that the rst detection for every sh was always in the initial state (i.e., upstream of the Dam where the tagged shad were released). Once a sh is detected at any other site, movement has occured . A sh with a detection history beginning upstream (T01), then through the intake (T02), followed by detection downstream of the Dam (T03), indicates passage through the ASG . If a sh was detected upstream of the Dam (T01), then subsequently downstream of the Dam (T03) without recapture at T02, the sh either spilled over the Dam or utilized the notch (Figure 2).
Operations and ow data used in this evaluation were available in an hourly format. Therefore, ow reported at the time of passage through the ASG is the nearest hourly average ow at the last detection upstream, detections within the intake, and the rst detections downstream. If the duration of passage occurred over multiple hours, then the two nearest hourly ows were averaged to calculate passage ows. Similarly, for sh that passed using the notch or via the spillway, passage ow reported represents the average of the ows at the time of last detection upstream and the rst detection downstream.

Results
Downstream Shad Passage: Of the 20 shad that were tagged and released in Hanover Pond, 16 shad (80%) were detected at Station T01. Eight of these shad detected upstream of the dam (50%), passed downstream, and were detected at Station T03. Of the eight sh that passed downstream, seven of these sh (87.5%) utilized the intake (T02), passing through the ASG before being detected at the downstream Station T03. The one sh that passed downstream without being detected at Station T02, passed downstream either over the spillway or the notch.
All 20 shad remained upstream for over 100 hours post-release (Fig. 3). Between 100 to 200 hours post release, over 50% of the Shad made a downstream movement to Station T03. There was then a lull in downstream movement from 200 to 300 hours post-release. At 320 hours post-release, another 15% of sh moved downstream to Station T03. A Kaplan-Meier Survival Analysis curve demonstrates the probability of downstream movement of shad through the telemetry network over time since release (Fig. 3).
The four sh that were not detected upstream of the dam at Station T01, either did not migrate, expelled their tag outside of the telemetry network, or experienced mortality outside of the telemetry network. The fate of the eight sh that were detected at the dam but did not pass downstream is unknown. The eight sh passed downstream between June 2, and June 13 of 2019. All sh that passed downstream, maintained a 2-second burst rate suggesting complete survival. Table 2 displays the frequency and unique ID code of each sh that passed downstream, including the route, and discharge (cfs) at the time of passage.
During downstream passage events, the average ow through the project was 169.9 cfs. The ASG averaged 76.8 cfs while the spillway was 93.2 cfs. The one sh that passed via spill did so when discharge through the ASG was at its greatest (195 cfs) and spill over the Dam (86.6 cfs) at its lowest.
The seven other sh passed through the ASG when spillway ows were greater than ASG ows ( Table 2). The telemetry equipment continued monitoring sh until June 15, 2019. Availability of data and materials: The data that support the ndings of this study are available from New England Hydropower Company, LLC but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data may be available from the authors upon reasonable request and with permission of New England Hydropower Company, LLC Competing interests: The authors declare that they have no competing interests.
Funding: This study was funded by New England Hydropower Company, LLC.