4-Alden Draft Norristown Dam Hydropower Feasibility Study 2017-12-19.pdf

Solving flow problems since 1894

ALD ALDEN Research Laboratory, Inc. Massachusetts | Colorado | Oregon | Washington

30 Shrewsbury Street, Holden, Massachusetts 01520 508-829-6000 • www.aldenlab.com

DRAFT Norristown Dam Hydropower Feasibility Study

Prepared for:

Montgomery County, Pennsylvania

December 2017

Norristown Dam Feasibility Study December 2017 i

Table of Contents

Executive Summary .............................................................................................................. vi

Introduction ................................................................................................................ 1 1.0

Existing Condition ....................................................................................................... 1 2.0

2.1 Background and History

2.2 Existing Site Information

Development Alternatives ........................................................................................... 7 3.0

3.1 Design Assumptions

3.2 Option 1 – Two Mavel Units Placed Shore Side

3.2.1 Design

3.2.2 Construction

3.2.3 Advantages and Disadvantages

3.3 Option 2 – Two Mavel Units Placed in River

3.3.1 Design

3.3.2 Construction

3.3.3 Advantages and Disadvantages

3.4 Option 3 – Three Far East Units Placed Shore Side

3.4.1 Design

3.4.2 Construction

3.4.3 Advantages and Disadvantages

3.5 Option 4 – Three Far East Units Placed in River

3.5.1 Design

3.5.2 Construction

3.5.3 Advantages and Disadvantages

3.6 Option 5 – 12 Voith Units Placed in River

3.6.1 Design

3.6.2 Construction

3.6.3 Advantages and Disadvantages

Technical Evaluation .................................................................................................. 37 4.0

4.1 General Characteristics

4.2 Head

4.3 Flows

ii

4.3.1 Minimum Flow Requirements

4.3.2 Turbine Flows

4.4 Efficiency

4.5 Energy and Power Modeling

4.5.1 Model Inputs

4.5.2 Power and Energy Modeling

Environmental Resources .......................................................................................... 60 5.0

5.1 Detailed Resource Investigation

5.2 Critical Habitat

Economics ................................................................................................................. 64 6.0

6.1 Costs

6.1.1 Equipment Costs

6.1.2 Development Cost Opinions

6.1.3 Operations and Maintenance (O&M)

6.2 Value of Energy

6.3 Grants and incentives

6.3.1 Microgrid

6.3.2 Renewable Energy Credits (RECs)

6.4 Financing

6.5 Estimated Payback Period and Return on Investment

Conclusion ................................................................................................................ 80 7.0

References ................................................................................................................ 81 8.0

Appendix A Norristown Dam Section Drawing with Approximate Bedrock Elevations

Appendix B Monthly Flow Duration Curves for Norristown

Appendix C Turbine Vendor Information

Appendix D Proforma Results iii

List of Tables

Table 1: Summary of rough field head measurements

Table 2: Environmental and aesthetic flows

Table 3: Modeled site flowrates

Table 4: Turbine characteristics

Table 5: Average of annual energy modeling results

Table 6: Summary of environmental permitting relative risk/uncertainty

Table 7: Relative risk/uncertainty ranking

Table 8: Summary of turbine vendor information

Table 9: Summary of cost categories and quantities

Table 10: Summary of cost opinion results

Table 11: Summary of estimated annual O&M costs

Table 12: Summary of the Montgomery County PECO power bill review

Table 13: Summary of available incentives review

Table 14: Summary of proforma inputs

Table 15: Summary of proforma results

Table 16: Maximum development cost for breakeven 20-year net present value

Table 17: Minimum total benefit required for breakeven 20-year net present value

List of Figures

Figure 1: Norristown Dam location map

Figure 2: Norristown Dam area map

Figure 3: Existing conditions at Norristown Dam

Figure 4: Typical cross section of existing dam

Figure 5: Plan view of existing fish ladder

Figure 6: Option 1 site layout

Figure 7: Option 1 plan view

Figure 8: Option 1 section view

Figure 9: Option 2 site layout

Figure 10: Option 2 plan view

Figure 11: Option 2 section view

Figure 12: Option 3 site layout iv

Figure 13: Option 3 plan view

Figure 14: Option 3 section view

Figure 15: Option 4 site layout

Figure 16: Option 4 plan view

Figure 17: Option 4 section view

Figure 18: Option 5 site layout

Figure 19: Option 5 plan view

Figure 20: Option 5 section view

Figure 21: Hydraulic turbine type efficiency comparison (ESRU 2017)

Figure 22: Hydraulic turbine application chart (Maskauskas 2007)

Figure 23: Typical layout of a Pelton (Impulse) turbine (Wiki 2017a)

Figure 24: Typical Francis turbine runner (Meskauskas 2007)

Figure 25: Typical layout of a Kaplan turbine (Voith-Siemens 2005)

Figure 26: Overview of net and gross head through a hydropower system

Figure 27: USGS Gauge 01473500 location (USGS 2017)

Figure 28: Headwater elevation derivation

Figure 29: Tailwater elevation derivation

Figure 30: Norristown Dam drainage area delineation (area in yellow) (StreamStats 2017)

Figure 31: Average monthly flowrate

Figure 32: Yearly minimum, average, and maximum flow

Figure 33: Project dam flow duration curve

Figure 34: Flow duration chart Option 2

Figure 35: Flow duration chart Option 4

Figure 36: Flow duration chart Option 5

Figure 37: Annual estimated power production

Figure 38: Critical habitat in Pennsylvania

Figure 39: Montgomery County monthly retail power rate

Figure 40: Average daily wholesale energy prices in PJM 2001 to 2017 v

TRANSMITTAL LETTER

December 19, 2017

Mr. Drew Shaw Montgomery County Courthouse P.O. Box 311 Norristown, PA 19404-0311

Norristown Dam Feasibility Study

Dear Mr. Shaw, Alden Research Laboratory, Inc. (Alden) is pleased to submit this Hydropower Feasibility Study Report for Norristown Dam. This report is a continuation of the Norristown Dam Resource Assessment submitted by Alden on March 22, 2017.

This Feasibility Study includes a review of existing site information (this was provided in more detail in the Resource Assessment), an overview of five conceptual development design options for the site, a technical evaluation including energy and power modeling, and an economic evaluation including conceptual financial proforma.

The five conceptual hydropower design options included two options on the shore side of the existing fish ladder and three options on the river side of the fish ladder. The two shore side options were determined infeasible, largely due to the close proximity of a bridge pier and utility tower just downstream of the project. Energy production and cost estimates were developed for the three in-river options. These estimated values and other data were used to develop financial proforma in which three assumed financing scenarios were applied to each option. The three in-river development options presented in this report appear to be technically feasible; however, the designs analyzed do not appear to be economically feasible.

Please let us know if you have any questions or comments.

Sincerely, Gregory S. Allen, P.E.

Director, Environmental and Engineering Services vi

Executive Summary

Interest in developing the hydropower potential at the Norristown Dan was generated following the U.S. Department of Energy’s Oak Ridge National Laboratory study An Assessment of Energy Potential at Non-Powered Dams in the United States mentioning the dam as one of the many existing non-powered dams in the United States with energy producing potential.

Alden Research Laboratory, Inc. (Alden) was contracted by Montgomery County (County) to explore the feasibility of developing a hydropower project at this site.

Five hydropower development conceptual designs options were considered for the Norristown Dam site. All five options were placed on the southern (Bridgeport) side of the dam for improved accessibility and the benefits of keeping the project in close proximity to the existing fish ladder. These options consisted of two land-based projects in which intake canals and a power house would be placed on the dry side of the existing fish ladder, and three in-river designs in which part of the dam adjacent to the fish ladder would be demolished and replaced by power house and gate structures. The design options are, Option 1 – Two Mavel Units Placed Shore Side, Option 2 – Two Mavel Units Placed in River, Option 3 – Three Far East Units Placed Shore Side, Option 4 – Three Far East Units Placed in River, and

Option 5 – 12 Voith Units Placed in River.

Following review of these options it was determined that the discharge of the two land-based options (Options 1 and 3) would be too close to one of the Southeastern Pennsylvania Transportation Authority (SEPTA) bridge piers and a trussed utility tower. This placement would result in poor hydraulics for the plant discharges and require additional scour protection to minimize the risk of undermining the foundations. For these reasons Options 1 and 3 were determined to be at a disadvantage to the in-river options and were not carried forward in analysis.

Technical and economic evaluations were then conducted for Options 2, 4, and 5. The technical evaluation included a review of head, flow, efficiency, and modeling to estimate the power and energy production potential for each option. The economic review included the development of Cost Opinions for each option, a review of financing alternatives, a review of the potential value of energy produced, and financial proforma modeling.

Based on the preliminary feasibility analysis, the Norristown Dam Hydroelectric Project appears to be technically feasible for design Options 2, 4, and 5 as presented in this report. However, designs considered to not appear to be economically feasible based upon the modeled power production, proforma, and assumed inputs presented in this report. However, if the assumptions (i.e. financing, power rates, development costs, etc.) in this report change the project has potential to be viable.

Introduction 1.0

The Norristown Dam (Norristown) is located on the Schuylkill River in Norristown and Bridgeport, Pennsylvania. The concrete and earthen structure is owned by Montgomery County, Pennsylvania (County). Alden Research Laboratory, Inc. (Alden) was contracted by the County to conduct a Resources Assessment and a subsequent Feasibility Study to better understand the power generating potential and financial return that could be realized through development at this site. The County authorized a pre-feasibility study (resource assessment) and a feasibility study of the Dam to understand the potential power generating capabilities of the site, and what this might translate to in terms of both tangible and non-tangible benefits to the local community. The Norristown Dam Resource Assessment (Resource Assessment), submitted to the County in March 2017, found no unsurmountable barriers to hydropower development at the site and high-level proforma suggested the project may be viable in limited scenarios. This report presents the findings of a more in-depth evaluation of hydropower potential for Norristown Dam.

A site visit was conducted by Alden on November 18, 2016 during which the site was visually inspected. Some minor dimensions were checked during the site visit, but a detailed survey was not completed for this project.

Existing Condition 2.0

2.1 Background and History

The Norristown Dam (also known as the Swede Street Dam) was constructed along with an adjacent canal and lock in the early 1800s to support a shipping route up the Schuylkill River.

The canal and lock were located on the Bridgeport side of the site, but have since been abandoned and filled. The site was later acquired by PECO Energy Company (PECO) and the impoundment used to supply water for their Barbadoes Island Power Station, located immediately upstream of the project. In the 1990s PECO surrendered the dam to the County.

The terms of PECO’s surrender included the complete rehabilitation of the spillway and the installation of the fish ladder on the Bridgeport side of the site.

In 2012 the U.S. Department of Energy’ s Oak Ridge National Laboratory released the study An Assessment of Energy Potential at Non-Powered Dams in the United States, in which the Norristown dam was identified as a non-powered dam with small hydropower development potential (Hadjerioua et. al 2012). This generated interest in exploring Norristown’s hydropower potential. The County then contracted Alden to conduct a site visit in 2016 and a Resources assessment and this Feasibility Study in 2017.

2.2 Existing Site Information

The Norristown Dam is located approximately 15 miles north-west of Philadelphia Pennsylvania, spanning the Schuylkill River between Norristown and Bridgeport Pennsylvania, as seen in Figure 1 and Figure 2. The existing site consists of an 869 ft long 12 ft high concrete capped timber-crib dam, set in a wide V shape approximately north to south across the river.

The dam terminates to a stone-block abutment on the north (Norristown) end and to a fish ladder structure to the south (Bridgeport). A SEPTA light rail bridge and the U.S. Route 202 vehicle and pedestrian bridge also span the river about 100 ft and 600 ft downstream of the dam, respectively. A general site layout is shown in Figure 3.

As mentioned above in Section 2.1, the site was surrendered by PECO Energy Company to the County in the mid-1990s. Terms of the surrender included reconstruction of the dam and installation of a fish ladder. The old timber-crib dam was lined with steel sheet piling on the upstream and downstream faces and capped with concrete; the concrete cap was also anchored diagonally into the existing structure. A general cross section of the existing dam is shown in Figure 4. The Denil fish ladder is set along the southern bank of the river with an entrance on the downstream face at about a 20 degree angle to the river bank and an exit at the upstream end of the river-side face, about 90 degrees to the embankment. At about the mid-point of the river-side face of the fish ladder structure is an intake for attraction flow for the fish ladder. Water drawn in at this point is piped to a diffuser at the entrance of the ladder;

the additional flow is intended to help migrating fish locate the entrance. The fishway operates seasonally from mid-April through the end of October and is designed to pass 25,000 American shad per year. Figure 5 displays a site layout of the existing fish ladder.

Figure 1: Norristown Dam location map

Figure 2: Norristown Dam area map

Figure 3: Existing conditions at Norristown Dam

Figure 4: Typical cross section of existing dam

Figure 5: Plan view of existing fish ladder

Development Alternatives 3.0

The following section outlines the design, construction process, advantages, and disadvantages of hydropower development options for the Norristown Dam. Five conceptual designs were developed:

Option 1 – Two Mavel Units Placed Shore Side, Option 2 – Two Mavel Units Placed in River, Option 3 – Three Far East Units Placed Shore Side, Option 4 – Three Far East Units Placed in River, and

Option 5 – 12 Voith Units Placed in River.

3.1 Design Assumptions

Each design considered the following criteria with respect to siting, intake velocities, and excavation:

1.5 feet per second (ft/sec) average intake approach velocity, Situate intake to minimize debris loading and risk of impingement and entrainment of fish exiting the fish ladder, Maintain fish ladder operation, Situate project discharge near the fish ladder entrance, Minimize sharp turns and abrupt contractions and expansions in hydraulic design, Work decks at or above the Federal Emergency Management Agency (FEMA) ten year flood water elevation of approximately 70 ft NAVD88, No change to the FEMA ten-year flood plain, Run-of river operations, Project operations will cease at river flows above 40,000 cfs, Minimize excavation below the assumed bed rock elevation, Bedrock assumed at and below approximately Elevation 41.5 ft NAVD88, No blasting during bedrock excavation, Minimize impact and potential risk of scour on the SEPTA bridge supports and trussed utility tower downstream of the dam, and

Maintain serviceability of hydropower equipment.

Each design option is placed on the right abutment (Bridgeport), abutting either the river or shore side of the existing fish ladder. This placement was chosen so that the water discharged from generation would be adjacent to the fishway which is expected to enhance the ability of migrating fish to locate the fishway entrance. Maintaining functionality of the existing fishway at Norristown is likely to be a point of interest for regulators in the licensing process and was considered a priority during design. Ease of access is also superior on this side of the dam.

The design intake approach velocity is an important consideration and impacts the size of the intake and trash rack. An approach velocity of 1.5 ft/sec was selected for the design of all options as this is the expected requirement requested by regulatory agencies to reduce entrainment of American eel; this is a somewhat conservative approach that may be negotiated with regulators. Orientation of the intake trash racks were placed to reduce debris loading.

Intake canals incorporate wide sweeping turns and avoided abrupt flow direction in an effort to optimize hydraulics and reduce head loss. Head and head losses are discussed in Section 4.2.

Drawings provided by the county show the dam placed directly on bedrock at approximately 16 ft below the dam crest, see Appendix A. Bedrock was assumed to exist at and below this elevation for all required excavation. With the close proximity of the light rail bridge it was assumed that blasting would not be feasible. If it is determined that blasting is acceptable excavation costs could be reduced considerably. Excavations below the assumed bedrock elevation were avoided wherever possible.

All options were designed assuming run-or-river operations, maintaining historic upper reservoir water surface elevations. Work decks were designed to remain above FEMA ten year flood elevations, and flood gates were designed to maintain FEMA ten year flood plains. Gates were incorporated to compensate for spill discharge capacity lost by in-river power house structures. The FEMA ten-year storm flow for the Schuylkill at Norristown is 62,900 cfs (FEMA 2016). This value was not reached or exceeded in the USGS stream gauge data in the period of 2001 to 2016 period of record examined for flow and head estimates. Development options that require flood compensation gates may affect the flood plain at flows exceeding the FEMA ten year flood, however gates large enough to compensate for 50-year and 100-year storm flows were not feasible.

It was assumed that hydro-plant operations would cease at river flows exceeding 40,000 cfs. At river flows exceeding 40,000 cfs the potential for damage to plant equipment would increase and gross head across estimated to be insufficient to justify production, see Section 4.0 for more on head and flow. The flow is also well below the FEMA ten year storm flow for which deck elevations and gate operations were designed.

A SEPTA light-rail bridge and a trussed utility tower are located immediately downstream of the Norristown dam. Development designs must avoid creating flow situations that would increase the potential for erosion or scour near these structures.

Options 1 through 4 use pit-type Kaplan turbines and Option 5 specifies bulb-type propeller units. A Kaplan turbine is similar to a propeller but the blade pitch is adjustable and adjustable wicket gates situated just upstream of the turbine. Adjusting wicket gate and blade angle allows operators control over flow rates though the turbine and the ability to maximize efficiency over a greater range of flow conditions. A pit-type setting directly connects the generator to the turbine by housing it in a water tight pit just upstream of the turbine. Water is first directed around the pit then constricted toward the turbine. The bulb propeller units house the generator in a water-tight bulb upstream of the turbine, and utilize a non-adjustable propeller turbine. The bulb and turbine units must be pulled out of the water with a hoist for maintenance. Turbine technology and selection is discussed further in Section 4.1.

All designs are preliminary in nature. Figures are not for construction, all dimensions are approximate, and drawings are not necessarily to scale.

3.2 Option 1 – Two Mavel Units Placed Shore Side

3.2.1 Design

Option 1 consists of two Mavel Kaplan pit-type turbine-generator units in a power house placed on the riverbank, south of the existing fish ladder. Water would be diverted from the river through a 165 ft wide trash rack situated about parallel to river flow. Downstream of the trash rack are two parallel intake canals that convey flow to the turbines. Head gates are located about 70 ft upstream of the turbines. The tailrace downstream of the power house would include sheet pile scour protection around one of the existing light rail bridge supports. Figure 6 provides a general site layout for Option 1, while Figure 7 and Figure 8 provide a plan view and section view respectively.

The orientation of the trash rack relative to river flow is intended to improve hydraulics as water may be drawn from the south side of Barbadoes Island as well as across the face of the dam from north of the island. This configuration may also reduce debris loading as surface flows may move debris past the intake and over the spillway, during high river flows. The downstream edge of the intake is about 75 ft from the fish ladder exit to limit potential of fish entrainment. The 25 ft tall trash rack (about 10 ft below average pond surface elevation) would be positioned at about 15 degrees off vertical and consists of 0.25 by 3 inch rectangular profile bars with one inch clear spacing. The trash racks would include an automated raking system capable of automated or manual operation.

The intake canal begins at the full width of the trash racks, and constricts into two approximately 26 ft wide channels as it makes the 90 degree turn toward the turbines. There are two arched concrete vanes downstream of the intake to improve the hydraulics as the flow is turned. Steel grating walkways would run along the canal walls to allow access to the trash racks and head gates. The canal invert was designed above the assumed bedrock elevation until just upstream of the powerhouse to reduce excavation. The turbine setting (centerline elevation) was determined by manufacturer’s specifications. Head gates and stop logs at the draft tubes discharge will allow the turbines to be dewatered for maintenance.

The turbine, generator, and controls would be housed in a concrete powerhouse set above the turbines in the area that is now part of the viewing park.

The draft tube discharge is positioned adjacent to the fish ladder entrance to enhance fish attraction; as migrating fish are attracted to higher flows. Downstream of the draft tubes, the tailrace would be cut into the bedrock. The SEPTA bridge pier in line with the turbine discharge would need to be evaluated for potential scour erosion. For the purposes of this evaluation a steel sheet pile cell has been included around the pier to mitigate risk of scour. However, the design of this structure would require a comprehensive engineering study.

3.2.2 Construction

The development of Option 1 would begin with the demolition of much of what is now the viewing park area and installation of upstream and downstream cofferdams. The upstream cofferdam would span from just upstream of the proposed intake to the upstream edge of the fish ladder curving out into the river only far enough to allow clearance for equipment and bracing. The downstream coffer dam would span from the downstream most point of the fish ladder approximately following the river’s edge to about 50 ft downstream to the SEPTA bridge.

This layout would minimize impact in the river while allowing the fish ladder to remain functional.

Erosion control and silt fencing would surround the work area on land and suspended silt curtains would surround all in river work. Work areas behind cofferdams would require continual dewatering while in place, water from dewatering pumps would discharge through silt bags before returning to the river. Spoils from excavation would be disposed of off-site.

Construction of Option 1 would not require additional access roads. Concrete, steel, and equipment placement would be accomplished with standard land-based cranes and construction equipment.

3.2.3 Advantages and Disadvantages

The following is a summary of the advantages and disadvantages for development Option 1 as compared to the other options presented in this report.

Advantages, No physical interference with fish ladder, No reduction in dam spill capacity, Minimal in river construction, Does not impact discharge capacity of the project, Ease of access during construction, Ease of access to equipment for service due to dry-pit configuration, Relative ease of integrating downstream fish passage, and

Disadvantages

Effects on light rail bridge pier and uncertainty of associated reinforcement requirements, Extensive excavation below assumed bedrock elevation, Impacts to recreation resources (i.e., viewing park), Risk of fall back to upstream migrating fish exiting fish ladder at a location downstream of the project intake, Concentrated discharge flow may impact local aquatic habitat, and

Ground disturbance and conversion activities may impact cultural, historic and/or recreational resources.

Option 1 has an advantage over the other land-based option (Option 3) by way of a smaller footprint, and ease of access during construction and operation gives both land-based designs an advantage over in-river options (Options 2, 4, and 5). However, the land-based options have a significant disadvantage when compared to the in-river projects in the volume of excavation required as well as the uncertainty associated with mitigation for scour protection of the SEPTA bridge pier and the trussed utility tower. For these reasons Option 1 was not considered for development and not carried forward to the costing and proforma analysis in Section 6.0.

Figure 6: Option 1 site layout

Figure 7: Option 1 plan view

Figure 8: Option 1 section view

3.3 Option 2 – Two Mavel Units Placed in River

3.3.1 Design

Option 2 consists of two Mavel Kaplan pit-type turbine-generator units in a powerhouse placed in the river adjacent to the existing fish ladder. Water would be diverted from the river through a 165 ft long intake trash rack situated about 20 degrees off parallel of river flow. Flow would be conveyed via two parallel channels downstream of the trash racks to the turbines. A set of head gates are set in the channels just upstream of the turbine pits. A 125 ft section of dam would be replaced with a series of ten ft high air-actuated spillway crest gates adjacent to the powerhouse. To avoid interference with the existing fish ladder the southern wall of the powerhouse and intake channel would be offset about eight feet from the face of the fish ladder. Figure 9 is a general site layout for Option 2, while Figure 10 and Figure 11 are a plan view and section view respectively.

The orientation of the trash rack relative to river flow is intended to improve hydraulics as water may be drawn from the south side of Barbadoes Island as well as across the face of the dam from north of the island. The 25 ft tall trash rack (about 10 ft below average pond surface elevation) would be positioned at about 15 degrees off vertical and consist of 0.25 by 3 inch rectangular profile bars with one inch clear spacing.. The trash racks would include automated raking system capable of automated or manual operation.

The intake canal begins at the full width of the trash racks, and constricts into two approximately 26 ft wide channels as it makes the 70 degree turn toward the turbines. Steel grating access walkways would run the length of the canals and the trash rack. The canal invert was designed above the assumed bedrock elevation until just upstream of the powerhouse to reduce costs associated with rock removal. The turbine setting (centerline elevation) was determined by manufacturer’s specifications. Head gates and stop logs at the draft tubes discharge will allow the turbines to be dewatered for maintenance.

The turbine, generator, and controls would be housed in a concrete powerhouse set above the turbines in an area that is now part of the river.

Approximately 77 ft of spillway would be occupied due to the in-river placement of the powerhouse. To maintain the spillway discharge capacity, a 125 ft section of ten ft tall air-actuated spillway crest gates would be added adjacent to the powerhouse. Under normal conditions these gates would allow control of spill to maintain existing head pond elevations under run-of-river operation. During flood flows the gates may be lowered to compensate for the flow capacity lost by the dam section occupied by the powerhouse. Further study would be required to determine potential impacts to the floodplain. A pier supporting the SEPTA bridge is located downstream of the gate section which may require scour protection.

Under the existing configuration, fish exit the fish ladder upstream of the dam from the river facing (northern) wall of the structure near the upstream corner and an inlet for attraction water is located near the center of the same face, see Figure 5 above. In an effort to maintain fish ladder functionality the new civil structures would be offset about eight feet from the exit and attraction flow inlet. A bridge capable of supporting necessary equipment would provide access over the fish ladder and to the powerhouse.

The draft tube discharge flow is positioned in proximity to the fish ladder entrance to enhance fish attraction. Downstream of the draft tubes, the tailrace would be cut in to the bedrock sloping gradually back up to existing elevations. The tailrace for Option 2 is expected to have minimal effect on existing structures, i.e. SEPTA bridge piers and the utility tower; however the SEPTA bridge piers downstream of the spillway gates may require scour protection.

3.3.2 Construction

The development of Option 2 would begin with the installation of upstream and downstream access roads and staging areas. Following the roads, an upstream cofferdam would be installed sweeping from about 170 ft upstream of the fish ladder to a point on the dam about 250 ft from the southern river bank along with a downstream cofferdam spanning from about the same point along the dam back to the southern river bank near the SEPTA bridge. A temporary crane trestle and work platform capable of supporting crane loads would be installed downstream of the project. About 200 ft of the existing dam would be demolished for the powerhouse and gate structures. River bed modifications would be conducted in the dry behind the coffer dams, no dredging equipment would be deployed.

Erosion control and silt fencing would surround the work area on land and suspended silt curtains would surround all in river work. Work areas behind coffer dams would require continual dewatering while in place, water from dewatering pumps would discharged through silt bags before reintroduction to the river. Spoils from excavation and would be disposed of off-site.

Structural steel, gates, and hydropower equipment would be placed by crane; concrete would be pumped from the viewing park area or placed by crane with a hopper.

3.3.3 Advantages and Disadvantages

The following is a summary of the advantages and disadvantages for development Option 2 as compared to the other options presented in this report.

Advantages

Shorter intake channel than land-based options, Ease of access to equipment for service due to dry-pit configuration, Reduced impact on the SEPTA light rail bridge pier as compared to land-based options, Potential reduction in dam spill capacity during flood conditions, Close proximity to fish ladder exit and associated uncertainty in performance, Requires dam demolition, In river construction, High level of excavation below assumed bedrock elevation, Large cofferdam requirements, Risk of fall back to upstream migrating fish exiting fish ladder at a location just upstream of the project intake, and

Direct permanent disturbance of riverine habitat.

The primary advantages Option 2 has over the land-based Options 1 and 3 is minimal interference with the SEPTA bridge supports, no effect on the utility tower, and reduced excavation requirements. Option 2 also has a smaller foot print than Options 1, 3, and 4. This option would require a smaller spillway gate section than the similar Far East based Option 4 but more than the Voith based Option 5. The primary disadvantage to Option 2 is a possible effect on the flood plain which would require further evaluation and review by FEMA, the United States Army Corps of Engineers (USACE), and FERC. Other disadvantages include possible effects on fish ladder operations, large coffer dam requirements, and other access issues associated with in-river construction.

Figure 9: Option 2 site layout

Figure 10: Option 2 plan view

Figure 11: Option 2 section view

3.4 Option 3 – Three Far East Units Placed Shore Side

Option 3 is similar to Option 1 above except three Far East turbines are used in place of the two Mavel units.

3.4.1 Design

Option 3 consists of three Far East Kaplan pit-type turbine-generator units in a powerhouse placed on the riverbank alongside of the existing fish ladder. Water would be diverted from the river through a 165 ft long intake trash rack situated about parallel to river flow. Intake flow would be conveyed downstream of the intake trash rack via three parallel water channels to the turbines. A set of head gates would be positioned in the canals about 80 ft upstream of the turbine pits. The tailrace for Option 3 would require the reshaping of the riverbank downstream of the project, including sheet pile scour protection surrounding an existing light rail bridge support and a trussed utility tower. Figure 12 is a general site layout for Option 3, while Figure 13 and Figure 14 are a plan and section views respectively.

The orientation of the trash rack relative to river flow is intended to improve hydraulics as water may be drawn from the south side of Barbadoes Island as well as across the face of the dam from north of the island. This configuration may also reduce debris loading as surface flows may move debris past the intake and over the spillway during high flow events. The downstream edge of the intake would be positioned about 75 ft from the fish ladder exit to help prevent fish entrainment. The 25 ft tall trash rack (about 10 ft below average pond surface elevation) would be positioned at about 15 degrees off vertical and consists of 0.25 by 3 inch rectangular profile bars with one inch clear spacing The trash racks would include automated raking system capable of automated or manual operation.

The intake canal begins at the full width of the trash racks, and constricts into three approximately 30 ft wide channels as it makes the 90 degree turn toward the turbines. Steel grating access walkways would run the length of the canals and the trash rack. The canal invert was designed above the assumed bedrock elevation until just upstream of the powerhouse to reduce excavation requirements. The turbine setting (centerline elevation) was determined by manufacturer’s specifications. Head gates and stop logs at the draft tubes discharge will allow the turbines to be dewatered for maintenance.

The turbine, generator, and controls would be housed in a concrete power house set above the turbines in the area that is now part of the viewing park.

The draft tubes discharge was positioned adjacent to the fish ladder entrance to enhance fish ladder performance. Downstream of the draft tubes, the tailrace would be cut in to the bedrock sloping gradually back up to existing elevations. Due to the reshaping of the river bank in the tailrace area, one of the light rail bridge piers and a utility line tower that are currently on land would be surrounded by water and in the path of the project discharge. The SEPTA bridge pier and utility tower support in line with the turbine discharge would need to be evaluated for potential scour erosion. For the purposes of this evaluation a steel sheet pile cell has been included around the piers to mitigate risk of scour. However, the design of these structures would require a comprehensive engineering study. In addition, the utlity company may require access to the utility tower, which would require tower relocation as opposed to the design in Option 3.

3.4.2 Construction

The development of Option 3 would begin with the demolition of much of what is now the park area on the south dam abutment and installation of upstream and downstream cofferdams.

The upstream cofferdam would span from just upstream of the proposed intake footprint to the upstream edge of the fish ladder out into the river far enough to allow clearance for equipment and bracing. The downstream cofferdam would span from the downstream most point of the fish ladder approximately following the river’s edge to about 50 ft downstream to the SEPTA bridge. This layout would minimize impact in the river while allowing the fish ladder to remain functional.

Erosion control and silt fencing would surround the work area on land and suspended silt curtains would surround all in river work. Work areas behind coffer dams would require continual dewatering while in place, water from dewatering pumps would discharge through silt bags before reintroduction to the river. Spoils from excavation would be disposed of off-site.

Sheet piling scour control surrounding the bridge pier and the utility tower would be driven in the dry before the excavation of the tailrace

Construction of Option 3 would not require additional access roads and concrete, steel, and equipment placement would be accomplished with standard land-based cranes and construction equipment.

3.4.3 Advantages and Disadvantages

The following is a summary of the advantages and disadvantages for development Option 3 as compared to the other options presented in this report.

Advantages

No physical interference with fish ladder, Does not impact discharge capacity of project, Less in river construction than other options, Ease of access during construction, Ease of access to equipment for service due to dry-pit configuration, Larger footprint than all other options, Effects on light rail bridge pier and uncertainty of associated required scour protection measures, Utility tower within the proposed tailrace alignment would require scour protection or relocation, High level of excavation below assumed bedrock elevation , Impacts to recreation resources (i.e., viewing park), Risk of fall back to upstream migrating fish exiting fish ladder at a location downstream of the project intake, and

Ground disturbance and conversion activities may impact cultural, historic and/or recreational resources.

Ease of access gives both land-based Options 1 and 3 an advantage over in-river options (Options 2, 4, and 5). However, the land-based Options 1 and 3 have a significant disadvantage when compared to the in-river options in the volume of excavation required and uncertainty associated with the proximity of the tailrace to the SEPTA bridge pier and the trussed utility tower. Additionally the larger footprint of Option 3 as compared to Option 1 is a disadvantage.

For these reasons Option 3 was not considered for development and not carried forward to the costing and proforma analysis in Section 7.0.

Figure 12: Option 3 site layout

Figure 13: Option 3 plan view

Figure 14: Option 3 section view

3.5 Option 4 – Three Far East Units Placed in River

Option 4 is similar to Option 2 above except three Far East turbines are used in place of the two Mavel units.

3.5.1 Design

Option 4 consists of three Far East Kaplan pit-type turbine-generator units in a powerhouse placed in the river adjacent to the existing fish ladder. Water is diverted from the river through a 165 ft long intake trash rack situated about 20 degrees off parallel of river flow. Flow would be conveyed downstream of the intake trash rack via three parallel water channels to the turbines. A set of head gates would be placed in the canals just upstream of the turbine pits. A 200 ft section of dam would be replaced with ten ft tall air-actuated spillway crest gates adjacent to the powerhouse. To avoid interference with the existing fish ladder the southern wall of the powerhouse and intake channel would be offset about eight feet from the face of the fish ladder. Figure 15 is a general site layout for Option 4, while Figure 16 and Figure 17 are a plan view and section view respectively.

The orientation of the trash rack relative to river flow is intended to improve hydraulics as water may be drawn from the south side of Barbadoes Island as well as across the face of the dam from north of the island. The 25 ft tall trash rack (about 10 ft below average pond surface elevation) would be positioned at about 15 degrees off vertical and consist of 0.25 by 3 inch rectangular profile bars with one inch clear spacing. The trash racks would include automated raking system capable of automated of manual operation.

The approximately 270 ft long intake canal begins at the full width of the trash racks, and constricts into three approximately 30 ft wide channels as it makes the 70 degree turn toward the turbines. Steel grating access walkways would run the length of the canals and the trash rack. The canal invert was designed above the assumed bedrock elevation until just upstream of the powerhouse to reduce excavation. The turbine setting (centerline elevation) was determined by manufacturer’s specifications Head gates and stop logs at the draft tubes discharge will allow the turbines to be dewatered for maintenance.

The turbine, generator, and controls would be housed in a concrete power house set above the turbines in an area that is now part of the river.

The turbines and powerhouse in Option 4 would displace approximately 122 ft of dam. To maintain the spillway discharge capacity during high flow events a 200 ft section of ten ft tall air-actuated spillway crest gates would be added adjacent to the powerhouse.

Under the existing configuration, fish exit the fish ladder upstream of the dam from the river facing (northern) wall of the structure near the upstream corner and an inlet for attraction water is located near the center of the same face, see Figure 5 above. In an effort to maintain fish ladder functionality the new civil structures would be offset about eight feet from the exit and attraction flow inlet. A bridge capable of supporting necessary equipment would connect the existing fish ladder deck to the powerhouse.

The draft tube discharge flow is positioned adjacent to the fish ladder entrance to enhance fish ladder performance. Downstream of the draft tubes, the tailrace would be cut in to the bedrock sloping gradually back up to existing elevations. The tailrace for Option 4 is expected to have minimal effect on existing structures; however the SEPTA bridge piers downstream of the spillway gates may require scour protection.

3.5.2 Construction

The development of Option 4 would begin with the installation of upstream and downstream access roads and staging areas. Following the roads, an upstream cofferdam would be installed sweeping from about 240 ft upstream of the fish ladder to a point on the dam about 370 ft from the southern river bank along with a downstream cofferdam spanning from about the same point along the dam back to the southern river bank near the SEPTA bridge. A temporary crane trestle and work platform capable of supporting crane loads would be installed downstream of the project. About 320 ft of the existing dam would be demolished for the powerhouse and gate structures. River bed modifications would be conducted in the dry behind the coffer dams, no dredging equipment would be deployed.

Erosion control and silt fencing would surround the work area on land and suspended silt curtains would surround all in river work. Work areas behind coffer dams would require continual dewatering while in place; water from dewatering pumps would discharge through silt bags prior to reintroduction to the river. Spoils from excavation and would be disposed of off-site.

Structural steel, gates, and hydropower equipment would be placed by crane; concrete would be pumped from the viewing park area or placed by crane with a hopper.

3.5.3 Advantages and Disadvantages

The following is a summary of the advantages and disadvantages for development Option 4 as compared to the other options presented in this report.

Advantages

Shorter intake channel than riverbank options, Relative ease of integrating downstream fish passage

Potential reduction in dam spill discharge capacity, Close proximity to fish ladder exit and associated uncertainty in performance

Requires dam demolition, In river construction

Operational and liability risks associated with spillway gate operations during flood conditions, High level of excavation below assumed bedrock elevation, Large cofferdam requirements, May affect SEPTA bridge pier, Larger footprint than two turbine option, Risk of fall back to upstream migrating fish exiting fish ladder at a location just upstream

Similar to Option 2, the primary advantages Option 4 has over the land-based Options 1 and 3 is reduced chance of interference with the SEPTA bridge supports, no effect on the utility tower, and reduced excavation requirements; though this option would require the most excavation of all the in-river options and the tailrace is in much closer proximity to one of the bridge piers.

Disadvantages include the largest dam demolition and cofferdam requirements, largest air-actuated spillway requirements, and increased potential effects on the flood plain. Other disadvantages include possible effects on fish ladder operations, large cofferdam requirements, and other access issues associated with in-river construction.

Figure 15: Option 4 site layout

Figure 16: Option 4 plan view

Figure 17: Option 4 section view

3.6 Option 5 – 12 Voith Units Placed in River

Option 5 includes 12 Voith StreamDiver turbine units. The Voith StreamDiver is a bulb-type propeller unit in which the generator is housed in a submersible bulb just upstream of a propeller runner. The turbines are significantly smaller than those in the previously options, resulting in a greater number of units, but much less excavation. Unlike the Kaplan turbines used in Options 1 through 4, propeller turbines do not have for the ability to regulate flow.

Each unit is either on or off and total generating flow is adjusted by selecting number of units operating for a given river flow condition.

3.6.1 Design

Option 5 consists of 12 StreamDiver units, grouped into sets of four adjacent to the existing fish ladder. Upstream of the StreamDiver units is a completely submerged 102 ft long by 24 ft wide trash rack positioned perpendicular to river flow and at about a 20 degree vertical incline.

Hinged access hatches would be placed within the trash rack above each unit; which may be swung open for routine unit installation and recovery. A set of c-channel tracks would be installed at each turbine/generator location to guide the units in and out of position. Each unit would have a shutoff gate between the turbine and the draft tube. Above the units, about at the elevation of the dam crest, would be a series of 2 ft tall air-actuated spillway crest gates.

Steel grating access walkways would run the length of the intake channels and the trash rack.

Controls for the project would be housed in a corrugated steel building on shore in what is now the adjacent park. Figure 18 is a general site layout for Option 5, while Figure 19 and Figure 20 are a plan view and section view respectively.

Unlike the previous options, the trash rack in Option 5 would be completely submerged and would not include automated trash rakes. The trash rack would be cleaned by periodically stopping flow through one four unit section while lowering the air-actuated gates above that section. The angle of the rake would let most debris pass over the spillway and additional hand racking may be carried out by operators from the service catwalk as needed.

The StreamDiver units would be hoisted out of the water for routine maintenance and repair by a hoist or gantry crane located on the service catwalk above. This would be accomplished by closing the isolation gates downstream of the turbines, opening the access gate in the trash rack, lowering an actuating clamp down the guide tracks, clamping the unit, and hoisting it out with the hoist.

The project would be observed and controlled from a 10 ft by 15 ft control room on the shore side of the existing fish ladder.

Option 5 is not anticipated to interfere with the operation of the existing fish ladder or require significant modifications to the tailrace area.

3.6.2 Construction

The development of Option 5 would begin with the installation of upstream and downstream access roads and staging areas. Following the roads, an upstream cofferdam would be installed spanning from about 30 ft upstream of the fish ladder to a point on the dam about 135 ft from the southern river bank along with a downstream cofferdam spanning from about the same point along the dam back to the southern river bank about 30 ft downstream of the fish ladder entrance. A temporary crane trestle and work platform capable of supporting crane loads would be installed downstream of the project. About 102 ft of the existing dam would be demolished and replaced with submerged turbines and spillway structure.