PREFABRICATED, MODULAR HYDROPOWER FOUNDATION SYSTEM FOR SOIL CONDITIONS

Abstract

A foundation system for modular hydropower systems and methods for constructing same. The foundation system is compatible with soils, particularly soils that are relatively loose or compressible, and thereby advantageous for the widespread implementation of low head modular hydropower systems. The foundation system includes pipe piles; sheet piles configured to be arranged transverse to the pipe piles; pile caps configured to be seated on top of the plurality of pipe piles; and a beam base slab configured to be securely positioned on top of the pile caps. A kit for the foundation system is also disclosed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Provisional Patent Application No. 63/143,328, filed Jan. 29, 2021, the disclosure of which is incorporated by reference as if fully set forth herein in its entirety.

FIELD OF THE INVENTION

Embodiments of the present invention relate to modular hydropower systems, and more particularly, to foundation systems for modular hydropower systems.

BACKGROUND OF THE INVENTION

Traditional dam engineering practice for sites where surficial geology is composed of soils often results in the design of an earthen embankment as the water retaining structure. Concrete structures can be constructed on soil, but typically only on a narrow range of dense, suitable material. Earthen dams are more common because an earthfill embankment with upstream and downstream faces often sloped at 3:1 horizontal to vertical has a very wide base. This wide base broadly distributes the load of the structure and impoundment, resulting in bearing pressures that are acceptable for the soil foundation. Seepage control must be provided both within the engineered embankment and the underlying foundation if the soils are granular. In modern dams, this is frequently done through a low permeability soil core for the embankment and a cutoff trench excavated deep into the foundation and refilled with compacted low permeability soil.

While the design and construction of earthen embankments is well understood and proven as a viable approach, there are many drawbacks with respect to environmental impacts and constructability. These include 1) a large physical footprint for the actual structure; 2) excavation of appropriate borrow to construct the embankment; 3) substantial cofferdams/water control (including foundation dewatering) to allow for embankment construction “in the dry”; 4) excavation of “unsuitable” soils below the embankment to control long-term settlement; 5) labor intensive and time consuming placement and compaction operations for earthfill materials; and 6) limitations on conditions under which earthfill materials can be placed (i.e. not during freezing or overly wet conditions.) A 30-foot high, 100-foot long earthen dam with a 15 foot deep cutoff trench could require the approximately 800 cubic yards of foundation excavation and then borrow excavation, placement, and compaction of approximately 13,000 cubic yards of soil embankment material (based on typically geometries described in such references as the USBR “Design of Small Dams.) Assuming excavation/placement rates of 100 cubic yards per day, this results in a minimum construction duration of at minimum 5 months, including site preparation, water control, permanent spillway construction of a small powerhouse, and unit installation. Thus, potential hydropower sites with soil foundations often result in the contemplation of large earthen embankments with the attendant high levels of impacts and cost and long construction durations.

By contrast, low-head modular hydropower systems offer the potential for small footprints, reduced costs, and quick construction. LPS estimates that its proposed modular system could reduce civil works costs by about 50% when compared to traditional construction. These advantages and cost savings can overcome many of the obstacles to new small hydropower production. However, there are a number of potential difficulties with placing modular systems on soil foundations, particularly if one goal is to reduce or eliminate excavation and the use of cast-in-place concrete. Because of the small footprint of typical modular systems, foundation bearing pressures are usually higher than for embankments. Modular systems that incorporate post-tensioning anchors cannot tolerate overall settlement that results in a loss of strain in the anchors. The numerous joint connections between modules/stacks for virtually all systems also make modular systems more sensitive to differential settlement. Finally, some modular systems simply rely on a mechanical shear connection to a bedrock foundation for structural stability against sliding, making such systems inherently incompatible with soil foundation sites. It is therefore clear that a foundation system for modular hydropower systems that allows such structures to be built on soil foundations is a necessity for expanding future development.

The promise of low-head modular hydropower systems is that they can lower cost and accelerate development through pre-engineered, generic designs and fabrication under controlled manufacturing conditions. However, the one aspect of any hydropower project that is never generic and cannot be controlled is the foundation. Subsurface conditions at desirable hydropower sites vary from exposed bedrock to deep sediments. Current modular designs typically are suitable for bedrock foundations, but struggle with soils, particularly soils that are relatively loose or compressible. Because soil foundations are present at such a high percentage of identified greenfield sites, a modular foundation system that is compatible with such conditions is critical to future widespread implementation of low head modular hydropower systems.

BRIEF SUMMARY OF THE INVENTION

The embodiments of the present invention provide a method for constructing and installing a modular foundation system, i.e., a foundation system for modular hydropower systems. Steps of the method include (a) installing a plurality of pipe piles advancing from a first abutment into a waterway; (b) installing upstream and downstream sheet pile rows between two or more of the plurality of pipe piles; (c) seating a plurality of pre-cast concrete pile caps; (d) placing a temporary construction matting to span between two rows of the plurality of pile caps to serve as an access staging platform for a crane; (e) advancing the crane to an end of the temporary access staging platform; (f) repeating steps (a)-(e) until all of the piles and pile caps have been installed across half of a width of a dam axis; (g) installing longitudinal pre-cast bottom beams of a base slab; (h) Installing temporary upstream and downstream water control plates for the half of the dam width to allow for additional work to be completed in the dry and maintain flow through the other half of the waterway; (i) installing top pre-cast beams for the base slab; (j) installing tie-downs, as needed; (k) erecting modules on the completed half of the foundation; and (l) removing the water control plates for the completed half of the foundation.

The method may include the further steps of (m) installing a second plurality of pipe piles advancing from a second abutment into the waterway; and (n) repeating steps (b)-(l) with in connection with the second abutment, to meet the completed construction in mid-stream. Another step involves preparing the first and second abutments and is performed before step (a). Step (a) may be performed through an associated water column using a movable template to maintain positioning of the pipe piles.

Further provided herein is a foundation system for modular hydropower systems including a plurality of pipe piles; a plurality of sheet piles configured to be arranged transverse to the pipe piles; a plurality of pile caps configured to be seated on top of the plurality of pipe piles; and a beam base slab configured to be securely positioned on top of the pile caps.

The beam base slab includes a first plurality of beams arranged in a first row, and a second row of beams arranged in a second row layered on top of the first row at a ninety-degree angle thereto. The beams of the first plurality of beams are tied together. In various embodiments, the first and second pluralities of beams are secured together by post-tensioned tie rods to create monolithic action between the first and second pluralities of beams, whereby the section modulus of the beam base slab is increased. The beams of the first plurality of beams can contain embedded hollow structural section (HSS) members to maximize tension capacity at top and bottom chords of such beams.

Also provided herein is a kit for constructing a foundation system for modular hydropower systems. The kit includes a plurality of pipe piles; a plurality of sheet piles configured to be arranged between the pipe piles; a plurality of pile caps configured to be seated on top of the plurality of pipe piles; and a beam base slab configured to be securely positioned on top of the pile caps, the beam base slab including a first plurality of beams arranged in a first row, and a second row of beams arranged in a second row layered on top of the first row

Other implementations are also described and recited herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustration, certain embodiments of the present invention are shown in the drawings described below. Like numerals in the drawings indicate like elements throughout. It should be understood, however, that the invention is not limited to the precise arrangements, dimensions, and instruments shown. In the drawings:

FIG. 1 is a schematic illustration of a modular foundation system according to the present invention.

FIG. 2a is a plan view of a commercially available pipe pile/sheet pile system.

FIG. 2b is a detailed view of the portion of FIG. 2a that is circled in dashed lines and labeled FIG. 2b.

FIG. 2c is a detailed view of the portion of FIG. 2a that is circled in dashed lines and labeled FIG. 2c.

FIGS. 3a, 3b and 3c shows pre-cast concrete base slab components of the foundation system of FIG. 1.

FIG. 4 shows the foundation system of FIG. 1 in use supporting an h-Modulor dam stack.

FIGS. 5a-5f show the construction and installation sequence for the foundation system of FIG. 1.

FIG. 6 shows an exemplary process for construction using the foundation system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

It is to be appreciated that certain aspects, modes, embodiments, variations and features of the invention are described below in various levels of detail in order to provide a substantial understanding of the present invention.

Definitions

For convenience, the meaning of some terms and phrases used in the specification, examples, and appended claims, are provided below. Unless stated otherwise, or implicit from context, the following terms and phrases include the meanings provided below. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is an apparent discrepancy between the usage of a term in the art and its definition provided herein, the definition provided within the specification shall prevail.

As used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the content clearly dictates otherwise. For example, reference to “a cell” includes a combination of two or more cells, and the like.

As used herein, the term “approximately” or “about” in reference to a value or parameter are generally taken to include numbers that fall within a range of 5%, 10%, 15%, or 20% in either direction (greater than or less than) of the number unless otherwise stated or otherwise evident from the context (except where such number would be less than 0% or exceed 100% of a possible value). As used herein, reference to “approximately” or “about” a value or parameter includes (and describes) embodiments that are directed to that value or parameter. For example, description referring to “about X” includes description of “X”.

As used herein, the term “or” means “and/or.” The term “and/or” as used in a phrase such as “A and/or B” herein is intended to include both A and B; A or B; A (alone); and B (alone). Likewise, the term “and/or” as used in a phrase such as “A, B, and/or C” is intended to encompass each of the following embodiments: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (alone); B (alone); and C (alone).

As used herein, the term “comprising” means that other elements can also be present in addition to the defined elements presented. The use of “comprising” indicates inclusion rather than limitation.

The term “consisting of” refers to compositions, methods, and respective components thereof as described herein, which are exclusive of any element not recited in that description of the embodiment.

Disclosed herein is a Terra-Modulor modular foundation system, an exemplary embodiment of which is shown in FIGS. 1, 4 and 5f. The system 10 both expands the range of soil conditions suitable for modular hydropower systems and improves constructability by also serving to facilitate access and staging. In various embodiments, the system 10 uses a combination of steel pipe piles 12 and sheet piles 14 as deep foundation elements which support pre-cast concrete components that in turn provide a base for a full range of hydropower modules. The system 10 creates a stable and level pad upon which any other module can be assembled. It also provides a means by which to sequentially construct access into a waterway without excavation and to deploy integrated temporary water control without separate cofferdam structures. The system renders the use of cast-in-place concrete unnecessary.

The Terra-Modulor foundation system 10 addresses the challenges of modular construction on reasonable soil foundations and does so without the need for significant excavation or the use of cast-in-place concrete. It does so through the use of two proven and commercially available primary components: A) steel pipe piles 12 in friction used as deep foundation elements for bearing in soil and contiguous steel sheet piles 14 for seepage cutoff and scour protection (as shown in FIGS. 1, 4, 5f and 6); and B) pre-cast concrete pile cap units 16 and pre-cast concrete beams 18a, 18b tied together to form a laminated base slab which serves at the pedestal for assembly of all other module units (as shown in FIGS. 1, 3a-3c, 4 and 5f). Both components are well understood from a design and performance standpoint, as they are widely used in many aspects of foundation, marine, and waterfront engineering. There are numerous instances of dams that are supported on piles, including the USACE-constructed Charles River New Dam in Boston, Mass. Sheet piles are also often described as an option for seepage cutoff in soil foundations under traditional dams. These two systems and their use in various embodiments of the Terra-Modulor foundation system are further described below:

A.1) Steel Pipe Pile Deep Foundation

Steel pipe piles are one type of what is commonly called a “deep foundation” system. Most dams utilize a “shallow foundation” system as the transfer of load from the structure to the underlying natural materials occurs at or near the ground surface through a wide horizontal distribution of stresses. In contrast, “deep foundations” convey superstructure loads below the surface, typically with relatively thin and stiff vertical structural elements, to rely on the bearing capacity of deep soil strata. Piles are one form of deep foundation. Piles can provide bearing capacity through end bearing, side friction, or a combination of both. In the case of shallow (up to 5 to 40 feet below surface) bedrock, end-bearing piles are appropriate. For sites where soils extend much deeper, friction piles (with minor end bearing contributions) are appropriate. The Terra-Modulor foundation system is suitable for both situations. Where shallow bedrock is present, piles will be driven to the bedrock. Where the bedrock is deep, piles will be exclusively in soil and rely on frictional resistance. If the bedrock is shallow enough to drive piles to the top of the bedrock, then the characteristics of the overlying soil are less important. Where the bedrock is very deep, the foundation system is intended for granular soils of medium density or greater and fine-grained soils that of at least medium stiff consistency.

There are a variety of pile materials and shapes. In various embodiments, the Terra-Modulor system 10 uses steel pipe piles 12 because they are commercially available, easily transportable in lengths of up to around 40 feet, and typically installed using machinery mounted on the same type of crane expected to be used to assemble a modular dam system. Steel pipe piles are driven into the ground using vibratory or impact hammers. Corrosion of steel pipe piles is addressed by continuous submergence and through oversizing of pipe wall thickness.

Example

To demonstrate the structural capacity of the system of the present invention to support a modular hydropower installation, a pipe pile foundation has been sized based on a three-high stack of a low-head modular hydropower system (Littoral Power Systems, Inc., New Bedford, Mass., hereinafter “LPS”), which is judged to be representative of such modular systems. Pile design was conducted as per the procedure described in the US Navy NAVFAC Design Manual 7.02 (Foundations and Earth Structures), with the calculations as summarized below:

Using an LPS modular hydropower system as an example of a typical modular dam system leads to the assumption of a total load of 1,000 kips uniformly distributed over a foundation pad of 35 feet in length and 8 feet in width, maximum vertical soil pressure was determined to be approximately 4 kips per square feet (ksf) without deep foundation. Required ultimate pile capacity was thus determined to be approximately 200 kips (or 100 tons) per pile.

Both end-bearing capacity and frictional capacity were considered, assuming a granular material with a typical frictional angle of 32° and interface friction angle of 20° between steel and soils. Both open and close end types were examined.

End bearing was not considered for cohesive soils. A typical cohesion of 750 psf (medium stiff clay) was used for calculation.

These calculations indicate that lines (upstream/downstream) of four 2-foot diameter steel piles with 1-inch (or greater) wall thickness, with lines on 6-foot centers, will be structurally appropriate in medium dense granular soils or medium stiff cohesive soils given piles lengths of approximately 40 feet. Greater embedment length may be required if open ended piles are used in granular soils.

For lower head dams, shorter piles could be used (resulting in cost savings.) Further analyses and development of the pipe pile foundation system, along with integration with the modular superstructure, could result in additional pile length reduction. The piles have the potential to also resist horizontal shear as well as vertical loads (both in compression and in tension). If analyses demonstrate that the pile could provide sufficient resistance to sliding, then the load on the post-tension anchor (for the LPS system) could be greatly reduced or even eliminated, thereby reducing the load on the piles.

A.2) Steel Sheet Pile Cutoff

The steel pipe piles discussed above will serve as the structural support for the modular dam superstructure on a soil foundation. These piles will not, however, effectively control seepage through the soil foundation under the dam. The dam superstructure impounds water aboveground, but water can also flow through the soil below the surface to a greater or lesser extent, depending on the hydraulic conductivity of the soil material. Foundation seepage is a concern because the differential pressure between the headwater and the tailwater has the potential to create seepage gradients that could result in the failure of the structure through heave or piping. Another threat to the foundation comes from the potential for erosion at the toe of the dam. Turbulence from water discharging through the turbine modules or over the spillway modules could result in scour of soil at and under the toe of the dam. The pipe piles will not be an effective mitigation against this potential failure mechanism.

To address both seepage and toe scour, the Terra-Modulor system 10 includes and uses steel sheet piles 14 to create a continuous, essentially impermeable, fundamentally non-erodible barrier at both the upstream and downstream limits of the structure. The sheet piles will be transverse to the upstream and downstream pipe piles and will extend across the full waterway and into both abutments. While the pipe piles are not sufficient to provide seepage and scour control, they can contribute. Commercial systems already exist which integrate and connect pipe piles with steel sheet piles. These include the Pipe-Z system from Nucor Skyline, as shown in FIGS. 2a, 2b and 2c (from Nucor Skyline Technical Product Manual (2019/2020 edition)).

B.1) Pre-Cast Concrete Pile Cap Units

Once the pipe and sheet piles 12, 14 have been driven into the ground, a short length will be left above the “mudline” to provide a seat for the pile caps 16. Pile caps are the structural elements that transfer loads axially into the pile walls. It is common practice in waterfront structures such as piers and docks to use pre-cast concrete elements seated on top of piles to support overlying beams and decks. The Terra-Modulor system 10 of the present invention use similar pre-cast units as pile caps 16. The pile caps 16 may be seated by gravity and/or with mechanical connections. In one embodiment, pile caps are 12 feet long so as to span across two piles 12 (transverse direction) and will be staggered to from row to row to more evenly distribute forces into the piles 12.

B.2) Pre-Cast Concrete Beam Base Slab

It is envisioned that any modular hydropower system would require a stiff, level, and impermeable base slab upon which to assemble and stack the actual modules. In traditional dam construction, this base slab would be constructed of reinforced, cast-in-place concrete. However, cast-in-place concrete has substantial drawbacks in support of a modular system, including: time and effort to assemble forms and reinforcing; need for proximity to a batch plant; placement and finishing labor; and curing time. The Terra-Modulor system uses pre-cast concrete beam elements 18a, 18b to create the base slab. The beam elements 18a, 18b are designed such that their size and weight allow them to be transportable and easily placed using the same crane as would be used to assemble the modules.

The bottom beam 18b is a full width member that seats directly on the pile caps 16 lengthwise in the direction of flow. This is the horizontal structural element that will bridge over underlying soil to transfer all vertical forces into the deep foundation system. In order to keep the weight of these long beams to an acceptable limit, these items will need to be relatively narrow. A first, bottom row of beams 18b is assembled. To assist in load distribution from loaded beams to adjacent ones, the beams 18b will be shaped to provide shear transfer and may be mechanically connected with post-tensioned rods. To address the potentially high levels of bending stress in these elements, the beams have been designed with embedded HSS members to maximize tension capacity at both the top and bottom chords of the beams 18b. These beams are not intended to bear on the underlying soil and in fact could be placed with a gap between the bottom and the underlying soils/sediments. This will eliminate the need for substantial foundation preparation and excavation beyond general leveling.

In order to add stiffness to the slab, a second, top row of beams 18a will be layered on top of the bottom beams 18b at a ninety-degree angle thereto. Post-tensioned tie rods will be used to create monolithic action between the upper and lower beams 18a, 18b, thus increasing the section modulus of the slab as a whole. These upper beams 18a will further serve to distribute loads more evenly to the bottom beams 18b and will improve the water-tight nature of the slab by spanning the lower beams longitudinal joints. As needed, block-outs can be provided for mechanical anchors extending into the foundation or connecting to the pipe piles. The bottom module of the hydropower system can also be seated to the slab by post-tensioning or mechanically connection. FIGS. 3a, 3b and 3c show pre-cast concrete base slab components (i.e., upper and lower beams 18a, 18b) of the system.

The Terra-Modulor foundation system provides a stable and level platform for multiple hydropower module types at sites with relatively shallow bedrock or generally competent soil. The system incorporates steel pipe piles 12, steel sheet piles 14, pre-cast concrete pile caps 16, and a pre-cast concrete laminated beam base slab system (formed from upper and lower beams 18a, 18b). FIG. 4 shows the full system with all components, as in use supporting an LPS modular dam stack.

In addition to providing an appropriate structural system, the Terra-Modulor foundation system 10 provides a system and sequence of constructability that is beneficial to the overall feasibility and cost effectiveness of a modular hydropower system. The foundation system components are commercially available or easily fabricated by regional pre-cast facilities. Component installation is by typical and easily understood construction methods using standard construction equipment of the same type needed to erect the modular dam. The system also serves to provide both access and water control facilities for construction.

The components of the Terra-Modulor foundation system 10 discussed above may be provided in a kit.

An embodiment of the construction and installation sequence for the Terra-Modulor system is described as follows, and as shown in FIG. 5a-5f:

1. Mobilization of equipment to the site (common to all types of dam construction).

2. General site preparation and construction of overland roads to site (common to all types of dam construction).

3. Abutment preparation (common to all types of dam construction).

4. Installation of first pipe piles 12 (˜4 rows) advancing from one abutment into a waterway. In one embodiment, the piles 12 are installed “in the wet” through the water column using a movable template to maintain positioning (FIG. 5a).

5. Installation of upstream and downstream sheet pile 14 rows between previously driven pipe piles 12 (FIG. 5a).

6. Seating of pre-cast concrete pile caps 16 on the piles 12, 14 (FIG. 5b).

7. Placement of temporary construction matting to span between two rows of pile caps to serve as an access staging platform for the crane.

8. Advance crane to the end of the new temporary access staging platform.

9. Repeat Steps 4-8 until all piles and pile caps installed across half width of dam axis.

10. Install longitudinal pre-cast bottom beams 18b of base slab (FIG. 5c).

11. Install temporary upstream and downstream water control plates for half width of dam to allow for additional work to be completed in the dry and maintain flow through other half of waterway.

12. Install top pre-cast beams 18a for base slab (FIGS. 5d and 5e).

13. Install tie-downs 20, as needed (FIG. 5f).

14. Erect modules on completed half of foundation.

15. Remove water control plates for completed half of structure and provide flow through low-level sluices in bottom modules.

16. Repeat process starting from opposite abutment and meeting completed construction in mid-stream.

FIG. 6 shows the positioning of a crane 22 on temporary access staging mats during the construction process of the foundation system 10, wherein the crane 22 is positioning one of the pre-cast concrete pile caps 16 on one of the piles 12. For the 100 foot-long, 30-foot-high dam referenced earlier, it is estimated that total time for construction would be approximately 2.5 months, or a 50 percent reduction over conventional methods. This assumes a pile installation rate of 12 per day and a module stack erection rate of 2 per day. Estimated cost of the foundation system based on unit rates from RS Means Heavy Construction manual is approximately $5,900 per linear foot of dam length.

The next steps for commercialization are refined engineering analyses of the pile foundation and specifically the interface between the foundation and the modules. Additional cost estimate data is needed to better refine installed costs. The actual construction methodologies needed are well-established and generally understood by heavy civil contractors. One clear advantage to the Terra-Modulor system is the ability to drive test piles to verify pile capacity prior to start of dam construction.

The Terra-Modulor foundation system disclosed herein can help to open up potentially thousands of greenfield low-head hydropower sites and allow for the deployment of generation modules at thousands more existing dam sites. Its advantages will assist in making the promise of low-head modular hydropower a reality.

Unless otherwise defined herein, scientific and technical terms used in connection with the present application shall have the meanings that are commonly understood by those of ordinary skill in the art to which this disclosure belongs. It should be understood that this invention is not limited to the particular methodology, protocols, examples, etc., described herein and as such can vary. The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention, which is defined solely by the claims.

Other terms are defined herein within the description of the various aspects of the invention.

The description of embodiments of the disclosure is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. While specific embodiments of, and examples for, the disclosure are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the disclosure, as those skilled in the relevant art will recognize. For example, while method steps or functions are presented in a given order, alternative embodiments may perform functions in a different order, or functions may be performed substantially concurrently. The teachings of the disclosure provided herein can be applied to other procedures or methods as appropriate. The various embodiments described herein can be combined to provide further embodiments. Aspects of the disclosure can be modified, if necessary, to employ the compositions, functions and concepts of the above references and application to provide yet further embodiments of the disclosure. These and other changes can be made to the disclosure in light of the detailed description. All such modifications are intended to be included within the scope of the appended claims.

Specific elements of any of the foregoing embodiments can be combined or substituted for elements in other embodiments. Furthermore, while advantages associated with certain embodiments of the disclosure have been described in the context of these embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the disclosure.

The foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the present aspects and embodiments. The present aspects and embodiments are not to be limited in scope by examples provided, since the examples are intended as a single illustration of one aspect and other functionally equivalent embodiments are within the scope of the disclosure. Various modifications in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and fall within the scope of the appended claims. The advantages and objects described herein are not necessarily encompassed by each embodiment. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. Such equivalents are intended to be encompassed by the following claims.

All patents and other publications; including literature references, issued patents, published patent applications, and co-pending patent applications; cited throughout this application are expressly incorporated herein by reference for the purpose of describing and disclosing, for example, the methodologies described in such publications that might be used in connection with the technology described herein. These publications are provided solely for their disclosure prior to the filing date of the present application. Nothing in this regard should be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention or for any other reason. All statements as to the date or representation as to the contents of these documents is based on the information available to the applicants and does not constitute any admission as to the correctness of the dates or contents of these documents.

Claims

1. A method for constructing and installing a modular foundation system, comprising the steps of:

(a) installing a plurality of pipe piles advancing from a first abutment into a waterway;

(b) installing upstream and downstream sheet pile rows between two or more of the plurality of pipe piles;

(c) seating a plurality of pre-cast concrete pile caps;

(d) placing a temporary construction matting to span between two rows of the plurality of pile caps to serve as an access staging platform for a crane;

(e) advancing the crane to an end of the temporary access staging platform;

(f) repeating steps (a)-(e) until all of the piles and pile caps have been installed across half of a width of a dam axis;

(g) installing longitudinal pre-cast bottom beams of a base slab;

(h) Installing temporary upstream and downstream water control plates for the half of the dam width to allow for additional work to be completed in the dry and maintain flow through the other half of the waterway;

(i) installing top pre-cast beams for the base slab;

(j) installing tie-downs, as needed;

(k) erecting modules on the completed half of the foundation; and

(l) removing the water control plates for the completed half of the foundation.

2. The method of claim 1, further comprising the steps of (m) installing a second plurality of pipe piles advancing from a second abutment into the waterway; and

(n) repeating steps (b)-(l) with in connection with the second abutment, to meet the completed construction in mid-stream.

3. The method of claim 2, further comprising the step of preparing the first and second abutments, the preparing step being performed before step (a).

4. The method of claim 1, wherein step (a) is performed through an associated water column using a movable template to maintain positioning of the pipe piles.

5. A foundation system for modular hydropower systems comprising:

a plurality of pipe piles;

a plurality of sheet piles configured to be arranged transverse to the pipe piles;

a plurality of pile caps configured to be seated on top of the plurality of pipe piles; and

a beam base slab configured to be securely positioned on top of the pile caps.

6. The foundation system of claim 5, wherein the beam base slab includes a first plurality of beams arranged in a first row, and a second row of beams arranged in a second row layered on top of the first row at a ninety-degree angle thereto.

7. The foundation system of claim 6, wherein the beams of the first plurality of beams are tied together.

8. The foundation system of claim 6, wherein the first and second pluralities of beams are secured together by post-tensioned tie rods to create monolithic action between the first and second pluralities of beams, whereby the section modulus of the beam base slab is increased.

9. The foundation system of claim 6, wherein the beams of the first plurality of beams contain embedded HSS members to maximize tension capacity at top and bottom chords of the first beams.

10. The foundation system of claim 5, wherein the pile caps are formed from pre-cast concrete.

11. The foundation system of claim 5, wherein the pile caps are seated by gravity, by mechanical connections or by a combination of gravity and mechanical connections.

12. The foundation system of claim 5, wherein the pile caps have a length that spans across two piles in a transverse direction.

13. The foundation system of claim 12, wherein the pile cap length is 12 feet.

14. The foundation system of claim 5, wherein the pile caps are staggered to more evenly distribute forces into the piles.

15. The foundation system of claim 5, wherein the pipe piles are formed from steel.

16. The foundation system of claim 5, wherein the sheet piles are formed from steel.

17. The foundation system of claim 5, wherein the plurality of pipe piles includes upstream pipe piles and downstream pipe piles.

18. The foundation system of claim 5, wherein one of the plurality of sheet piles is arranged between two of the plurality of pipe piles.

19. The foundation system of claim 5, further including at least one tie-down securable to the base slab.

20. A kit for constructing a foundation system for modular hydropower systems; comprising:

a plurality of pipe piles;

a plurality of sheet piles configured to be arranged between the pipe piles;

a plurality of pile caps configured to be seated on top of the plurality of pipe piles; and

a beam base slab configured to be securely positioned on top of the pile caps, the beam base slab including a first plurality of beams arranged in a first row, and a second row of beams arranged in a second row layered on top of the first row.