Woodcliff Lake Dam Study Hillsdale, New Jersey

Geotechnical Environmental Water Resources Ecological

Submitted to: Borough of Hillsdale 380 Hillsdale Avenue Hillsdale, NJ 07642-2794

Submitted by: GEI Consultants, Inc. 1 Greenwood Avenue, Suite 210 Montclair, NJ 07042

May 2013 Project 132029-0

______Sean T. DiBartolo, P.E., LEED AP Project Manager WOODCLIFF LAKE DAM S TUDY REPORT BOROUGH OF HILLSDALE M A Y 2 0 1 3

Table of Contents

Executive Summary iv ES.1 Overall Summary of Findings iv ES.2 Summary Response to Requested Scope Items from the Borough’s Request for Qualifications v

1. Introduction 1 1.1 Scope of Work 1 1.2 Authorization 1 1.3 Project Personnel 1 1.4 Limitations 2

2. Background 3 2.1 General 3 2.2 Elevation Datum 3

3. Hydraulics and Hydrology Reports and Models 4 3.1 Existing Documentation 4 3.1.1 Review of “Woodcliff Lake Dam PMF Determination” (GFI, 2006) 4 3.1.2 Review of “HEC-HMS, HEC-RAS Hydrology and Hydraulic Analysis” (BS&J, 2010) 5 3.2 Conclusions Related to Hydraulics and Hydrology 7 3.2.1 Conclusions and Recommendations for the Inflow Hydrology and Spillway Sizing Calculations 7 3.2.2 Conclusions and Recommendations for Stream Routing 8

4. New Jersey Rules and Regulations for Dam Safety 9 4.1 General 9 4.1.1 Safe Dam Act 9 4.1.2 Dam Safety Standards 9 4.2 Operation Practices 10 4.3 New Jersey Department of Environmental Protection Dam Application Permit 11 4.4 Conclusions Related to NJDEP Rules, Regulations and Permitting 12 4.4.1 Conclusions and Recommendations Related to Rules, Regulations, and Operational Procedures 12 4.4.2 Conclusions and Recommendations Related to the Construction Permit 12

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5. Flooding Exposure during Construction 13 5.1 General 13 5.1.1 Background on Water Control during Construction 13 5.2 Auxiliary Spillway Construction 13 5.3 Rehabilitation of the Low-Level Outlet 14 5.3.1 Flood Exposure during Drawdown and Cofferdam Construction 14 5.3.2 Embankment Excavation/Backfill and Pipe Repair 15 5.3.3 Reservoir Refilling 15 5.4 Raising the Low-Lying Embankment Areas 15 5.5 Conclusions Related to Flood Exposure during Construction 16

6. Flood Protection Alternatives 17 6.1 General 17 6.2 U.S. Army Corps of Engineers Flood Protection Feasibility Study 17 6.3 Off-site Flood Storage Alternative 18 6.4 Floodwater Conveyance Alternative 18 6.5 Conclusions Related to Flood Protection Alternatives 19 6.5.1 Conclusions and Recommendations Related to Downstream Flood Protection Alternatives 19 6.5.2 Conclusions and Recommendations Related to Rehabilitation Alternatives Impact on Flood Protection 19

7. Recommendations for Future Actions to Evaluate Pascack Brook Flood Mitigation 21 7.1 Request a Review of the Inflow Hydrology and Spillway Design 21 7.2 Proceed with Dam Rehabilitation Efforts 21 7.3 Develop a Water Resource System Model 22

References 23

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Table of Contents (cont.)

Tables 1 USACE Flood Protection Feasibility Study Results 2 Historic Event Precipitation and Peak Inflow (BS&J, 2010)

Figures 1 Cross Section 1.11 (from BS&J HEC-RAS Model) 2 Cross Section 1.11 with Obstructions and Revised Manning’s “n” 3 Significant Structures along Pascack Brook 4 Flood Control via Water Transfers Alternatives 5 Profile from Woodcliff Lake to Wood Dale County Park 6 Profile from Woodcliff Lake to Musquapsink Brook

Appendices A Construction Activities and Temporary Water Control B Specifications for Cofferdam and Reservoir Lowering, Fish Salvage, and Relocation

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Executive Summary

ES.1 Overall Summary of Findings This report presents an independent evaluation performed by GEI Consultants, Inc. (GEI) for the Borough of Hillsdale of the improvements to the Woodcliff Lake Dam located in Hillsdale, New Jersey, proposed by United Water New Jersey, Inc. as designed and submitted by Buck, Seifert & Joist, Inc. (BS&J). Based on our review of the information provided, we have developed the following overall opinions concerning the design of the safety improvements proposed for the dam and their potential impacts on downstream flooding conditions.

As it is currently constructed, the Woodcliff Lake Dam and spillway cannot safely pass the current Spillway Design Flood (SDF) without overtopping of the dam. The NJDEP has issued a compliance order to United Water mandating the dam undergo rehabilitation to safely pass the SDF. The rehabilitated spillways should be large enough to pass the SDF and prevent the dam crest from overtopping. If the spillways are not capable of passing the SDF, the dam is at risk of failure and while the risk of failure is low, it is important to correctly rehabilitate the dam in a timely manner.

Based on our review of the inflow hydrology and spillway sizing calculations, we think the design flood may be larger than is currently estimated and the spillway capacity to convey floodwater may be less than currently estimated. This implies the dam may be undersized to pass the SDF without overtopping the dam. We recommend the magnitude of the SDF and capacity of the spillways be verified by United Water and NJDEP to ensure the current proposed design provides adequate protection against failure.

It is our opinion that there will not be a significant change in flood scenarios once the dam is reconstructed and the areas downstream will still have flooding conditions during significant storm events.

The flooding of Pascack Brook under smaller, more frequent events was qualitatively analyzed to the extent possible. We have reviewed the HEC-RAS (Army Corps Hydrologic Engineering Center - River Analysis System) model prepared by BS&J and found that it is unsuitable for evaluation of flooding of Pascack Brook downstream of the dam because it lacks sufficient site-specific detail to reliably predict flood impacts. In its present configuration, the model cannot be used effectively to evaluate downstream flooding.

Significant modifications to the HEC-RAS model would be required in order to quantitatively analyze various flooding scenarios. However, we have reviewed the available data and it is GEI’s general opinion that the primary cause of the downstream flooding is

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related to the limited channel capacity of Pascack Brook, constrictions along its length, and encroachment into the floodplain. Without significant modifications of these elements, Pascack Brook will continue to flood regardless of the dam configuration.

ES.2 Summary Response to Requested Scope Items from the Borough’s Request for Qualifications GEI was contracted by the Borough of Hillsdale to address nine specific tasks for our evaluation. Our summary responses for these tasks are as follows. More detail discussion is presented in the body of this report.

1. Review NJDEP Dam Permit issued by NJDEP for improvements plan.

We reviewed the dam permit issued by NJDEP and recommend that Hillsdale request the NJDEP Bureau of Dam Safety review the final construction water control plan and inspect water control facilities upon construction.

2. Review the hydraulic model used for maximum precipitation/flood determination. Determine if the project will increase downstream flooding of the Pascack Brook.

We have reviewed the HEC-RAS (Army Corps Hydrologic Engineering Center - River Analysis System) model prepared by BS&J and found that is unsuitable for evaluation of flooding of Pascack Brook downstream of the dam because it lacks sufficient site-specific detail to reliably predict flood impacts. In its present configuration, the model should not be used to evaluate downstream flooding and significant modifications to the HEC-RAS model would be required in order to complete this task. Note that it was not a part of our scope to develop a suitable HEC-RAS model to evaluated downstream flooding.

3. Review dam improvements plan and consider design alternates to affect similar, but better possible outcome.

As stated above, it is GEI’s opinion that the primary cause of the downstream flooding is related to the limited channel capacity of Pascack Brook, constrictions along its length, and encroachment into the floodplain. Without significant modifications of these elements, Pascack Brook will continue to flood regardless of the dam configuration. Also, development of a more comprehensive HEC-RAS model would be required to evaluate possible dam operation scenarios that may help to mitigate some downstream flooding issues for some of the more minor flooding events.

4. Identify adverse effects of reconstruction, if any, during typical flood scenarios (i.e. 5-, 25-, 50-, 100-year type storm frequencies) to the Borough both at dam and downstream in Hillsdale.

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As described in Item 2, the existing HEC-RAS model is not sufficiently developed for flood routing analyses purposes and we were not able to address this item.

5. Identify adverse effects to stream corridor performance, if any, during 2-year anticipated reconstruction period i.e. reservoir surface lowering and fixation of bascule gates.

Under all likely scenarios, it is our opinion that the proposed construction would not increase flood exposure in the downstream reach of Pascack Brook above what would be observed under current conditions or after construction is completed.

6. Recommend dam design/construction technique changes to affect potentially better dam safety and flood mitigation outcome, if any, for Hillsdale.

We recommend that Hillsdale request the NJDEP Bureau of Dam Safety review the final construction water control plan and inspect water control facilities upon construction to ensure flood mitigation measures are adequately addressed.

7. Will the energy dissipaters at the toe of the dam be sufficient to reduce floodwater velocity to protect the downstream Pascack Brook channel?

As described in Item 2, the existing HEC-RAS model is not sufficiently developed for analysis purposes and we were not able to be evaluate this question with the information we were provided.

8. Attend one conference with Mayor & Council representatives, and one municipal public hearing.

If desired by Hillsdale upon receipt of our final report, we will attend these meetings to present our findings.

9. The reconstruction of the dam will not increase flooding to the Borough of Hillsdale.

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1. Introduction

GEI Consultants, Inc. (GEI) prepared this report to present an independent evaluation of the improvements to the Woodcliff Lake Dam located in the Borough of Hillsdale (Hillsdale) proposed by United Water New Jersey, Inc. (United Water) as designed and submitted by Buck, Seifert & Joist, Inc. (BS&J).

1.1 Scope of Work We performed the following scope of work for this evaluation:

. Reviewed existing documents provided to us, including the New Jersey Department of Environmental Protection (NJDEP) Dam Permit, BS&J hydrologic models, Boswell McClave Engineering Report and the United Water dam improvements plan. Specific document references are provided below; . Evaluated adverse effects to stream corridor performance, if any, during the 2-year anticipated reconstruction period (i.e., reservoir surface lowering and fixation bascule gates in place); . Developed conceptual alternatives for improving the functionality of the dam and improving the downstream flooding conditions; and . Developed recommendations for possible dam design/construction technique changes to affect potentially better dam safety and flood mitigation outcomes for Hillsdale.

1.2 Authorization This work was authorized by the Borough of Hillsdale and was performed according to an agreement dated December 14, 2012, and executed December 31, 2012, between GEI and the Borough of Hillsdale to provide engineering services to the Borough of Hillsdale for the Woodcliff Lake Dam Study Project.

1.3 Project Personnel The following GEI personnel are responsible for the work described in this Report:

. Sean T. DiBartolo, P.E., LEED AP Project Manager . Kerri Price, P.E. Project Engineer . Richard Westmore, P.E. Technical Reviewer . Joseph Engels, P.E. In-House Consultant

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1.4 Limitations The professional services for preparing this report were performed in accordance with generally accepted engineering practices; no other warranty, express or implied, is made.

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2. Background

2.1 General Woodcliff Lake Dam, located in Bergen County, New Jersey, was built in 1903 and upgraded in 1984 and 2001. The existing 35-foot-high, 1,500-foot-long earthen dam is a Class I High Hazard Dam under New Jersey Dam Safety Standards. Water discharges to Pascack Brook through the 130-foot-long primary spillway. Pascack Brook runs through Hillsdale for approximately 6.5 miles before discharging into Oradell Reservoir.

The dam is owned by United Water and is operated for water supply purposes. United Water’s storage system consists of Lake Deforest, Lake Tappan, Woodcliff Lake Reservoir, and Oradell Reservoir.

As it is currently constructed, the Woodcliff Lake Dam and spillway cannot safely pass the current Spillway Design Flood (SDF) without overtopping of the dam. The NJDEP has issued a compliance order to United Water mandating the dam undergo rehabilitation to safely pass the SDF. United Water has proposed several improvements to the existing Woodcliff Lake Reservoir Dam and has obtained the approval and permits for the project from the NJDEP in November 2011. The proposed improvements include:

. Construction of an auxiliary “over-the-dam” reinforced concrete spillway with overtopping protection; . Rehabilitation of the low-level outlet; . Raising of two low-lying reservoir embankment areas; . Removal of the existing downstream gatehouse and appurtenances; and . Installation of two new toe drain weir chambers.

The intent of the dam rehabilitation is ensure the dam can safety pass large flood events and to prevent catastrophic failure of the dam. The rehabilitation and improvements are not being performed for flood mitigation purposes.

2.2 Elevation Datum Elevations provided in this report are referenced to the National Geodetic Vertical Datum of 1929 (NGVD29).

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3. Hydraulics and Hydrology Reports and Models

3.1 Existing Documentation A number of hydrology studies have been conducted in the past 20 years to estimate the magnitude of the Spillway Design Flood (SDF) to be used in designing the spillway dimensions. A timeline of relevant work is presented below.

. 1994 – BS&J prepared a Spillway Design Flood Report (not provided to GEI). . June 2003 – BS&J conducted HEC-1 modeling (not provided to GEI). . February 2006 – Gannet Fleming, Inc. (GFI) modeled the SDF by modifying the 2003 BS&J HEC-1 model. GFI estimated that the peak design inflow was 29,700 cubic feet per second (cfs). . July 2007 – BS&J prepared a SDF report proposing to decrease the design flood to 27,500 cfs. . December 2007 – NJDEP rejected the 2007 BS&J reduced design flood and established the peak design inflow to be 29,700 cfs. . July 2010 – BS&J prepared a report on the hydrologic and hydraulic elements of the project (HEC-HMS model and report not provided to GEI). . August 2010 – NJDEP reviewed the BS&J model and report and made several comments to be considered during final design. . October 2010 – BS&J revised the 2010 report and estimated the peak inflow to be 30,450 cfs. Pascack Brook downstream of the dam is modeled using HEC-RAS. . January 2011 – BS&J prepared the Engineer’s Design Report summarizing the design elements related to the rehabilitation of Woodcliff Lake Dam.

Of the reports that were provided to GEI, the two most significant for our review are the GFI (February 2006) and BS&J (October 2010) reports, the salient aspects of which are summarized below.

3.1.1 Review of “Woodcliff Lake Dam PMF Determination” (GFI, 2006) The Probable Maximum Flood (PMF) accepted by the NJDEP and used as the SDF in the proposed dam improvements is 29,700 cfs. This SDF was developed by GFI in 2006 and is documented in the report titled, “Woodcliff Lake Dam PMF Determination” (GFI, 2006). A digital version of the supporting HEC-1 files was not provided to GEI but a printout of the model input files was provided in Appendix B of that report.

The procedures used by GFI to estimate the magnitude of the PMF are generally conservative and are consistent with accepted practices. The drainage basin (18.5 square miles) was modeled using 11 sub-basins that were further broken down into 76 subdivisions defined by

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soil type. Delineation of a relatively small drainage basin into 11 sub-basins is not typical, but it appears GFI was attempting to achieve a higher level of refinement.

Based on our review, it is our opinion that GFI prepared a generally thorough and complete report that describes the procedures used. Aspects of their study that may impact the magnitude of the new spillway design flood are discussed below.

There are several soil types that were assumed to have a very high saturated conductivity 1 (KSAT), with the greatest KSAT used in the HEC-1 model being 25.47 inches per hour . GEI cross-checked the numerical values of saturated conductivity published in the Natural Resources Conservation Service (NRCS) Soil Survey database and it is our opinion that the values used are correct for the given soil type. However, the GFI loss rate was estimated using the conductivity for all soils contained within the upper three layers of the soil profile and many of the high conductivity soils appear in the lower layers of the soil profile. General guidelines for estimating KSAT suggest that for infrequent events (greater than the 100-year 2 storm) the upper 18 inches of soil be examined and the KSAT of the confining layer be used throughout (Sabol, 2008). The overall effect of changing KSAT, as described above, will likely be an increase in the magnitude of the PMF in terms of runoff volume and peak discharge.

3.1.2 Review of “HEC-HMS, HEC-RAS Hydrology and Hydraulic Analysis” (BS&J, 2010) In 2010, BS&J prepared a report to finalize the hydrologic and hydraulic analysis for the Woodcliff Lake Dam and make recommendations for spillway sizing. This report also includes: the BS&J estimate of the SDF (routed outflow); hydraulic analyses, including HEC-RAS modeling, of the primary spillway, auxiliary spillway and Pascack Brook between Woodcliff Lake Dam and Oradell Reservoir; and the spillway sizing methodology.

3.1.2.1 Inflow Hydrology Review (HEC-HMS) To finalize the hydrologic analyses presented in their “Spillway Design Flood Recommendations” (BS&J, 2007), BS&J updated the existing GFI HEC-1 model. The HEC-1 model was revised to run in HEC-HMS to account for software updates and the results from the HEC-HMS and HEC-1 models were compared. The HEC-HMS model files were not provided to GEI.

BS&J states the only minor changes to the GFI HEC-1 model were made when it was updated to run in HEC-HMS. The HEC-HMS modeling results differ from the HEC-1 results calculated in 2007 and the change in the magnitude of the peak inflow magnitude can

1 The relationship between saturated conductivity and runoff is inversely proportional; higher saturated conductivity results in less runoff (lower runoff volumes and lower peak flows). 2 The layer with the lowest saturated conductivity.

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be attributed to variations in the software packages. The GFI SDF peak inflow is 29,700 cfs (HEC-1) and the updated BS&J SDF peak inflow is 30,450 cfs, an increase of 750 cfs.

Despite the documented increase to the SDF, future BS&J work, including the “Engineer’s Design Report” that describes the final design (BS&J, 2011), uses 29,700 cfs as the design flood. Based on the information we reviewed, it is unclear why the peak inflow was not increased to 30,450 cfs.

3.1.2.2 Spillway Sizing Review The proposed spillway system is composed of two spillways, the primary and auxiliary spillways. Design inflows are routed through Woodcliff Lake Dam and discharge through the spillways. The spillways are sized to pass a SDF of 29,700 cfs.

The primary spillway elevation-discharge curve should be re-evaluated to account for the following considerations:

. The bridge spanning the spillway is likely to reduce its capacity during the SDF and this effect should be modeled. . The bascule gate discharge curve should be examined. A weir equation with coefficient of 3.2 to 3.95 is likely not appropriate and may overestimate the spillway capacity under some conditions. Under upright conditions the gate would behave similarly to a sharp-crested weir with a coefficient of 3.33. As the gate is lowered into a horizontal position, the gate acts similarly to a broad-crested weir and the discharge coefficient would likely vary between 3.3 (near vertical) and 2.7 (horizontal).

The auxiliary spillway discharge should be re-evaluated:

. It may be more appropriate to plan the vertical curves at 30 to 35 miles per hour in order to reflect more realistic driving speeds. This would extend the length of the vertical curve and decrease the auxiliary spillway capacity. . The auxiliary spillway should be evaluated as a broad-crested weir with a single discharge coefficient for all water surface elevations to be consistent with accepted methodology. . The methodology for estimating spillway outflow above reservoir El. 102 needs to be explained. (Do the primary and auxiliary spillways act as a single weir? Is bridge deck interference ignored?).

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3.1.2.3 Stream Routing Review (HEC-RAS) The HEC-RAS model developed by BS&J would require significant refinement so that it could be used to more accurately analyze the downstream flood conditions or to further evaluate the different spillway configuration designs.

Generally, the model contains insufficient detail to accurately represent the site conditions and the model, as provided to GEI, is not developed to level where it should be used to analyze spillway design scenarios, develop a tailwater rating curve, or estimate inundation limits and flood depths downstream of the dam.

The following is a list of issues that in our opinion would need to be addressed prior to the model being used for the analyses described above. These items should be considered applicable for both the existing and proposed dam models.

. Additional cross sections are required to improve model stability and convergence. . Downstream structures need to be modeled. The current model does not appear to account for any development in the channel or floodplain. o The buildings, houses, and other structures within the floodplain need to be modeled as obstructions to flow. Figures 1 and 2 depict two versions of the same cross section. Figure 1 shows Cross Section 1.11 as modeled by BS&J and Figure 2 shows the same cross section accounting for obstructions and an increased in the value of Manning’s n-value. Figure 3 shows where Cross Section 1.11 is located.

o Based on our review of aerial photographs, there are 10 downstream roadway bridges and one railroad bridge that cross the downstream reach. These need to be included in the HEC-RAS model. Figure 3 shows the location of the bridges located between Woodcliff Lake Dam and Oradell Reservoir.

Manning’s n-value should be revised to reflect the presence of vegetation, trees, and structures. We would expect n-values to vary along the downstream reach to reflect changing floodplain conditions. The current n-value is too low and does not change between Woodcliff Lake and Oradell Reservoir.

3.2 Conclusions Related to Hydraulics and Hydrology

3.2.1 Conclusions and Recommendations for the Inflow Hydrology and Spillway Sizing Calculations Based on our review of the inflow hydrology and spillway sizing calculations, we have the following comments, conclusions and recommendations:

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. The inflow hydrology (GFI, 2006) may be overestimating the saturated hydraulic conductivity and, therefore, the total runoff may be underestimated. . The higher SDF resulting from updating the HEC-1 model into HEC-HMS is not accounted for in the final design (BS&J, 2010). . The primary and auxiliary spillways calculations may overestimate the flow capacity (BS&J, 2010).

The combination of these elements produces a situation where the design flood is larger than currently estimated and the spillway capacity to convey floodwater may be less than currently estimated. This implies the dam may be undersized to pass the SDF without overtopping the dam. We feel the proposed dam design will adequately pass very large events but may be unable to safely pass the SDF when the considerations discussed in Sections 3.1.2.1 and 3.1.2.2 are addressed.

We recommend the magnitude of the SDF and capacity of the spillways be verified by United Water and NJDEP to ensure the current proposed design provides adequate protection against failure. Additionally, if the inflow hydrology is reevaluated, we recommend that the magnitude of the probable maximum precipitation (PMP) be verified. Significant rainfall events have been observed since 2007 (including Hurricane Irene and Hurricane Sandy) and these events may influence the PMP magnitude.

3.2.2 Conclusions and Recommendations for Stream Routing The HEC-RAS model developed by BS&J requires significant refinement prior to being used to accurately analyze the downstream flood conditions or to further evaluate the different spillway configuration designs. Generally, the existing HEC-RAS model developed by BS&J is not, in GEI’s opinion, adequately developed to a level where it should be used to analyze spillway design scenarios, develop a tailwater rating curve, or estimate inundation limits and flood depths downstream of the dam.

Unless additional modeling has been performed to prepare inundation mapping, and was not provided to GEI, it is recommended that the adjacent communities request that a better model be used to develop inundation mapping. This will ensure that all property owners within the flood zone are properly identified and may be contacted in case of an emergency.

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4. New Jersey Rules and Regulations for Dam Safety

4.1 General To develop a plan for long-term successful and safe dam operation, it is important for the downstream communities to understand the responsibilities of the dam owner. The dam owner, United Water, is held to the safety and operational standards documented in the Safe Dam Act (N.J.S.A. 58:4) and the Dam Safety Standards (N.J.A.C. 7:20). These documents and their implications for the nearby residents are further discussed below.

4.1.1 Safe Dam Act The Safe Dam Act (N.J.S.A. 58:4) was originally put into New Jersey law in 1912. It generally asserts that all dams must be properly cared for by the owner and the NJDEP must be involved when modifications to the dam are taking place. Specific clauses that help protect the upstream and downstream users are outlined below:

. All dams must be inspected by a professional engineer – the frequency of inspection varies depending on the size and classification of the dam. . No dams can be built, repaired, altered, or removed without consent of the NJDEP. . Any party owning or representing property that could be damaged by the breaching of the dam can submit a written request to the NJDEP for a thorough inspection of the dam or reservoir. . When a dam has been in existence for over 20 years and property owners and communities rely on its presence and added value, the dam owner may not remove the dam or decrease the water level without consent from the NJDEP.

With respect to the downstream users’ interests, the Safe Dam Act serves two important functions: 1) gives power to the State to ensure proper dam construction, maintenance and operation is taking place, and 2) assures that the dam cannot be removed after a community has developed around it.

4.1.2 Dam Safety Standards The Dam Safety Standards (N.J.A.C. 7:20) outline the submittals required for dam owners to acquire permits. There are a few clauses that help protect the adjacent property owners:

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. Backwater created by a dam during a 100-year storm shall be the minimum which is contained within the applicant's property unless written consent is obtained from all potentially affected property owners. . The diversion facility during construction must remain open and no water may be permanently stored in the reservoir until the owner demonstrates to the NJDEP that storage of water will neither interfere with construction activities nor create a hazard to life, health or property. . The owner or operator of all Class I and II dams shall prepare and use an Emergency Action Plan (EAP), as described in N.J.A.C. 7:20-1.7(f).

To produce documentation related to the first and third items, the client would require inundation mapping to be developed. As described in Section 3.1.2.3, the existing HEC-RAS model developed by BS&J is not, in GEI’s opinion, adequately developed to prepare inundation mapping.

Implications of the second item are further discussed in Section 5.1.

4.2 Operation Practices The NJDEP Office of Dam Safety and Flood Control does not maintain a guidance document specifically addressing the responsibilities and best practices dam owners should follow relative to operations practices. However, general guidelines from other state agencies and the Association of State Dam Safety Officials (ASDSO) are available. While proper operation practices for dam owners can be a complicated issue, the guidelines relating to downstream flooding can be simplified into the following statements:

. The dam owner shall not operate the dam in a manner that will increase flooding above what would be observed if the dam were not in place. o During a flood event, the mere presence of a dam and reservoir usually decreases the peak flow because attenuation is created.

. The dam owner shall do whatever is necessary to keep the dam from failing. o If the dam does fail, the dam owner will be (in almost all cases) strictly responsible for damages.

It should be noted that there is no guideline stating that the dam owner should change operations in anticipation of a flood event. In fact, the NJDEP advises dam owners to not modify their operational procedures (i.e., lowering the water level or trying to time releases) to try to mitigate flooding (Dewey Lima, NJDEP, personal communication). The NJDEP give the following reasons for this recommendation:

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. Increasing discharge may create flooding downstream. . Decreasing discharge may protect downstream property but cause flooding or other damage upstream. . New Jersey contains 1,600 dams and there is no coordination between owners making releases in anticipation of flood events. Therefore, the effects of released water could compound throughout a drainage system and additional properties could flood, possibly properties that may not have flooded without releases in advance of flood events.

4.3 New Jersey Department of Environmental Protection Dam Application Permit The Dam Application Permit (Permit) was issued by NJDEP on November 07, 2011, and is set to expire November 07, 2013. Issuance of the Permit was based on submittal of the construction drawings (last revised July 22, 2011) and the technical specifications (dated July 2011), both prepared by BS&J. The Permit grants permission to construct an auxiliary spillway, rehabilitate the low-level outlet, and rehabilitate the dikes on Woodcliff Lake Dam.

The portion of the Permit of most interest to the adjacent residents relates to the construction water control plan. The typical procedure for design and construction of a water control/diversion plan is described further in Section 5.1.1 and is summarized below:

1. The design engineer produces a conceptual design of the water control plan and provides applicable specifications describing the water control plan design requirements; 2. The conceptual design, along with the final construction drawings, specifications, and Engineer’s Design Report, is submitted for a construction permit; 3. NJDEP reviews the submitted documents, may request changes, and ultimately approves a permit; 4. The contractor designs the final water control plan; 5. The design engineer reviews the final water control, may request changes, and ultimately approves the final water control plan; 6. The water control plan is constructed and operated.

The only reference to the water control/diversion plan is found in Paragraph 5 of the Terms and Conditions in the NJDEP Permit and indicates that “…safety requirements and special construction techniques, including a water diversion plan…may be included in the contract specifications. If not, these items, especially those that may involve the safety of personnel during construction, should be detailed in the inspection program.” In this case, the water control/diversion plan is addressed in the specifications and, therefore, the water control plan is not required to be part of the formal inspection program performed by the NJDEP.

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4.4 Conclusions Related to NJDEP Rules, Regulations and Permitting

4.4.1 Conclusions and Recommendations Related to Rules, Regulations, and Operational Procedures It is important for downstream communities to understand the governing laws that are in place to help minimize the hazards to life, health, and/or property created by dams. Safe and responsible dam operation is critical to downstream residents’ well-being and using a water supply dam as a flood mitigation system needs to be approached cautiously. There are no rules stating that the dam owner should change operations in anticipation of a flood event and the NJDEP advises dam owners not to modify their operational procedures to try to mitigate flooding. With this in mind, it appears United Water is still amenable to discussions regarding using the dam to mitigate downstream flooding.

GEI recommends that prior to making any operational changes (i.e., lowering the water surface elevation or trying to time releases) several tools and data points be developed to prevent the unintentional increase in flooding. These include:

. Accurate rainfall forecasts with sufficient lead-time to allow for releases (the rule-of-thumb for lowering the water surface is that the rate of lowering should not exceed 1 foot per day); . The controlling channel capacity downstream of the reservoir needs to be identified; . HEC-RAS modeling capable of predicting flood depths and optimizing release timing needs to be developed. The model should be able to be run by a qualified operator in advance of a storm to help optimize operational changes.

The downstream communities need to be aware that there is little legal benefit for a dam owner to change operations on an event-by-event basis and reliance upon an owner to help mitigate flood flows may not be a viable long-term solution to flood mitigation.

4.4.2 Conclusions and Recommendations Related to the Construction Permit The portion of the Permit of most concern to the downstream communities is the construction water control plan and the fact that the final water control plan are not required to be submitted for review by the NJDEP. Unless a review of the final water control plan by NJDEP is required in documents not provided to GEI, it is recommended that the downstream communities request such a review. Additionally, due to the nature of flood downstream of Woodcliff Lake Dam, it is also recommended an inspection of the constructed water control facilities be performed.

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5. Flooding Exposure during Construction

5.1 General There are three main elements to the proposed construction:

. Auxiliary spillway construction. . Rehabilitation of the low-level outlet. . Raising the low-lying embankment area.

GEI performed an analysis of the proposed design description contained in the Engineer’s Design Report (BS&J, 2011) and a BS&J memo dated January 25, 2011, describing the temporary water control procedures. These documents are reproduced in Appendix A.

5.1.1 Background on Water Control during Construction According to standard practice, responsibility for water control during a construction process ultimately falls to the contractor. The design engineer usually creates a conceptual design for water control (pumping, piping, diversions, cofferdams, etc.) that will prevent water from entering the area of construction and/or protect it from a design storm. While this conceptual design appears in the design drawings and bid documents, the contractor is responsible for submitting his own work plan that is designed and stamped by a Professional Engineer. The contractor generally must submit his work plan a few weeks prior to when the water control is needed to continue construction. The work plan is then reviewed by the design engineer and the project owner and they can request revisions be made or accept the work plan as designed.

Because the contractor is allowed to establish his means and methods for construction, some elements of the water control plan are not specified in the concept design and will not be communicated by the contractor until later in the construction process. The construction specifications outline the responsibilities of the contractor and the submittal timeline. The specifications for this project relevant to the water control are shown in Appendix B.

5.2 Auxiliary Spillway Construction The first phase of construction was scheduled to run from March 1 to September 1, 2012 (about 7 months) based on the project delivery schedule provided in the Engineer’s Design Report (BS&J, 2011). During Phase I, the contractor will notch out a piece of the top of the dam to form an auxiliary spillway, provide overtopping protection, and widen Church Road. The bascule gate will be fully lowered (El. 89) and the observed flow in Pascack Brook should be approximately equal to the flows that would occur without construction activities.

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These proposed construction activities should not interfere with the structural integrity of the dam.

In the event of a large flood event, the dam operations will be unaffected up to a flow rate of 7,200 cfs (about a 50-year event). This assumes the contractor is required to over excavate below the proposed roadway elevation of El. 96.75 to El. 95. Flows that raise the water surface elevation to the level of the contractor’s excavation would overtop the dam through the area being constructed and damage to the dam could occur.

5.3 Rehabilitation of the Low-Level Outlet The second phase of construction was scheduled to run from September 1 to November 1, 2012 (about 2 months). Over the first 30 days of Phase II construction, the contractor will lower the reservoir level to El. 60 by opening the low-level outlet. When the reservoir is drained, the contractor will construct a cofferdam around the outlet works intake structure. The design concept presented by BS&J sizes the cofferdam for the 100-year event, although the contractor may consider designing for a lesser event. The cofferdam is designed using sheet piles and sheeting, similar to the cofferdam that was used during construction in 1984.

After the cofferdam is constructed, the contractor will excavate through the dam to expose the existing outlet pipe at which time repairs/replacement of the pipe will occur. The excavation will be backfilled and the dam will be rebuilt to the original dam crest elevation. With the outlet works construction protected by the cofferdam, the reservoir will be refilled to El. 89. At the end of construction, the cofferdam sheeting and above-grade sheet piles will be removed by divers.

As described in Section 5.1.1, the water control design will not be finalized until near the time of drawdown. Additionally, the design concept presented by BS&J does not present a method of water control for inflow from Pascack Brook but leaves the streamflow control method up to the contractor. With this in mind, it is not possible to fully evaluate the additional exposure to flooding during this phase of the construction. It should be noted that the proposed construction procedures appear consistent with standard practice.

In lieu of a full evaluation, the construction stages required can be described and analyzed. The analyses below assume no additional water control measures are in place than those that are described in the engineering design report and memo shown in Appendix A (e.g., water from Pascack Brook would enter the reservoir uncontrolled).

5.3.1 Flood Exposure during Drawdown and Cofferdam Construction During drawdown, the dam is fully intact and the spillways are operational. Should a flood event occur under the most critical conditions (water level not yet lowered), the bascule gate

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will be fully opened (El. 89), and the observed flow in Pascack Brook should be approximately equal to the flows that would occur without construction activities. If a flood event were to occur during drawdown, or during the construction of the cofferdam, the reservoir would begin to fill and floodwaters would be stored. This scenario would lessen flood exposure in the downstream reach of Pascack Brook.

5.3.2 Embankment Excavation/Backfill and Pipe Repair In the scenario where the reservoir is lowered and there is an open excavation through the dam, the flooding would be similar to pre-dam conditions. Pascack Brook water would flow into the reservoir area following the approximate location of its historical channel, and would leave through the open excavation and discharges into Pascack Brook downstream of the dam. Floodwaters entering the reservoir would pass downstream without attenuation and the flood exposure will not increase during this stage of Phase II construction.

There is a single hypothetical exception to the above description. For a case where the inflow exceeds the flow capacity of the opening of the excavation, the reservoir would begin to fill. Because the dam would have an open excavation, the structural integrity of the dam could be compromised and the dam could be damaged or even fail and release any stored water from the flood. In this unlikely, hypothetical scenario, the flood exposure downstream of the dam would be greater.

5.3.3 Reservoir Refilling While the reservoir is being refilled, the exposure is the same as described in Section 5.3.1.

5.4 Raising the Low-Lying Embankment Areas The third phase of construction is scheduled to run from November 1 to December 1 the following year (about 13 months). During Phase III, the contractor will fill two low-lying embankment areas to raise and protect them from wave run-up. The bascule gate will be fully lowered (El. 89) and the observed flow in Pascack Brook should be approximately equal to the flows that would occur without construction activities. The proposed construction activities should not interfere with the structural integrity of the dam.

In the event of a large flood event, the primary and auxiliary spillways should be fully operational and the dam spillway should be able to pass the SDF safely. Flows and/or wave action that rise to the level of the contractor’s embankment could damage ongoing construction but damage in excess of the current conditions is not expected.

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5.5 Conclusions Related to Flood Exposure during Construction Under all likely scenarios, we do not feel a flood event during construction would increase flood exposure in the downstream reach of Pascack Brook above what would be observed if the dam were not in place.

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6. Flood Protection Alternatives

6.1 General Fundamentally, there are a limited number of methods for providing flood control: 1) floodwater can be stored, either on site or conveyed to storage off site; 2) floodwater can be diverted and released into another stream or conveyance mechanism; 3) making channel improvements to increase flow capacity; and 4) protecting individual properties. Some of these alternatives have been looked at in detail for Pascack Brook over the years while others have not.

As discussed in Section 4, storing floodwater behind Woodcliff Lake Dam does not appear to be a viable long-term solution for flood control downstream of the Dam. The U.S. Army Corps of Engineers (USACE) studied the feasibility of channel improvements in 1977. Boswell McClave Engineering briefly evaluated the alternative of piping flows between Woodcliff Lake and Oradell Reservoir. However, additional alternatives for flood control have not been evaluated. The USACE 1977 study and two conceptual alternatives are discussed below.

The two alternatives proposed by GEI described in Sections 6.3 and 6.4 are conceptual and no consideration has been given to construction costs, land acquisition, permitting, water rights, environmental regulations, or engineering concerns. To evaluate if they are viable alternatives for flood control, further studies would need to be conducted.

6.2 U.S. Army Corps of Engineers Flood Protection Feasibility Study The USACE performed a flood protection study for Pascack Brook in 1977 (USACE, 1977). The intent of this study was to evaluate the feasibility of providing flood control measures along Pascack Brook to mitigate flood damages. The USACE-evaluated flood protection scenarios that included excavating Pascack Brook and widening the channel top width and providing flood wall and levee improvements.

The results of the USACE study are provided in Table 1 and reflect channel improvements between Woodcliff Lake Dam and Oradell Reservoir. The 1977 costs presented in the table below are updated to 2013 costs and are estimated. Many elements critical to the USACE analysis have changed since 1977: record storm events, additional development, flood analysis computing/modeling technology, construction methods, and even Woodcliff Lake Dam itself has changed. It is likely the costs and flood mitigation measures presented in Table 1 would change significantly if the USACE study were to be redone today.

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Table 1: USACE Flood Protection Feasibility Study Results

Number of Bridges Estimated First Flood Mitigation Estimated First Design Storm Requiring Cost (2013 Measures Cost (1977 USD) 1 Replacement USD) Excavate channel 4 to 5 feet, widen 100-year 4 $5,833,000 $76,000,000 top width to 70 to 90 feet Excavate channel 4 to 5 feet, widen 200-year 5 $7,040,000 $92,000,000 top width to 90 to 110 feet 9-foot-high walls 100-year and 10-foot-high 0 $8,890,000 $116,000,000 levees 1 The conversion between 1977 USD and 2013 USD was based on the ENR Construction Cost Index (CCI). The index values for 1977 and 2013 were 2,576 and 9,437, respectively.

6.3 Off-site Flood Storage Alternative This alternative proposes that water be pumped from Woodcliff Lake to the nearest open area located to the east of Woodcliff Lake, near Wood Dale County Park. A flood storage facility could be constructed in the wooded area south of Prospect Avenue. A preliminary sizing from aerial imagery shows a facility approximately 2,000 feet by 500 feet might fit in this area. If water were stored to a depth of 5 feet (the maximum water level raise allowable without having to construct a dam), the area could hold about 115 acre-feet of water storage. This storage volume is approximately equal to the volume of water stored in Woodcliff Lake between El. 94.25 and El. 95. The water could be released into the natural drainage and return to the Hackensack River downstream of Lake Tappan.

The primary elements of this alternative would include:

. A new low-level outlet at Woodcliff Lake . Minimum of one pumping station . About 0.60 miles of pressure pipe . A constructed diked storage facility

Figure 4 shows the location of the proposed pipe and Figure 5 shows the profile along the proposed alignment.

6.4 Floodwater Conveyance Alternative This alternative proposes water be pumped from Woodcliff Lake to the nearest drainage to the west of Woodcliff Lake. Water would be pumped into Musquapsink Brook (a tributary to Pascack Brook). Water would be conveyed in stream through Schlegel Lake until the

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confluence of Musquapsink Brook and Pascack Brook near Cedar Lane. This would allow water to bypass the most often flooded reach of Pascack Brook.

The quantity of water that might be conveyed by Musquapsink Brook is unknown and the feasibility of this option would depend on whether Musquapsink Brook typically has extra capacity between its banks.

The primary elements of this alternative would include:

. A new low-level outlet at Woodcliff Lake . Minimum of one pumping station . About 0.70 miles of pressure pipe . Outlet works to discharge flow into Musquapsink Brook

Figure 4 shows a possible location of the proposed pipe and Figure 6 shows approximate profile along the proposed alignment.

6.5 Conclusions Related to Flood Protection Alternatives

6.5.1 Conclusions and Recommendations Related to Downstream Flood Protection Alternatives Should Hillsdale wish to move forward with developing a flood protection design, GEI recommends a comprehensive effort be made to identify possible alternatives for flood mitigation. Due to the level of development downstream of Woodcliff Lake Dam, it is likely any alternative will carry a significant financial cost. For this reason, it is also recommended that all parties that may see social or economic benefit from flood mitigation be identified and contacting as potential funding partners. These parties might include Federal Emergency Management Agency, residential/business flood insurance providers, and the New Jersey Department of Transportation.

6.5.2 Conclusions and Recommendations Related to Rehabilitation Alternatives Impact on Flood Protection In September 2009, BS&J prepared the Rehabilitation Alternatives Report for Woodcliff Lake Dam (BS&J, 2009). BS&J developed four primary alternatives:

. Alternative 1 – Provide additional spillway capacity to pass the SDF maintaining reservoir levels less than or equal to El. 100; . Alternative 2 – Provide overtopping protection at all reservoir embankments areas affected by SDF maximum reservoir levels up to El. 102; . Alternative 3 – Raise the top of the dam; and . Alternative 4 – Breach and eliminate the dam.

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Multiple configurations were proposed for Alternatives 1 and 3 and a total of 14 alternatives were developed.

As described in Section 3.1.2.3, it is GEI’s opinion that the existing HEC-RAS model is insufficient to predict flood depths without further refinement. As such, we were unable to evaluate the impact of the various alternative configurations on downstream flooding. However, it can be said that flooding is very likely to occur due to large storm events with any of the proposed alternative configurations. The downstream channel capacity is small in relation to the magnitude of flows observed and whenever the magnitude of flows surpasses the capacity of the channel flooding will occur regardless of how the water was delivered.

The maximum capacity of Pascack Brook between Woodcliff Lake Dam and Oradell Reservoir is unknown, but Boswell McClave (2011) indicates that the Patterson Street Bridge is capable of passing about 1,400 cfs (less than the 1-year event) without overtopping. The magnitude of the 1-year event is about 1,900 cfs (BS&J, 2010) (Table 2). Assuming 1,400 cfs is the controlling capacity, Pascack Brook could flood annually, regardless of the dam configuration.

Table 2: Historic Event Precipitation and Peak Inflow (BS&J, 2010) Return Period 24-hour Precipitation Peak Inflow (cfs) 1 year 2.8 inches 1,900 2 year 3.3 inches 2,450 5 year 4.3 inches 3,450 10 year 5.1 inches 4,450 25 year 6.3 inches 5,950 50 year 7.3 inches 7,250 100 year 8.4 inches 8,650

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7. Recommendations for Future Actions to Evaluate Pascack Brook Flood Mitigation

7.1 Request a Review of the Inflow Hydrology and Spillway Design Based on our review of the inflow hydrology and spillway sizing calculations we have the following comments, conclusions, and recommendations:

7.2 Proceed with Dam Rehabilitation Efforts After the review/redesign process described in Section 7.1 is complete, dam rehabilitation efforts should commence. The Woodcliff Lake Dam needs to be rehabilitated to protect the downstream residents from a potential dam failure. The dam design should be verified to account for the changes described in Section 3 and the dam should be rehabilitated as quickly as possible.

It is GEI’s opinion that the primary cause of the downstream flooding is related to the limited channel capacity of Pascack Brook, constrictions along its length, and encroachment into the floodplain. Without significant modifications of these elements, Pascack Brook will continue to flood regardless of the dam configuration.

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7.3 Develop a Water Resource System Model Because the four reservoirs within United Water’s Hackensack System function as a connected water supply system, it is important to analyze the hydrology and hydraulics of the system as a whole. Ideally, the water resource system model would be a comprehensive model that incorporates the watershed drainage area, operations of, and channels within the entire Hackensack System. To develop a comprehensive system model the following elements would be required:

. Topographic information including Digital Elevation Model (DEM) data and select stream cross sections; . Geometry for all bridges and other flow restrictions within the study area; . Location and sizes of structures within the floodplain (likely obtained from aerial photography); . Reservoir data for Lake DeForest Reservoir, Woodcliff Lake Reservoir, Lake Tappan Reservoir, and Oradell Reservoir; . Dam and spillway data for Lake DeForest Reservoir, Woodcliff Lake Reservoir, Lake Tappan Reservoir, and Oradell Reservoir; and . United Water and DEP operational restrictions and requirements.

In lieu of a comprehensive water resource system model, a smaller model incorporating the Woodcliff Lake/Oradell Reservoir system could be developed. The required elements would be the same for both models but would not include inflow from Lake DeForest Reservoir and Lake Tappan Reservoir. A smaller model designed to analyze the reach of Pascack Brook between Woodcliff Lake Reservoir and Oradell Reservoir would allow for analysis of channel capacity, identify channel constrictions and analyze some flood mitigation scenarios. However, a smaller model would limit the number of flood mitigation scenarios that can be evaluated for the four-reservoir water resource system because inflow from Lake DeForest Reservoir and Lake Tappan Reservoir would not be modeled.

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References

Association of State Dam Safety Officials, n.d. “Responsibility and Liability of Dam Ownership” [Brochure], Lexington, Kentucky.

Boswell McClave Engineering, 2011. “Pascack Brook Flood Study, Woodcliff Lake and Oradell Reservoirs”, December 2011.

BPU Docket No. WM12050358, n.d. “Responses to Rate Counsel Discovery RCR-1 through RCR-22”.

Bradley, J.N., 1952. “Discharge Coefficients for Irregular Overfall Spillways”. U.S. Bureau of Reclamation (USBR) Engineering Monograph No. 9. Denver, CO.

Brater, E.F. and King, H.W., 1976, Handbook of hydraulics, 6th ed.: New York, McGraw- Hill, variable pagination.

Buck, Seifert & Jost, Inc. (BS&J), 2011. “Woodcliff Lake Dam Engineer’s Design Report”, January 2011.

Buck, Seifert & Jost, Inc. (BS&J), 2010. “HEC-HMS, HEC-RAS Hydrology and Hydraulic Analysis”, October 2010.

Buck, Seifert & Jost, Inc. (BS&J), 2009a. “Operations and Maintenance Manual Woodcliff Lake Dam”, December 2009.

Buck, Seifert & Jost, Inc. (BS&J), 2009b. “Woodcliff Lake Dam Rehabilitation Alternatives Report”, September 2009.

Buck, Seifert & Jost, Inc. (BS&J), 2007. “Spillway Design Flood Recommendations”, updated July 2007.

Buck, Seifert & Jost, Inc. (BS&J), 2004. “Woodcliff Lake Dam Formal Inspection Report”, June 2004.

Chow, V.T., 1959. “Open–Channel Hydraulics.” McGraw-Hill, New York, New York.

Gannet Fleming Inc., 2006. “Woodcliff Lake Dam PMF Determination”, February 2006.

Interagency Advisory Committee on Water Data, 1982. Guidelines for determining flood- flow frequency: Bulletin 17B of the Hydrology Subcommittee, Office of Water Data Coordination, U.S. Geological Survey, Reston, Va., 183 p., http://water.usgs.gov/osw/bulletin17b/bulletin_17B.html.

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King, H.W. and E.F. Brater, 1963. “Handbook of Hydraulics.” McGraw-Hill, New York, New York.

Lima, Dewey. “Dam Safety Question”. Email to Kerri Price. March 25, 2013.

Lima, Dewey, personal communication, March 27, 2013.

New Hampshire Department of Environmental Services, 2011. “Liability and Responsibility of Dam Owners”, Concord, New Hampshire.

New Jersey Department of Environmental Protection (NJDEP), 2007-2012. Various correspondences, October 2007 to September 2012.

New Jersey Department of Environmental Protection (NJDEP), 1996. “Dam Safety Standards Act (N.J.A.C. 7:20)” Revised 1996.

New Jersey Department of Environmental Protection (NJDEP), 1996. “Dam Safety Act (N.J.S.A. 58:4)” Revised 1996.

Pennsylvania Department of Environmental Protection, 2012. “Liability and Responsibility of Dam Owners”, Harrisburg, Pennsylvania.

Sabol, George, 2008. “Hydrologic Basin Response Parameter Estimation Guidelines”, State of Colorado, Office of the State Engineer, Dam Safety Branch.

U.S. Army Corps of Engineers (USACE), Hydrologic Engineering Center, 1998, HEC-1, Flood Hydrograph Package, User’s Manual.

U.S. Army Corps of Engineers (USACE), 2008. “HEC-HMS Hydrologic Modeling System User’s Manual,” September 2008.

U.S. Army Corps of Engineers (USACE), 2010. “HEC-RAS River Analysis System User’s Manual,” January 2010.

U.S. Army Corps of Engineers (USACE), 1977. “Hackensack River Basin, New York and Pascack Brook Flood Control Feasibility Study” September 1977.

U.S. Bureau of Reclamation (USBR), 1987. “Design of Small Dams.” United States Government Printing Office, Denver, CO.

24 WOODCLIFF LAKE DAM S TUDY REPORT BOROUGH OF HILLSDALE M A Y 2 0 1 3

Figures

WOODCLIFF LAKE DAM S TUDY REPORT BOROUGH OF HILLSDALE M A Y 2 0 1 3

Appendix A

Construction Activities and Temporary Water Control

WOODCLIFF LAKE DAM S TUDY REPORT BOROUGH OF HILLSDALE M A Y 2 0 1 3

Appendix B

Specifications for Cofferdam and Reservoir Lowering, Fish Salvage, and Relocation