CLINTON DAYLIGHTING FEASIBILITY STUDY FINAL REPORT

PREPARED BY

719 GRISWOLD, SUITE 1040 DETROIT, MI 48226 313‐963‐6600

AND

NOVEMBER, 2008 TABLE OF CONTENTS

Executive Summary ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ iii

1.0 Background ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 1

2.0 Purpose of Study ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 3

3.0 Existing Conditions and Constraints ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 5 3.1 New Route Can Not Follow Old Bed ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 5 3.2 conveying the total High Flow in an Open is Impractical ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 5 3.3 A Naturally Flowing channel Should Maintain Existing Hydraulic Grade ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 6 3.4 New Route must Respect Existing Structures ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 6 3.5 New Route must Allow for the development of “Lot 9” ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 6 3.6 Access to the Phoenix Center Must be Maintained‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 7 3.7 Public and Private Utilities Serving the Area Must be Maintained/Relocated ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 7

4.0 Hydrologic and Hydraulic Analysis ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 8

5.0 Flow Diversion Alternatives ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 10 5.1 Option A – Construction of a Pump Station‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 10 5.2 Option B – Construction of Gravity Conduit ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 12 5.3 Option C – Construction of in the Box ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 14 5.4 Selected Diversion Method ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 16

6.0 Open Channel Route Selection ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 17

7.0 Environmental Site Review ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 20

8.0 Habitat Impact ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 21

9.0 Engineer’s Opinion of Conceptual Project Cost ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 22

10.0 Conclusions and Constraints ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 24

LIST OF FIGURES

Figure 1‐1: Clinton Watershed Map showing Pontiac ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 1 Figure 1‐2: Location of enclosed conduit through downtown Pontiac ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 2 Figure 3‐1: Bottom profile of shallower daylighted river ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 5 Figure 3‐2: Typical Cross Section ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 6 Figure 4‐1: Expected Flow Rates and Depths in Existing Enclosure ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 8 Figure 4‐2: Well locations ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 9 Figure 5‐1: Option A Location ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 10 Figure 5‐2: Option A preliminary engineering drawing ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 11

Clinton River Daylighting Feasibility Study i Final Report November, 2008

Figure 5‐3: Option B Location ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 12 Figure 5‐4: Option B preliminary engineering drawing ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 13 Figure 5‐5: Option C Location ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 14 Figure 5‐6: Option C preliminary engineering drawing ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 15 Figure 6‐1: Proposed Route ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 17 Figure 6‐2: Siphon conceptual design ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 18

LIST OF TABLES

Table 5‐1: Option A – New Pump Station Engineer’s Preliminary Estimate ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 11 Table 5‐2: Option B – New Dry Weather Flow Sewer Engineer’s Preliminary estimate ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 13 Table 5‐3: Option C – Diversion Chamber and Engineer’s Preliminary Estimate ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 15 Table 6‐1: Proposed Siphon Crossing Engineer’s Preliminary Estimate ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 19 Table 9‐1: Engineer’s Opinion of Conceptual Project Cost ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 22

Clinton River Daylighting Feasibility Study ii Final Report November, 2008

EXECUTIVE SUMMARY

The Oakland County Commissioner (OCWRC) – previously known as the Oakland County Drain Commissioner – retained Environmental Consulting & Technology, Inc. (ECT) to study the feasibility of daylighting the Clinton River through downtown Pontiac, Michigan. In 1963 the Clinton River was enclosed in two 10 foot by 10 foot rectangular conduits through this area to alleviate the serious flooding that had occurred during the previous two decades. Since then, all river flow has been transported underground through the central part of Pontiac. In fact, the Phoenix Center has been built over the top of the conduits – covering about 20% of the entire buried segment.

City Officials requested that the OCWRC investigate the possibility of removing the flow from the conduits and returning all or portions of it to a more natural open channel that would flow through downtown. This type of activity is becoming more common recently in areas where urban have been previously enclosed – and is commonly referred to as “daylighting.” Daylighting can return many of the natural benefits of the stream and daylighted streams have often served as catalysts for development of surrounding underutilized urban properties.

Environmental Consulting & Technology, with the assistance of Applied Science, Inc. (ASI), evaluated the historic and flows within the Clinton River through Pontiac and developed scenarios under which low and moderate flow could be routed away from the enclosure through a newly constructed channel generally paralleling the present route. High level flows and all “” flows would remain within the enclosure which would need to remain in place. Three alternatives were evaluated for diverting flows into the new channel. All were determined to be feasible and comparable in cost – as determined at a planning level estimate.

During the driest times of the year the Clinton River through Pontiac can often experience extended periods of extremely low or zero flow within the existing conduits. To maintain a flowing stream through downtown flow augmentation will be required. It has been determined that the City of Pontiac has in place a number of flow augmentation wells – two of which are upstream of the proposed project – that could be used for this purpose.

The proposed daylighted channel will need to be significantly lower in elevation than the existing ground level throughout its route. In order to maintain a natural flow within the open channel the will need to be approximately 20 to 24 feet below existing grade. To accomplish this – and maintain an aesthetically pleasing appearance – a river‐walk concept has been envisioned. The depressed stream is planned to be paralleled by a pedestrian walkway just a few feet above water level.

The river‐walk concept will require significant modification to the current traffic patterns for both vehicular and pedestrian flow in this part of downtown Pontiac. Water Street will be eliminated under the proposed route, and crossings will need to be provided to allow both vehicles and pedestrians access to the Phoenix Center. Similarly, in these areas a relocation of public and private utilities currently making use of street rights‐of‐way will be required.

Future development of the vacant parcel immediately north of the Phoenix Center (often referred to as “Lot 9”) will be impacted by the stream relocation. However a developer could well capitalize on the stream located at a lower level in the rear of a newly constructed building by providing for a lower “plaza level” adjacent to the stream.

Clinton River Daylighting Feasibility Study iii Final Report November, 2008

A large volume of excavated material will be generated by the construction of this stream and river‐walk through downtown. This excavation may involve some environmental challenges associated with appropriate soil handling, transportation and disposal. The removal and disposal of soils in historically industrial/commercial or highly urbanized areas requires a higher awareness of the potential environmental impacts of the soils to be excavated. For the purpose of this feasibility study – and associated cost estimate – it was assumed that all excavated material would need to be disposed of at a Type II landfill.

The existing enclosure being evaluated for daylighting currently provides no habitat for macroinvertebrates and fish. The newly daylighting project would create habitat that would support macroinvertebrate and fish communities. The fish that would likely return to the daylighted stream would probably be similar to that of the adjacent portions of the Clinton River and be characterized by low diversity, dominance of tolerant species, such as blacknose dace and creek chubs, and a low abundance of desired game fish species, such as bass, walleye, northern pike, bluegill, and crappie.

The overall project cost based on: the alignment [route] identified; the excavation and construction required to create a naturally flowing stream and adjacent pedestrian way; necessary diversion structures; necessary vehicle and pedestrian crossings; and allowances for utility relocation and flow augmentation is estimated to be $47,000,000.

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1.0 BACKGROUND

The Clinton River has historically defined the City of Pontiac. The city was founded in 1818 at the location where the Saginaw Indian Trail crossed the Clinton River. Downtown Pontiac, to this day, remains at this location. The city has expanded around the downtown area. Significant industrial and commercial development as well as residential subdivisions created a city of major importance to the region.

The main branch of the river rises from wetlands in Oakland County’s Springfield Township, northwest of Pontiac. A series of create a number of small lakes west of Pontiac which impact the flow of the river through the city. While these impoundments can act to mitigate high flows, in the past periods of high flow caused flooding problems in downtown Pontiac. A map of the Clinton River watershed showing the location of Pontiac is shown in Figure 1‐1.

During the 1940s and 1950s the Clinton River experienced a number of high flow periods which caused severe flooding in downtown Pontiac adjacent to the river. City Leaders petitioned the Oakland Figure 1‐1: Clinton Watershed showing Pontiac County Water Resources Commissioner to take action to prevent future flooding.

The office of the Oakland County Water Resources Commissioner (OCWRC) conducted a study of flood reduction options that resulted in the design and construction of an enclosure of the Clinton River from downstream of Crystal Lake, through downtown Pontiac, to a location east of Northbound Woodward Avenue.

Construction of the Clinton River Drain No. 1 project was completed around 1963 and eliminated the flooding problems for downtown Pontiac. The Clinton River was enclosed through downtown Pontiac in a 10‐foot high by 10‐foot wide reinforced concrete double box conduit. The overall length of the enclosure is about 3000 ft, and its upstream and downstream invert elevations are about 896.2 feet and 889.4 feet, respectively. The full cross‐sectional area of the double box conduits is approximately 199.5 square feet, and the bottom slope is approximately 0.24%.

The structure was sized to allow all flows – including flood flows – to be contained within the structure and eliminate any surface flooding within downtown Pontiac. The alignment of the conduit followed the alignment of the original stream bed which at the time of construction did not impact downtown development. However,

Clinton River Daylighting Feasibility Study 1 Final Report November, 2008

since that time, this portion of downtown Pontiac has experienced redevelopment. In fact, the Phoenix Center has been built over the conduit that enclosed the river.

Figure 1‐2 shows the location of the enclosed conduit through Downtown Pontiac.

Figure 1‐2: Location of enclosed conduit through downtown Pontiac

Clinton River Daylighting Feasibility Study 2 Final Report November, 2008

2.0 PURPOSE OF STUDY

The enclosed portion of the Clinton River’s main brain runs through historic downtown Pontiac. In order to provide a catalyst for renewed downtown development and to assist in the revitalization of Pontiac, it is the desire of the City of Pontiac to potentially return the river to a natural condition through as much of this portion of the City as is practical and cost‐effective.

Current flows from upstream portions of the Clinton River are controlled by dams that create a number of impoundments on the Clinton River and numerous streams. The most downstream impoundment is Crystal Lake, immediately upstream of the enclosed portion of the river. These dams present both opportunities and challenges to the proposed daylighting. Their existence can allow appropriate management of flow to assure a minimum flow rate during some dry periods when the stream segment could go dry. However, the minimum impoundment water elevations were established by law to assure adjacent property owners minimum lake levels. For a number of weeks each year, minimum lake levels combined with periods of low flow result in the enclosed segment of the river experiencing zero flow. Thus any efforts to daylight this portion of the Clinton River needs to consider the need for flow augmentation during these dry weather periods.

A previous study, completed in 2000, considered the potential of creating an open through a portion of the downtown area which would “enhance the urban setting and provide aesthetic value to the area.” The 2000 study looked at creating the in a small portion of the downtown area near the eastern terminus of the enclosed stream. It only considered a stream cross section approximately 5 feet deep at existing grade with flow pumped to it from either the enclosed stream or – during no flow periods – from flow augmentation wells. While creating the desired urban water element this plan would not maintain existing hydraulic grade lines for future flows. Maintaining natural grade increases the value of the daylighting effort with respect to flow variability and habitat development.

The overall goals of this project feasibility study were defined at the onset as follows:  River Daylighting Goals – Restore River to “close to natural” state – Provide focal point for Downtown Development  Determine the technical feasibility of daylighting  Investigate hydraulics of Clinton River at Pontiac  Determine possible routes for open channel  Identify hindrances to implementation

Early in the investigation, ECT met with City of Pontiac staff and staff from the OCWRC, Oakland County Planning Department to establish the specific goals of this feasibility study. The following is a synopsis of the desired outcome of the various attendees:  Maximize the length of river exposed  Consider daylighting entire length – not just downstream section  All properties – including “Lot 9” [parking north of Phoenix Center] available  Route river to go ‘through’ city rather than ‘around’ it  River should be accessible to the community at large  River should fit within the existing master plan

Clinton River Daylighting Feasibility Study 3 Final Report November, 2008

 Route should include open space and pedestrian ways as a catalyst for re‐development  Report should include detailed costs for planners to balance with benefits  Report should be a tool for informed decision making as they reshape downtown.

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3.0 EXISTING CONDITIONS AND CONSTRAINTS

Daylighting an urban stream such as the Clinton River can have numerous positive benefits. and pipes usually prevent the passage of fish and reduce natural habitat for other species. is a particularly effective way of increasing the integration of nature in urban areas because of their inherent beauty and because of the high level of biological diversity that accompanies riparian corridors. In order to achieve these benefits within the highly urbanized portion of Pontiac a number of constraints presented by the existing conditions have been identified and must be overcome. They include the following:  New Route can not follow old stream bed  Conveying the entire expected peak flow rate in a new open channel is impractical  A naturally flowing channel should maintain existing hydraulic grade  Route must respect existing structures  Route must allow for development on “Lot 9”  Access to Phoenix Center must be maintained  Public and private utilities serving the area must be maintained / relocated

Additional discussion for each of the above constraints is provided below.

3.1 New Route Can Not Follow Old Stream Bed The existing duel box culvert was constructed within the original stream bed of the Clinton River. Since initial construction of the enclosed river, the City of Pontiac has constructed the Phoenix Center, a multi‐use complex of office, amphitheatre, and parking structure, over the top of the enclosed river. Due to this constraint the route of the daylighted river needs to be outside the original river bed location, thus requiring excavation within the downtown lots and streets.

3.2 Conveying the Total High Flow in an Open Channel is Impractical A new open channel capable of handling the entire expected peak flood flow rates of the Clinton River would require an exceptionally deep and wide channel. If a shallower channel is built to carry all of the flow, then the upstream flood elevations would likely be raised and would increase designations for adjacent and upstream properties. Increasing flooding elevations is not allowable. Therefore, the proposed daylighted river will be shallower than the existing enclosure and will be designed to only carry a low flow portion of the total flow rates. The existing enclosure will remain in service to carry a higher flow rates and will operate in parallel with the daylighted channel. Also this will require that the route selected be outside that of the current enclosure. A bottom profile of the shallower daylighted river is given on Figure 3‐1. Figure 3‐1: Bottom profile of shallower daylighted river

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3.3 A Naturally Flowing Channel Should Maintain Existing Hydraulic Grade In order to achieve maximum ecological benefits for the project, it is desirable to maintain existing hydraulic grade to avoid the need for pumping and allow for natural flow variability within the channel. Additionally, it is critical that the daylighted channel not negatively impact the upstream hydraulic grade during high flow events.

Due to this constraint, a cross‐section that is on average about 24 feet deep will be required through downtown. And, to assure the aesthetics of such a deep cross section, a wide ‘river‐walk’ concept has been envisioned. This would allow for a flowing stream approximately 14 feet below current road level with a pedestrian way adjacent to the stream. This typical cross section is shown in Figure 3‐2.

Figure 3‐2: Typical Cross Section

3.4 New Route must Respect Existing Structures The portion of downtown Pontiac through which the daylighted stream will be located is extremely congested. Existing commercial buildings, the Phoenix Center, a senior citizens complex and the library crowd the potential route. Although final design criteria may allow for the abandonment or reconstruction of some of these structures the currently proposed route would allow existing major structures to remain in place.

The buildings would remain; however certain road rights‐of‐way would be utilized for the stream location. Since the stream cross section would be significantly lower in elevation than the first floor of some adjacent structures, it was assumed that these structures may be redeveloped with a pedestrian accessible ‘basement’ level at the same elevation as the walkway adjacent to the stream.

3.5 New Route must Allow for the Development of “Lot 9” A large undeveloped parcel is located at the north westerly corner of the Phoenix Center. This property – known to Pontiac City Planners as “Lot 9” – is at the upstream most part of the proposed daylighted stream. The Pontiac Master Plan calls for this property to play a key role in the redevelopment of the area. The route selected for the daylighted stream must maintain the develop‐ability of this parcel – and if possible enhance the desirability of its development through access to a water amenity. The City Planners confirmed that the proposed channel alignment would maintain sufficient developable portions of the property and allow for integration of the daylighted stream into a future development.

Clinton River Daylighting Feasibility Study 6 Final Report November, 2008

3.6 Access to the Phoenix Center Must be Maintained Currently the Phoenix Center garage is accessed through an entrance at the south end of South Saginaw Street – where it intersects with Water Street. Pedestrian access from the downtown area is provided along Water Street between South Saginaw and South Perry Streets. The introduction of an open stream and pedestrian walkway that is depressed below grade will significantly affect access to the Phoenix Center from downtown.

To address the issue of access it was assumed that two vehicular crossings and three pedestrian crossings (bridges) of the stream and a pedestrian walkway would be required.

3.7 Public and Private Utilities Serving the Area Must be Maintained / Relocated The introduction into a highly developed downtown area of a water feature that is located significantly below existing grade will require the identification and relocation of water main, sanitary sewer, storm drainage, natural gas, electric, telephone, cable television, and other underground utilities.

Preliminary investigations conducted as part of this feasibility study indicate that local and transmission utilities exist within the proposed route of the daylighted stream. Service connections, lateral sewers and local distribution mains will need to be relocated as part of the potential daylighting. Most complicated will be relocation of a network of sanitary sewers up to 24‐inch in diameter. A conservative allowance for utility relocation has been included in the project cost estimate.

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4.0 HYDROLOGIC AND HYDRAULIC ANALYSIS

The enclosed river is expected to carry the following range of flow rates. These data were obtained from the Flood Insurance Study (FIS) for the City of Pontiac and from the USGS stream gage just downstream of downtown Pontiac on the Clinton River at Auburn Road.  100 Year Flood = 2,600 cfs  10 Year Flood = 1,600 cfs  Maximum Monthly Mean Flow Rate = 172 cfs  Mean Flow Rate = 100 cfs  Minimum Monthly Mean Flow Rate = 57 cfs  Seven Day Minimum Flow Rate = 6 cfs

The flood profiles given in the FIS were evaluated and it was found that the existing drain enclosure is not expected to be backwater affected by the downstream section of the Clinton River. At the upstream and downstream ends of the enclosure the 100 year flood elevations are approximately 911 feet and 900 feet, respectively.

The expected flow rates and depths in the existing enclosure are detailed on the cross section shown on Figure 4‐1. These depths were determined using an existing HEC‐RAS model of the Clinton River and are normal depths calculated with a Mannings ‘n’ value of 0.012. The enclosure is expected to flow nearly full with a velocity of approximately 13 feet per second for the 100‐year flood flow rate of 2,600 cubic feet per second.

Figure 4‐1: Expected Flow Rates and Depths in Existing Enclosure

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In the downtown Pontiac area, approximately 2,600 feet of daylighted channel was deemed feasible and the route this channel is further discussed in Section 6.0. The cross‐section of the proposed daylighted channel was previously shown in Figure 3‐2. The proposed daylighted channel has a low flow channel designed to convey up to 170 cfs.

A profile for the daylighted channel bottom was shown previously in Figure 3‐1. In order to maintain only low flow rates in the daylighted channel, the new channel must be higher than the existing enclosure flood levels.

The daylighted channel will need to terminate at Pike Street or cross the existing enclosure near Pike Street in a siphon structure. A concept for the siphon structure is discussed in Section 6.0.

During dry summer months sufficient flow will not exist to maintain continuous flow within the daylighted stream. To maintain flow for both aesthetic and natural habitat reasons flow augmentation will be necessary. The City of Pontiac has previously been required to provide certain augmentation to Clinton River flows during drought conditions to maintain a minimum receiving water flow for wastewater treatment plant . A series of wells are in place for this purpose. As part of this feasibility study it was determined that two of these wells are located upstream of the currently enclosed portion of the river. Although detailed information on the capacities and conditions of these wells was not available, it was assumed that with limited upgrades these wells could be the source of flow at times that augmentation would be required. The location of these wells is shown in Figure 4‐2.

Figure 4‐2: Well locations

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5.0 FLOW DIVERSION ALTERNATIVES

Redirecting a portion of Clinton River flow from the box culverts into a new open channel can be accomplished in a number of ways. Three methods of diversion were identified and investigated as part of this feasibility study. Each of the three diversion methods were evaluated as to their viability within a true daylighted stream context, their general maintenance requirements and their construction cost. The three alternatives considered which will be discussed below were:  Option A – Construction of a Pump Station to pump flow into the new channel  Option B – Construction of Gravity Conduit from the existing open channel to the new channel  Option C – Construction of Weirs in the Box Culvert to direct flow into the new channel

5.1 Option A – Construction of a Pump Station This option consists of design and construction of a pump station adjacent to the existing box culverts just upstream of where they cross under the Phoenix Center. The location is shown in Figure 5‐1.

Figure 5‐1: Option A Location

The pump station would be sized to convey up to 170 cfs from the enclosed drain to the upstream end of the proposed new open channel. This option would require minimal disruption to the existing box culvert but would not allow passage of fish through the new channel to upstream habitat. It’s long term operational and maintenance requirements would consist of cost of power for continual pump operation, routine pump maintenance, and eventual renewal and replacement of the pumps.

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A preliminary Engineering drawing of this option is shown in Figure 5‐2.

Figure 5‐2: Option A preliminary engineering drawing

The estimated total cost of this option is $ 843,980. The cost is broken down in the Table 5‐1.

Table 5‐1: Clinton River Daylighting Project ‐ Pontiac Michigan Option A ‐ New Pump Station Engineer's Preliminary Estimate Item No. Description Unit Quantity Unit Price Item Cost General 1 Mobilization (Assume = 10% of Total) Each 1 $80,000 $80,000 2 Traffic control Month 6 $3,500 $21,000 Storm Sewer System 3 4' dia concrete storm sewer LF 60 $200 $12,000 4 3' x 6' box LF 32 $640 $20,480 5 24 " forcemain LF 150 $160 $24,000 6 5' dia MH 17 ft deep Each 1 $3,500 $3,500 Pump Station 7 Excavation with Sheeting and Shoring LS 1 $100,000 $100,000 8 Concrete CY 244 $250 $61,000 9 Electrical and Control LS 1 $10,000 $10,000

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Item No. Description Unit Quantity Unit Price Item Cost 10 Flygt Submersible Pump. CP 3501 20"discharge incl hatch Each 4 $97,000 $388,000 11 4' dia concrete end section w/ animal guard Each 1 $1,000 $1,000 12 Jack & Bore under existing road 24" force main LF 100 $500 $50,000 13 Pavement removal and repair LS 1 $1,000 $1,000 14 Install standard 4' dia manhole over existing 10' box sewer. Incl. sawcut opening in roof Each 2 $5,000 $10,000 15 Sawcut 3' x 6'box opening in wall of existing 10' box culvert Each 3 $3,000 $9,000 16 Install 10 LF x 3' weir in ex. 10' box sewer Each 2 $1,500 $3,000 Allowances 18 Unforeseen site conditions LS 1 $50,000 $50,000 TOTAL $843,980

5.2 Option B – Construction of Gravity Conduit This option consists of design and construction of a new gravity flow conduit from the end of the current Clinton

Figure 5‐3: Option B Location River open channel – at approximately Orchard Lake Road and Bagley Street to the upstream end of the new daylighted channel near the northwest corner of the Phoenix Center. The location is shown in Figure 5‐3.

The new conduit would be sized to convey up to 170 cfs from the Clinton River to the upstream end of the proposed open channel. This option would require no disruption to the existing box culvert and would likely allow passage of certain fish through the new channel to upstream habitat. It’s long term operational and maintenance requirements would be minimal. The only long term cost would be eventual renewal and

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replacement of the conduit. Additionally, if property could be obtained west of the railroad the length of conduit could be reduced and additional daylighted channel created.

A preliminary engineering drawing of this option is shown below in Figure 5‐4.

Figure 5‐4: Option B preliminary engineering drawing

The estimated total cost of this option is $ 797,000. The cost is broken down in Table 5‐2.

Table 5‐2: Clinton River Daylighting Project ‐ Pontiac Michigan Option B ‐ New Dry Weather Flow Sewer Engineer's Preliminary Estimate Item No. Description Unit Quantity Unit Price Item Cost General 1 Mobilization (Assume = 10% of Total) Each 1 $80,000 $80,000 2 Traffic Control Month 6 $3,500 $21,000 Storm Sewer System 3 60" dia concrete storm sewer LF 1350 $310 $418,500 4 Precast 6' dia. MH 15 ft ‐18ft deep each 5 $3,500 $17,500 5 Special MH cast in place 16' x 10' concrete box with weir each 1 $20,000 $20,000 6 60" dia concrete end section w/ animal guard Each 1 $2,000 $2,000 7 Jack & Bore under existing roads and railroad tracks 3 locations LF 230 $600 $138,000 8 Pavement removal and repair LS 1 $30,000 $30,000 9 Restoration LS 1 $10,000 $10,000 Utility Repairs 10 Utility relocations/crossings LS 1 $10,000 $10,000

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Item No. Description Unit Quantity Unit Price Item Cost Allowances 11 Unforeseen site conditions LS 1 $50,000 $50,000 TOTAL $797,000

5.3 Option C – Construction of Weirs in the Box Culvert This option consists of design and construction of a set of diagonal weirs within the upstream end of the existing box culvert at a location just upstream of where it passes under the Phoenix Center. These weirs would be designed to redirect flows less than approximately 170 cfs to a short conduit connecting the box culvert to the upstream end of the new daylighted channel near the northwest corner of the Phoenix Center. The location is shown in Figure 5‐5.

Figure 5‐5: Option C Location

The weir structure would be sized to convey up to 170 cfs from the Clinton River to the upstream end of the proposed new open channel while providing sufficient cross sectional area above the weirs to allow excess flows – including storm flows – to continue downstream within the existing structure. This option would require extensive disruption to the existing box culvert and would likely allow passage of certain fish through the new channel to upstream habitat. It’s long term operational and maintenance requirements would consist of periodic flushing or mechanical removal of that would build up upstream of the weirs and periodic operation of gates provided to allow emergency bypass of the weir structures. The only long term cost would be eventual renewal and replacement of the mechanical components of the structure.

A preliminary engineering drawing of this option is shown in Figure 5‐6.

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Figure 5‐6: Option C preliminary engineering drawing

The estimated total cost of this option is $ 808,100. The cost is broken down in Table 5‐3.

Table 5‐3: Clinton River Daylighting Project ‐ Pontiac Michigan Option C ‐ Diversion Chamber and Weir Engineer's Preliminary Estimate Item No. Description Unit Quantity Unit Price Item Cost General 1 Mobilization (Assume = 10% of Total) Each 1 $80,000 $80,000 2 Traffic control Month 6 $3,500 $21,000 Storm Sewer System 3 5' dia concrete storm sewer LF 128 $310 $39,680 4 Jack & Bore under existing road LF 100 $700 $70,000 5 Twin 3' x 6' concrete box LF 24 $640 $15,360 6 Special MH 14' x 8' box Each 1 $12,000 $12,000 7 Headwall with wingwall for twin 3 x 6' box Each 1 $20,000 $20,000 8 Install 150 LF x 8' weir in ex. 10' box sewer Each 2 $45,000 $90,000 9 Install 36" slide gate with crank operator Each 2 $15,100 $30,200 11 Sheet & shore construction pit 25' x 50' LS 1 $190,000 $190,000 12 Sheet & shore construction pit for jack and bore LS 1 $50,000 $50,000

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Item No. Description Unit Quantity Unit Price Item Cost 13 Install 10 x 8 maintenance hatch over box sewer. LS 1 $12,000 $12,000 14 Sawcut 5' dia opening in wall of existing 10' box culvert. Each 3 $3,000 $9,000 15 Remove 50 LF of ex. box culvert roof brace existing box culvert during construction LS 1 $50,000 $50,000 16 Add 5' of reinforced concrete to existing walls CY 30 $898 $26,940 17 Replace Roof CY 40 $1,050 $42,000 Allowances 18 Unforeseen site conditions LS 1 $50,000 $50,000

TOTAL $808,180

5.4 Selected Diversion Method The cost estimates associated with each of the three alternatives are very comparable. Therefore, for the purposes of this study, a preferred method of flow diversion was not selected. However, for the purposes of maintaining a most favorable habitat for fish and wildlife Option B would be most preferred since it allows the most unobstructed passage for fish.

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6.0 OPEN CHANNEL ROUTE SELECTION

The proposed route of the proposed daylighted channel was selected to maximize the length of watercourse within the Downtown Pontiac. The alignment provides a number of challenges due to the congested urban nature of the area. The proposed route can allow open channel flow of the Clinton River through much of the Downtown Pontiac area, as shown in Figure 6‐1. Additional discussion of the route, including project challenges and description of changes in vehicular and pedestrian flow patterns required for the project is provided below.

Figure 6‐1: Proposed Route

The route begins just east of Southbound Woodward at the northwest corner of the Phoenix Center. It is conceived to pass through “Lot 9” in such a way as to allow future structural development on that site that would have ‘street level’ access on Pike and Saginaw Streets and ‘plaza level’ access to the lower level watercourse at the rear (south) side of the future development.

The daylighted Clinton River would then turn eastwardly and follow the alignment of Water Street which would be eliminated as part of the project. To allow vehicular access to the Phoenix Center, a bridge over the newly constructed depressed stream and pedestrian way connecting the end of Saginaw Street to the parking garage has been assumed.

It is anticipated that structures adjacent to Water Street on the north would remain in place, and construction cost estimates include appropriate sheet pile reinforcement to maintain stability. Perry and Mill Streets would

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be terminated, for vehicular use north of the new channel. Pedestrian access from north of the stream to areas to the south has been provided for in the cost estimate by the inclusion of three pedestrian bridges, likely to be located at Perry and Mill Streets, as well as a third – unspecified – location.

The proposed route would turn to the north south of the current Water and Mill Street intersection. The open channel would be located to the west of the Library Building south of Pike Street.

Near Pike Street, if the route of the proposed channel is to continue it must cross the existing box conduits. This presents a significant challenge – and associated cost – since the elevation of the channel bottom would be lower than the top of the existing conduit. To provide a complete assessment of the feasibility of daylighting the maximum length of river possible the concept of constructing a siphon to carry the box culvert – with associated storm flows – under the new channel was explored.

The siphon would not only present a challenge during initial construction, but would also require long term maintenance to assure no build‐up of or debris would occur and restrict storm flows. Figure 6‐2 depicts the conceptual design of a siphon under the proposed channel.

Figure 6‐2: Siphon conceptual design

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The estimated total cost of the siphon is nearly $2,000,000. The cost is broken down in the Table 6‐1 below.

Table 6‐1: Clinton River Daylighting Project ‐ Pontiac Michigan Proposed Siphon Crossing Engineer's Preliminary Estimate Item No. Description Unit Quantity Unit Price Item Cost General 1 Mobilization (Assume = 10% of Total) Each 1 $100,000 $100,000 2 Traffic control Month 6 $3,500 $21,000 Storm Sewer System 3 Install new twin 10x10 concrete box LF 175 $2,100 $367,500 4 Excavation CY 11000 $8 $88,000 5 compacted backfill CY 8000 $5 $40,000 6 Install 25x12 maintainence hatch/drop connection on box sewer. LS 2 $120,000 $240,000 7 Sheet & shore construction pit LS 1 $500,000 $500,000 8 Pavement removal and repair LS 1 $20,000 $20,000 9 Remove existing twin 10' box culvert LF 175 $1,000 $175,000 10 Utility relocation LS 1 $50,000 $50,000 11 Flow diversion during construction LS 1 $200,000 $200,000 Allowances 12 Unforeseen site conditions LS 1 $100,000 $100,000

TOTAL $1,901,500

The route then continues across Pike Street where a second vehicular bridge has been provided for. The channel would then proceed through two vacant parcels which are now used as parking lots, to an end point near Northbound Woodward and West Huron Street (M‐59). At this point the open channel would be diverted back into the existing box culvert and cross the intersection to the northeast where the Clinton River currently returns to an open channel.

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7.0 ENVIRONMENTAL SITE REVIEW

The process of soil excavation and removal during the Clinton River daylighting process may involve a series of environmental challenges associated with appropriate soil handling, transportation and disposal conditions. These challenges generally focus on the “generator knowledge” position that is necessary for the proper disposal of soils and waste soils, and more importantly is associated the actual “lack of knowledge” regarding the soils to be encountered.

The removal and disposal of soils in historically industrial/commercial or highly urbanized areas requires a higher awareness of the potential environmental impacts associated with the soils to be excavated. These areas often have multiple historical uses, from early residential use, to industrial uses during the 1940s to 1970s, followed by miscellaneous passive uses (parking, warehouse storage, abandoned and vacant).

Landfills require a waste characterization process before accepting waste for disposal, with a heavy emphasis on “generator knowledge.” This process must identify potential impacts to the soil, both from current and historical activities. Where “generator knowledge” information is minimal or lacking, landfills will require an analytical evaluation of the proposed waste materials. The level of analytical testing is also related to the knowledge of potential impacts (less knowledge – more testing)

The excavation process associated with this project, a linear excavation event over many parcels, will then require some basis of “generator knowledge” over each parcel involved. Even after landfill approval is granted, the generator must always be aware of field condition changes which may alter the waste characterization. For instance, if the waste characterization of a certain areas soil is based on the lack of any known contamination and an area of soil is encountered during the excavation process that exhibits a change in that characteristic (odor, soil staining, etc.), then a new or updated waste characterization would be required. This can happen multiple times during a linear site to site excavation process. Landfills may also require updated waste characterizations, with new analytical testing, based on the amount of soils submitted for disposal (new lab sample round for every certain quantity).

An example of the historical conditions that may be encountered are described in the AKT Peerless environmental report (September 2004) regarding the 3.71 acre parcel of property located at the northeast corner of North Mill and Pike Streets (within the proposed excavation area). The reports describe a property currently used entirely for vehicle parking, however, with numerous past industrial uses, many involving a wide array of potential chemical uses. These historical uses include felting operations, miscellaneous manufacturing, junkyard, lumber storage, paint storage, machine repair, leather works, tile manufacturing and tin shop. Soil sampling has been performed, with results indicating the presence of numerous chemical impacts, including various volatile organic compounds, semi volatile organic compounds and metals. These contaminants are found at different locations across the parcel. Based on this “generator knowledge,” it may be quite likely that the landfill waste approval process could require numerous sampling events during soil removal activities to verify the condition of the waste soils. Any “hot” spots may have to be characterized individually during the excavation process.

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8.0 HABITAT IMPACT

The Clinton River upstream and downstream of the existing stream enclosure is characterized by its urbanized watershed. Generally, the stream is impacted by altered hydrology, channelization, loss of floodplain and riparian habitat, and and sedimentation. Physical habitat is degraded by streambank and streambed erosion, sedimentation, instability, low base flow, elevated water temperature, and increased peak flow magnitude and frequency. Important macroinvertebrate attachment sites like large woody debris and cobble is either unstable (frequently transported) or affected by sedimentation.

Macroinvertebrate populations consist of tolerant taxanomic groups and species such as midges, aquatic worms, freshwater shrimp, snails, and aquatic flies. Sensitive taxa such as the mayflies, some caddisfly species, stoneflies, dragonflies, and some beetles are absent or present in low numbers. Fish populations are also dominated by tolerant species and low diversity. Common tolerant fish species include common carp, creek chub, bluntnose minnow, green sunfish, white suckers, Johnny darter, and blacknose dace. Some tolerant species such as blacknose dace and creek chubs are often found in high abundance if habitat conditions are present. Game fish abundance is typically low. Desirable game fish include smallmouth and largemouth bass, walleye, northern pike, bluegill, rock bass, and crappie. Due to recent efforts by the Michigan Department of Natural Resources, Unlimited, the Clinton River Watershed Council, and several municipalities, there are also efforts to establish a cold‐water fishery in portions of the mainstem Clinton River, with recent focus on anadromous (i.e. steelhead).

The existing enclosure being evaluated for daylighting currently provides no habitat for macroinvertebrates and fish. Therefore, the daylighting project would directly create habitat that would support macroinvertebrate and fish communities. Macroinvertebrate and fish communities within the daylighted portion of the Clinton River would probably be similar to that of the Clinton River upstream and downstream. Both communities would be characterized by low diversity, dominance of tolerant species, and, in the case of fish, low abundance of desired game fish species. Habitat within the daylighted portion would be limited by altered hydrology (especially low flows), altered , limited riparian habitat, elevated water temperatures, and the engineered characteristics of the channel.

The daylighting project would not benefit the Clinton River upstream of the daylighing project due to the significant length of enclosure that will remain and impacts associated with development and water level control in the upper watershed that could not be addressed by the daylighting project. Likewise, a length of enclosure will remain downstream, and the daylighting would not improve conditions within the Clinton River downstream of the enclosure. The Clinton River downstream of the enclosure is impacted by channelization, altered hydrology, loss of floodplain and riparian habitat, and sedimentation. The enclosures that would remain upstream of the daylighting project would limit habitat connectivity and fish passage between the daylighted portion and the Clinton River upstream of the enclosures.

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9.0 ENGINEER’S OPINION OF CONCEPTUAL PROJECT COST

1‐2 pages plus tables

The Engineer’s Opinion of Conceptual Project Cost for this project is $47,000,000 as summarized in the Table 9‐ 1.

Table 9‐1: Clinton River Daylighting Project ‐ Pontiac Michigan Engineer's Opinion of Conceptual Project Cost Item Qty Unit Unit Price Total Price Wet Weather Flow Diversion 1 EA $ 800,000 $ 800,000 Surface Demolition 10,000 SY $ 10 $ 100,000 Public Utility Relocation 1 LS $ 1,000,000 $ 1,000,000 Private Utility Relocation 20 EA $ 7,500 $ 150,000 Sheet Piling, Permanent 33,000 SF $ 40 $ 1,320,000 Channel Excavation 120,150 CY $ 50 $ 6,007,500 Inlet / Outlet Structures 2 EA $ 125,000 $ 250,000 Plaza Level Excavation 30,000 CY $ 50 $ 1,500,000 Concrete Lining, (including walk) 10" thick 32,200 SY $ 60 $ 1,932,000 Cobble / Earthen Lining for Channel 9,400 CY $ 140 $ 1,316,000 Perry & Mill St Cul‐de‐Sac 2 EA $ 75,000 $ 150,000 Vehicular Bridge 2 LS $ 300,000 $ 600,000 Pedestrian Bridges 3 LS $ 150,000 $ 450,000 Walkway Landscaping, Lighting & Amenities 1 LS $ 300,000 $ 300,000 Water, Drainage, Emergency Communication 1 LS $ 250,000 $ 250,000 Walkway Access (Stairs, Ramps) 4 LS $ 150,000 $ 600,000 Fencing, Decorative 5,200 LF $ 150 $ 780,000 Flow Augmentation Well Upgrade 1 LS $ 250,000 $ 250,000 Clinton River Siphon 1 LS $ 2,000,000 $ 2,000,000 Misc Surface Restoration 1 LS $ 250,000 $ 250,000 Downtown Traffic Planning / Implementation 1 LS $ 100,000 $ 100,000 Mobilization / Demobilization 10% $ 2,000,550 Unforseen Conditions 15% $ 3,000,825

Construction Sub Total $25,106,875 Design / Inspection 25% $ 6,276,719 Legal / Administrative 20% $ 5,021,375

Sub Total $36,404,969 Contingency 30% $10,595,031 TOTAL $47,000,000

Cost estimates for the three flow diversion options were prepared and it was determined that the conceptual cost associated with each option was approximately $800,000. Therefore, a selection of flow diversion option was not needed to complete the total conceptual project cost.

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Information from Phase I reports indicates a likelihood that in‐situ soils are likely to be contaminated. Although detailed soil testing has not been completed to confirm the extent of the contamination, it was assumed that all excavated material would need to be disposed of at a Type II landfill.

Permanent sheet piling was assumed to be required along both sides of Mill Street to provide protection for the road and buildings and along one side of Water Street to provide protection for the existing buildings.

A geomorphic analysis was not part of this study. Therefore, it is unclear if the proposed channel cross section and plan form would be stable. As the proposed channel is located within an urban area, immediately adjacent to roads and buildings, it is critical that the channel plan form not shift from the design plan form. Additionally, the channel cross section may require slopes steeper than what could be stabilized by natural methods. Therefore, it was assumed that a concrete lining would be required to prevent any channel evolution that is common with natural channels. In order to provide a natural river feel, an earthen lining, including cobbles and smaller sediments would be provided over the concrete lining.

A walkway, 25‐foot wide was assumed along the length of the channel. Additional amenities for the walkway include stairs, ramps, three pedestrian bridges, decorative fencing, water utilities and emergency communication facilities. Excavation for two plazas, approximately 30,000 cubic yards, was also included in the cost estimate. Additional amenities (surface restoration, furniture, utilities, etc.) for the plazas were not included.

Two vehicular bridges were assumed although specific locations were not determined at this time. It was assumed that cul‐de‐sacs would be required at Mill Street Perry Street. Costs for completion of detailed traffic analysis and planning effort along with minor modifications to downtown signage were included. No improvements to roads outside of the project limits were assumed.

The City of Pontiac owns well sites that were previously used to augment discharge from the Waste Water Treatment Plant. The wells are no longer in use and their capacity and condition are unknown. It was assumed that the existing wells could be utilized with upgrades to the well pumps and equipment. Drilling of new wells was not included.

Contingencies for unforeseen conditions, approximately 15% of the construction cost subtotal were included to account for the conceptual nature of this estimate. Design and administrative costs were also assumed based on the conceptual construction costs and typical percentages.

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10.0 CONCLUSIONS AND CONSTRAINTS

The Clinton River through downtown Pontiac, Michigan currently is totally enclosed in underground conduits. These conduits are capable of carrying high level – even flood stage – flows safely through the area. During dry periods flow through the conduits can be reduced to zero.

The existing conduits follow the original channel of the Clinton River. These conduits need to remain in place to handle flood flows. Thus any daylighting will require a new channel to be constructed.

The new channel will need to be depressed about 20 feet below current grade to allow natural flow grades. This will require a wide depressed corridor across downtown Pontiac. It is envisioned that the daylighted stream would be paralleled by pedestrian walkways at the lower level.

Constraints imposed by the location of existing buildings dictate a relatively tight channel route. The existing Water Street, north of the Phoenix Center, would need to be eliminated to make room for the stream.

In order to allow the relocated channel to reconnect to the Clinton River at its current location under Northbound Woodward Avenue, it would have to cross the existing conduit. For this to happen, the conduit will need to be rebuilt as a siphon under the open channel.

Three options for diverting flow into the daylighted channel were evaluated. All had comparable costs. For the purposes of this study, a preferred method of flow diversion was not selected. However, for the purposes of maintaining a most favorable habitat for fish and wildlife Option B, construction of a Gravity Conduit from the existing upen channel to the newly daylighted channel, would be most preferred since it allows the most unobstructed passage for fish.

Excavation of the new channel will be through an area of highly non‐homogeneous urban fill. This will require that the new channel’s natural streambed materials be supported by a concrete liner. And, based upon the previous work done in the area, the excavated material is likely to exhibit levels of contamination requiring special handling and disposal.

The proposed daylighting will positively impact the natural habitat of the stream, allowing habitat for certain fish and other species to be developed within the newly created channel and along stream banks. The channel, however, will not be a truly natural stream and will still have fish impediments at the upstream end thereby limiting the species within the daylighted section.

The proposed route has been coordinated with the conceptual plan for downtown Pontiac and fits within the overall conceptual framework. Proposed future development on Lot 9 can take advantage of the depressed channel by opening the rear of the buildings to a plaza level approximately at stream elevation.

Vehicle and pedestrian crossings of the depressed stream and pedestrian way will need to be provided. And, traffic patterns in downtown Pontiac will be significantly altered by the elimination of Water Street.

The overall project cost based on: the alignment [route] identified; the excavation and construction required to create a naturally flowing stream and adjacent pedestrian way; necessary diversion structures; necessary vehicle and pedestrian crossings; and allowances for utility relocation and flow augmentation is estimated to be $47,000,000.

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