Prepared for: City of Oshkosh Oshkosh, Wisconsin

Subsurface Exploration and Geotechnical Engineering Evaluation for the Proposed Tipler Retention Pond Project

AECOM, Inc. April 2009 Document No.: 60099626

AECOM

i May 2009

Contents Executive Summary ......................................................................................................................................ES-1

1.0 Field Procedures.................................................................................................................................... 1-1

2.0 Exploration Results ............................................................................................................................... 2-1

3.0 Monitoring Well Installation.................................................................................................................. 3-2

4.0 Environmental Screening ..................................................................................................................... 4-1

5.0 Construction Considerations............................................................................................................... 5-1

6.0 General Qualifications........................................................................................................................... 6-1

List of Appendices Appendix A Boring Location Diagram / Boring Logs / Abandonment Forms / Monitoring Well Construction Forms

Appendix B AECOM General Notes

Appendix C AECOM Field and Laboratory Procedures

Appendix D AECOM Soil Classification System Chart

AECOM

ES-1 May 2009

Executive Summary

The City of Oshkosh is proposing that a retention pond be constructed in the field located to the west of Tipler Middle School. Excavations up to 15 feet in depth will be required for the retention pond construction.

The purpose of this exploration program was to identify the soil and groundwater conditions within the depths of the excavations proposed, with special emphasis on any apparent bedrock conditions encountered within the depth of the borings. In addition, field screening of the soil samples with a PID was completed to identify potential environmentally impacted soil.

AECOM

60099623-Tipler Retention Pond 1-1 May 2009

1.0 Field Procedures

The subsurface exploration program consisted of drilling 12 soil borings to depths ranging from 12 to 15 feet below the existing ground surface. Boring identification numbers are recorded on the top right-hand corner of the boring logs and correspond to City of Oshkosh drawing which can be found in Appendix A.

The borings were performed using a Mobile B-61 rotary drill rig. The borings were advanced using solid stem flight auger drilling techniques. Representative soil samples were obtained in the borings using split barrel techniques in general conformance with ASTM D 1586. A copy of the standard boring log procedures is included in Appendix C. Ground surface elevations and the boring locations were established by the City of Oshkosh.

A log of soils recovered in the borings was maintained by the drill crew. Soil samples obtained from the drilling operations were sealed immediately in the field and returned to our Oshkosh laboratory for further examination and testing. Observations of water levels encountered in the borings, both during and after sampling, are noted on their respective boring logs. Upon completion of the borings, the boreholes were backfilled with a 3/8-inch bentonite chip material. Two of the borings were converted into temporary monitoring wells to observe groundwater conditions.

AECOM

60099623-Tipler Retention Pond 2-1 May 2009

2.0 Exploration Results

One of the twelve borings encountered a surface pavement section. The concrete and base course thickness was recorded and appears on the boring log.

Underlying the surface fill materials, which were mainly composed of topsoil except for Borings 7 and 12 which encountered pavement and base course, the fill material extended to a depth of 0.5 to 3.5 feet below grade. A reddish-brown to brown silty clay was encountered that extended to a depth of 1 to 15 feet below grade. This natural silty clay generally ranged in consistency from very stiff to hard, as indicated by the unconfined compressive strength estimates. Below the silty clay, a gray or brown sandy silt or silty sand was encountered in a few of the borings to the termination depth of the borings. This hardpan type material ranged in relative density from medium dense to extremely dense, as indicated by the Standard Penetration Test blow counts.

In general, groundwater was not encountered while advancing the borings through the overburden soils with solid-stem flight augers. Groundwater was observed in Boring 4 at a depth of 13.5 feet and Boring 8 at a depth of 8.3 feet. However, the majority of the soils within the profile were cohesive in nature and have a relatively low permeability. The two monitoring wells will be monitored to accurately determine groundwater levels.

AECOM

60099623-Tipler Retention Pond 3-2 May 2009

3.0 Monitoring Well Installation

Monitoring wells were installed in soil borings B-4 and B-6. The wells were set at a depth of 15 feet. The wells were constructed with schedule 40 PVC with a 10-foot screen. A 2-foot stick-up was extended above the ground surface. The monitoring well construction form can be found in Appendix A. Groundwater levels will be monitored to observe where groundwater may be encountered during excavation.

AECOM

60099623-Tipler Retention Pond 4-1 May 2009

4.0 Environmental Screening

All soil samples were screened using a photoionization detector (PID). There were no elevated PID readings.

AECOM

60099623-Tipler Retention Pond 5-1 May 2009

5.0 Construction Considerations

The overburden soils encountered within the depth of the borings can be excavated effectively with backhoe-type equipment. A few cobbles and boulders were encountered within the profile which could hinder excavation depending on their actual dimension. Sideslopes of the excavations in the cohesive soils and hardpan soils will be reasonably stable at relatively steep slopes of approximately 1H:1V. However, all excavations should conform to local, state, federal and OSHA requirements.

AECOM

60099623-Tipler Retention Pond 6-1 May 2009

6.0 General Qualifications

This report has been prepared in general accordance with normally accepted geotechnical engineering practices to aid in the evaluation of this site and to assist our Client in the design of this project. We have prepared this report for the purpose intended by our Client, and reliance on its contents by anyone other than our Client is done at the sole risk of the user. No other warranty, either expressed or implied, is made.

The scope is limited to the specific project and location described herein, and our description of the project represents our understanding of the significant aspects relevant to the geotechnical characteristics.

The analysis and recommendations submitted in this report are based on the data obtained from the soil borings performed at the locations indicated on the boring logs and from the information discussed in this report. This report does not reflect any variations which may occur between the borings. In the performance of subsurface explorations, specific information is obtained at specific locations at specific times. However, it is a well-known fact that variations in soil and rock conditions exist on most sites between boring locations and that seasonal and annual fluctuations in groundwater levels will likely occur. The nature and extent of variations may not become evident until the course of construction.

The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria, viruses, and the byproducts of such organisms) assessment of the site, or identification of or prevention of pollutants, hazardous materials, or conditions. Other studies beyond the scope of this project would be required to evaluate the potential of such contamination or pollution.

AECOM

May 2009

Appendix A Boring Location Diagram / Boring Logs / Abandonment Forms / Monitoring Well Construction Forms

S W

ES

TF

IE

LD

ST

WITZEL AVE

BISMARCK AVE

4210

8

0

6

0

8

8

8

8

10

8

8

8

8

8

10

8

8

8

CAMPBELL CREEK WATERSHED

CITY OF OSHKOSH

TIPLER DETENTIONPOND BORING

LOCATIONS

Legend

12' Boring Depth

15' Boring Depth

Storm Manholes

Sanitary Manholes

Water Fittings

Water Hydrants

Water Valves

Existing Storm Sewer

Existing Sanitary Sewer

Existing Water Main

City Parcels

0 200100 Feet

I:\Engineering\Storm Water Information\Campbell Creek Watershed\Tipler Dry Detention\

GIS\Tipler Detention Pond Boring Locations.pdf

B-6 (Well)B-5

B-3

B-2

B-1

B-4 (Well)B-7

B-8

B-9

B-10

B-11

B-12

1.5

15.0* Calibrated Penetrometer

1

2

3

4

5

6

7

SS

SS

SS

SS

SS

SS

SS

Fill: Topsoil - Moist

Reddish brown silty clay - trace gravel - moist - very st