Attached are new Highway Design Manual pages for various Indicies, Figures and Tables in Chapter 800 - Highway Drainage Design.

Major revisions within Chapter 800 have been made to; provide guidance on drainage design where contact with groundwater is likely; completely revise discussion on joint performance with regard to soil and water migration through pipe joints; revise discussion on culvert coatings to provide additional service life data for polymerized asphalt and Department of Fish and Game concerns regarding culvert coatings; and expand discussion of stormwater management to reference recent guidance documents and relationship between water quality and water quantity.

The most significant revisions are summarized below:

Index 821.3 - Selection of Design Flood

De-emphasize use of greatest flood of record in establishing design flood for both bridges and culverts. While the greatest flood of record should still be evaluated, it need not typically take precedence over the 50 or 100 year event as previously indicated.

Topic 822 - Debris Control

Provide text for indicies 822.1, 822.3 and 822.4.

Index 831.4 - Other Considerations

New index provides guidance on wrapping of pipe joints with filter fabric where soil migration through joints may be of concern, and directs designers to contact the Roadway Geotechnical Branch of the Engineering Service Center when groundwater control is necessary.

Index 839.6 - Groundwater Considerations

New index to provide guidance on special considerations where groundwater is encountered at pumping stations.

Index 841.1 - Introduction

Provide information on when assistace from the Roadway Geotechnical Branch and Structure Foundations Branch should be requested.

Index 842.5 - Types of Underdrain Pipe

Remove text which references types of underdrain pipe no longer commonly used.

Index 853.1 (3) - Basic Policy: Joint Performance

New and expanded discussion of current types of pipe joints and the level of performance to be expected. New Table 853.1C is provided to simplify joint selection process. Key considerations in joint selection are presence of free water in the surrounding soils and susceptibility of soils to migrate. Designers should specify appropriate joint type(s) on project plans.

Index 854.3 (1) - Corrugated Steel Pipe and Pipe Arches: Durability

Expanded discussion on additional service life to be expected from protective coatings. Inclusion of recently approved polymerized asphalt coating in text and in Table 854.3A. Discussion of Department of Fish and Game concerns on the use of bituminous coatings. Also, recent alalysis shows that aluminized steel pipe (type 2) performs significantly better than previously suggested. Table 854.3B has been revised to indicate that 1.6 mm thick aluminized steel (type 2) will provide 50-year service life with respect to corrosion throughout its range of application.

Tables 854.3B thru 854.6D - Corrugated Metal Pipe and Pipe Arch Fill Height Tables

Various revisions to tables of maximum fill heights to change or add fill height values, modify metal pipe thickness to conform to industry and AASHTO / ASTM designations, modify arch span x rise dimensions to conform to recent industry selected designations, etc.

Table 854.8 - Thermoplastic Pipe Fill Height Tables

Revised fill heights on High Density Corrugated Pipe to 9 m for all sizes up to 900 mm. Also added recently approved 1050 and 1200 mm sizes with maximum fill height of 6 m.

Chapter 890 - Stormwater Management

Chapter revised to incorporate limited discussion on water quality issues. Provides reference to recently developed Water Quality Handbooks as primary source of design information for both temporary and permanent water quality control features. Advises designers that water quality features must also include provision for handling peak rainfall events as well as the smaller events for which they are typically designed.

The attached sheets are effective May 30, 1997, and shall be applied to on-going projects in accordance with the policy and instructions contained in Highway Design Manual Index 82.5 - Effective Date for Implementing Revisions to Design Standards.

Please remove superseded sheets and insert the revised sheets at or before the effective date.

Attachment

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