WATER SOURCE QUALITY SELECTION BASICS AND TUTORIALS

QUALITY OF WATER SOURCE
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The quality will be determined by the planned use. Physical, chemical, and bacteriological testing of source waters is required to determine the level of treatment to supply the necessary water quality.

When the quantity withdrawn exceeds the recharge rate, quality inherently decreases; therefore, this must be considered during design.

a. Physical characteristics. The physical characteristics of the raw water source that must be evaluated are total suspended solids (TSS) and temperature. Turbidity and silt density index (SDI).

(1) Total suspended solids. The total suspended solids level of raw water sources must be evaluated to determine the level of pretreatment processes required. Raw water having low total suspended solids levels generally requires less pretreatment. The source with the lowest total suspended solids is preferred.

(2) Temperature. The temperature of the raw water source must be matched to the specific desalination process. In extreme cases, the water temperature may control the desalination process selection. A climatological survey must be made prior to finalization of process selection to determine the seasonal maximum and minimum water temperatures of the proposed water sources.

(3) Turbidity and silt density index. These two characteristics provide two different measures of the amount of fine particulate matter in the water.

Turbidity is measured in nephelometric turbidity units (a measure of the amount of light scattered by a known water sample thickness). Silt density index is a measure of the amount of 0.45-micron filter plugging caused by passing a sample of water through the filter for 15 minutes.

Turbidity must be determined for all desalination processes. Also, the silt density index must be determined for water being considered for reverse osmosis treatment.

b. Chemical constituents. The chemical constituents of the raw water must be determined to provide information for treatment selection.

c. Bacteriological quality. The bacteriological testing of the raw water must include a type of a coliform indicator organism count.

Procedures for filter membrane, most probable number fermentation tube, and standard plate count, coliform organism bacteriological testing techniques can be found in Standard Methods for the Examination of Water and Wastewater and TB Med 576.

Manufacturers' recommendations as to the media and procedures used to identify microbiological activity detrimental to the operation of a particular desalination system shall be followed.

STRUCTURAL DETAILER RESPONSIBILITY ON BRIDGE DESIGN

STRUCTURAL DETAILER RESPONSIBILITY
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The structural detailer is responsible for the structural plan sheets. The plans shall be neat, correct, and easy to follow and drawn to scale. The structural detailer may also assist the designer and design checker in such areas as determining control dimensions and elevations, geometry, and calculating quantities.

Some detailing basics and principles:

a. Refer to BDM for detailing practices.

b. Provide necessary and adequate information. Try to avoid repetition of information.

c. Avoid placing too much information into any one sheet.

d. Plan sheets should detail in a consistent manner and follow accepted detailing practices.

e. Provide clear and separate detail of structural geometrics. Use clear detailing such as “stand alone” cross sections or a framing plan to define the structure.

f. Avoid reinforcing steel congestion.

g. Check reinforcement detail for consistency. Beware of common mistakes about placement of stirrups and ties (such as: stirrups too short, effect of skew neglected, epoxy coating not considered, etc.). Check splice location and detail, and welding locations.

h. Use cross references properly.

i. Use correct and consistent terminology. For example, the designation of Sections, Views, and Details.

j. Check for proper grammar and spelling.

k. On multiple bridge contracts, the structural detailing of all bridges within the contract shall be coordinated to maximize consistency of detailing from bridge to bridge. Extra effort will be required to assure uniformity of details, particularly if multiple design units and/or consultants are involved in preparing bridge plans. This is a critical element of good quality bridge plans.

l. Refer to the Bridge Book of Knowledge for current special features and details used on other projects.