Question

3. Curve Number and SCS Travel Time Assignment (2 pts) You need to calculate the curve number for a site which is composed of: 25 acres industrial buildings, 125 acres 1 acre lots, 60 acres parks/open space with good cover, 40 acres of commercial development, and 225 acres of meadows. The soil was determined to be 50% Sand, 25 % Silt and 25% Clay. a. Determine the Soils Type b. Determine Curve Number for AMC III.

Answer 1

It is given that the soil consists of :

Sand -- 50 %

Silt -- 25 %

Clay -- 25 %

Clay is present in the soil and so it has a very slow infiltration rates when the soil is thoroughly wetted.

a). Therefore the type of soil bis HSG Group D.

b). It is give that :

Industrial building is 25 acres, i.e.

CN = 93

adjusted CN = 93 x 1 = 93

I acre lots is 125 acres, i.e.

CN = 84

Adjusted CN = 84 x 1.07 = 89.88

= 90 (approx.)

60 acres of open or park space, i.e.

CN = 80

Adjusted CN = 80 x 1.14 = 91.2

= 91 (approx.)

225 acres of the meadows

CN = 78

Adjusted CN = 78 x 1.14 = 88.92

= 89 (approx.)

Commercial development of 40 acres, i.e.

CN = 95

Adjusted CN = 95 x 1 = 95

Therefore the curve number is given by :

Thus, the curve number for the site for AMC III = 85

Step-by-step explanation:

Answer 2

It is given that the soil consists of :

Sand -- 50 %

Silt -- 25 %

Clay -- 25 %

Clay is present in the soil and so it has a very slow infiltration rates when the soil is thoroughly wetted.

a). Therefore the type of soil bis HSG Group D.

b). It is give that :

Industrial building is 25 acres, i.e.

CN = 93

adjusted CN = 93 x 1 = 93

I acre lots is 125 acres, i.e.

CN = 84

Adjusted CN = 84 x 1.07 = 89.88

= 90 (approx.)

60 acres of open or park space, i.e.

CN = 80

Adjusted CN = 80 x 1.14 = 91.2

= 91 (approx.)

225 acres of the meadows

CN = 78

Adjusted CN = 78 x 1.14 = 88.92

= 89 (approx.)

Commercial development of 40 acres, i.e.

CN = 95

Adjusted CN = 95 x 1 = 95

Therefore the curve number is given by :

`$=((25 * 93)+(125 * 90)+(60 * 91)+(40 * 95)+(225 * 78))/(25+125+60+40+225)$`

`$= 85.02$`

`$\sim 85$`

Thus, the curve number for the site for AMC III = 85