Design_Report_0005.pdf

ORGAN PIPE CACTUS NATIONAL MONUMENT

AJO, AZ

REHABILITATE PRIMARY PARK WATER SYSTEMS

ORPI

PMIS: 240821

BASIS OF DESIGN REPORT (BDR)

NATIONAL PARK SERVICE (NPS)

DENVER SERVICE CENTER (DSC)

CAD

Highlight existing trench as much as possible to reduce impacts, but maintain an adequate setback from existing asbestos concrete pipe to prevent disturbing pipe.

e. Service lines: Domestic service lines will be HDPE (PEX) pipe except for any above grade portions which will be Type K copper.

Directional drilling was considered for the campground area, but open trenching is preferred to the following factors;

i. Directional Drilling (DD) requires water main to be 6-ft deep minimum. Location of water main would be below an area rich in vegetation as well as concrete campsite pads and shade structures. Exposing pipe for emergency repairs would create a large impact that should be avoided.

ii. DD is preferred in locations where tees and services are minimal. Campground requires multiple tees for comfort station and spigots, therefore each location would need to be exposed reducing any efficiency or impact gains created by the DD method.

f. Asbestos Concrete Pipe Removal and Disposal:

i. Per Arizona Department of Environmental Quality (ADEQ) as long as AC pipe is not made friable, it’s handling, and disposal is not regulated.

ii. Project specifications will state that contractor is not to crush, saw, pulverize, or otherwise make AC pipe friable.

iii. Per State Historic Preservation Office (SHPO), existing water system dates from the Mission 66 era (1960s) and is therefore considered historic. SHPO recommends pipe remain in the ground to prevent the need for SHPO compliance.

iv. Design is locating new water mains in locations where direct impacts to AC pipe will be minimized and AC pipe can remain in current location with minimal disturbance.

2. Water Tank Sizing: Proposed water tanks will be sized as follows;

a. Provide the average daily demand during the peak month, plus

i. Average daily demand is based on meter readings provided by NPS for a 2 year period.

b. An equalization volume equal to the average daily demand, plus

c. Fire Storage Volume based on NFPA 1142, plus

d. Backwash Filter volume (if applicable), and

e. Dead storage volume of approximately 10% at the top of the tank

3. Water Tank Design

a. Proposed water tanks will be designed to minimize maintenance and improve monitoring capability. No specific performance of the tanks needs to be improved.

Specific requirements include;

i. Tanks will be glass-fused steel tanks

CAD

Highlight

CAD

Highlight