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Meeting Date:	05/29/2018
Sewer Mapping Survey, Engineering Services, Porras Nance Engineering
Submitted for:	Adrian Montemayor	Submitted By:	Adrian Montemayor
Department:	Water Utilities


Subject:
Discussion with possible action to authorize the Purchasing Agent to solicit Requests for Qualifications for engineering and surveying services for Rio Bravo and El Cenizo wastewater collection system in order to provide a GIS map of the system and inventory the known infrastructure [Account #7220-7270-001-432001; 2016 Bond Series, Wastewater Professional Services] Issue: Currently staff only has operation identified hand written flow maps of the wastewater collection system that does not provide the necessary information regarding collection main flow patterns and capacities to identify the improvement needs. Solution: Conduct manhole and clean out investigations of approximately 300 manhole/clean outs and measure all elements of the infrastructure for further evaluation and GIS coordinate based mapping. Result: Accurate mapping for future utilization in operation, maintenance, and infrastructure improvements.
Background:
We will conduct GPS field surveys of all locatable MH/CO lids, interconnecting pipe sizes and pipe inverts (dropdown depths) to update the sewer collection system maps into a GIS format for County mapping records. This will provide an accurate inventory of these facilities and allow more precise mapping of the connecting sewer mains in the system. All points will be tied to the NAD 83, Texas State Plane, 4205 South Zone, NAVD 88 (grid oordinates) by GPS equipment to match the County’s GIS database. The survey data will be processed into a CAD and GIS format for final system mapping. Connecting sewer mains will be color coded by line size and presented on large scale 24”x36” aerial exhibits. The existing 11”x17” block maps will be updated. Two (2) hardcopies of each will be submitted with a CD containing digital formats of all mapping files. A preliminary evaluation of the existing capacity of all surveyed sewer mains will be conducted based on calculated pipe slopes flowing full. This evaluation will be general in nature to identify pipe sections with inadequate grade to convey estimated discharge, which will be calculated based on residential lot unit estimates and lift station point discharge measurements provided by the County. We will submit a technical memorandum that summarizes our findings.
Previous Court Action:
None