WSMU_MEBA_ordinanceboundarychange engineering info_20240528

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May 28, 2024 _�' 41 °'
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To: Ashley Ownbey, Development Director f''r �,q S. J4 X�`\,�
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From: Josh Johnson, P.E. Stormwater Administrator
Subject: Water Supply Watershed Ordinance and Map Changes
In preparation for the Council meeting on June 3rd, I wanted to provide a little additional information on
the process for the water supply watershed (WSW) ordinance and map revisions. The City's WSW map
was prepared in 1993/1994 based on the best available data available to NC DEQ at the time. Since that
time, GIS and other topographical information has improved greatly and there are areas of the map that
we know are inaccurate. The current WSW ordinance is based upon NC DEQ's maps rather than a local
map and does not include any way to change the WSW map (including the boundaries of the WSW)
without going to NC DEQ and asking them to change the official map. The proposed changes to the WSW
ordinance will allow the City to amend the map locally and then submit to DEQ after the fact showing the
corrected version.
The inaccurate maps have come up several times with regard to downtown development, primarily in the
West Clay and West Center Street areas. These areas are quite flat and storm drainage takes runoff from
these areas to the south and away from the protected water supply watershed for the Graham-Mebane
Lake. As a proactive first step in addressing issues that the City is aware of, we reviewed the boundary
area from the Mebane Community Park to Eleventh Street. In reviewing these areas, we reviewed GIS
contours, available field topographic surveys, as well as storm drainage layouts. After the initial map was
completed then we walked the areas in question to verify that the storm drainage took water the same
way that our initial reviews said it did. Our review showed that there are several areas where the ridgeline
between the protected WSW and the non-WSW is a road centerline or a building roofline. This is pretty
typical of urbanized development areas but the straight lines that show this are not something you would
see in a rural setting or that are shown on the original map.
In total, the update removed quite a few parcels from the WSW zoning layer while adding a little bit of
additional area on lots that were already in the WSW zoning layer. It is also worth noting that the work
didn't change any field conditions, it just updated the zoning layer and map to match what actually
happens.
CITY OF MEBANE 106 East Washington Street I Mebane,NC 27302 [phone] [e-mail]
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