Friday, March 10, 2017

UPDATED, 3/30 The challenge and need for "dewatering" downtown construction sites

Station House Lofts -- This "deep-dig" sits over and in our aquifer 
Completion of the above "Station House Lofts" is expected in early 2018.  According to the project Superintendent, it will be a 6-stories with 197 apartments and two levels of underground parking.  The construction site is across the street from the Redmond United Methodist Church on 16533 NE 80th St.  It looks well engineered.  The tall grey building in the background is the Old Redmond Firehouse Teen Center.  

To help scale the size of the dig look for the workers...those orange and yellow specks. (Click on the photo to see the influence of the camera angle on size.)  The city aquifer is close to the surface so the site has to be "dewatered" and sealed off.  Notice the white water pipe in the foreground.  Six inch diameter water pipes also surround the site, and can't be seen in this picture. Owing to extreme rains there's a lot of aquifer water that must be pumped out. The mixed aquifer and rain water are tested every two weeks for oil and lubricants before it's dumped into the stormwater system. Many downtown developments need dewatering.

Public Works is somewhat concerned about contaminated construction water entering the aquifer -- the aquifer being a major source of our drinking water.  Thus, the city wrote a new ordinance to protect the aquifer during development; and to bill those developers who excessively drain the aquifer and our wells.

In a few places around the city, the aquifer can be as close as 3 feet from the surface. According to the Superintendent it's my understanding they had to dig 2-3 feet into the alluvial aquifer in places. 

Bob Yoder
by

This is an excellent article explaining  the process and challenges of dewatering construction sites.

This is an archive of all my aquifer and groundwater posts over the years.   .

3 comments:

Bob Yoder said...

A FB reader made a good point: the angle of the camera should be considered.

Susan Wilkikns said...

I have a copy of the Wellhead Protection Report that was written for the City in 1997. I copied some significant tables and the map that shows time-of-travel for groundwater to the wells.

Wells #1 & #2 are in Anderson Park. They were redrilled and upgrade a few years ago. The city gets 40% of its downtown water from these two wells. Station House Lofts is 2 blocks from Anderson Park and all the other buildings with underground garages are also very close to Wells #1 & #2.

The Costco fuel tanks hold 90,000 gallons of gas and are less than 1/2 mile from Well #5. The city has allowed its contractor to spray Roundup on the Keller Farm to get rid of weeds. Evans Creek and Bear Creek run through the Keller Farm and the farm fields recharge Well #5.

The city wants to put a new community center on top of Well #4.

The city annual water right is 1.8 BILLION gallons of water. We have the water right to pump the well water, but it may all be contaminated.

Bob Yoder said...

A memo on recent study session agenda says the city gets 35% of their drinking water from the aquifer. When Overlake is developed the percentage will be much less.

I thought all our potable water east of the Samm. River was supplied by the aquifer