MITIGATED NEGATIVE DECLARATION- SKATE PARK PROJECT

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To: L A Wood, Berkeley July 11, 2001
Subject: SUBSEQUENT MITIGATED NEGATIVE DECLARATION- SKATE PARK PROJECT AT HARRISON PARK IN BERKELEY

Mr. Wood:

This letter will respond to the comments transmitted in your letter dated July 2nd concerning the subject environmental document. As a general response to various comments in your letter concerning the adequacy and/or content of the original Mitigated Negative Declaration (MND) adopted by the Council on December 7, 1999 and by the Zoning Board of Adjustments on January 13, 2000, please note that by these actions the MIND is now a legally complete environmental document. Any challenge to aspects of this document should have been made during the appropriate appeal periods.

Therefore, it is not appropriate, nor legally required, to now discard the adopted Mitigated Negative Declaration, close the playing fields, and undertake an extensive Environmental Impact Report to reanalyze issues addressed in your letter concerning transportation, air quality, wetlands, emergency response, etc. With that understanding, I will address your comments that relate to the redesign of the skate park, which is the project described in the Subsequent Mitigated Negative Declaration.

The California Environmental Quality Act (CEQA) provides that a lead agency prepare, circulate for public review, and adopt a Subsequent Mitigated Negative Declaration if new site conditions are evident after approval of the original Mitigated Negative Declaration (MIND). Since hexavalent chromium was found in the groundwater under the project site after approval of the MIND, this obviously qualifies as a new, site condition. Therefore, the City prepared a Subsequent Mitigated Negative Declaration arid circulated it for public review. The sole purpose of this new environmental document is to describe the redesign of the skate park in light of the hexavalent chromium found in the groundwater, including any mitigation measures, and to provide for public review of this information.

Dewatering

The new design does not require a  dewatering system, as stated in your letter. The park will be built above the groundwater table and a professional, highly qualified civil engineering firm has advised that the highest point of the groundwater will be at 6.6 ft. elevation. A six-inch concrete pad will be built above this elevation to provide a cap on the engineered gravel base. This pad will also serve as the bottom of the skate park bowls. There will be a drain line to collect rainwater in the bowls arid carry it to the storm drain. Rather than "isolate" the groundwater plume as stated in your letter, the purpose of this new design is to avoid the groundwater and to prevent it from surfacing at the skate park site.

Structural Cracking

The engineering/design team has stated the skate park will not crack due to the site's hydrology. The engineered fill serves two main purposes: 1) it establishes a sub-grade elevation above the static groundwater elevation; and 2) it breaks the capillary action of the groundwater so it will move laterally through the fill and not upwards. Since the upward capillary action has been eliminated, the risk of potential cracking from upward groundwater pressure has been addressed.

In the event of an earthquake, there is a possibility that structural cracks could develop and a very remote chance that groundwater will surface through these cracks (because of the engineered fill and membrane material located beneath the facility). However, in that event, repairs to the cracks will be made to prevent any groundwater from reaching the surface.

Flooding

The skate park has been elevated above the groundwater so that it is now only partially below ground. The concept of building the facility totally above ground was considered and rejected because the height of the structure would inhibit security by blocking views into the bowls and into the adjacent playing fields.

The northwestern portion of Harrison park has been deliberately designed to serve as a flood plain in those events when the holding capacity of Codornices Creek is exceeded due to under-sized culverts at the Union Pacific Railroad and 1-80. The excess water will flow onto the western playing field until it either flows through the culverts or runs south along the railroad tracks. The new storm drain on Harrison Street with catch basins at the foot of the street near the tracks will contain this water, except in unusual events. The Harrison House Homeless Shelter has been re-configured to mitigate flooding. Since the skate park is at a higher elevation than the land along the railroad tracks and since the land slopes naturally to the southwest, it is very unlikely that excess water from Codornices Creek will impact the facility. As noted above, any water (such as rain water) that enters the skate park will be conveyed by drains to the adjacent storm drain system.

Thank you for your continued interest.

Edward Murphy
City of Berkeley Department Parks and Waterfront project Manager

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